Microbial source tracking identifies sources of contamination for a river flowing into the Yellow Sea

Advances in chemical and microbial source tracking (MST) of fecal pollution in coastal waters: a review

Coastal waters are the ultimate destination for both point and non-point sources of contamination. The uncontrolled dicharge of fecal waste into the ocean harms natural resources, marine life, and poses health risks to humans. Regular monitoring of coastal water quality and source tracking is important to prevent disease outbreaks. This review discusses all the fecal source tracking (FST) methods, ranging from traditional enumeration techniques to recent next-generation sequencing approaches, in the light of application on coastal waters. The advantages and disadvantages of the individual markers, method comparisons based on performance, correlation of marker with fecal indicator bacteria, and stability under waste water treatment and in field applications are mainly focused on enlightening the "tool box" approach for the marine environment.

Limited Microbial Contribution in Salt Lake Sediment and Water to Each Other's Microbial Communities

Climate change and human activities have led to frequent exchanges of sedimentary and aquatic microorganisms in lakes. However, the ability of these microorganisms to survive in their respective habitats between saline lake sediment and water remains unclear. In this study, we investigated microbial sources and community composition and metabolic functions in sediments and water in Yuncheng Salt Lake using a combination of source tracking and Illumina MiSeq sequencing. The results showed that 0.10-8.47% of the microbial communities in the sediment came from the corresponding water bodies, while 0.12-10.78% of the sedimentary microorganisms contributed to the aquatic microbial populations, and the microbial contributions depended on the salinity difference between sediment and water. Habitat heterogeneity and salinity variations led to the differences in microbial diversity, community composition, and assembly between sediment and water communities. The assembly of sedimentary communities was mainly controlled by stochastic processes (>59%), whereas the assembly of aquatic communities was mainly controlled by deterministic processes (>88%). Furthermore, sediments had a higher potential for metabolic pathways related to specific biogeochemical functions than lake water. These results provide insights into the survival ability of microorganisms and the mechanisms of microbial community assembly under frequent exchange conditions in saline lakes.

The source of microbial transmission influences niche colonization and microbiome development

Early life microbial colonizers shape and support the immature vertebrate immune system. Microbial colonization relies on the vertical route via parental provisioning and the horizontal route via environmental contribution. Vertical transmission is mostly a maternal trait making it hard to determine the source of microbial colonization in order to gain insight into the establishment of the microbial community during crucial development stages. The evolution of unique male pregnancy in pipefishes and seahorses enables the disentanglement of both horizontal and vertical transmission, but also facilitates the differentiation of maternal versus paternal provisioning ranging from egg development, to male pregnancy and early juvenile development. Using 16S rRNA amplicon sequencing and source-tracker analyses, we revealed how the distinct origins of transmission (maternal, paternal and horizontal) shaped the juvenile internal and external microbiome establishment in the broad-nosed pipefish Syngnathus typhle. Our data suggest that transovarial maternal microbial contribution influences the establishment of the juvenile gut microbiome whereas paternal provisioning mainly shapes the juvenile external microbiome. The identification of juvenile key microbes reveals crucial temporal shifts in microbial development and enhances our understanding of microbial transmission routes, colonization dynamics and their impact on lifestyle evolution.

The presence of antibiotic-resistant bacteria at four Norwegian wastewater treatment plants: seasonal and wastewater-source effects

Wastewater treatment plants receive low concentrations of antibiotics. Residual concentrations of antibiotics in the effluent may accelerate the development of antibiotic resistance in the receiving environments. Monitoring of antimicrobial resistance genes (ARGs) in countries with strict regulation of antibiotic use is important in gaining knowledge of how effective these policies are in preventing the emergence of ARGs or whether other strategies are required, for example, at-source treatment of hospital effluents. This study evaluates the presence of certain common resistance genes (bla SHV-1, bla TEM-1, msrA, ermA, ermC, tetM, tetL, tetA, vanA, and vanC) in the influent, sludge, and effluent of four wastewater treatment plants (WWTPs) in the North Jæren region of Norway at two different sampling times (January and May). These WWTPs vary in drainage area and wastewater composition and were selected based on their differing wastewater characteristics. Randomly selected colonies from the activated sludge samples were used to determine the minimum inhibitory concentration (MIC) for ampicillin, vancomycin, and tetracycline. In addition, variations in the bacterial composition of the wastewater were characterized via 16S rRNA sequencing and were analyzed in terms of bacterial host taxa that explain the presence of the ARGs in wastewater. The MIC tests revealed MIC90 values of >128 µg/mL for ampicillin, ≥128 µg/mL for vancomycin, and 32 µg/mL for tetracycline. In addition, the three resistance genes, ermB, tetA, and tetM, that were present in the influent and activated sludge were still present in the effluent. These results indicate that WWTPs represent a direct route into the environment for resistance genes and do not significantly reduce their abundance. Hence, the development of treatment methods for the removal of these genes from WWTPs in the future is of utmost importance.