Bacterial Secondary Production Research Articles

Endophytic Streptomyces population induced by L-glutamic acid enhances plant resilience to abiotic stresses in tomato.

Endophyte bacteria, which colonize plants including roots, stem, flower, and fruit, it can derive their nutrients from the host, are recognized for their mutualistic relationship with the host plant. They play a critical role in promoting host growth and modulating abiotic stress. Carbon and nitrogen have a significant impact on bacterial population and secondary metabolite production, which are highly specific in various categories such as bacterial growth regulation, anti-compounds production. Application of L-glutamic acid can significantly enhance Streptomyces globisporus population buildup in plants. However, the effectiveness of this population buildup against abiotic stresses such as salinity and drought has not been investigated. Therefore, in this study, we tested the bacteria and their prebiotic activity against salinity and drought stress in tomato plants. Three different amino acids were treated on the tomato plants, and it was observed that L-asparagine and L-proline had a negative effect on plant growth and phenotype, while L-glutamic acid promoted plant growth and increased bacteria population density. The bacteria were found to colonize the rhizosphere and root endosphere, with colonization being promoted by L-glutamic acid. Additionally, Streptomyces was found to have plant growth promotion effects and provided protection against abiotic stresses. Interestingly, L-glutamic acid reduced the damage caused by salinity stress, but not drought stress. These findings suggest that L-glutamic acid plays a role in providing tolerance to salinity stress with the core microbiota, thus the current study demonstrated their prebiotic activity in the agriculture system.

Quorum Sensing and Antimicrobial Production Orchestrate Biofilm Dynamics in Multispecies Bacterial Communities.

Microbial interactions are often mediated by diffusible small molecules, including secondary metabolites, that play roles in cell-to-cell signaling and inhibition of competitors. Biofilms are often "hot spots" for high concentrations of bacteria and their secondary metabolites, which make them ideal systems for the study of small-molecule contributions to microbial interactions. Here, we use a five-member synthetic community consisting of Roseobacteraceae representatives to investigate the role of secondary metabolites on microbial biofilm dynamics. One synthetic community member, Rhodobacterales strain Y4I, possesses two acylated homoserine lactone (AHL)-based cell-to-cell signaling systems (pgaRI and phaRI) as well as a nonribosomal peptide synthase gene (igi) cluster that encodes the antimicrobial indigoidine. Through serial substitution of Y4I with mutants deficient in single signaling molecule pathways, the contribution of these small-molecule systems could be assessed. As secondary metabolite production is dependent upon central metabolites, the influence of growth substrate (i.e., complex medium versus defined medium with a single carbon substrate) on these dynamics was also considered. Depending on the Y4I mutant genotype included, community dynamics ranged from competitive to cooperative. The observed interactions were mostly competitive in nature. However, the community harboring a Y4I variant that was both impaired in quorum sensing (QS) pathways and unable to produce indigoidine (pgaR variant) shifted toward more cooperative interactions over time. These cooperative interactions were enhanced in the defined growth medium. The results presented provide a framework for deciphering complex, small-molecule-mediated interactions that have broad application to microbial biology. IMPORTANCE Microbial biofilms play critical roles in marine ecosystems and are hot spots for microbial interactions that play a role in the development and function of these communities. Roseobacteraceae are an abundant and active family of marine heterotrophic bacteria forming close associations with phytoplankton and carrying out key transformations in biogeochemical cycles. Group members are aggressive primary colonizers of surfaces, where they set the stage for the development of multispecies biofilm communities. Few studies have examined the impact of secondary metabolites, such as cell-to-cell signaling and antimicrobial production, on marine microbial biofilm community structure. Here, we assessed the impact of secondary metabolites on microbial interactions using a synthetic, five-member Roseobacteraceae community by measuring species composition and biomass production during biofilm growth. We present evidence that secondary metabolites influence social behaviors within these multispecies microbial biofilms, thereby improving understanding of bacterial secondary metabolite production influence on social behaviors within marine microbial biofilm communities.

Wheat Metabolite Interferences on Fluorescent Pseudomonas Physiology Modify Wheat Metabolome through an Ecological Feedback.

Plant roots exude a wide variety of secondary metabolites able to attract and/or control a large diversity of microbial species. In return, among the root microbiota, some bacteria can promote plant development. Among these, Pseudomonas are known to produce a wide diversity of secondary metabolites that could have biological activity on the host plant and other soil microorganisms. We previously showed that wheat can interfere with Pseudomonas secondary metabolism production through its root metabolites. Interestingly, production of Pseudomonas bioactive metabolites, such as phloroglucinol, phenazines, pyrrolnitrin, or acyl homoserine lactones, are modified in the presence of wheat root extracts. A new cross metabolomic approach was then performed to evaluate if wheat metabolic interferences on Pseudomonas secondary metabolites production have consequences on wheat metabolome itself. Two different Pseudomonas strains were conditioned by wheat root extracts from two genotypes, leading to modification of bacterial secondary metabolites production. Bacterial cells were then inoculated on each wheat genotypes. Then, wheat root metabolomes were analyzed by untargeted metabolomic, and metabolites from the Adular genotype were characterized by molecular network. This allows us to evaluate if wheat differently recognizes the bacterial cells that have already been into contact with plants and highlights bioactive metabolites involved in wheat—Pseudomonas interaction.

Pseudomonas chlororaphis PA23 metabolites protect against protozoan grazing by the predator Acanthamoeba castellanii.

BackgroundPseudomonas chlororaphis strain PA23 is a biocontrol agent that is able to protect canola against the pathogenic fungus Sclerotinia sclerotiorum. This bacterium secretes a number of metabolites that contribute to fungal antagonism, including pyrrolnitrin (PRN), phenazine (PHZ), hydrogen cyanide (HCN) and degradative enzymes. In order to be successful, a biocontrol agent must be able to persist in the environment and avoid the threat of grazing predators. The focus of the current study was to investigate whether PA23 is able to resist grazing by the protozoan predator Acanthamoeba castellanii (Ac) and to define the role of bacterial metabolites in the PA23-Ac interaction.MethodsAc was co-cultured with PA23 WT and a panel of derivative strains for a period of 15 days, and bacteria and amoebae were enumerated on days 1, 5, 10 and 15. Ac was subsequently incubated in the presence of purified PRN, PHZ, and KCN and viability was assessed at 24, 48 and 72 h. Chemotactic assays were conducted to assess whether PA23 compounds exhibit repellent or attractant properties towards Ac. Finally, PA23 grown in the presence and absence of amoebae was subject to phenotypic characterization and gene expression analyses.ResultsPRN, PHZ and HCN were found to contribute to PA23 toxicity towards Ac trophozoites, either by killing or inducing cyst formation. This is the first report of PHZ-mediated toxicity towards amoebae. In chemotaxis assays, amoebae preferentially migrated towards regulatory mutants devoid of extracellular metabolite production as well as a PRN mutant, indicating this antibiotic has repellent properties. Co-culturing of bacteria with amoebae led to elevated expression of the PA23 phzI/phzR quorum-sensing (QS) genes and phzA and prnA, which are under QS control. PHZ and PRN levels were similarly increased in Ac co-cultures, suggesting that PA23 can respond to predator cues and upregulate expression of toxins accordingly.ConclusionsPA23 compounds including PRN, PHZ and HCN exhibited both toxic and repellent effects on Ac. Co-culturing of bacteria and amoebae lead to changes in bacterial gene expression and secondary metabolite production, suggesting that PA23 can sense the presence of these would-be predators and adjust its physiology in response.

Microbioreactor Techniques for the Production and Spectroscopic Characterization of Microbial Peptides.

We have demonstrated that the simple and low-cost microbioreactor can speed up the bioprocessing techniques by using small amount of reagents and very few seed cultures to give results comparable with those obtained from the shake flask. The microbioreactor has the potential of replacing the normal conventional-scale process and offers a high-throughput efficient and analytical technique in addressing some of the challenges encountered in bioprocessing starting that includes bacterial growth and secondary metabolites production targeting the discovery of new antibacterial peptides. In our case studies, we proved that microbes were capable of growing in the microbioreactor and the production of microbial secondary metabolites (i.e., peptides) was detectable in HPLC-DAD-MS. We used QTOF-MS/MS to detect the production of peptides in the microbial culture. The purified peptides were characterized using 1D and 2D NMR, QTOF-MS/MS, and Marfey's analysis.

Electron transfer ferredoxins with unusual cluster binding motifs support secondary metabolism in many bacteria.

The proteins responsible for controlling electron transfer in bacterial secondary metabolism are not always known or characterised. Here we demonstrate that many bacteria contain a set of unfamiliar ferredoxin encoding genes which are associated with those of cytochrome P450 (CYP) monooxygenases and as such are involved in anabolic and catabolic metabolism. The model organism Mycobacterium marinum M contains eleven of these genes which encode [3Fe-4S] or [4Fe-4S] single cluster containing ferredoxins but which have unusual iron-sulfur cluster binding motif sequences, CXX?XXC(X) n CP, where '?' indicates a variable amino acid residue. Rather than a cysteine residue, which is highly conserved in [4Fe-4S] clusters, or alanine or glycine residues, which are common in [3Fe-4S] ferredoxins, these genes encode at this position histidine, asparagine, tyrosine, serine, threonine or phenylalanine. We have purified, characterised and reconstituted the activity of several of these CYP/electron transfer partner systems and show that all those examined contain a [3Fe-4S] cluster. Furthermore, the ferredoxin used and the identity of the variable motif residue in these proteins affects the functionality of the monooxygenase system and has a significant influence on the redox properties of the ferredoxins. Similar ferredoxin encoding genes were identified across Mycobacterium species, including in the pathogenic M. tuberculosis and M. ulcerans, as well as in a wide range of other bacteria such as Rhodococcus and Streptomyces. In the majority of instances these are associated with CYP genes. These ferredoxin systems are important in controlling electron transfer across bacterial secondary metabolite production processes which include antibiotic and pigment formation among others.

Diversity and Bioactivity of Marine Bacteria Associated with the Sponges Candidaspongia flabellata and Rhopaloeides odorabile from the Great Barrier Reef in Australia

Sponges and their associated microbial communities have sparked much interest in recent decades due on the abundant production of chemically diverse metabolites that in nature serve as functional compounds required by the marine sponge host. These compounds were found to carry therapeutic importance for medicinal applications. In the presented study, 123 bacterial isolates from the culture collection of the Australian Institute of Marine Science (AIMS) previously isolated from two different sponge species, namely Candidaspongia flabellata and Rhopaloeides odorabile, originating from different locations on the Great Barrier Reef in Queensland, Australia, were thus studied for their bioactivity. The symbiotic bacterial isolates were first identified using 16S rRNA gene analysis and they were found to belong to five different dominating classes of Domain Bacteria, namely Alphaproteobacteria, Gammaproteobacteria, Flavobacteria, Bacilli and Actinobacteria. Following their taxonomical categorization, the isolates were screened for their antimicrobial activity against human pathogenic microbial reference strains: Escherichia coli (ATCC® BAA-196™), E. coli (ATCC® 13706™), E. coli (ATCC® 25922™), Klebsiella pneumoniae (ATCC® BAA-1705™), Enterococcus faecalis (ATCC® 51575™), Bacillus subtilis (ATCC® 19659™), Staphylococcus aureus (ATCC® 29247™), Candida albicans (ATCC® 10231™) and Aspergillus niger (ATCC® 16888™). Over 50% of the isolates displayed antimicrobial activity against one or more of the reference strains tested. The subset of these bioactive bacterial isolates was further investigated to identify their biosynthetic genes such as polyketide synthase (PKS) type I and non-ribosomal peptide synthetase (NRPS) genes. This was done using polymerase chain reaction (PCR) with degenerate primers that have been previously used to amplify PKS-I and NRPS genes. These specific genes have been reported to be possibly involved in bacterial secondary metabolite production. In 47% of the bacterial isolates investigated, the PKS and NRPS genes were located. Some of the bacterial isolates were found to possess both gene types, which agrees with the previous reported biosynthetic ability of certain sponge-symbiotic bacteria such as the Actinobacteria or Gammaproteobacteria to produce secondary metabolites with antimicrobial activity. All these reported activities further confirm that sponge-symbiotic bacteria hold significant bioactivity with medicinal and biotechnological importance.

Coomassie Blue G250 for Visualization of Active Bacteria from Lake Environment and Culture.

Bacteria play a fundamental role in the cycling of nutrients in aquatic environments. A precise distinction between active and inactive bacteria is crucial for the description of this process. We have evaluated the usefulness of Coomassie Blue G250 for fluorescent staining of protein containing potentially highly active bacteria. We found that the G250 solution has excitation and emission properties appropriate for direct epifluorescence microscopy observations. It enables fast and effective fluorescent visualization of living, protein-rich bacteria, both in freshwater environment and culture. Our results revealed that the number of G250-stained bacteria from eutrophic lake was positively correlated with other standard bacterial activity markers, like number of bacteria containing 16S rRNA, bacterial secondary production or maximal potential leucine-aminopeptidase activity. In case of the E. coli culture, the percentage of bacteria visualized with G250 was similar to that of bacteria which accumulated tetracycline. Compared to other common methods utilizing fluorogenic substances for bacteria staining, the approach we evaluated is inexpensive and less hazardous (for example mutagenic) to the environment and researchers. It can be regarded as an additional or alternative method for protein rich, active bacteria staining.

Microbial Activity Response to Solar Radiation across Contrasting Environmental Conditions in Salar de Huasco, Northern Chilean Altiplano.

In high altitude environments, extreme levels of solar radiation and important differences of ionic concentrations over narrow spatial scales may modulate microbial activity. In Salar de Huasco, a high-altitude wetland in the Andean mountains, the high diversity of microbial communities has been characterized and associated with strong environmental variability. Communities that differed in light history and environmental conditions, such as nutrient concentrations and salinity from different spatial locations, were assessed for bacterial secondary production (BSP, 3H-leucine incorporation) response from short-term exposures to solar radiation. We sampled during austral spring seven stations categorized as: (a) source stations, with recently emerged groundwater (no-previous solar exposure); (b) stream running water stations; (c) stations connected to source waters but far downstream from source points; and (d) isolated ponds disconnected from ground sources or streams with a longer isolation and solar exposure history. Very high values of 0.25 μE m-2 s-1, 72 W m-2 and 12 W m-2 were measured for PAR, UVA, and UVB incident solar radiation, respectively. The environmental factors measured formed two groups of stations reflected by principal component analyses (near to groundwater sources and isolated systems) where isolated ponds had the highest BSP and microbial abundance (35 microalgae taxa, picoeukaryotes, nanoflagellates, and bacteria) plus higher salinities and PO43- concentrations. BSP short-term response (4 h) to solar radiation was measured by 3H-leucine incorporation under four different solar conditions: full sun, no UVB, PAR, and dark. Microbial communities established in waters with the longest surface exposure (e.g., isolated ponds) had the lowest BSP response to solar radiation treatments, and thus were likely best adapted to solar radiation exposure contrary to ground source waters. These results support our light history (solar exposure) hypothesis where the more isolated the community is from ground water sources, the better adapted it is to solar radiation. We suggest that factors other than solar radiation (e.g., salinity, PO43-, NO3-) are also important in determining microbial productivity in heterogeneous environments such as the Salar de Huasco.

海水中天然细菌对不同生源要素有机物的矿化作用

PDF HTML阅读 XML下载 导出引用 引用提醒 海水中天然细菌对不同生源要素有机物的矿化作用 DOI: 10.5846/stxb201408291720 作者: 作者单位: 中国海洋大学化学化工学院,中国海洋大学海洋生命学院,美国加州大学圣芭芭拉分校海洋科学系,加州 圣芭芭拉 CA-,中国海洋大学化学化工学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家海洋局海洋生态环境科学与工程重点实验室开放基金(MESE-2014-03) Mineralization of different dissolved organic matter containing various biogenic elements by natural bacteria in seawater Author: Affiliation: College of Chemistry and Chemical Engineering,Ocean University of China,College of Marine Life Sciences,Ocean University of China,Marine Science Institute,University of California,Santa Barbara,California ,USA,College of Chemistry and Chemical Engineering,Ocean University of China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:海洋异养细菌是微食物网中非常重要的一部分,它消耗海洋中的溶解有机物并进行细菌的二次生产。细菌对不同种类的溶解有机物分解速率不同,并且有机物的生物利用率影响细菌的生长。研究了含有不同生源要素的4种溶解有机物(DOM)在海洋异养细菌存在下的矿化作用及对细菌生长的影响。结果表明:添加不同生源要素的有机物,对海洋天然异养细菌的生长均有促进作用,其比生长速率(μ)的大小顺序为:N > C > P > S > 对照组,说明含氮有机物更有助于细菌的生长;细菌生长效率(BGE)的大小顺序为:对照组 > C > P > N > S,说明细菌的二次生产跟有机物的分解速率没有直接相关性;单个细菌对有机物的消耗速率I为:N > C >P > S > 对照组,说明细菌生长速率与有机物消耗速率直接相关;有机物的生物可利用性顺序为:N > C > P > S > 对照组,与有机物的消耗速率顺序一致。上述结果表明,具有相同结构但不同生源要素的有机物的矿化速率存在差异,含氮有机物最容易分解,其次是含碳有机物,然后是含磷有机物,含硫有机物分解最慢,说明细菌对含有不同生源要素有机物的分解利用存在差异。 Abstract:Heterotrophic bacteria in seawater play an important role in biogeochemical cycling of biogenic elements. The decomposition rate of different dissolved organic matter (DOM) is related to the amount of heterotrophic bacteria, and the biological utilization ratio of DOM influences the growth of bacteria. In this study, mineralization and the effect of four kinds of DOM with similar structure but different biogenic elements on bacterial growth were investigated. The results suggested that organic matter added to cultures promoted the growth of natural marine heterotrophic bacteria, and the order of specific growth rate (μ) was as follows: N > C > P > S > control. DOM with nitrogen and carbon was the most effective in accelerating the growth of bacteria. The order of bacterial growth efficiency was as follows: Control > C > P > N > S; these results indicated that bacterial secondary production has no direct correlation with the decomposition rate of organic matter. The consumption rate of organic matter per individual bacterium (I) was in the following order: N > C > P > S > control, which was the same for biological availability of different organic matter. These results suggested that the mineralization rate is different for various organic matters having similar structure but different biogenic elements. The organic matter with nitrogen was decomposed most easily, followed by carbonaceous organic matter and organic phosphorus, but organic sulfur remained somewhat refractory to decomposition. 参考文献 相似文献 引证文献

Bacterial abundance, processes and diversity responses to acidification at a coastal CO2 vent.

Shallow CO2 vents are used as natural laboratories to study biological responses to ocean acidification, and so it is important to determine whether pH is the primary driver of bacterial processes and community composition, or whether other variables associated with vent water have a significant influence. Water from a CO2 vent (46 m, Bay of Plenty, New Zealand) was compared to reference water from an upstream control site, and also to control water acidified to the same pH as the vent water. After 84 h, both vent and acidified water exhibited higher potential bulk water and cell-specific glucosidase activity relative to control water, whereas cell-specific protease activities were similar. However, bulk vent water glucosidase activity was double that of the acidified water, as was bacterial secondary production in one experiment, suggesting that pH was not the only factor affecting carbohydrate hydrolysis. In addition, there were significant differences in bacterial community composition in the vent water relative to the control and acidified water after 84 h, including the presence of extremophiles which may influence carbohydrate degradation. This highlights the importance of characterizing microbial processes and community composition in CO2 vent emissions, to confirm that they represent robust analogues for the future acidified ocean.

Algal extracellular release in river-floodplain dissolved organic matter: response of extracellular enzymatic activity during a post-flood period.

River-floodplain systems are susceptible to rapid hydrological events. Changing hydrological connectivity of the floodplain generates a broad range of conditions, from lentic to lotic. This creates a mixture of allochthonously and autochthonously derived dissolved organic matter (DOM). Autochthonous DOM, including photosynthetic extracellular release (PER), is an important source supporting bacterial secondary production (BSP). Nonetheless, no details are available regarding microbial extracellular enzymatic activity (EEA) as a response to PER under variable hydrological settings in river-floodplain systems. To investigate the relationship between bacterial and phytoplankton components, we therefore used EEA as a tool to track the microbial response to non-chromophoric, but reactive and ecologically important DOM. The study was conducted in three floodplain subsystems with distinct hydrological regimes (Danube Floodplain National Park, Austria). The focus was on the post-flood period. Enhanced %PER (up to 48% of primary production) in a hydrologically isolated subsystem was strongly correlated with β-glucosidase, which was related to BSP. This shows that—in disconnected floodplain backwaters with high terrestrial input—BSP can also be driven by autochthonous carbon sources (PER). In a semi-isolated section, in the presence of fresh labile material from primary producers, enhanced activity of phenol oxidase was observed. In frequently flooded river-floodplain systems, BSP was mainly driven by enzymatic degradation of particulate primary production. Our research demonstrates that EEA measurements are an excellent tool to describe the coupling between bacteria and phytoplankton, which cannot be deciphered when focusing solely on chromophoric DOM.

LC-MS-based metabolomics study of marine bacterial secondary metabolite and antibiotic production in Salinispora arenicola.

An LC-MS-based metabolomics approach was used to characterise the variation in secondary metabolite production due to changes in the salt content of the growth media as well as across different growth periods (incubation times). We used metabolomics as a tool to investigate the production of rifamycins (antibiotics) and other secondary metabolites in the obligate marine actinobacterial species Salinispora arenicola, isolated from Great Barrier Reef (GBR) sponges, at two defined salt concentrations and over three different incubation periods. The results indicated that a 14 day incubation period is optimal for the maximum production of rifamycin B, whereas rifamycin S and W achieve their maximum concentration at 29 days. A “chemical profile” link between the days of incubation and the salt concentration of the growth medium was shown to exist and reliably represents a critical point for selection of growth medium and harvest time.

Diel and seasonal variations in bacterioplankton production in a hypertrophic shallow lagoon

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 72:255-267 (2014) - DOI: https://doi.org/10.3354/ame01701 Diel and seasonal variations in bacterioplankton production in a hypertrophic shallow lagoon Gabriela Onandia*, Maria Rosa Miracle, Cristina Blasco, Eduardo Vicente Department of Microbiology and Ecology, ICBiBE, University of Valencia, Calle Dr. Moliner 50, 46100 Burjassot, Valencia, Spain *Corresponding author: gabriela.onandia@uv.es ABSTRACT: Diel and seasonal variations in bacterial secondary production (BP) were investigated in the hypertrophic Albufera de Valencia (Spain) by measuring 3H-leucine and 3H-thymidine incorporation rates (LIR and TIR). LIR and TIR were positively correlated. Seasonal variations in the LIR:TIR ratio seemed to be related to dissolved organic carbon (DOC) availability, with higher concentrations favoring protein synthesis. The light:dark ratio of the incorporation rates of both radiotracers was close to 1. However, this ratio tended to be >1 when DOC was lower, namely in winter. A clear diel pattern in bacterial activity was found, with an increasing trend during the night hours. The opposite diel pattern was observed for DOC. BP remained similar across seasons but showed a decrease in late winter during a period of high water discharge through the lagoon and concurrent minimum chlorophyll a concentrations. A comparison between hypertrophic systems aiming to explore the upper BP limit indicated that our BP estimates were considerably high but did not surpass previous values in hypertrophic lakes. KEY WORDS: Bacterioplankton production · Carbon flux · Shallow hypertrophic lake Full text in pdf format PreviousNextCite this article as: Onandia G, Miracle MR, Blasco C, Vicente E (2014) Diel and seasonal variations in bacterioplankton production in a hypertrophic shallow lagoon. Aquat Microb Ecol 72:255-267. https://doi.org/10.3354/ame01701 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 72, No. 3. Online publication date: July 10, 2014 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2014 Inter-Research.

Size‐spectrum based differential response of phytoplankton to nutrient and iron‐organic matter combinations in microcosm experiments in a Chilean Patagonian Fjord

SummaryThe Patagonian fjords have been recognized as a major region of relatively high primary productivity systems during spring–summer bloom periods, where iron‐organic matter forms may be essential complexes involved in key growth processes connected to the carbon and nitrogen cycles. We used two dissolved organic matter (DOM) types, marine polysaccharide and siderophore, as a model to understand how they affect the bioavailability of Fe to phytoplankton and bacteria and to assess their ecological role in fjord systems. A 10‐day microcosm study was performed in the Comau Fjord during summer conditions (March 2012). Pico‐, nano‐, and microphytoplankton abundance, total chlorophyll‐a and bacteria abundance, and bacterial secondary production estimates were analyzed in five treatments: (i) control (no additions), (ii) only nutrients (NUT: PO4, NO3, Si), (iii) nutrients + Fe(II), (iv) polysaccharide (natural diatoms extracted: 1–3 beta Glucan), and (v) Hexandentate Desferroxiamine B (DFB, siderophore). Our results showed that while DFB reduced Fe bioavailability for almost all phytoplankton assemblages in the fjord, polysaccharide did not have effects on the iron bioavailability. At Nutrients + Fe and Polysaccharide treatments, chlorophyll‐a concentration abruptly increased from 0.9 to 20 mg m−3 during the first 4–6 days of the experimental period. Remarkably, at the Nutrients + Fe treatment, the development of the bloom was accompanied by markedly high abundances of Synechococcus, picoeukaryotes, and autotrophic nanoflagellates within the first 4 days of the experiment. Our study indicated that small plankton (phytoplankton <20 μm and bacteria) were the first to respond to dissolved Nutrients + Fe compared to large sized micro‐phytoplankton cells (>20 μm). This could be at least partially attributed to biological utilization of Fe (2 to 3 nM) by <20 μm phytoplankton and bacteria through the interaction with organic ligands released by bacteria that eventually could increase solubility of the Fe dissolved fraction thus having a positive effect on the small‐sized phytoplankton community.

富营养化湖泊溶解性有机碳生物可利用性研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 富营养化湖泊溶解性有机碳生物可利用性研究进展 DOI: 10.5846/stxb201209241349 作者: 作者单位: 南通大学地理科学学院,中国科学院南京地理与湖泊研究所湖泊与环境国家重点实验室,中国科学院南京地理与湖泊研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41201076，31270507，31070420）；湖泊与环境国家重点实验室开放基金资助项目（2012SKL006） The bioavailability of dissolved organic carbon in the eutrophic lakes Author: Affiliation: Geographical Sciences College,Nantong University,State key Laboratory of Lake Environment Science,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,State key Laboratory of Lake Environment Science,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:富营养化湖泊溶解性有机碳（DOC）包括内源和外源性碳源，不同来源碳源在物质化学结构组成和分子量级等方面具有显著差异，进而影响到对细菌的生物可利用性和碳素在食物网中的传递效率。根据国内外文献，综述了内外源DOC在碳稳定同位素值域上的显著差异，建议通过对DOC碳稳定同位素的分析来识别富营养化湖泊中DOC的主要来源；通过对比内外源DOC在碳水化合物、结合态中性糖和腐殖质含量上的差异，并结合细菌生长参数如细菌二级生产力、细菌呼吸作用及细菌生长效率来分析内外源DOC对细菌的生物可利用性。从富营养化湖泊DOC来源的角度探讨其生物可利用性和碳素传递效率，有助于了解富营养化湖泊食物网中碳素循环特征，加强对湖泊生态学的认识，为湖泊环境治理与保护提供科学依据。 Abstract:The dissolved organic carbon (DOC) pool is composed of both autochthonous and allochthonous DOC, and its concentration in lakes generally increases with the trophic status. Accumulation of the autochthonous DOC was observed in the eutrophic lake, and the allochthonous DOC was highest in the dystrophic lake. Carbohydrates constitute a large component of the DOC, the consumption of DOC by heterotrophic bacteria is one of the largest fluxes of carbon in most aquatic ecosystems, but the bioavailability and the efficiency of carbon transfer in lakes food web is affected by the distribution of molecular weight and chemical composition. The DOC can be separated into high and low molecular weight DOC fractions by cross-flow ultrafiltration, but which fraction is more bioreactive is still in dispute.Stable carbon isotope can be used to trace the origins of organic carbon, and the approach depends on the fact that DOC from different origins has different stable isotopic compositions. The riverine DOC has a δ13C value of -27‰, which is different from freshwater phytoplankton, with a range from -35‰ to -25‰. This paper reviewed the researches on the stable carbon isotope ratio of the autochthonous and allochthonous DOC, suggesting that the main sources of DOC in eutrophic lakes can be identified by using natural stable carbon isotope ratio of DOC; the difference on the total dissolved carbohydrates (TCHO) and dissolved combined neutral sugar (DCNS) concentrations, as well as the humic substances (HS) was compared between the autochthonous and allochthonous DOC. Net increases in TCHO and DCNS were observed in the autochthonous DOC during phytoplankton blooms, whereas the HS fraction was quantitatively important in the allochthonous DOC. Many studies have reported the bacterial availability of TCHO and DCNS, and the ratio of TCHO/DOC is used to characterize the bioavailability of DOC, whereas HS can also increase bacterial secondary production and support bacterial growth if labile substrates are abundant.Furthermore, to elucidate the bioavailability of the two sources of DOC, the bacterial secondary production, bacterial respiration and bacteria growth efficiency (BGE) was analyzed together. The DOC can be either transformed to bacterial secondary production or respired to inorganic carbon. BGE is the fraction of assimilated organic carbon that supports growth. The source of DOC and its chemical composition could be a key regulator of BGE. Traditionally, the autochthonous DOC has been considered to be the main source for bacterial as well as other secondary production, the allochthonous DOC was long considered relatively recalcitrant to bacterial degradation. However, in lakes which are both humic-rich and oligotrophic, the ecosystem respiration exceeds gross primary production, suggesting that the allochthonous DOC can be incorporated into the bacteria biomass and makes a significant carbon and energy subsidy for lakes food web, but little of the allochthonous carbon assimilated by bacteria is likely to reach higher consumers. Recent studies suggest that bacterial BGE increases with the concentration of the low molecular weight DOC in allochthonous DOC.Discussing the bioavailability and efficiency of carbon transfer in the food web from the sources of DOC, will be helpful to investigate the characterization of carbon cycling in the eutrophic lakes, enhance our understanding of the lake ecology and to provide scientific references for the lake management and protection. 参考文献 相似文献 引证文献

Origin, enzymatic response and fate of dissolved organic matter during flood and non-flood conditions in a river-floodplain system of the Danube (Austria)

Spectroscopic techniques and extracellular enzyme activity measurements were combined with assessments of bacterial secondary production (BSP) to elucidate flood-pulse-linked differences in carbon (C) sources and related microbial processes in a river-floodplain system near Vienna (Austria). Surface connection with the main channel significantly influenced the quantity and quality of dissolved organic matter (DOM) in floodplain backwaters. The highest values of dissolved organic carbon (DOC) and chromophoric DOM (CDOM) were observed during the peak of the flood, when DOC increased from 1.36 to 4.37 mg l−1 and CDOM from 2.94 to 14.32 m−1. The flood introduced DOC which consisted of more allochthonously-derived, aromatic compounds. Bacterial enzymatic activity, as a proxy to track the response to changes in DOM, indicated elevated utilization of imported allochthonous material. Based on the enzyme measurements, new parameters were calculated: metabolic effort and enzymatic indices (EEA 1 and EEA 2). During connection, bacterial glucosidase and protease activity were dominant, whereas during disconnected phases a switch to lignin degradation (phenol oxidase) occurred. The enzymatic activity analysis revealed that flooding mobilized reactive DOM, which then supported bacterial metabolism. No significant differences in overall BSP between the two phases were detected, indicating that heterogeneous sources of C sufficiently support BSP. The study demonstrates that floods are important for delivering DOM, which, despite its allochthonous origin, is reactive and can be effectively utilized by aquatic bacteria in this river-floodplain systems. The presence of active floodplains, characterized by hydrological connectivity with the main channel, creates the opportunity to process allochthonous DOC. This has potential consequences for carbon flux, enhancing C sequestration and mineralization processes in this river-floodplain system.

Impact of change in climate and policy from 1988 to 2007 on environmental and microbial variables at the time series station Boknis Eck, Baltic Sea

Abstract. Phytoplankton and bacteria are sensitive indicators of environmental change. The temporal development of these key organisms was monitored from 1988 to the end of 2007 at the time series station Boknis Eck in the western Baltic Sea. This period was characterized by the adaption of the Baltic Sea ecosystem to changes in the environmental conditions caused by the conversion of the political system in the southern and eastern border states, accompanied by the general effects of global climate change. Measured variables were chlorophyll, primary production, bacteria number, -biomass and -production, glucose turnover rate, macro-nutrients, pH, temperature and salinity. Negative trends with time were recorded for chlorophyll, bacteria number, bacterial biomass and bacterial production, nitrate, ammonia, phosphate, silicate, oxygen and salinity while temperature, pH, and the ratio between bacteria numbers and chlorophyll increased. Strongest reductions with time occurred for the annual maximum values, e.g. for chlorophyll during the spring bloom or for nitrate during winter, while the annual minimum values remained more stable. In deep water above sediment the negative trends of oxygen, nitrate, phosphate and bacterial variables as well as the positive trend of temperature were similar to those in the surface while the trends of salinity, ammonia and silicate were opposite to those in the surface. Decreasing oxygen, even in the surface layer, was of particular interest because it suggested enhanced recycling of nutrients from the deep hypoxic zones to the surface by vertical mixing. The long-term seasonal patterns of all variables correlated positively with temperature, except chlorophyll and salinity. Salinity correlated negatively with all bacterial variables (as well as precipitation) and positively with chlorophyll. Surprisingly, bacterial variables did not correlate with chlorophyll, which may be inherent with the time lag between the peaks of phytoplankton and bacteria during spring. Compared to the 20-yr averages of the environmental and microbial variables, the strongest negative deviations of corresponding annual averages were measured about ten years after political change for nitrate and bacterial secondary production (~ −60%), followed by chlorophyll (−50%) and bacterial biomass (−40%). Considering the circulation of surface currents in the Baltic Sea we interpret the observed patterns of the microbial variables at the Boknis Eck time series station as a consequence of the improved management of water resources after 1989 and – to a minor extent – the trends of the climate variables salinity and temperature.

Land–ocean gradient in haline stratification and its effects on plankton dynamics and trophic carbon fluxes in Chilean Patagonian fjords (47–50°S)

Patagonian fjord systems, and in particular the fjords and channels associated with the Baker/Pascua Rivers, are currently under conspicuous natural and anthropogenic perturbations. These systems display very high variability, where limnetic and oceanic features overlap generating strong vertical and horizontal physicochemical gradients. The CIMAR 14-Fiordos cruise was conducted in the Chilean fjords located between 47° and 50°S during the spring (October–November) of 2008. The main objectives were to study vertical and horizontal gradients in physical, chemical and biological characteristics of the water column, and to assess plankton dynamics and trophic carbon fluxes in the fjords and channels of central-south Patagonia.The water column was strongly stratified, with a pycnocline at ca. 20m depth separating a surface layer of silicic acid-rich freshwater discharged by rivers, from the underlying nitrate- and orthophosphate-rich Subantarctic waters. The outflows from the Baker and Pascua Rivers, which range annually between 500 and 1500m3s−1, generate the strong land–ocean gradient in salinity (1–32psu) and inorganic nutrient concentrations (2–8 and 2–24μM in nitrate and silicic-acid, respectively) we observed along the Baker Fjord. The POC:chl-a ratio fluctuated from 1087 near the fjord’s head to 175 at its oceanic end in the Penas Gulf. This change was mainly due to an increase in diatom dominance and a concurrent decrease in allochthonous POC towards the ocean.Depth-integrated net primary production (NPP) and bacterial secondary production (BSP) fluctuated between 49 and 1215 and 36 and 150mgCm−2d−1, respectively, with higher rates in oceanic waters. At a time series station located close to the Baker River mouth, the average NPP was lower (average 360mgCm−2d−1) than at more oceanic stations (average 1063mgCm−2d−1), and numerically dominated (45%) by the picoplankton (<2μm) and nanoplankton (2–20μm) size fractions. The high average vertical carbon flux (234mgm−2d−1) and high export production (65% of the NPP) support the idea that Patagonian fjords may behave as a net sink for CO2 during the productive (spring) season. Trophic fluxes near the head of the fjords, with oligotrophic low-salinity waters, were dominated by heterotrophic nanoflagellates (HNF) and small copepods (52mgCm−2d−1, each), suggesting that the microbial food web is the main trophic pathway in these environments.

Bioavailability and diagenetic state of dissolved organic matter in riparian groundwater

Riparian groundwater can exhibit considerable patchiness in the concentration and reactivity of dissolved organic matter (DOM), which ultimately shapes subsurface biogeochemical transformations. Free and combined amino acids are bioavailable constituents of DOM, and their concentration and composition can provide valuable information about the diagenetic state of DOM. Based on riparian groundwater samples and relevant DOM end‐member samples, we adapted the amino‐acid‐based marine DOM degradation index (DI) to groundwater. The groundwater DI was applied to evaluate the spatial and temporal variability in the bioavailability and diagenetic state of riparian DOM in a restored and a channelized section of the River Thur, Switzerland. Among different indicators for DOM diagenetic state (total hydrolysable amino acid concentrations, C‐normalized yields, and the contribution of nonprotein amino acids), the groundwater DI correlated best with the activity of the enzyme leucine‐aminopeptidase and bacterial secondary production in riparian groundwater. The “freshest” DOM was consistently found in the channel and during high‐flow conditions in the groundwater of the restored riparian section and was spatially constrained to a zone inhabited by a dense willow population. The use of amino acid data and the newly developed DI for DOM in groundwater is a promising approach for characterizing the spatial and temporal dynamics of DOM reactivity and diagenesis within riparian groundwater.