Microbial Activity Degradation Research Articles

Physiological response and molecular mechanism of glyphosate degradation by Pseudomonas alcaligenes Z1–1

The accumulation of glyphosate during its application in agriculture and its toxicity seriously threaten ecosystems and human health. Currently, glyphosate residual contamination is mainly accomplished through bioremediation techniques based on enhanced microbial degradation activity. However, there are drawbacks, such as poor environmental adaptability of strains and low degradation efficiency. Therefore, in this study, an efficient glyphosate-degrading strain, Pseudomonas alcaligenes Z1–1, was isolated from herbicide-contaminated environments and was capable of completely degrading glyphosate at a concentration of 200 mg/L within 7 days. Kinetics analysis showed that glyphosate degradation was concentration-dependent, with a maximum tolerant concentration of 800 mg/L. Mass spectrometric analysis indicated that AminoMethylPhosphonic acid (AMPA) was the predominant intermediate produced in the degradation pathway of glyphosate, revealing that glyphosate destruction began with breaking the C-N bond. Whole genome sequencing identified the key genes potentially involved in glyphosate degradation, including the thiO, glpA, aroA, soxB, and argA genes. Furthermore, in contrast to the majority of the metabolic pathways previously reported for glyphosate degradation via glyphosate oxidoreductase, the breaking of the C-N bond was primarily catalyzed by glycine oxidase. Overall, this research provides novel insights into the mechanisms of glyphosate degradation, offering valuable degradation enzyme resources for future applications.

Characterizing landfill extent, composition, and biogeochemical activity using electrical resistivity tomography and induced polarization under varying geomembrane coverage

Landfill monitoring is essential for sustainable waste management and environmental protection. Geophysical methods can provide quasicontinuous spatial and temporal insights into subsurface physical properties and processes in a nonintrusive manner. The effectiveness of monitoring landfill extent, composition, and degradation under varying geomembrane coverage is evaluated using electrical resistivity tomography (ERT) and induced polarization (IP) methods. Synthetic electrical models for landfills with different geomembrane damage degrees are inverted to assess data reliability. The current conduction channels into the geomembrane during the electrical survey are quantified. Reliable electrical data are obtained when the inverted conduction channel ratio of the geomembrane (representing the damage to the geomembrane) is 51.6% or higher. This criterion is validated in a landfill experiencing aeration and anaerobic treatments. ERT and IP data capture construction and domestic waste distribution and identify the landfill boundary. The chargeability of domestic waste proves sensitive to microbial degradation activity, corroborated by characteristic ammonium and nitrate ions and a linear relation between chargeability and subsurface temperature. Temperature variations between the aerobic and anaerobic reaction zones ([Formula: see text] and [Formula: see text]) are observed to correlate with high chargeability values ([Formula: see text]), signifying the presence of biogeochemically active zones. IP excels in characterizing geomembrane-covered landfill boundaries and discerning biogeochemical activity, thereby enhancing landfill monitoring and waste management strategies.

Method to evaluate the microbial degradation activity in silage, cow rumen with in vitro test, and in manure and slurry

Microorganisms are present everywhere and can influence a variety of processes. In agriculture and husbandry, the level of microbial activity can be crucial information, yet the methods for determining microbial activity are usually very long, complex, and costly. In this work, a novel and easy-to-use method, already in use for determining soil microbial activity, named Fertimetro was tested as a fast and cheap solution for measuring microbial activity in silages, in vitro rumen fluids, and manure and slurry. The method was adjusted for the specific conditions of the new testing environments. The results indicate that this method is adequate for measuring cellulolytic microbial activity in vitro rumen fluids, with a coefficient of repeatability (RT%) 92.2 at 24 h and 87.5 at 48 h, and also for cellulolytic microbial activity measures in manure RT% 39.0. While, due to the specific conditions in silages and slurry, this method is less adequate for measuring cellulolytic microbial activity in these environments. This work demonstrates that Fertimetro method can be used in different environments as an easy and cheaper alternative for measuring microbial activity, especially if the interest is only in quantifying the microbial activity and not in knowing the microbial species.1.Fertimetro is an easy-to-use and not costly method to evaluate microbial activity in different environments.2.This method is very adequate for measuring cellulolytic microbial activity in vitro rumen fluids and manure.

Effect and its mechanism of potassium persulfate on aerobic composting process of vegetable wastes.

Vegetable waste (VW) is a potential organic fertilizer resource. As an important way to utilize vegetable wastes, aerobic composting of VW generally has the problems of long fermentation cycle and incomplete decomposition of materials. In this study, 0.3-1.2% of potassium persulfate (KPS) was added to promote the maturity of compost. The results showed that the addition of KPS promoted the degradation of materials, accelerated the temperature rise of compost. KPS also promoted the formation of humic substances (HS). Compared with the control, HS contents of treatments with KPS addition increased by 7.81 ~ 17.52%. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) analysis reveal the mechanism of KPS affecting the composting process: KPS stimulated the degradation of various organic substances such as lignin at high temperature stage, and the degradation of lignin could accelerate the release and decomposition of other components; KPS made the structure of the material looser, with more voids and pores, and more specific surface area of the material, which was more suitable for microbial degradation activities. Therefore, the addition of KPS can promote the decomposition of organic matter in the early stage of composting, accelerate the process of thermophilic phase, and shorten the composting process and improve product maturity.

Differences in gut microbial fructoselysine degradation activity between breast-fed and formula-fed infants.

The Amadori product fructoselysine is formed upon heating of food products and is abundantly present in infant formula while being almost absent in breast milk. The human gut microbiota can degrade fructoselysine for which interindividual differences have been described for adults. The aim of this study is to compare functional differences in microbial fructoselysine degradation between breast-fed and formula-fed infants, in view of their different diets and resulting different fructoselysine exposures. First, a publicly available metagenomic dataset with metagenome-assembled genomes (MAGs) from infant fecal samples was analyzed and showed that query genes involved in fructoselysine degradation (frlD/yhfQ) were abundantly present in multiple bacterial taxa in the fecal samples, with a higher prevalence in the formula-fed infants. Next, fecal samples collected from exclusively breast-fed and formula-fed infants were anaerobically incubated with fructoselysine. Both groups degraded fructoselysine, however the fructoselysine degradation activity was significantly higher by fecal samples from formula-fed infants. Overall, this study provides evidence that infant formula feeding, leading to increased dietary fructoselysine exposure, seems to result in an increased fructoselysine degradation activity in the gut microbiota of infants. This indicates that the infant gut microbiota adapts towards dietary fructoselysine exposure.

201 Forage Biodegradation: Advances in Ruminal Microbial Ecology

Abstract The rumen microbial ecosystem provides ruminant animals a selective advantage, the ability to utilize forages, which allows ruminant animals to flourish around the world in a wide variety of environments. The ability of the microbial population to convert sunlight captured in forages to high quality meat, milk, and fiber has been recognized for many years. However, the rumen microbial population composition and degradative activity has remained a “black box” with only the most active (and most amenable to laboratory growth) cellulolytic and hemicellulolytic organisms being recognized and understood. The limitation of reliance upon growth of forage degrading organisms in a test tube in order to measure the catabolic activity, severely limited the development of knowledge of the microbial ecology of ruminal forage degradation. The past 15 years has seen the development and implementation of numerous Next-Generation Sequencing (NGS) approaches, which have greatly contributed to a better understanding of the microbial ecology of ruminants fed a variety of forages. NGS has provided new insights into changes in the microbial population of ruminants fed different diets, or undergoing dietary changes. The ability to take a “snapshot” of the composition of the ruminal microbial population has furthered our understanding of the impacts of forage maturity, forage type, and phytochemicals on the degradation and fermentation of forages. We now better understand the microbial pathways that are enriched by feeding of forages and are impacted by forage quality or composition, which can further our understanding of metabolomics of the rumen. As NGS data continues to accumulate on ruminants fed forage, our understanding of the ruminal microbial ecosystem will grow both deeper and broader, allowing us to build predictive models of rumen function during forage degradation and fermentation.

Geochemical features of altered carbonaceous mudstones from Troyanovo-3 mine borehole (Maritsa Iztok lignite field, Bulgaria)

We sampled and studied a borehole located in the southern part of Maritsa Iztok lignite field (Bulgaria) which comprises Late Miocene-Pliocene sediments of Maritsa Formation. The current report of Troyanovo-3 Mine sequence is the first to our knowledge. It represents a lignite-mudstone succession with variations in organic matter (OM) maturity. Thirty eight coal and mudstone core samples showed predictable ash and sulfur content. The XRD study showed illite/muscovite, illite/smectite, kaolinite, chlorite and quartz as main constituents that argue for a detrital origin. Additionally, we identified pyrite and gypsum and some peaks of marcasite and elemental sulfur. A set of eight mudstone samples rich in OM was selected for further geochemical analyses. The OM was classified as type III and II/III kerogen based on Rock-Eval pyrolysis data. The low amounts of extractable organic matter (0.01–2.25%) we found are consistent with the samples' low maturity and kerogen type. The yields of two samples were too low for further fractionation. Asphaltene amount (26.1–79.7%) predominates in the extracts. Diterpenoids (neutral fraction) and their polar analogues (slightly polar fraction) are highly abundant. In slightly polar fractions we registered ketotriterpenoids (mainly lupenones) in addition to the linear n-alkan-2-ones.OM elevated maturity of the deepest sample (59.60 m depth) was evidenced mainly by hopane distributions, i.e. Ts/(Tm + Ts), homohopane H31αβ index, hopane ratios (H29αβ/H30αβ) and H27β/H27α. The organic geochemistry results do not fit the ordinary regional maturity trend. OM maturity variation, superimposed over natural low coalification degree, could be ascribed to an interaction with ascending hot reductive fluids. The sulfide mineralization found in the fractures also gives indications about the fluid circulation. Another thermal alteration affecting the middle part samples (24.0–28.3 m) was suggested due to elevated Tmax values and HI and OI relation for a charcoal piece and carbonaceous mudstone. Smoldering processes affecting these samples were presumed.Low-temperature alteration processes were identified by n-alkanes, n-alkan-2-ones, and n-alcohols expulsion and downwards migration (from 18.0 m to 30.0 m) accompanied by a clear terpenoids depletion. The 17,21-seco-hopane-17,21-dione found for the first time for Maritsa Iztok Basin (MIB) samples further suggested processes of water seepage and wash-out. Microbial degradation activities usually accompanying water-washing possibly led to a specific n-alkan-2-one distribution. All the features we report point to either an even-numbered n-alkanoic acid decarboxylation or to a selective microbial degradation of odd-numbered n-alkanes to n-alkan-2-ones. In all, the history of the coal-mudstone sequence is complex, overprinted by variable alteration processes, first ever reported for MIB samples.

13C assimilation as well as functional gene abundance and expression elucidate the biodegradation of glyphosate in a field experiment

Glyphosate (N-phosphonomethylglycine; GLP) and its main metabolite AMPA (aminomethylphosphonic acid), are frequently detected in relatively high concentrations in European agricultural topsoils. Glyphosate has a high sorption affinity, yet it can be detected occasionally in groundwater. We hypothesized that shrinkage cracks occurring after dry periods could facilitate GLP transport to greater depths where subsoil conditions slow further microbial degradation. To test this hypothesis, we simulated a heavy rainfall event (HRE) on a clay-rich arable soil. We applied 2.1 kg ha−1 of 100% 13C3, 15N-labeled GLP one day before the simulated rainfall event. Microbial degradation of translocated GLP over a 21-day period was assessed by quantifying 13C incorporation into phospholipid fatty acids. Microbial degradation potential and activity were determined by quantifying the abundance and expression of functional genes involved in the two known degradation pathways of GLP; to AMPA (goxA) or sarcosine (sarc). We confirmed that goxA transcripts were elevated in the range of 4.23 x 105 copy numbers g−1 soil only one day after application. The increase in AMPA associated with a rise in goxA transcripts and goxA-harboring microorganisms indicated that the degradation pathway to AMPA dominated. Based on 13C-enrichment 3 h after the HRE, fungi appeared to initiate glyphosate degradation. At later time points, Gram+-bacteria proved to be the main degraders due to their higher 13C-incorporation. Once GLP reached the subsoil, degradation continued but more slowly. By comparing GLP distribution and its microbial degradation in macropores and in the bulk soil, we demonstrated different time- and depth-dependent GLP degradation dynamics in macropores. This indicates the need for field studies in which soil properties relevant to GLP degradation are related to limiting environmental conditions, providing a realistic assessment of GLP fate in soils.

Pectin as a non-toxic crosslinker for durable and water-resistant biopolymer-based membranes with improved mechanical and functional properties

Biopolymer-based hydrophilic membranes with very high stability in aqueous systems were developed by using pectin as a non-toxic crosslinker. The unique properties of pectin as an efficient crosslinker were demonstrated using poly(vinyl alcohol) as a model for a highly water-soluble biopolymer. The chemical crosslinking strategy using glutaraldhehyde has proven successful in improving the stability of poly(vinyl alcohol) membranes. However, the use of non-toxic biological crosslinking agents has not been fully explored. We hypothesized that pectin, as a biopolymer bearing numerous carboxyl groups, could be a very efficient crosslinker compared to carboxylic acids, promoting unprecedented membrane stability. A systematic characterization of the chemical, thermal, mechanical, and functional properties of membranes prepared from poly(vinyl alcohol) crosslinked with pectin confirmed the excellent stability of the membranes in water, tested at the boiling point and at acidic and basic pH. The use of pectin also resulted in membranes with very high tensile strength, resistance to microbial degradation, antiradical and antibacterial activity, and improved water vapor barrier properties.

Probe-based qPCR assay enables the rapid and specific detection of bacterial degrading genes for the pesticide metaldehyde in soil

Metaldehyde, a molluscicide pesticide, has been identified as a pollutant of concern due to its repeated detection in drinking water, thereby generating numerous compliance failures for water utilities. Biological degradation potential for metaldehyde is widespread in soils, occurring at different rates, but to date, no molecular methods for its assessment have been reported. Here, three genes belonging to a shared metaldehyde-degrading gene cluster present in bacteria were used as candidates for development of a quantitative PCR (qPCR) assay for assessing the metaldehyde-degrading potential in soil. Screening of gene targets, primer pairs and optimization of reaction conditions led to the development of a sensitive and specific probe-based qPCR method for quantifying the mahY metaldehyde-degrading gene from soil. The technique was tested across 8 soils with different compositions and origins. The degrading pathway was detected in 4/8 soils, in which a higher number of gene copies correlated with periods of greater metaldehyde removal. Additionally, swift elimination of the pesticide was observed in soils with an elevated initial number of mahY gene copies. The gene cluster was not detected in other soils, even though metaldehyde removal occurred, indicating that other biological degrading pathways are also important in nature. The method described here is the first one available to estimate the microbial metaldehyde degradation potential and activity in soils, and can also be used to detect degrading microorganisms in systems such as sand filters for water purification or to monitor degrading strains in engineered processes.

The Capability of Utilizing Abiotic Enantiomers of Amino Acids by Halomonas sp. LMO_D1 Derived From the Mariana Trench

D-amino acids (D-AAs) have been produced both in organisms and in environments via biotic or abiotic processes. However, the existence of these organic materials and associated microbial degradation activity has not been previously investigated in subduction zones where tectonic activities result in the release of hydrothermal organic matter. Here, we isolated the bacterium Halomonas sp. LMO_D1 from a sample obtained from the Mariana trench, and we determined that this isolate utilized 13 different D-AAs (D-Ala, D-Glu, D-Asp, D-Ser, D-Leu, D-Val, D-Tyr, D-Gln, D-Asn, D-Pro, D-Arg, D-Phe, and D-Ile) in the laboratory and could grow on D-AAs under high hydrostatic pressure (HHP). Moreover, the metabolism of L-AAs was more severely impaired under HHP conditions compared with that of their enantiomers. The essential function gene (Chr_2344) required for D-AA catabolism in strain LMO_D1 was identified and confirmed according to the fosmid library method used on the D-AAs plate. The encoded enzyme of this gene (DAADH_2344) was identified as D-amino acid dehydrogenase (DAADH), and this gene product supports the catabolism of a broad range of D-AAs. The ubiquitous distribution of DAADHs within the Mariana Trench sediments suggests that microorganisms that utilize D-AAs are common within these sediments. Our findings provide novel insights into the microbial potential for utilizing abiotic enantiomers of amino acids within the subduction zone of the Mariana trench under HHP, and our results provide an instructive significance for understanding these abiotic enantiomers and allow for insights regarding how organisms within extraterrestrial HHP environments can potentially cope with toxic D-AAs.

Bioremediation of heavy oil contaminated intertidal zones by immobilized bacterial consortium

Heavy oil contamination adversely affects on the intertidal ecological environment and human health. In this study, immobilized bacterial consortium was used in remediating intertidal zones contaminated with heavy oil, and its effectiveness was investigated in simulation experiment pools constructed in the coastal areas. After 100 days, the heavy oil degradation efficiency of immobilized bacterial consortium was 52.99%, which was 13.57% and 30.61% higher than that of biostimulation and natural attenuation, respectively. The immobilized bacterial consortium significantly increased the microbial degradation activity, heavy oil-degrading microbial count, and heavy oil degradation efficiency. Gas Chromatography–Mass Spectrometry results revealed that the biodegradation efficiency of C15–C35 n-alkanes and 2–5-ring polycyclic aromatic hydrocarbons was 25.98–95.80% and 58.93–97.97%, respectively. Microbial community structural analysis showed that Acinetobacter sp. and Bacillus sp. were prominently involved in heavy oil biodegradation. Furthermore, the immobilized bacterial consortium not only resisted the invasion of adverse intertidal environment and promoted the biodegradation of heavy oil pollutants in sediments but also effectively increased the competitiveness between the indigenous oil-degrading microorganisms and other microorganisms. This study can be a promising approach to remediate heavy oil contaminated intertidal zone.

Enhanced biodegradation of hydrocarbons by Pseudomonas aeruginosa-encapsulated alginate/gellan gum microbeads

Pseudomonas aeruginosa-encapsulated alginate/gellan gum microbeads (PAGMs) were prepared at the condition of 10 g/L alginate, 1 g/L gellan gum, and 2.57 mM calcium ions, and investigated for the biodegradation of a diesel-contaminated groundwater. The degradation of diesel with PAGMs reached 71.2% after 10days in the aerobic condition, while that of suspended bacteria was only 32.0% even after 30days. The kinetic analysis showed that PAGMs had more than two-order higher second-order kinetic constant than that of the suspended bacteria. Interestingly, the degradation of diesel was ceased due to the depletion of the dissolved oxygen after 10 day in the PAGM reactor, but the microbial degradation activity was immediately restored after the addition of oxygen to 10.5 mg/L. The change in ATP concentration and the viability of bacteria showed that the microbial activity in PAGMs were maintained (66.4%, and 84.3%, respectively) even after 30days of experiment with PAGMs due to the protective barrier of the microbeads, whereas those of suspended bacteria showed significant decrease to 6.2% and 14.4% of initial value, respectively, due to the direct contact to toxic hydrocarbons. The results suggested that encapsulation of bacterial cells could be used for the enhanced biodegradation of diesel hydrocarbons in aqueous systems.

Changes of microbial community and activity under different electric fields during electro-bioremediation of PAH-contaminated soil

Electro-bioremediation is a promising technology for remediation of soil contaminated with persistent organic compounds such as polycyclic aromatic hydrocarbons (PAHs). During electro-bioremediation, electrical fields have been shown to increase pollutant degradation. However, it remains unclear whether there is an optimal strength for the electrical field applied that is conductive to the maximum role played by microbes. This study aimed to determine the optimal strength of electric field through the analysis of the effects of different voltages on the microbial community and activity. Four bench-scale experiments with voltages of 0, 1, 2 and 3 V cm−1 were conducted for 90 days in an aged PAH-contaminated soil. The spatiotemporal changes of the soil pH, moisture content and temperature, microbial biomass and community structure, and the degradation extent of PAHs were researched over 90 days. The results indicated that the total microbial biomass and degradation activity were highest at voltages of 2 V cm−1. The concentration of total phospholipid fatty acids, used to quantify soil microbial biomass, reached 65.7 nmol g−1 soil, and the mean degradation extent of PAHs was 44.0%. Similarly, the maximum biomass of actinomycetes, bacteria and fungus also occurred at the voltage of 2 V cm−1. The Gram-positive/Gram-negative and (cy17:0+cy 19:0)/(16:1ω7+18:1ω7) ratios also showed that the intensity of electric field and electrode reactions strongly influenced the microbial community structure. Therefore, to optimize the electro-bioremediation of PAH-contaminated soil, the strength of electric field needs to be selected carefully. This work provides reference for the development of novel electrokinetically enhanced bioremediation processes.

Quantification of microbial degradation activities in biological activated carbon filters by reverse stable isotope labelling

Biological activated carbon (BAC) filters are frequently used in drinking water production for removing dissolved organic carbon (DOC) via adsorption of organic compounds and microbial degradation. However, proper methods are still missing to distinguish the two processes. Here, we introduce reverse stable isotope labelling (RIL) for assessing microbial activity in BAC filters. We incubated BAC samples from three different BAC filters (two granular activated carbon- and one extruded activated carbon-based) in a buffer amended with 13C-labelled bicarbonate. By monitoring the release of 12C–CO2 from the mineralization of DOC, we could demonstrate the successful application of RIL in analysing microbial DOC degradation during drinking water treatment. Changing the water flow rates through BAC filters did not alter the microbial activities, even though apparent DOC removal efficiencies changed accordingly. Microbial DOC degradation activities quickly recovered from backwashing which was applied for removing particulate impurities and preventing clogging. The size distributions of activated carbon particles led to vertical stratification of microbial activities along the filter beds. Our results demonstrate that reverse isotope labelling is well suited to measure microbial DOC degradation on activated carbon particles, which provides a basis for improving operation and design of BAC filters.

Quantification of microbial degradation activities in biological activated carbon filters by reverse stable isotope labelling

Quantification of microbial degradation activities in biological activated carbon filters by reverse stable isotope labelling

Simulation tests of in situ groundwater denitrification with aquifer-buried biocathodes

Bioelectrochemical systems (BES) application was proposed for a variety of specific uses, due to these systems’ characteristics: electrodes can act as virtually inexhaustible electron acceptors/donors, offering a growth-support surface for microorganisms, and stimulating naturally-occurring microbial degradation activities. In situ, groundwater denitrification therefore seems to be a potential candidate for their use. In this study, buried biocathodes were operated in laboratory settings for the simulation of in situ groundwater denitrification. Two alternative configurations were tested: biocathode buried in sand, and biocathode buried in gravel. A control test with a biocathode in absence of sand/gravel was also performed. In all the cases, biocathodes were driven by power supply or potentiostat to guarantee a steady electron flux to the cathode. The presence of sand and gravel strongly influenced the denitrification process: in both configurations, accumulation of intermediate N-forms was detected, suggesting that the denitrification process was only partially achieved. In addition, a significant decrease (in the 20–36% range) in nitrate removal rates was measured in sand and gravel setups compared to the control reactor; this issue could be attributed to lack of recirculation that limited contact between substrate and electrode-adherent biofilm. Biocathodes buried in gravel obtained better results than those buried in sand due to the lower packing of the medium. The results of this study suggest that, in order to achieve successful in situ treatment, special design of submerged-biocathodic BESs is necessary.

Applying reverse stable isotope labeling analysis by mid-infrared laser spectroscopy to monitor BDOC in recycled wastewater

Biological stability of treated wastewater is currently determined by methods such as biological oxygen demand, ATP-quantification, or flow-cytometric cell counting. However, the continuous increase in water reclamation for wastewater reuse requires new methods for quantifying degradation of biodegradable dissolved organic carbon (BDOC) ranging from very small to high concentrations of dissolved organic carbon (DOC). Furthermore, direct activity measures or absolute concentrations of BDOC are needed that produce comparable and reproducible results in all laboratories. Measuring carbon mineralization by CO2 evolution presents a suitable approach for directly measuring the microbial degradation activity. In this work, we investigated the extent of BDOC in water samples from effluent of a wastewater treatment plant and after purification by ultrafiltration over 204 days. BDOC monitoring was performed with the recently introduced reverse stable isotope labeling (RIL) analysis using mid-infrared spectroscopy for the monitoring of microbial CO2 production. Average BDOC degradation rates ranged from 0.11 to 0.32 mg L−1 d−1 for wastewater treatment plant effluent and from 0.03 to 0.22 mg L−1 d−1 after ultrafiltration. BDOC was degraded over >90 days indicating the long-term instability of the DOC. Degradation experiments over 88 days revealed first order kinetic rate constants for BDOC which corresponded to 12.7 · 10−3 d−1 for wastewater treatment plant effluent and 2.7 · 10−3 d−1 after ultrafiltration, respectively. A thorough sensitivity analysis of the RIL showed that the method is very accurate and sensitive with method detection limits down to 10 μg· L−1 of measured CO2.

Passive warming effect on soil microbial community and humic substance degradation in maritime Antarctic region.

Although the maritime Antarctic has undergone rapid warming, the effects on indigenous soil-inhabiting microorganisms are not well known. Passive warming experiments using open-top chamber (OTC) have been performed on the Fildes Peninsula in the maritime Antarctic since 2008. When the soil temperature was measured at a depth of 2-5 cm during the 2013-2015 summer seasons, the mean temperature inside OTC (OTC-In) increased by approximately 0.8 °C compared with outside OTC (OTC-Out), while soil chemical and physical characteristics did not change. Soils (2015 summer) from OTC-In and OTC-Out were subjected to analysis for change in microbial community and degradation rate of humic substances (HS, the largest pool of recalcitrant organic carbon in soil). Archaeal and bacterial communities in OTC-In were minimally affected by warming compared with those in OTC-Out, with archaeal methanogenic Thermoplasmata slightly increased in abundance. The abundance of heterotrophic fungi Ascomycota was significantly altered in OTC-In. Total bacterial and fungal biomass in OTC-In increased by 20% compared to OTC-Out, indicating that this may be due to increased microbial degradation activity for soil organic matter (SOM) including HS, which would result in the release of more low-molecular-weight growth substrates from SOM. Despite the effects of warming on the microbial community over the 8-years-experiments warming did not induce any detectable change in content or structure of polymeric HS. These results suggest that increased temperature may have significant and direct effects on soil microbial communities inhabiting maritime Antarctic and that soil microbes would subsequently provide more available carbon sources for other indigenous microbes.

Inoculation with bacteria in floating treatment wetlands positively modulates the phytoremediation of oil field wastewater

The aim of the present study was to investigate the potential of plant-bacterial synergism in floating treatment wetlands (FTWs) for efficient remediation of an oil field wastewater. Two plants, Brachiara mutica and Phragmites australis, were vegetated on floatable mats to develop FTWs, and inoculated with bacterial cons which were then inoculated with a consortium of hydrocarbon-degrading bacteria (Bacillus subtilis strain LORI66, Klebsiella sp. strain LCRI87, Acinetobacter Junii strain TYRH47, Acinetobacter sp. strain LCRH81). Both plants successfully removed organic and inorganic pollutants from wastewater, but bioaugmentation of P. australis significantly enhanced the plant’s efficiency to reduce oil content (97%), COD (93%), and BOD (97%), in wastewater. Analysis of alkane-degrading gene (alkB) abundance and its expression profile further validated a higher microbial growth and degradation activity in water around P. australis as well as its roots and shoots. This study provides insight into the available phytotechnology for remediation of crude oil-contaminated water and introduces a wetland macrophyte, P. australis, with tailor-made bacterial consortium as an effective tool for improved phytoremediation efficiency of FTWs.