Optimizing electrochemically active microorganisms as a key player in the bioelectrochemical system: Identification methods and pathways to large-scale implementation.

The rapid global economic growth driven by industrialization and population expansion has resulted in significant issues, including reliance on fossil fuels, energy scarcity, water crises, and environmental emissions. To address these issues, bioelectrochemical systems (BES) have emerged as a dual-purpose solution, harnessing electrochemical processes and the capabilities of electrochemically active microorganisms (EAM) to simultaneously recover energy and treat wastewater. This review examines critical performance factors in BES, including inoculum selection, pretreatment methods, electrodes, and operational conditions. Further, authors explore innovative approaches to suppress methanogens and simultaneously enhance the EAM in mixed cultures. Additionally, advanced techniques for detecting EAM are discussed. The rapid detection of EAM facilitates the selection of suitable inoculum sources and optimization of enrichment strategies in BESs. This optimization is essential for facilitating the successful scaling up of BES applications, contributing substantially to the realization of clean energy and sustainable wastewater treatment. This analysis introduces a novel viewpoint by amalgamating contemporary research on the selective enrichment of EAM in mixed cultures. It encompasses identification and detection techniques, along with methodologies tailored for the selective enrichment of EAM, geared explicitly toward upscaling applications in BES.

Marine plastisphere selectively enriches microbial assemblages and antibiotic resistance genes during long-term cultivation periods.

Several studies have focused on identifying and quantifying suspended plastics in surface and subsurface seawater. Microplastics (MPs) have attracted attention as carriers of antibiotic resistance genes (ARGs) in the marine environment. Plastispheres, specific biofilms on MP, can provide an ideal niche to spread more widely through horizontal gene transfer (HGT), thereby increasing risks to ecosystems and human health. However, the microbial communities formed on different plastic types and ARG abundances during exposure time in natural marine environments remain unclear. Four types of commonly used MPs (polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC)) were periodically cultured (46, 63, and 102 d) in a field-based marine environment to study the co-selection of ARGs and microbial communities in marine plastispheres. After the first 63 d of incubation (p < 0.05), the initial 16S rRNA gene abundance of microorganisms in the plastisphere increased significantly, and the biomass subsequently decreased. These results suggest that MPs can serve as vehicles for various microorganisms to travel to different environments and eventually provide a niche for a variety of microorganisms. Additionally, the qPCR results showed that MPs selectively enriched ARGs. In particular, tetA, tetQ, sul1, and qnrS were selectively enriched in the PVC-MPs. The abundances of intl1, a mobile genetic element, was measured in all MP types for 46 d (5.22 × 10-5 ± 8.21 × 10-6 copies/16s rRNA gene copies), 63 d (5.90 × 10-5 ± 2.49 × 10-6 copies/16s rRNA gene copies), and 102 d (4.00 × 10-5 ± 5.11 × 10-6 copies/16s rRNA gene copies). Network analysis indicated that ARG profiles co-occurred with key biofilm-forming bacteria. This study suggests that the selection of ARGs and their co-occurring bacteria in MPs could potentially accelerate their transmission through HGT in natural marine plastics.

Insight into the marine microplastic abundance and distribution in ship cooling systems.

Microplastics (MPs) are becoming widely recognized as one of many global environmental issues. Although recently, it has been suggested that marine plastics may affect a ship's operation, the presence of MPs in a ship's cooling system has not received significant attention. In this study, samples of 40 L each were taken from each of the five main pipes (sea chest (SC), ejector pump (EP), main engine jacket freshwater pump (MJFP), main engine jacket freshwater cooler (MJFC), and expansion tank (ET)) in each season (February, May, July, October 2021) to identify and characterize MPs in the five main pipes of the ship cooling system from the training ship Hanbada, Korea Maritime and Ocean University. As a result of FTIR analysis, the total MP abundance was 24,100 particles/m3 in the cooling system of the ship. MP concentrations were observed to be higher (p < 0.05) in winter and spring (dry season: 1578 ± 604 particles/m3) than in summer and autumn (wet season: 990 ± 390 particles/m3). In addition, the MP concentration in the seawater cooling system (SCS) (1509 ± 553 particle/m3) was slightly higher (p > 0.05) than that in the freshwater cooling system (FCS) (1093 ± 546 particles/m3). Compared to previous studies, it was confirmed that the quantitative amount of MPs on board was similar to or slightly less than the concentration of MPs investigated along the coast of Korea (1736 particles/m3). To identify the chemical composition of MPs, an optical microscope and FTIR analysis was carried out, and PE (polyethylene), PP (polypropylene), and PET (polyethylene terephthalate) were identified as major chemicals in all samples. MPs in the form of fibers and fragments accounted for approximately 95% of the total. This study provided evidence of MP contamination in the main pipe in the cooling system of the ship. These findings confirm that marine MPs existing in seawater may have flowed into the ship's cooling system, and it is necessary to understand the effect of marine MPs on the ship's engine and cooling system through continuous monitoring.

Metatranscriptional characterization of metabolic dynamics in anaerobic membrane bioreactor producing methane from low-strength wastewater.

An anaerobic membrane bioreactor (AnMBR) with media is an emerging carbon-neutral biotechnology for low-strength wastewater (LSWW) treatment and methane recovery. Understanding metabolic dynamics among methanogens and syntrophic bacteria is important in optimizing the design and operation of AnMBR. However, little is known about it, especially in media-attached microbial communities. This study explored metabolic dynamics to compare media-attached and suspended conditions. Accordingly, metagenomes and metatranscriptomes from AnMBRs with polymeric media and fed with different influent concentrations (350 and 700 mg-COD/L) were analyzed. Metabolic dynamics were profoundly influenced by the different growth habitats and influent conditions, although the applied influent concentrations are within the range of typical LSWW. Metabolic dynamics prediction results suggest that media-attached-growth habitats may have provided a more favorable microenvironment for methanogens to grow and produce methane, especially under low influent conditions. These findings provide significant implications for optimizing floating media design and operation of AnMBR-producing methane from LSWW.

Diminazene aceturate attenuates hepatic ischemia/reperfusion injury in mice.

Hepatic ischemia/reperfusion (I/R) injury is one of the leading causes of mortality following partial hepatectomy, liver transplantation, hypovolemic shock and trauma; however, effective therapeutic targets for the treatment of hepatic I/R injury are lacking. Recent studies have shown that diminazene aceturate (DIZE) has protective effects against inflammation, oxidative stress and cell death, which are the main pathogenetic mechanisms associated with hepatic I/R injury. However, the mechanistic effects DIZE exerts on hepatic I/R remain unknown. C57BL/6 male mice were pretreated with either 15 mg/kg DIZE or vehicle control (saline) and subjected to partial liver ischemia for 60 min. One day after induction of hepatic I/R, liver damage, inflammatory responses, oxidative stress and apoptosis were analyzed. By evaluating plasma alanine aminotransferase levels and histology, we found that DIZE treatment attenuated liver failure and was associated with a reduction in histologically-apparent liver damage. We also found that DIZE-treated mice had milder inflammatory responses, less reactive oxidative damage and less apoptosis following hepatic I/R compared to vehicle-treated mice. Taken together, our study demonstrates that DIZE protects against ischemic liver injury by attenuating inflammation and oxidative damage and may be a potential therapeutic agent for the prevention and treatment of ischemic liver failure.

Biohydrogen production and purification: Focusing on bioelectrochemical systems.

Innovative technologies on green hydrogen production become significant as the hydrogen economy has grown globally. Biohydrogen is one of green hydrogen production methods, and microbial electrochemical cells (MECs) can be key to biohydrogen provision. However, MECs are immature for biohydrogen technology due to several limitations including extracellular electron transfer (EET) engineering. Fundamental understanding of EET also needs more works to accelerate MEC commercialization. Interestingly, studies on biohydrogen gas purification are limited although biohydrogen gas mixture requires complex purification for use. To facilitate an MEC-based biohydrogen technology as the green hydrogen supply this review discussed EET kinetics, engineering of EET and direct interspecies electron transfer associated with hydrogen yield and the application of advanced molecular biology for improving EET kinetics. Finally, this article reviewed biohydrogen purification technologies to better understand purification and use appropriate for biohydrogen, focusing on membrane separation.

A review of the emergence of antibiotic resistance in bioaerosols and its monitoring methods.

Despite significant public health concerns regarding infectious diseases in air environments, potentially harmful microbiological indicators, such as antibiotic resistance genes (ARGs) in bioaerosols, have not received significant attention. Traditionally, bioaerosol studies have focused on the characterization of microbial communities; however, a more serious problem has recently arisen due to the presence of ARGs in bioaerosols, leading to an increased prevalence of horizontal gene transfer (HGT). This constitutes a process by which bacteria transfer genes to other environmental media and consequently cause infectious disease. Antibiotic resistance in water and soil environments has been extensively investigated in the past few years by applying advanced molecular and biotechnological methods. However, ARGs in bioaerosols have not received much attention. In addition, ARG and HGT profiling in air environments is greatly limited in field studies due to the absence of suitable methodological approaches. Therefore, this study comprehensively describes recent findings from published studies and some of the appropriate molecular and biotechnological methods for monitoring antibiotic resistance in bioaerosols. In addition, this review discusses the main knowledge gaps regarding current methodological issues and future research directions.

Transcriptomic Analysis of Degradative Pathways for Azo Dye Acid Blue 113 in Sphingomonas melonis B-2 from the Dye Wastewater Treatment Process.

BACKGROUND: Acid Blue 113 (AB113) is a typical azo dye, and the resulting wastewater is toxic and difficult to remove. METHODS: The experimental culture was set up for the biodegradation of the azo dye AB113, and the cell growth and dye decolorization were monitored. Transcriptome sequencing was performed in the presence and absence of AB113 treatment. The key pathways and enzymes involved in AB113 degradation were found through pathway analysis and enrichment software (GO, EggNog and KEGG). RESULTS: S. melonis B-2 achieved more than 80% decolorization within 24 h (50 and 100 mg/L dye). There was a positive relationship between cell growth and the azo dye degradation rate. The expression level of enzymes involved in benzoate and naphthalene degradation pathways (NADH quinone oxidoreductase, N-acetyltransferase and aromatic ring-hydroxylating dioxygenase) increased significantly after the treatment of AB113. CONCLUSIONS: Benzoate and naphthalene degradation pathways were the key pathways for AB113 degradation. NADH quinone oxidoreductase, N-acetyltransferase, aromatic ring-hydroxylating dioxygenase and CYP450 were the key enzymes for AB113 degradation. This study provides evidence for the process of AB113 biodegradation at the molecular and biochemical level that will be useful in monitoring the dye wastewater treatment process at the full-scale treatment.

Yes-associated protein 1 as a prognostic biomarker and its correlation with telomerase in various cancers.

OBJECTIVE: The aims of this study were to investigate the expression of Yes-associated protein 1 (YAP1), its prognostic significance, and the correlation between YAP1 and telomerase in various cancers. METHODS: The Gene Expression Profiling Interactive Analysis database was used to analyze RNA sequencing data and the survival rate of patients with various cancers in The Cancer Genome Atlas (TCGA) database. PrognoScan was used to analyze the prognostic value of YAP1 expression in various cancers. Tumor Immune Estimation Resource was used to determine the correlation between YAP1 expression and telomerase in various cancer types based on TCGA data. RESULTS: The analysis suggested that YAP1 was differentially expressed between tissues of various cancers and non-tumor tissues. High YAP1 expression was also related to a poor prognosis in adrenocortical carcinoma, bladder urothelial carcinoma, and pancreatic adenocarcinoma. Moreover, YAP1 expression was correlated with the expression of telomerase reverse transcriptase and telomerase RNA component in various cancer types. CONCLUSION: These results suggest that YAP1 is a potential biomarker with prognostic significance and relevance for oncogene research in various cancer types. The correlation between the expression of YAP1 and telomere-associated genes will help to understand their cancer-promoting mechanisms and interactions.

Metagenomic Insight of a Full Scale Eco-Friendly Treatment System of Textile Dye Wastewater Using Bioaugmentation of the Composite Culture CES-1.

Effects of bioaugmentation of the composite microbial culture CES-1 on a full scale textile dye wastewater treatment process were investigated in terms of water quality, sludge reduction, dynamics of microbial community structures and their functional genes responsible for degradation of azo dye, and other chemicals. The removal efficiencies for Chemical Oxygen Demand (COD), Total Nitrogen (T-N), Total Phosphorus (T-P), Suspended Solids (SS), and color intensity (96.4%, 78.4, 83.1, 84.4, and 92.0, respectively) 300-531 days after the augmentation were generally improved after bioaugmentation. The denitrification linked to T-N removal appeared to contribute to the concomitant COD removal that triggered a reduction of sludge (up to 22%) in the same period of augmentation. Azo dye and aromatic compound degradation and other downstream pathways were highly metabolically interrelated. Augmentation of CES-1 increased microbial diversity in the later stages of augmentation when a strong microbial community selection of Acinetobacterparvus, Acinetobacterjohnsonii, Marinobacter manganoxydans, Verminephrobacter sp., and Arcobacter sp. occurred. Herein, there might be a possibility that the CES-1 augmentation could facilitate the indigenous microbial community successions so that the selected communities made the augmentation successful. The metagenomic analysis turned out to be a reasonable and powerful tool to provide with new insights and useful biomarkers for the complex environmental conditions, such as the full scale dye wastewater treatment system undergoing bioaugmentation.

Investigation of the Prevalence of Antibiotic Resistance Genes According to the Wastewater Treatment Scale Using Metagenomic Analysis.

Although extensive efforts have been made to investigate the dynamics of the occurrence and abundance of antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs), understanding the acquisition of antibiotic resistance based on the WWTP scale and the potential effects on WWTPs is of relatively less interest. In this study, metagenomic analysis was carried out to investigate whether the WWTP scale could be affected by the prevalence and persistence of ARGs and mobile genetic elements (MGEs). As a result, 152 ARG subtypes were identified in small-scale WWTP samples, while 234 ARG subtypes were identified in large-scale WWTP samples. Among the detectable ARGs, multidrug, MLS (macrolide-lincosamide-streptogramin), sulfonamide, and tetracycline resistance genes had the highest abundance, and large and small WWTPs had similar composition characteristics of ARGs. In MGE analysis, plasmids and integrons were 1.5-2.0-fold more abundant in large-scale WWTPs than in small-scale WWTPs. The profile of bacteria at the phylum level showed that Proteobacteria and Actinobacteria were the most dominant bacteria, representing approximately 70% across large- and small-scale WWTPs. Overall, the results of this study elucidate the different abundances and dissemination of ARGs between large- and small-scale WWTPs, which facilitates the development of next-generation engineered wastewater treatment systems.

An Improved Approach to Identify Bacterial Pathogens to Human in Environmental Metagenome.

The identification of bacterial pathogens to humans is critical for environmental microbial risk assessment. However, current methods for identifying pathogens in environmental samples are limited in their ability to detect highly diverse bacterial communities and accurately differentiate pathogens from commensal bacteria. In the present study, we suggest an improved approach using a combination of identification results obtained from multiple databases, including the multilocus sequence typing (MLST) database, virulence factor database (VFDB), and pathosystems resource integration center (PATRIC) databases to resolve current challenges. By integrating the identification results from multiple databases, potential bacterial pathogens in metagenomes were identified and classified into eight different groups. Based on the distribution of genes in each group, we proposed an equation to calculate the metagenomic pathogen identification index (MPII) of each metagenome based on the weighted abundance of identified sequences in each database. We found that the accuracy of pathogen identification was improved by using combinations of multiple databases compared to that of individual databases. When the approach was applied to environmental metagenomes, metagenomes associated with activated sludge were estimated with higher MPII than other environments (i.e., drinking water, ocean water, ocean sediment, and freshwater sediment). The calculated MPII values were statistically distinguishable among different environments (p<0.05). These results demonstrate that the suggested approach allows more for more accurate identification of the pathogens associated with metagenomes.

A Sporolactobacillus-, Clostridium-, and Paenibacillus- Dominant Microbial Consortium Improved Anaerobic RDX Detoxification by Starch Addition.

In the present study, an anaerobic microbial consortium for the degradation of hexahydro-1,3,5- trinitro-1,3,5-triazine (RDX) was selectively enriched with the co-addition of RDX and starch under nitrogen-deficient conditions. Microbial growth and anaerobic RDX biodegradation were effectively enhanced by the co-addition of RDX and starch, which resulted in increased RDX biotransformation to nitroso derivatives at a greater specific degradation rate than those for previously reported anaerobic RDX-degrading bacteria (isolates). The accumulation of the most toxic RDX degradation intermediate (MNX [hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine]) was significantly reduced by starch addition, suggesting improved RDX detoxification by the co-addition of RDX and starch. The subsequent MiSeq sequencing that targeted the bacterial 16S rRNA gene revealed that the Sporolactobacillus, Clostridium, and Paenibacillus populations were involved in the enhanced anaerobic RDX degradation. These results suggest that these three bacterial populations are important for anaerobic RDX degradation and detoxification. The findings from this work imply that the Sporolactobacillus, Clostridium, and Paenibacillus dominant microbial consortium may be valuable for the development of bioremediation resources for RDX-contaminated environments.

Exploring the antibiotic resistome in activated sludge and anaerobic digestion sludge in an urban wastewater treatment plant via metagenomic analysis.

Antibiotic resistance genes (ARGs) are emerging contaminants that pose a potential threat to human health worldwide. Urban wastewater treatment plants (WWTPs) are a main source of both antibiotic-resistant bacteria and ARGs released into the environment. Nevertheless, the propagation of ARGs and their underlying mechanisms and the dynamics of mobile genetic elements (MGEs) in WWTPs have rarely been investigated in South Korea. In this study, shotgun metagenomic analysis was used to identify comprehensive ARGs and their mechanisms, bacterial communities, and MGEs from 4 configurations with 2 activated sludge (AS) and 2 anaerobic digestion sludge (ADS) samples. A total of 181 ARG subtypes belonging to 22 ARG types were broadly detected, and the ARG abundances in the AS samples were 1.3-2.0 orders of magnitude higher than in the ADS samples. Multidrug and bacitracin resistance genes were the predominant ARG types in AS samples, followed by ARGs against sulfonamide, tetracycline, and ß-lactam. However, the composition of ARG types in ADS samples was significantly changed. The abundance of multidrug and ß-lactam resistance genes was drastically reduced in the ADS samples. The resistance genes of MLS were the predominant, followed by ARGs against sulfonamide and tetracycline in the ADS samples. In addition, plasmids were the dominant MGEs in the AS samples, while integrons (intI1) were the dominant MGEs in the ADS samples. These results provide valuable information regarding the prevalence of ARG types and MGEs and the difference patterns between the AS and ADS systems.

Methane-based denitrification kinetics and syntrophy in a membrane biofilm reactor at low methane pressure.

A methane-based membrane biofilm reactor (MBfR) was assessed for a tertiary nitrogen removal process in domestic wastewater treatment. To mitigate effluent dissolved methane concentrations, the MBfR was operated with a 20% methane mixing ratio and a low pressure of 0.003 atm. The nitrate concentration was reduced from 20 to 4 mg/L with a low methane concentration of 3.3 mg/L in the effluent at 4 h hydraulic retention time (HRT). An in situ dissolved oxygen sensor showed a concentration of 0.045 mg/L in the MBfR, demonstrating methane oxidation under hypoxic conditions. Both 16S rRNA gene sequencing and metagenomic analysis identified bacteria capable of oxidation of methane coupled to denitrification (Methylocystis), whereas other bacteria were implicated in either methane oxidation (Methylococcus) or nitrate reduction (Escherichia). Reduced genetic potential for nitrate reduction to nitrite at a shorter HRT coincided with a decreased efficiency of denitrification, suggesting rate limitation by this initial step of denitrification. Genes encoding nitrite reduction to dinitrogen were at similar relative abundance under both HRT conditions. Our results provide mechanistic evidence for microbial syntrophy between aerobic methanotrophs and denitrifiers in methane-fed MBfRs operated under varying HRTs, with important implications for novel biological nitrogen removal to dilute wastewater.

The capacity of wastewater treatment plants drives bacterial community structure and its assembly.

Bacterial communities in wastewater treatment plants (WWTPs) affect plant functionality through their role in the removal of pollutants from wastewater. Bacterial communities vary extensively based on plant operating conditions and influent characteristics. The capacity of WWTPs can also affect the bacterial community via variations in the organic or nutrient composition of the influent. Despite the importance considering capacity, the characteristics that control bacterial community assembly are largely unknown. In this study, we discovered that bacterial communities in WWTPs in Korea and Vietnam, which differ remarkably in capacity, exhibit unique structures and interactions that are governed mainly by the capacity of WWTPs. Bacterial communities were analysed using 16S rRNA gene sequencing and exhibited clear differences between the two regions, with these differences being most pronounced in activated sludge. We found that capacity contributed the most to bacterial interactions and community structure, whereas other factors had less impact. Co-occurrence network analysis showed that microorganisms from high-capacity WWTPs are more interrelated than those from low-capacity WWTPs, which corresponds to the tighter clustering of bacterial communities in Korea. These results will contribute to the understanding of bacterial community assembly in activated sludge processing.

Bacillus-Dominant Airborne Bacterial Communities Identified During Asian Dust Events.

Asian dust (AD) events have received significant attention due to their adverse effects on ecosystems and human health. However, detailed information about airborne pathogens associated with AD events is limited. This study monitored airborne bacterial communities and identified AD-specific bacteria and the potential hazards associated with these bacteria during AD events. Over a 33-month period, 40 air samples were collected under normal atmospheric conditions (non-AD events; n = 34) and during AD events (n = 6). The airborne bacterial communities in the air samples collected during non-AD events (non-AD sample) and AD events (AD sample) were evaluated using both culture-dependent and culture-independent methods. The bacterial diversity increased significantly, along with the 16S rRNA gene copy number, in AD samples (p < 0.05) and was positively correlated with PM10 concentration. High throughput sequencing of the 16S rRNA gene revealed that the relative abundance of the phylum Firmicutes increased substantially in AD samples (44.3 ± 5.0%) compared with non-AD samples (27.8 ± 4.3%). Within the phylum Firmicutes, AD samples included a greater abundance of Bacillus species (almost 23.8%) than non-AD samples (almost 13.3%). Both culture-dependent and culture-independent methods detected common predominant species closely related to Bacillus cereus during AD events. Subsequent multilocus sequence typing (MLST) and enterotoxin gene assays confirmed the presence of virulence factors in B. cereus isolates from AD samples. Furthermore, the abundance of bceT, encoding enterotoxin in B. cereus, was significantly higher in AD samples (p < 0.05). The systematic characterization of airborne bacterial communities in AD samples in this study suggests that B. cereus pose risks to public health.

Classification and Regression Tree Approach for Prediction of Potential Hazards of Urban Airborne Bacteria during Asian Dust Events.

Despite progress in monitoring and modeling Asian dust (AD) events, real-time public hazard prediction based on biological evidence during AD events remains a challenge. Herein, both a classification and regression tree (CART) and multiple linear regression (MLR) were applied to assess the applicability of prediction for potential urban airborne bacterial hazards during AD events using metagenomic analysis and real-time qPCR. In the present work, Bacillus cereus was screened as a potential pathogenic candidate and positively correlated with PM10 concentration (p < 0.05). Additionally, detection of the bceT gene with qPCR, which codes for an enterotoxin in B. cereus, was significantly increased during AD events (p < 0.05). The CART approach more successfully predicted potential airborne bacterial hazards with a relatively high coefficient of determination (R2) and small bias, with the smallest root mean square error (RMSE) and mean absolute error (MAE) compared to the MLR approach. Regression tree analyses from the CART model showed that the PM10 concentration, from 78.4 µg/m3 to 92.2 µg/m3, is an important atmospheric parameter that significantly affects the potential airborne bacterial hazard during AD events. The results show that the CART approach may be useful to effectively derive a predictive understanding of potential airborne bacterial hazards during AD events and thus has a possible for improving decision-making tools for environmental policies associated with air pollution and public health.

A comparison study of the potential risks induced in arable land and forest soils by carcass-derived pollutants.

Improper decisions concerning animal carcass disposal sites pose grave threats to environmental biosecurity. However, only a few studies have focused on the effects of different land-use types on the composition of carcass-derived pollutants and microbial responses to the disturbances. This study was conducted using soil microcosms with minced pork built from arable land and forest soils for 5 weeks. To compare the risk induced from different land-use types by carcass burial, the soil properties, the microbial community, and multiple-antibiotic-resistant bacteria were evaluated for microcosm containing 0, 1.5 and 7.5 g of minced pork. The abiotic properties, including pH, organic carbon, nitrogen and phosphorus compounds, significantly increased, regardless of the land-use types and applied load masses. The microbial diversity indices of the forest soil were reduced, whereas those of the arable land remained relatively stable. The disturbances produced from carcass-derived pollutants altered the bacterial community structures differently for the different land-use types. The treatment increased multiple-antibiotic-resistant bacteria in the both soil samples, although the increase in the forest soil was significantly less compared to the arable land soils.

Short-term Effects of Great Cormorant Droppings on Water Quality and Microbial Community of an Artificial Agricultural Reservoir.

Agricultural reservoirs are established to improve the management of water resources. Waterbirds in protected waters have become a nuisance, however, as nutrients from fecal deposits transported by the waterbirds have served to severely deteriorate water quality. Despite the importance of clean water resources, the microecology of small agricultural reservoirs regularly colonized by transitory waterbirds are seldom reviewed. To improve our understanding of the influence of waterbirds on small bodies of water, a microcosm study was conducted using water and sediment from an agricultural reservoir inhabited by 300 to 500 great cormorants. Temporal changes in total nitrogen, total phosphorous, chemical oxygen demand, NH-N, PO-P, and chlorophyll-a concentrations, in addition to the microbial community, were evaluated for microcosms containing 0, 0.5, 1.0, and 5.0 g of feces collected from a great cormorant colony. Chemical analysis of the water microcosm revealed that all microcosms showed both immediate and prolonged increases in nutrients due to the addition of feces. Additionally, a mere 0.5 g of feces doubled the concentration of chlorophyll-a from 2.1 ± 0.99 to 5.2 ± 1.1 µg L within 1 mo. Nonmetric multidimensional scaling of the microbial community structure revealed disturbances in both water and sediment microcosms. Disturbances to the microbial community in the water microcosm were significant only when 5.0 g of feces was added; however, disturbances to sediment microbial communities were induced by a smaller mass of feces. These results confirm the short-term water quality impairment and shift in microbial community structure caused by waterbird droppings and bird colony surface runoff in an agricultural reservoir.