Aerobic Bacterial Communities Research Articles

Investigation of lysing excess sludge slurry using hydrolase secreting thermophilic bacterial communities

Sludge reduction is a critical challenge in biological wastewater treatment. Combining excess sludge slurry lysis technology with traditional activated sludge processes is a promising approach for in-situ sludge reduction. Here, a strategy for excess sludge slurry lysis based on thermophilic bacterial communities (LTBC) was proposed. This investigation focused on the process of excess sludge slurry lysis dominated by thermophilic bacterial communities domesticated at different temperatures (55–75 °C). The evolution of sludge lysate was analyzed, and the mechanism of excess sludge slurry lysis under the action of thermophilic bacterial communities was elucidated through amplicon sequencing analysis. The results demonstrated that the aerobic thermophilic bacterial communities adapted to 75 °C exhibit the highest efficiency in sludge slurry lysis. During LTBC process, the removal efficiency of volatile suspended solids reached 53.9 ± 1.8% within 2 h, and 97.0 ± 1.0% of the protein and 96.0 ± 1.0% of the polysaccharide in the extracellular polymers was solubilized, and bacterial cell walls in sludge were disrupted. Fourier transform infrared spectroscopy and excitation-emission matrix spectroscopy of the sludge lysate demonstrated that the LTBC process was accompanied by humification process. The accumulation of humic acid primarily occurred at 55 °C and 65 °C, while fulvic acid occurred at 75 °C. The thermophilic bacterial communities adapted to 75 °C were dominated by Thermus and Thermaerobacter. Phylogenetic studies showed that the LTBC hydrolase system comprises enzymes related to protein hydrolysis, carbohydrate hydrolysis, and peptidoglycan hydrolysis, including metalopeptidase MepB, neutral α-glucosidase C, N-acetyl Muramyl-L-alanine amidase, and others enzymes. These results provide a theoretical basis for the application of LTBC technology in the reduction of sludge which generated in traditional waste water activated sludge processes.

Biodegradation of Benzene Under Microaerobic Conditions: a Groundwater Microcosm Experiment Combined with a Multiomics Approach and DNA Stable Isotope Probing

Monoaromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene (BTEX) are the most common contaminants of the groundwater and can easily contaminate drinking water sources due to their relatively high water solubility. Among these compounds, benzene is known to have carcinogenic properties and is considered to be persistent under anoxic conditions. Although deep knowledge was acquired both on the aerobic and anaerobic degradation of benzene in the past three decades, the diversity of those bacteria which are able to degrade it under microaerobic conditions, is still unknown. To come over this limitation aerobic and microaerobic benzene-degrading microcosms were established using groundwater sediment of a BTEX-contaminated site and the evolved bacterial communities were investigated through a polyphasic approach including multiomics analysis and DNA stable isotope probing. The obtained results shed light on the fact that the aerobic and microaerobic benzene-degrading bacterial communities were distinctly different. In the aerobic microcosms members of the genus Pseudomonas overwhelmingly dominated the bacterial communities by showing even 40-50% abundance. In contrast, under microaerobic conditions members of the genera Azovibrio and Malikia dominated the communities, while the abundance of Pseudomonas drastically decreased compared to that of was observable in the aerobic microcosms. Results obtained by the analysis of microcosms spiked with 13C6-benzene confirmed these observations. In heavy DNA fractions obtained from the aerobic microcosms the enrichment of Pseudomonas and Rhizobiaceae-related 16S rRNA gene fragments was observable. At the same time, labelled DNA from the microaerobic microcosms contained mostly Azovibrio and Malikia-related sequences, while the abundance of Pseudomonas 16S rRNA gene sequences was below 2%. Besides, by using metagenomic dataset of a previous microaerobic experiment we managed to reconstruct an Azovibrio genome, in which a complete meta-cleavage pathway for the aerobic degradation of aromatic hydrocarbons was identified. Overall, it can be concluded that under microaerobic conditions members of Comamonadaceae and Rhodocyclaceae can be the key benzene degraders in contaminated subsurface environments.

Phenol and nitrogen removal in microalgal–bacterial granular sequential batch reactors

AbstractBACKGROUNDMicroalgal–bacterial systems work on the principle of the symbiotic relationship between algae and bacteria. The ability of algal–bacterial photobioreactors for the treatment of wastewater containing ammonia and phenol has been poorly addressed. In this work a self‐sustaining synergetic microalgal–bacterial granular sludge process was thus developed to treatment of industrial wastewater based upon the low cost of photosynthetic oxygenation and the simultaneous phenol and nitrogen removal. The performance of a conventional sequential batch reactor (SBR) based on aerobic bacterial communities (SBRB) and a microalgal–bacterial granular SBR (SBRMB) were comparatively assessed. The major challenges associated with microalgal–bacterial systems were discussed.RESULTSA complete removal of phenol (100 mg L−1) was achieved in both reactors. The reactors SBRB and SBRMB showed similar performance in term of removal of inorganic nitrogen. Nitrogen mass balances estimated nitrogen assimilation, nitrification and denitrification. Higher simultaneous nitrification and denitrification (70% SND) occurred in SBRB as determined by mass balances. The higher nitrogen assimilation (17.9%) by the microalgal–bacterial biomass compensated the lower denitrifying activity in SBRMB (54% SND), resulting in a removal of inorganic nitrogen (61%) similar to that obtained in SBRB (66%). N2O was not detected in the headspace of any system.CONCLUSIONGranular microalgal–bacterial consortia implemented in SBR constitute an efficient method for industrial wastewater treatment achieving complete removal of ammonia and phenol. The application of SBRMB would be more cost effective than SBRB mainly due to the significant energy savings in SBRMB resulting in a sustainable system that contributes to the circular bioeconomy. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Fermentation profile, aerobic stability, and microbial community dynamics of corn straw ensiled with Lactobacillus buchneri PC-C1 and Lactobacillus plantarum PC1-1

Corn straw is suitable for preservation as silage despite being neglected due to its varying chemical composition, yield, and pathogenic influence during ensiling. This study examined the effects of beneficial organic acid-producing lactic acid bacteria (LAB), including Lactobacillus buchneri (Lb), L. plantarum (Lp), or their combination (LpLb), on fermentation profile, aerobic stability, and microbial community dynamics of corn straw harvested at late maturity stage after 7d, 14d, 30d, and 60d of ensiling. Higher levels of beneficial organic acids, LAB counts, and crude protein (CP), and lower levels of pH and ammonia nitrogen were detected in LpLb-treated silages after 60d. Lactobacillus, Candida, and Issatchenkia abundances were higher (P < 0.05) in Lb and LpLb-treated corn straw silages after 30d and 60d ensiling. Additionally, the positive correlation between Lactobacillus, Lactococcus and Pediococcus, and the negative correlation with Acinetobacter in LpLb-treated silages after 60d emphasizes a potent interaction mechanism initiated by organic acid and composite metabolite production to reduce pathogenic microorganisms' growth. Also, a significant correlation between Lb and LpLb-treated silages with CP and neutral detergent fiber after 60d further highlights the synergistic effect of incorporating L. buchneri and L. plantarum for improved nutritional components of mature silages. The combination of L. buchneri and L. plantarum improved aerobic stability, fermentation quality, and bacterial community and reduced fungal population after 60d of ensiling, which are properties of well-preserved corn straw.

Combined Omics Approach Reveals Key Differences between Aerobic and Microaerobic Xylene-Degrading Enrichment Bacterial Communities: Rhodoferax─A Hitherto Unknown Player Emerges from the Microbial Dark Matter.

Among monoaromatic hydrocarbons, xylenes, especially the ortho and para isomers, are the least biodegradable compounds in oxygen-limited subsurface environments. Although much knowledge has been gained regarding the anaerobic degradation of xylene isomers in the past 2 decades, the diversity of those bacteria which are able to degrade them under microaerobic conditions is still unknown. To overcome this limitation, aerobic and microaerobic xylene-degrading enrichment cultures were established using groundwater taken from a xylene-contaminated site, and the associated bacterial communities were investigated using a polyphasic approach. Our results show that the xylene-degrading bacterial communities were distinctly different between aerobic and microaerobic enrichment conditions. Although members of the genus Pseudomonas were the most dominant in both types of enrichments, the Rhodoferax and Azovibrio lineages were only abundant under microaerobic conditions, while Sphingobium entirely replaced them under aerobic conditions. Analysis of a metagenome-assembled genome of a Rhodoferax-related bacterium revealed aromatic hydrocarbon-degrading ability by identifying two catechol 2,3-dioxygenases in the genome. Moreover, phylogenetic analysis indicated that both enzymes belonged to a newly defined subfamily of type I.2 extradiol dioxygenases (EDOs). Aerobic and microaerobic xylene-degradation experiments were conducted on strains Sphingobium sp. AS12 and Pseudomonas sp. MAP12, isolated from the aerobic and microaerobic enrichments, respectively. The obtained results, together with the whole-genome sequence data of the strains, confirmed the observation that members of the genus Sphingobium are excellent aromatic hydrocarbon degraders but effective only under clear aerobic conditions. Overall, it was concluded that the observed differences between the bacterial communities of aerobic and microaerobic xylene-degrading enrichments were driven primarily by (i) the method of aromatic ring activation (monooxygenation vs dioxygenation), (ii) the type of EDO enzymes, and (iii) the ability of degraders to respire utilizing nitrate.

Effect of biochar on the mitigation of organic volatile fatty acid emission during aerobic biostabilization of biosolids and the underlying mechanism

In order to declare the effect and the underlying mechanism of biochar amendment on volatile fatty acid (VFA) emission during aerobic biostabilization of biosolids, different types of biochar (i.e., wheat straw biochar [WHB], sawdust biochar [SDB], and food waste digestate biochar [FRB]; 5% in dry weight) on carbon transformation and VFA emissions during 45-day aerobic biostabilization of biosolids were investigated. The results showed that biochar amendment improved thermophilic phase evolution and product dephytotoxification. During the 45-day period, in comparison to control, biochar addition promoted CH4 reduction by 44.46%–76.90% and enhanced the content of total organic carbon reduction by 20.60%–56.80%. In addition, biochar addition lowered the emissions of acetic, propanoic, isobutyric, butyric, isovaleric, and valeric acids by respectively 23.43%–41.21%, 23.10%–43.92%, 42.62%–56.11%, 26.70%–58.20%, 10.56%–58.27%, and 33.74%–49.45% compared with control values. Moreover, biochar amendment facilitated organic matter humification during biosolid bioconversion as well. Among the applied types of biochar, SDB, with a higher surface area, was more efficient in organic matter degradation and VFA emission mitigation than WHB and FRB. In particular, biochar amendment increased the abundance and diversity of aerobic bacterial communities such as Acinetobacter, Desemzia, Georgenia, Nonomuraea, Psycharobacter, Planococcus, Paenisporosarcina, Physchrobacillus, Staphylococcus, Thermobifida, and Thermopolyspora, while inhibiting the reproduction of anaerobic bacteria including Bacillus, Bacteroides, Corynebacterium, Ruminofilibacter, and Terrisporobacter during biosolid stabilization, thus improving biosolid maturity and stabilization and reducing VFA emissions. These findings offer a novel method with appropriate recommendations for the use and the selection of biochar in increasing the efficiency of biosolid aerobic biostabilization.

Novel insights into aerobic denitrifying bacterial communities augmented denitrification capacity and mechanisms in lake waters

Scanty attention has been paid to augmenting the denitrification performance of polluted lake water by adding mix-cultured aerobic denitrifying bacterial communities (Mix-CADBCs). In this study, to solve the serious problem of nitrogen pollution in lake water bodies, aerobic denitrifying bacteria were added to lake water to enhance the nitrogen and carbon removal ability. Three Mix-CADBCs were isolated from lake water and they could remove >94 % of total nitrogen and dissolved organic carbon, respectively. The balance of nitrogen analysis shown that >70 % of the initial nitrogen was converted to gaseous nitrogen, and <11 % of the initial nitrogen was converted into microbial biomass. The batch experiments indicated that three Mix-CADBCs could perform denitrification under various conditions. According to the results of nirS-type sequencing, the Hydrogenophaga sp., Prosthecomicrobium sp., and Pseudomonas sp. were dominated genera of three Mix-CADBCs. The analysis of network indicated Pseudomonas I.Bh25.14 and Vogsella LIG4 were correlated with the removal of total nitrogen (TN) and dissolved organic carbon in the Mix-CADBCs. Compared with lake raw water, the addition of three Mix-CADBCs could promote the denitrification capacity (the removal efficiencies of TN > 78.72 %), microbial growth (optical density increased by 0.015–0.138 and the total cell count increased by 2 times), and organic degradation ability (the removal efficiency chemical oxygen demand >38 %) of lake water. In general, the findings of this study demonstrated that Mix-CADBCs could provide a new perspective for biological treatment lake water body.

The Dynamic Shift of Bacterial Communities in Hybrid Anaerobic Baffled Reactor (ABR)—Aerobic Granules Process for Berberine Pharmaceutical Wastewater Treatment

Because of its anticancer, anti-inflammatory, and antibiotic properties, berberine has been used extensively in medication. The extensive production of berberine results in the generation of wastewater containing concentrated residual berberine. However, to date, limited related studies on the biological treatment of berberine wastewaters have been carried out. A lab-scale anaerobic baffled reactor (ABR)–aerobic granular sludge (AGS) process was developed for berberine removal from synthetic wastewater. The system showed effective removal of the berberine. In order to better understand the roles of the bacterial community, the ABR–aerobic granular sludge system was operated in the state with the highest BBR removal rate in this study. The bacterial community dynamics were studied using the 16S rDNA clone library. The results showed that the hybrid ABR-AGS process achieved 92.2% and 94.8% overall removals of berberine and COD, respectively. Bacterium was dominant species in ABR, while the CFB group bacteria and Betaproteobacteria were dominant species in AGS process. The uncultured bacterium clone B135, Bacillus endophyticus strain a125, uncultured bacterium mle1-42, uncultured bacterium clone OP10D15, and uncultured bacterium clone B21.29F54 in ABR, and uncultured bacterium clone F54, uncultured bacterium clone ZBAF1-105, uncultured bacterium clone SS-9, and uncultured bacterium clone B13 in AGS process were identified as functional species in the biodegradation of berberine and/or its metabolites. Both anaerobic and aerobic bacterial communities could adapt appropriately to different berberine selection pressures because the functional species’ identical functions ensured comparable pollutant removal performances. The information provided in this study may help with future research in gaining a better understanding of berberine biodegradation.

The influence of anaerobic dechlorination on the aerobic degradation of PCBs in e-waste-contaminated soils in an anaerobic-aerobic two-stage treatment

The combination of microbial reductive dechlorination and aerobic oxidation (RD-AO) process was proposed to be a promising strategy for extensive bioremediation of highly chlorinated polychlorinated biphenyls (PCBs). Nonetheless, experimental evidence on the impact of the RD on subsequent AO in anaerobic-aerobic two-stage treatment remains scarce. The present study applied stable-isotope probing (SIP) to explore the RD-AO mediated degradation of PCBs in an e-waste-contaminated soil. The RD-AO treatment resulted in 37.1 % and 48.2 % degradation of PCB180 and PCB9, respectively, while the PCB9 degradation efficiency decreased compared to the sole AO (81.2 %). The inhibition of PCB aerobic degradation might be caused by the alteration of aerobic bacterial community, which was proved by a higher abundance of anaerobic bacteria and a lower abundance of aerobic bacteria being observed in the aerobic stage of RD-AO. Further evidence was obtained using DNA-SIP that the anaerobic stage altered the PCB degraders' community structures and changed three of the five degraders. There were four lineages (Arenimonas, Steroidobacter, Sulfurifustis, and Thermoanaerobacterales) identified as PCB degraders for the first time. Interestingly, three of them were found in RD-AO microcosm, suggesting that anaerobic-aerobic two-stage treatment can recruit novel bacteria involved in PCBs aerobic degradation. The present study provided novel insight into the synergistic integration of anaerobic and aerobic processes for extensive degradation of highly chlorinated PCBs.

Indigenous cellulolytic aerobic and facultative anaerobic bacterial community enhanced the composting of rice straw and chicken manure with biochar addition

Microbial degradation of organic matters is crucial during the composting process. In this study, the enhancement of the composting of rice straw and chicken manure with biochar was evaluated by investigating the indigenous cellulolytic bacterial community structure during the composting process. Compared with control treatment, composting with biochar recorded higher temperature (74 °C), longer thermophilic phase (> 50 °C for 18 days) and reduced carbon (19%) with considerable micro- and macronutrients content. The bacterial community succession showed that composting with biochar was dominated by the cellulolytic Thermobifida and Nocardiopsis genera, which play an important role in lignocellulose degradation. Twenty-three cellulolytic bacterial strains were successfully isolated at different phases of the composting with biochar. The 16S rRNA gene sequencing similarity showed that they were related to Bacilluslicheniformis, Bacillussubtilis,Bacillusaerius, and Bacillushaynesii, which were known as cellulolytic bacteria and generally involved in lignocellulose degradation. Of these isolated bacteria, Bacilluslicheniformis, a facultative anaerobe, was the major bacterial strain isolated and demonstrated higher cellulase activities. The increase in temperature and reduction of carbon during the composting with biochar in this study can thus be attributed to the existence of these cellulolytic bacteria identified.

Solid digestate biochar amendment on pig manure composting: Nitrogen cycle and balance

Effect of solid digestate biochar (DB) on nitrogen cycle and balance was evaluated during composting by adding DB into mixtures of pig manure and Lycium chinensis branch filings. Results indicated that DB addition improved composting microenvironment and increased the total N content of the final product. Furthermore, N balance calculation indicated that the NH3 and N2O emissions accounted for 72.14%–81.39% and 0.49%–2.37% of the total N loss without DB addition, respectively. After using DB, the N reductions in the form of NH3 and N2O reduced from 10.78% to < 5.73% and from 0.34% to < 0.041% of total N, respectively. Addition of DB affected N fixation with 92.32%–93.67% of total N fixed in the compost than that of the T1 treatment (85.63%). DB amendment enhanced the aerobic bacterial communities and hindered anaerobic bacterial growth, thus benefiting the NH3 and N2O emission mitigation and N conservation.

Preliminary Identification of the Aerobic Cervicovaginal Microbiota in Mexican Women With Cervical Cancer as the First Step Towards Metagenomic Studies.

Cervical cancer (CC) is considered a public health problem. Recent studies have evaluated the possible relationship between the cervicovaginal microbiome and gynecologic cancer but have not studied the relationship between aerobic bacterial communities and neoplasia. The study aimed to identify the cultivable aerobic bacterial microbiota in women with cervical cancer as a preliminary approach to the metagenomic study of the cervicovaginal microbiome associated with cervical cancer in Mexican women. An observational cross-sectional study was conducted, including 120 women aged 21-71 years, divided into two study groups, women with locally advanced CC (n=60) and women without CC (n=60). Sociodemographic, gynecological-obstetric, sexual, and habit data were collected. Cervicovaginal samples were collected by swabbing, from which standard microbiological methods obtained culturable bacteria. The strains were genetically characterized by PCR-RFLP of the 16S rRNA gene and subsequently identified by sequencing the same gene. Variables regularly reported as risk factors for the disease were found in women with CC. Differences were found in the prevalence and number of species isolated in each study group. Bacteria commonly reported in women with aerobic vaginitis were identified. There were 12 species in women with CC, mainly Corynebacterium spp. and Staphylococcus spp.; we found 13 bacterial species in the group without cancer, mainly Enterococcus spp. and Escherichia spp. The advanced stages presented a more significant number of isolates and species. This study provided a preliminary test for cervicovaginal metagenomic analysis, demonstrating the presence of aerobic cervicovaginal dysbiosis in women with CC and the need for more in-depth studies.

Spatial and Temporal Distribution of Aerobic Denitrification Bacterial Community in Sediments of Gangnan Reservoir

In order to study the spatial and temporal distribution characteristics of aerobic denitrification bacteria in the sediments of Gangnan Reservoir, the aerobic denitrification bacterial community was analyzed using a MiSeq high-throughput sequencing technique based on the napA gene. Moreover, the composition, diversity, difference, and network analysis of the aerobic denitrification bacterial community were investigated. The results showed higher α-diversity (Chao1 index, Observed species index, and Shannon index) in autumn and winter than that in spring and summer; that is, the richness and diversity of sampling sites in autumn and winter were higher. In terms of spatial distribution, the Chao1 index, Observed species index, Shannon index, and Simpson index of the bacterial community in the sampling sites in the transition zone were higher than those in the sampling sites in the inflow area and the main reservoir area, indicating that the richness and diversity of the bacterial community in the sampling sites in the transition zone were the highest. The aerobic denitrifying bacteria in the sediments of Gangnan Reservoir mainly belong to Protebacteria. The first dominant class was β-Proteobacteria, and the first dominant genus was Thauera. A Venn diagram analysis indicated that the community of aerobic denitrification bacteria exhibited significant spatial and temporal differences. At the spatial level, there were higher numbers of different species based on LEfSe analysis than that at the seasonal level. Among the marker species screened by random forest analysis, Comamonas had the highest contribution in all spatial sampling sites, whereas Pectobacterium had the highest contribution in all seasonal sampling sites. Network analysis showed that there were nine modules, including 565 edges of 297 nodes; 47 keystone species were obtained based on the indicator OTUs analysis and network analysis. The principal co-ordinates analysis revealed that keystone species in the spatial distribution exhibited significant differences (Adonis, P<0.001). The results of this study provide scientific basis for the separation and identification of efficient aerobic denitrifying bacteria.

Aerobic denitrifying bacteria community structure and response of aerobic denitrifying bacteria to dissloved organic matter in the sediments in Lake Baiyangdian in the spring

好氧反硝化因其独特优势成为近年来生物脱氮的研究热点，溶解性有机物（DOM）作为微生物碳源是造成群落差异的重要原因，为了探究白洋淀不同功能区好氧反硝化菌群落结构对溶解性有机物碳源的响应，本文结合荧光区域积分法以及napA反硝化基因的高通量测序技术，对白洋淀春季沉积物中的好氧反硝化菌群落结构特征以及好氧反硝化菌对溶解性有机物的响应进行研究.结果表明，春季白洋淀沉积物有机质组分类蛋白质组分高于类腐殖质组分，其中养殖区的类蛋白质组分最大，达到79.63%±3.79%，原始区的类腐殖质组分最大，达到33.91%±6.32%；高通量测序得到3693个OTUs，共分为9个主要门类，其中，变形菌门占比最大，达到99%以上；α多样性Chao1指数呈现显著的空间差异，并且旅游区>生活区>入淀区>原始区>养殖区；该时期好氧反硝化菌主要物种组成包括Aeromonas、Sulfuritortus、Cupriavidus、Pseudomonas和Thauera，Ferrimonas作为指示物种，差异贡献最大；冗余分析发现，可见光区类富里酸物质和微生物代谢产物组分分别是不同功能区好氧反硝化菌群落纲水平和属水平差异的主要原因.综上，通过对白洋淀好氧反硝化菌群与溶解性有机物的相关关系研究，不仅有助于进一步认识天然环境中氮循环微生物的特征；还可以为将来适于实际环境的高效菌筛选的碳源选择提供参考.;Aerobic denitrification has become a research hotspot in biological denitrification in recent years due to its unique advantages. Dissolved organic matter (DOM) as a carbon source is the important reason for community differences. To explore the responding mechanism of aerobic denitrifying bacteria community structure to dissolved organic matter in different functional areas of Lake Baiyangdian, this paper combines the fluorescence area integration method and the high-throughput sequencing technology of napA denitrification genes to study the characteristics of the aerobic denitrifying bacterial community structure and responding mechanism in Lake Baiyangdian. The results showed that the concentration of protein-like components was higher than that of humic-like components in the organic matter of Lake Baiyangdian sediments in spring. Among them, the protein-like components in the culture area were the largest, reaching 79.63%±3.79%, and the humus-like component in the primitive area was the largest, reaching 33.91%±6.32%; A total of 3693 OTUs were acquired high Throughput sequencing, which was divided into 9 main phyla. Among them, the Proteobacteria accounted for the largest proportion, reaching over 99%; the α diversity Chao1 index showed significant spatial differences, and the travel area>the living area>the entry area>the original area>the breeding area; the main species of aerobic denitrifying bacteria include Aeromonas, Sulfuritortus, Cupriavidus, Pseudomonas and Thaurea, Ferrimonas, as an indicator species, contributes the most to the difference; Redundant analysis found that the components of fulvic acid-like substances and microbial metabolites in the visible light area are the main reasons for the differences in aerobic denitrifying bacteria in different functional areas. In summary, this research will not only help to further understand the characteristics of the nitrogen cycle microorganisms in the natural environment; it will also provide a reference for the selection of carbon sources suitable for efficient bacterial screening in the practical environment.

Structure of Aerobic Denitrification Bacterial Community in Response to Dissolved Organic Matter in Baiyangdian Lake During the Water Delivery Period

Dissolved organic matter (DOM) plays an important role in the evolution of microbial communities. Meanwhile, ecological water delivery is an important feature of Baiyangdian Lake. To explore how the structure of the aerobic denitrification bacteria community responds to DOM during the water delivery period, the DOM components of water were examined and high-throughput sequencing of aerobic denitrification bacteria was performed. The results showed significant differences in DOM concentration in Baiyangdian Lake, with the estuary area exhibiting lower DOM concentrations. The water exhibited strong autogenous source, while DOM in the estuary area had a higher molecular weight and degree of humification. Three protein-like substances (C1, C2, and C4) and one humic-like substance (C3) were identified through PARAFAC. The protein-like substances accounted for the major proportion of DOM, which was consistent with the results of fluorescence regional integration (FRI). The genera of the water body were mainly in the Protebacterice phylum, including Cupriavidus, Aeromonas, Thauera, Shewanella, and Pseudomonas. Meanwhile, Cupriavidus, Thauera, Shewanella, Agrobacterium, and Pseudomonas were the main indicator species, according to random forest (RF) analysis. Through network analysis, 35 key nodes of the network were obtained, belonging to Thauera, Cupriavidus, and Unclassified_bacteria, respectively. Redundancy analysis (RDA) showed that a humic-like substance was the main environmental factor regulating the whole structure of the aerobic denitrification bacterial community, while protein-like substances played important roles in changes to the indicator species and key nodes of the community. Overall, protein-like substances could provide an important reference for selecting carbon sources during the screening of efficient and cold resistance aerobic denitrification bacteria that are adapted to actual water bodies.

Mix-cultured aerobic denitrifying bacterial communities reduce nitrate: Novel insights in micro-polluted water treatment at lower temperature

Three mix-cultured aerobic denitrifiers were screened from a source water reservoir and named HE1, HE3 and SU4. Approximately 72.9%, 68.6% and 66.2% of nitrate were effectively removed from basal medium, respectively, after 120 h of cultivation at 8 °C. The nitrogen balance analysis revealed about one-fifth of the initial nitrogen was converted into gaseous denitrification products. According to the results of Biolog, the three microfloras had high metabolic capacity to carbon sources. The dominant genera were Pseudomonas and Paracoccus in these bacterial communities based on nirS gene sequencing. Response surface methodology elucidated that the denitrification rates of identified bacteria reached the maximum under the following optimal parameters: C/N ratio of 7.51–8.34, pH of 8.03–8.09, temperature of 18.03–20.19 °C, and shaking speed of 67.04–120 rpm. All results suggested that screened aerobic denitrifiers could potentially be applied to improve the source water quality at low temperature.

An autochthonous aerobic bacterial community and its cultivable isolates capable of degrading fluoxetine

AbstractBACKGROUNDFluoxetine is an antidepressant and recalcitrant fluorine pharmaceutical that is poorly biodegraded, so it enters the hydric resources and causes hazardous effects to aquatic environments. According to these fluoxetine features, the main aim of the present research was to find resistant bacteria in environmental samples with a high degradation efficiency.RESULTSThe results obtained from raw municipal wastewater spiked with fluoxetine and inoculated with aerobic sludge from a Portuguese wastewater treatment plant under highly aerobic conditions showed that more than half and ≈89% of the drug was degraded after 48 and 144 h, respectively. During the assay, the initial population (mainly composed of Arcobacter, Bacteroides, and Macellibacteroides) shifted with an increase of members of the Acinetobacter, Rheinheimera, Shewanella, Pseudomonas, Methylobacillus, Piscinobacter genera and Aeromonadales order and the Pseudomonadaceae family, all of which were likely responsible for fluoxetine biodegradation. From the same sludge, six bacterial isolates were selected and identified as follows: Pseudomonas putida, Enterobacter ludwigii, Pseudomonas nitritireducens, Alcaligenes faecalis, Pseudomonas aeruginosa, and Pseudomonas nitroreducens; all of them grew with fluoxetine as sole carbon source. Pseudomonas nitroreducens showed the highest removal of 55 ± 1% at 20 mg L–1 fluoxetine after 24 h.CONCLUSIONAn autochthonous aerobic bacterial community and its cultivable isolates showed the capacity to biodegrade fluoxetine. Biodegradation, rather than adsorption, appears to play the main role in the fluoxetine removal in aerobic conditions using bacteria simply obtained from an environmental sample. As far as is known, those bacteria are reported for the first time as fluoxetine biodegraders; thus, these bacteria are a promising option to integrate into new bioremediation processes aiming at the removal of fluoxetine. © 2021 Society of Chemical Industry (SCI).

Simultaneous nitrification and phosphate removal by bioaugmented aerobic granules treating a fluoroorganic compound.

The presence of toxic compounds in wastewater can cause problems for organic matter and nutrient removal. In this study, the long-term effect of a model xenobiotic, 2-fluorophenol (2-FP), on ammonia-oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB) and phosphate accumulating organisms (PAO) in aerobic granular sludge was investigated. Phosphate (P) and ammonium (N) removal efficiencies were high (>93%) and, after bioaugmentation with 2-FP degrading strain FP1, 2-FP was completely degraded. Neither N nor P removal were affected by 50 mg L-1 of 2-FP in the feed stream. Changes in the aerobic granule bacterial communities were followed. Numerical analysis of the denaturing gradient gel electrophoresis (DGGE) profiles showed low diversity for the ammonia monooxygenase (amoA) gene with an even distribution of species. PAOs, including denitrifying PAO (dPAO), and AOB were present in the 2-FP degrading granules, although dPAO population decreased throughout the 444 days reactor operation. The results demonstrated that the aerobic granules bioaugmented with FP1 strain successfully removed N, P and 2-FP simultaneously.

Aerobic Bacterial Community of the Rice Striped Stem Borer: A Step towards Finding Bacterial Candidates for Paratransgenesis and RNAi Control

It is recognized that insects have close associations with a wide variety of microorganisms, which play a vital role in the insect's ecology and evolution. The rice striped stem borer, Chilo suppressalis, has economic importance at the global level. With the development of insecticide resistance, it is widely recognized that control of this pest is likely to need new tools that are not available today. Here, we focus on the aerobic bacterial community of the pest, to seek candidates for paratransgenesis or RNAi biocontrol of C. suppressalis. Culture-dependent PCR-direct sequencing was used to characterize the midgut bacterial communities of C.suppressalis at different life stages, collected in northern Iran, both from rice plants and from weeds on which the insect feeds. Our results show that the predominant genera of the Firmicutes and Proteobacteria phyla were Bacillus, Enterobacter and Klebsiella in all life stages, and they displayed differences in abundance. The high levels of B. subtilis and Enterobacter found in C. suppressalis suggests their potential utility for paratransgenesis and RNAi approaches to control this pest.

Description of the ovarian microbiota of Aedes aegypti (L) Rockefeller strain

Aedes aegypti is one of the vectors responsible for transmitting the viruses that cause dengue, Zika and chikungunya in the human population. Mosquitoes have bacterial communities in different organs, mainly in the midgut, but to a lesser extent in their reproductive organs, such as the ovaries, where replication and vertical transmission is decisive for dengue virus. These bacteria also influence metabolic and physiological processes such as ingestion and digestion of blood. In this study, aerobic bacterial communities associated with ovaries of A. aegypti Rockefeller strain were determined, describing their potential function during ovocitary development. The groups of mosquitoes were separated into three treatments: diet with 10% sugar solution, diet with blood supply, and blood feeding combined with tetracycline. The ovaries were extracted from the mosquitoes, and then put in enriched culture media (blood and nutritive agar) by direct inoculation, for subsequent isolation and macroscopic and microscopic characterization of the colonies. The taxonomic determination of bacterial isolates was achieved by sequence analysis of the 16S rRNA gene. A higher bacterial load was observed in the sugar feeding group (6 × 10³ CFU/ml) in contrast to the group fed only with blood, with and without an antibiotic (4.03-4.04 × 10³CFU/ml; 4.85-5.04 × 10³CFU/ml). As a result, a total of 35 colonies were isolated, of which 80% were gram-negative and 20% gram-positive; 72% were lactose negative and 8% lactose positive. Of the total bacteria, 83% had gamma hemolysis, 17% alpha hemolysis, and none presented beta hemolysis. After phenotypic and biochemical characterization, 17 isolates were selected for molecular identification. Only phyla Actinobacteria and Proteobacteria were found. Bacteria associated with ovaries of A. aegypti were mainly identified as belonging to the Serratia and Klebsiella genera. Some bacteria (Serratia marcescens, Pantoea dispersa and Klebsiella oxytoca) have wide biotechnological potential due to their entomopathogenic power and their bioactivity against different pathogens.