Plants, fungi, bacteria and protozoa are highly interconnected in constructed wetlands. These heterogeneous groups of organisms constitute a single system with complex internal trophic interactions. Thus, the joint activity of micro- and macroorganisms in constructed wetlands provides highly efficient wastewater treatment: both nutrients and complex organic substances can be effectively removed in branched trophic chains. The bacterial community of constructed wetlands has recently received much attention, while the fungal component remains less studied, particularly saprotrophic fungi. This paper reveals a taxonomic analysis of the cultivated saprotrophic fungi combined with the bacterial community in vertical flow constructed wetlands (VSCWs) operated by the Azoé-NP^® process. These systems have unique features to affect the microbial community, which results in a high treatment efficiency and nitrogen removal. There are very few studies of saprotrophic fungi in VFCWs, while this work shows their abundance and diversity in VFCWs. We found 62 species of cultivated microscopic fungi and described the taxonomic composition of bacterial and fungal community at all wastewater treatment stages. In the studied VFCWs, we identified the species of micromycetes, which proved effective in the removal of contaminants. The data obtained can provide a deeper insight into the characteristics of Azoé-NP^® systems and the treatment processes occurring in constructed wetlands. Full article

Tonle Sap Lake is the largest freshwater lake in Southeast Asia, and it is regarded as one of the most biodiverse freshwater ecosystems in the world. Studies concerning aquatic cellulolytic bacteria from Tonle Sap Lake remain scarce. Cellulolytic bacteria and their cellulases play a vital role in the biogeochemical cycles of lake environments, and their application in biotechnological industries is likewise an important component of their usage. This study aimed to assess the isolation, genetic identification, bioinformatic analyses, and activity characterization of aquatic cellulolytic bacteria. The cellulolytic bacteria isolated from sedimentary water samples in the littoral zone of the lake belong to the genera Aeromonas, Bacillus, and Exiguobacterium. Several isolated aquatic bacteria were designated as rare cellulolytic microbes. Remarkably, B. mojavensis strain REP303 was initially evidenced by the aquatic cellulolytic bacterium in freshwater lake ecosystems. It was considered a highly active cellulolytic bacterium capable of creating a complete cellulase system involving endoglucanase, exoglucanase, and β-glucosidase. The encoded endoglucanase belongs to the glycosyl hydrolase family 5 (GH5), with a carboxymethylcellulase (CMCase) activity of 3.97 ± 0.05 U/mL. The optimum temperature and pH for CMCase activity were determined to be 50 °C at a pH of 7.0, with a stability range of 25–55 °C at a neutral pH of 7.0–8.0. The CMCase activity was enhanced significantly by Mn²⁺ and was inhibited considerably by EDTA and ethyl-acetate. In conclusion, this study is the first to report data concerning aquatic cellulolytic bacteria isolated from the littoral zone of Tonle Sap Lake. A novel strain of isolated cellulolytic B. mojavensis could be applied in various cellulose-based industries. Full article

Polyaluminium chloride (PAC) has been widely used as a chemical coagulant in water treatment. However, little is known about the impact of PAC performance on the microbial community in sediments. In this study, the archaeal, bacterial, and fungal communities in urban river sediments with and without PAC treatment were investigated. Prokaryotic diversity decreased at the PAC addition site (A2) and increased along with the river flow (from A3 to A4), while eukaryotic diversity was the opposite. The abundance of core microbiota showed a similar trend. For example, the dominant Proteobacteria presented the highest relative abundance in A1 (26.8%) and the lowest in A2 (15.3%), followed by A3 (17.5%) and A4 (23.0%). In contrast, Rozellomycota was more dominant in A2 (56.6%) and A3 (58.1%) than in A1 (6.2%) and A4 (16.3%). Salinity, total dissolved solids, and metal contents were identified as the key physicochemical factors affecting the assembly of core microorganisms. The predicted functions of archaea and fungi were mainly divided into methane cycling and saprotrophic nutrition, respectively, while bacterial function was more diversified. The above findings are helpful to enhance our understanding of microorganism response to PAC and have significance for water treatment within the framework of microecology. Full article

The occurrence of microbial communities harboring antibiotic resistance bacteria and antibiotic resistance genes in the drinking water distribution system pose a significant threat to the aquatic ecosystem and to public health, especially in developing countries. In this study, we have used next-generation sequencing technology to explore bacterial community diversity and the abundance of antibiotic resistance genes in biofilms collected from the drinking water distribution system of Peshawar, the capital city of the Khyber Pakhtunkhwa province of Pakistan. The results showed that Proteobacteria were the most abundant phyla (89.79%) in all biofilm samples, followed by Bacteroidetes (3.48%) and Actinobacteria (2.79%). At genus level, Pseudomonas was the most common (22.45%) in all biofilm samples. Overall, bacterial diversity and richness was higher in biofilm samples collected from the consumer end than the source site. Bacterial diversity was also dependent on the piping material (GI vs. PVC) and water supply (direct vs. indirect). Functional annotation reveals a differential abundance of common metabolic pathways at source and consumer end. Resistome analysis revealed a prevalence of resistance genes against 12 classes of antibiotics in all samples with macrolides resistance being the commonest at the consumer end (42.1%) and fluoroquinolone resistance at the source end (24%). To our knowledge, this is the first study that provides new insight and evidence into the microbial community diversity and antibiotic resistance in the drinking water supply system of Peshawar. These findings may ultimately help the authorities to design and implement effective strategies for controlling biofilms and ensuring a continuous supply of safe drinking water to the community. Full article

The extensive and random application of major organic pollutants, mainly pesticides, threatens ecosystems and human health. The present study was conducted to isolate and identify microorganisms from some water resources contaminated with pesticides. We investigated the ability of the identified microbes to grow in water spiked with dimethoate and methomyl. We also evaluated the potential effect of the identified microbial isolates on dimethoate and methomyl biodegradation in water. In addition, the total detoxification of dimethoate and methomyl residues in water after treatment with the most effective microbial isolates was confirmed using toxicity tests and analyzing biochemical parameters and histopathological changes in the kidney and liver of treated rats. The microbial isolates were identified as Xanthomonas campestris pv. Translucens and Aspergillus fumigates. Results showed that X. campestris pv. Translucens and A. fumigatus grow in media supplemented with dimethoate and methomyl faster than in other media without both pesticides. About 97.8% and 91.2% of dimethoate and 95% and 87.8% of methomyl (initial concentration of both 5 mg L⁻¹) were biodegraded within 32 days of incubation with X. campestris pv. Translucens and A. fumigatus, respectively. There was no remaining toxicity in rats treated with dimethoate- and methomyl-contaminated water with respect to biochemical parameters and histopathological changes. Collectively, the identified bacterial isolate showed high potential for the complete degradation of dimethoate and methomyl residues in water. Full article

Nitrogen is one of the essential elements limiting growth in aquatic environments. Being primarily of anthropogenic origin, it exerts negative impacts on freshwater ecosystems. The present study was carried out at the nitrate-vulnerable zone within the alluvial aquifer of the large lowland Drava River. The main aim was to investigate the ecosystem’s functionality by characterizing the bacterial and phytoplankton diversity of a small inactive gravel pit by using interdisciplinary approaches. The phytoplankton community was investigated via traditional microscopy analyses and environmental DNA (eDNA) metabarcoding, while the bacterial community was investigated by a molecular approach (eDNA). Variations in the algal and bacterial community structure indicated a strong correlation with nitrogen compounds. Summer samples were characterized by a high abundance of bloom-forming Cyanobacteria. Following the cyanobacterial breakdown in the colder winter period, Bacillariophyceae and Actinobacteriota became dominant groups. Changes in microbial composition indicated a strong correlation between N forms and algal and bacterial communities. According to the nitrogen dynamics in the alluvial aquifer, we emphasize the importance of small water bodies as potential buffer zones to anthropogenic nitrogen pressures and sentinels of the disturbances displayed as algal blooms within larger freshwater systems. Full article

The plankton radiolarian community was investigated in the spring season during the two-month cruise ‘Shiyan1’ (10 April–13 May 2014) in the Eastern Indian Ocean. This is the first comprehensive plankton tow study to be carried out from 44 sampling stations across the entire area (80.00°–96.10° E, 10.08° N–6.00° S) of the Eastern Indian Ocean. The plankton tow samples were collected from a vertical haul from a depth 200 m to the surface. During the cruise, conductivity–temperature–depth (CTD) measurements were taken of temperature, salinity and chlorophyll a from the surface to 200 m depth. Shannon–Wiener’s diversity index (H’) and the dominance index (Y) were used to analyze community structure. There was a total of 168 plankton species, composed of Acantharia, Phaeodaria, Polycystina, Collodaria and Taxopodida (monospecific—Sticholonche zanclea, Hertwig is the only recognized species). Hence, it included both celestine-based and siliceous organisms, which are also described here for the first time from this region. Total radiolarians ranged from 5 to 5500 ind/m⁻³, dominated by co-occurrences of Sphaerozoum punctatum and Stichonche zanclea species at the south-equator zone (SEQ)-transect 80° E and equator zone (EQ)-transect Lati-0. The possible environmental variables were tested through RDA analysis; although no result was obtained for the full species dataset, the samples from the equatorial transect related strongly to mixed-layer chlorophyll a concentration and those of a north–south transect to surface silicate concentrations or mixed-layer nitrate were significantly correlated (p < 0.01) to the radiolarian community. Our results indicate that the silicate and chlorophyll-a concentrations are the two major factors affecting the radiolarian distribution along two of the investigated transects (southern equator and equator) in the study area. Full article

Planktonic eukaryotes are widespread in aquatic ecosystems, and the study of their community composition and driving factors is of great significance to protecting and maintaining the balance of these ecosystems. This study evaluates five typical ecological sites in the Danjiangkou Reservoir—the water source for the project. This was done to comprehensively understand the composition of Danjiangkou Reservoir planktonic eukaryotes, and ensure the ecological balance of the water source for the South-to-North Water Diversion Project. The diversity of the planktonic eukaryotes in surface water and the factors driving changes in their abundance are analyzed with an 18S ribosomal DNA sequencing approach. Monitoring shows that the Danjiangkou Reservoir has good water quality. The Danjiangkou Reservoir planktonic eukaryote community is mainly composed of 11 phyla, of which Cryptomonadales is dominant, accounting for an average percentage of 65.19% of the community (47.2–84.90%). LEFSe analysis shows significant differences among samples in the abundances of 13 phyla, 20 classes, 23 orders, 26 families, and 27 genera, and there are also significant differences in the diversity of planktonic eukaryotes at different temporal and spatial scales. Redundancy analysis (RDA) show that water temperature, DO, SD, TN, and Chla are significant factors that affect the composition of the planktonic eukaryote community. Spearman rank correlation analysis combined with taxonomic difference analysis shows that Kathablepharidae and Choanoflagellida are not sensitive to environmental or physicochemical factors and that the interannual variations in their abundance are not significant. Network analysis shows that Protalveolata, Basidiomycota, P1-31, Bicosoecida, and Ochrophyta represent important nodes in the single-factor network, while Chytridiomycota, P1-31, Cryptomycota, Ochrophyta, Ichthyosporea, Bicosoecida, Protalveolata, and physicochemical factors (ORP, TN, WT, DO, SD, NH₃-N, and NO₃-N) represent important nodes in the two-factor network. Full article

Fungi are an important, yet often, neglected component of the aquatic microflora, and is responsible for primary decomposition and further processing of organic matter. By comparison, the ecological roles of terrestrial fungi have been well-studied, but the diversity and function of fungi that populate aquatic environments remain poorly understood. Here, the impact of urbanization on fungal diversity and community composition in the canal system of Suzhou was assessed by sequencing the internal transcribed spacer 1 (ITS1) region of the rRNA operon. It was amplified from environmental DNA that has been extracted from water samples and pre-deployed decomposing leaves collected from nine sampling locations (high, medium and low urbanization) over two seasons. The fungal diversity and community composition were determined by bioinformatic analysis of the large DNA sequence datasets generated to identify operational taxonomic units (OTUs) for phylogenetic assignment; over 1 million amplicons were sequenced from 36 samples. The alpha-diversity estimates showed high differences in fungal diversity between water and leaf samples, and winter versus summer. Higher numbers of fungal OTUs were identified in both water and leaf samples collected in the summer, and fungal diversity was also generally higher in water than on colonized leaves in both seasons. The fungal community on leaves was usually dominated by Ascomycetes, especially in winter, while water samples contained more diversity at phylum level with Chytridiomycetes often prominent, particularly in summer. At a genus level, a very high relative abundance of Alternaria on leaves was observed in winter at all locations, in contrast to very low abundance of this genus across all water samples. Fungal community composition also varied between sampling locations (i.e., urbanization); in cluster analysis, samples from high urbanization locations formed a distinct cluster, with medium and low urbanization samples clustering together or in some instances, separately. Redundancy analysis shed further light on the relationships between variation in fungal community composition and water physico-chemical properties. Fungal community diversity variation and correlation with different parameters is discussed in detail, but overall, the influence of season outweighed that of urbanization. This study is significant in cataloguing the impact of urbanization on fungal diversity to inform future restoration of urban canal systems on the importance of protecting the natural aquatic fungal flora. Full article

Aquatic macrophytes rhizosphere are biogeochemical cycling hotspots in freshwater ecosystems. However, little is known regarding the effect of aquatic macrophytes on bacterial community and interactions in the riparian zones. We investigated the bacterial community composition and network structures along a gradient of the riparian zone as follows: The supralittoral and eulittoral zones with Phragmites australis, the eulittoral and infralittoral zones without P. australi. The bacterial communities in the four zones differed significantly based on taxonomic dissimilarity, but the two zones with P. australis exhibited phylogenetic closeness of the bacterial communities. The characteristics of the bacterial networks, such as connectivity, modularity, and topological roles of OTUs, were totally different between the P. australis and non-P. australis zones. Some bacterial phyla enriched in the P. australis zones were found to be putative keystone taxa in the networks, which might be involved in the regulation of bacterial interactions and plant growth. Moreover, the hydrological regime and particle size were shown to be determinants of the bacterial community and network structures in the riparian zones. In summary, our results show that the role of P. australis and local factors are crucial for constructing bacterial community and interactions in the riparian zones of lakes. Full article

The effects of fish cannery discharge (FCD) on bacteria in marine coastal sediments were investigated. Redox potentials were measured, and granulometry was determined by wet ASTM sieving, and with the Sedigraph method. Prokaryotic abundance (PA) was determined by epifluorescence microscopy (DAPI staining), and faecal indicator bacteria (FIB) enumerated with the multiple test tube and most probable number method. Total lipids were determined gravimetrically, and sterols analysed by GC/MSD. Bacterial community composition was determined after total DNA isolation, Illumina MiSeq amplification, and SILVAngs processing pipeline. The FCD was rich in lipids, heterotrophic prokaryotes and FIB. The bacterial community of the FCD was dominated by Firmicutes and Gammaproteobacteria and many potentially pathogenic bacteria. Highly porosusgravelly sands clogged with fish remains transitioned to less permeable sandy muds away from the FCD. All sediments were anoxic with extremely negative potentials around the outfall. High surface PA and FIB spread 300 m from the outfall. Gammaproteobacteria and Deltaproteobacteria appeared in all sediments. Sulfurovum and Anaerolineaceae characterized the most polluted locations where gammaproteobacterial Woeseiaceae/JTB255 marine benthic group declined. Gammaproteobacteria and Bacteroidetes characterized surface sediments, while Chloroflexi and Deltaproteobacteria prevailed in deeper layers. The FCD enriched sediments in lipids and allochthonous bacteria degrading sanitary quality, lowering the permeability, redox potential, and bacterial diversity. Full article

The Southern Adriatic Sea is a dynamic region under the influence of diverse physical forces that modify sea water properties as well as plankton dynamics, abundance, and distribution in an intricate way. The most pronounced being: winter vertical convection, lateral exchanges between coastal and open sea waters, and the ingression of water masses of different properties into the Adriatic. We investigated the distribution and abundance of tintinnid species in this dynamic environment in pre- and post-winter conditions in 2015/2016. A strong ingression of the saline Levantine Intermediate Water, supported by the cyclonic mode of the North Ionian Gyre in 2015 and 2016, in December was associated with a high diversity of oceanic species. An unusual spatial distribution of neritic-estuarine species Codonellopsis schabi was observed in deeper layers along the analyzed transect, which emphasizes the strong influence of physical processes on deep water biology in the South Adriatic. A shift of population toward greater depths (mesopelagic) and modification of deep sea community structure was recorded in April as a consequence of the winter convection-driven sinking of tintinnids. Our findings indicate that tintinnid abundance and composition is heavily influenced by physical conditions and they are good indicators of the impact of physical forces, including climate changes, on marine environment. Full article

Virus-like particles (VLPs) are thought to increase the dissolved organic carbon by releasing the contents of the host cell, which, in turn, can affect bacterial growth in natural aquatic environments. Yet, experimental tests have shown that the effect of VLPs on the bacterial growth rate at different depths has seldom been studied. Bacteria–VLP interaction and the effect of VLPs on bacterial growth rate in the sunlit surface (3 m) and dark, deep ocean (130 m) environments were first explored at a test site in the southern East China Sea of the northwest Pacific. Our experimental results indicated that bacterial and virus-like particle (VLP) abundance decreased with depth from 0.8 ± 0.3 × 10⁵ cells mL⁻¹ and 1.8 ± 0.4 × 10⁶ VLPs mL⁻¹ at 3 m to 0.4 ± 0.1 × 10⁵ cells mL⁻¹ and 1.4 ± 0.3 × 10⁶ VLPs mL⁻¹ at 130 m. We found that the abundance of VLPs to Bacteria Ratio (VBR) in the dark deep ocean (VBR = 35.0 ± 5.6) was higher than in the sunlit surface environment (VBR = 22.5 ± 2.1). The most interesting finding is that in the dark, deep ocean region the bacterial growth rate in the presence of VLPs was higher (0.05 h⁻¹) than that in virus-diluted treatments (0.01 h⁻¹). However, there was no significant difference in the bacterial growth rates between the treatments in the sunlit surface ocean region. Deep-sea ecosystems are dark and extreme environments that lack primary photosynthetic production, and our estimates imply that the contribution of recycled carbon by viral lysis is highly significant for bacterial growth in the dark, deep ocean environment. Further work for more study sites is needed to identify the relationship of VLPs and their hosts to enable us to understand the role of VLPs at different depths in the East China Sea. Full article