Bacterial Indicators Are Ubiquitous Members of Pelagic Microbiome in Anthropogenically Impacted Coastal Ecosystem

Coastal zones are exposed to various anthropogenic impacts, such as different types of wastewater pollution, e.g., treated wastewater discharges, leakage from sewage systems, and agricultural and urban runoff. These various inputs can introduce allochthonous organic matter and microbes, including pathogens, into the coastal marine environment. The presence of fecal bacterial indicators in the coastal environment is usually monitored using traditional culture-based methods that, however, fail to detect their uncultured representatives. We have conducted a year-around in situ survey of the pelagic microbiome of the dynamic coastal ecosystem, subjected to different anthropogenic pressures to depict the seasonal and spatial dynamics of traditional and alternative fecal bacterial indicators. To provide an insight into the environmental conditions under which bacterial indicators thrive, a suite of environmental factors and bacterial community dynamics were analyzed concurrently. Analyses of 16S rRNA amplicon sequences revealed that the coastal microbiome was primarily structured by seasonal changes regardless of the distance from the wastewater pollution sources. On the other hand, fecal bacterial indicators were not affected by seasons and accounted for up to 34% of the sequence proportion for a given sample. Even more so, traditional fecal indicator bacteria (Enterobacteriaceae) and alternative wastewater-associated bacteria (Lachnospiraceae, Ruminococcaceae, Arcobacteraceae, Pseudomonadaceae and Vibrionaceae) were part of the core coastal microbiome, i.e., present at all sampling stations. Microbial source tracking and Lagrangian particle tracking, which we employed to assess the potential pollution source, revealed the importance of riverine water as a vector for transmission of allochthonous microbes into the marine system. Further phylogenetic analysis showed that the Arcobacteraceae in our data set was affiliated with the pathogenic Arcobacter cryaerophilus, suggesting that a potential exposure risk for bacterial pathogens in anthropogenically impacted coastal zones remains. We emphasize that molecular analyses combined with statistical and oceanographic models may provide new insights for environmental health assessment and reveal the potential source and presence of microbial indicators, which are otherwise overlooked by a cultivation approach.

Coliphages as a Complementary Tool to Improve the Management of Urban Wastewater Treatments and Minimize Health Risks in Receiving Waters

Even in countries with extensive sanitation systems, outbreaks of waterborne infectious diseases are being reported. Current tendencies, such as the growing concentration of populations in large urban conurbations, climate change, aging of existing infrastructures, and emerging pathogens, indicate that the management of water resources will become increasingly challenging in the near future. In this context, there is an urgent need to control the fate of fecal microorganisms in wastewater to avoid the negative health consequences of releasing treated effluents into surface waters (rivers, lakes, etc.) or marine coastal water. On the other hand, the measurement of bacterial indicators yields insufficient information to gauge the human health risk associated with viral infections. It would therefore seem advisable to include a viral indicator—for example, somatic coliphages—to monitor the functioning of wastewater treatments. As indicated in the studies reviewed herein, the concentrations of somatic coliphages in raw sewage remain consistently high throughout the year worldwide, as occurs with bacterial indicators. The removal process for bacterial indicators and coliphages in traditional sewage treatments is similar, the concentrations in secondary effluents remaining sufficiently high for enumeration, without the need for cumbersome and costly concentration procedures. Additionally, according to the available data on indicator behavior, which is still limited for sewers but abundant for surface waters, coliphages persist longer than bacterial indicators once outside the gut. Based on these data, coliphages can be recommended as indicators to assess the efficiency of wastewater management procedures with the aim of minimizing the health impact of urban wastewater release in surface waters.

Exploring the use of new water quality indicators based on microbial communities

The growing concern for the quality of water in aquatic ecosystems makes it essential to develop new indicators that allow evaluating and predicting their state against anthropogenic impact. Microorganisms are able to reflect quickly changes in their habitat, through both its taxonomic and functional characteristics, and that is why they are in consideration as indicators of environmental quality (*1). The objective of this work was to identify attributes of the composition and functionality of microbial communities, to be evaluated as an indicator of water quality, focusing on emerging pollutants (ECs). For that, ECs and bacterial communities were analyzed along the basins of two coastal lagoons encompassing an anthropogenic gradient, looking for taxonomic and functional indicators. Taxonomic indicators were looked using Illumina sequencing of 16S RNAr gene V4 region followed by identification of amplicon secuence variants (ASVs) and taxonomic annotation. In the case of functional indicators, shotgun sequencing was used added to identification and annotation of open reading frames (ORFs). Clustering techniques were implemented to define groups of sites based on the concentration of different categories of ECs. Then, the indicator value analysis (IndVal) (*2) was performed to identify taxonomic and functional traits that could be used as indicators of those groups. Finally, each sample was assigned to the corresponding group based on the indicators. A first analysis involved the search of taxonomic indicators for all the set of samples including three groups of sites of low, medium and high impact of emerging contamination. It was possible to find indicators with a very high IndVal value for the three groups of samples. All indicators were based on the co-occurrence of three ASVs belonging to several of the most abundant bacteria phyla (Actinobacteria, Bacteroidetes, Cyanobacteria, Planctomycetes, Proteobacteria). The bacterial indicators correctly assigned 100% and 93% of the samples to their corresponding group for streams and lagoons respectively. Then, a comparison between taxonomic and functional indicators using a subset of 41 samples was made, including two groups of samples: high and low-medium impact. Both the taxonomic and functional indicators showed high IndVal values for the high and low impact groups, being the highest in the case of functional genes Table 1. The high impact group was perfectly predicted for both taxonomic and functional indicators. The low-medium impact group was perfectly predicted by the functional indicators and 85% of the samples were correctly assigned by the taxonomic indicators. In conclusion, widespread availability of NGS technology allows for deep characterization of microbial diversity, enabling the use of robust ecological tools. Taking into account the high indval and prediction values, taxonomic and functional bacterial indicators appear as promissory candidates to evaluate for aquatic systems monitoring and conservation strategies.

Microbiological contamination and content of heavy metals in unlined landfill sites of Ulaanbaatar

<p class="abstract"><strong>Background:</strong> The aim of the study was to investigate bacterial and heavy metal pollution in four landfill sites of Ulaanbaatar. Surveyed landfills included closed and currently operating unlined landfills.</p><p class="abstract"><strong>Methods:</strong> In order to sample, we divided each landfill sites into three zones including zone 1: cover soil or in the boundary of the landfill, zone 2: from the boundary of the landfill to hygiene zone (25 м² to 500 м² out of cover soil), zone 3: from hygiene zone to settlement areas and compared the pollution. </p><p class="abstract"><strong>Results:</strong> The titre of <em>Cl. perfringens, </em>presence of <em>Salmonella </em>and total bacteria were not significantly different for landfill sites. The titre of <em>E. coli and </em>the titre of <em>Proteus </em>for industrial landfill site<em> </em>were significantly different than other sites. The titre of <em>E. coli</em> and the titre of <em>Proteus</em> for the zone 1 were significantly different than the zone 3. The presence of <em>Salmonella</em> and the total bacteria for the zone 1 was significantly different than the zone 2 and zone 3. The titre of <em>Cl. perfringens</em> was not significantly different for landfill zones. The bacterial indicators were not significantly different for seasons of the year. Content of heavy metals in soil landfills were Pb 0.1-63 mg/kg, Cr 0.4-5124 mg/kg, Ni 3.2-84 mg/kg, Zn 21.7-776 mg/kg, Cd 0.01-2.8 mg/kg.</p><p class="abstract"><strong>Conclusions:</strong> Microbiological contamination and content of heavy metals in closed unlined landfill are not different from currently operating unlined landfills.</p><p class="abstract"> </p>