Diversity and Distribution of Potential Pathogens and Antibiotic Resistance Genes in Anthropogenic Disturbances Aquatic Environment and Their Relationship with Microbial Indicators

Microbial indicators are often used as alternative indicators of microbial safety in water. However, information regarding the correlation between microbial indicators and ecotoxicological factors such as potential pathogens and antibiotic resistance genes (ARGs) in anthropogenically impacted waters remains highly limited. Combining 16S rRNA and metagenomic sequencing data, we investigated the composition of bacterial community and potential pathogens, ARGs diversity, ARGs host and horizontal gene transfer (HGT) potential in water samples under the influence of different exogenous pollutants in Chaohu Lake basin. The water body that receives a large amount of domestic sewage showed a significant decrease in microbial diversity and a significant enrichment of potential pathogens. A total of 14 main types and 461 subtypes of ARGs were detected in all samples, dominated by multidrug resistance (MDR) efflux pump (53.6%), aminoglycoside (6.0%), fluoroquinolone (5.8%) and polymyxin (5.46%). Host-tracking analysis showed that Escherichia coli and Bacteroides graminisolvens carried a wealth of ARG subtypes. Correlation analysis showed that potential pathogens and some ARG subtypes such as dfrE, sul2, PmrE exhibits significant correlation with indicator bacteria. Overall, next-generation sequencing (NGS) has the ability to conduct preliminary surveys of environmental samples to access potential health risks, thus providing ideas for water resources management.

Solar disinfection of turbid hygiene waters in Lexington, KY, USA

Solar disinfection (SODIS) could be a key to providing a clean, hygiene water for birthing uses, but the recommended climate zone is limited, the microbial indicators are related to gastrointestinal illness and not wound infections. SODIS feasibility was investigated to remove Escherichia coli from turbid water at temperatures less than 50 °C in Lexington, KY. Increasing turbidity from 0 to 200 NTU decreased E. coli inactivation from 5 to 1 log. With the same experimental protocol, more than 4-log inactivation of Staphylococcus aureus and Staphylococcus epidermidis (common human-skin microorganisms related to serious post-partum infections of both mother and child) was achieved at different turbidity levels with a maximum, in-bottle temperature of 49.2 °C after 5.5 h. The thermal inactivation of the bacterial indicators was assessed without UV radiation and turbidity in water at 37 and 47 °C. Skin bacteria were inactivated completely after 9.5 h at 47 °C, but only 58% removal happened for thermo-tolerant E. coli. These results suggest that SODIS application may be expanded geographically to treat water for hygiene purposes. However, as E. coli is also capable of causing wound infections, UV with thermal inactivation may be required to produce safe hygiene water by SODIS outside of recommended latitudes.

Soil Microbial Indicators within Rotations and Tillage Systems

Recent advancements in agricultural metagenomics allow for characterizing microbial indicators of soil health brought on by changes in management decisions, which ultimately affect the soil environment. Field-scale studies investigating the microbial taxa from agricultural experiments are sparse, with none investigating the long-term effect of crop rotation and tillage on microbial indicator species. Therefore, our goal was to determine the effect of rotations (continuous corn, CCC; continuous soybean, SSS; and each phase of a corn-soybean rotation, Cs and Sc) and tillage (no-till, NT; and chisel tillage, T) on the soil microbial community composition following 20 years of management. We found that crop rotation and tillage influence the soil environment by altering key soil properties, such as pH and soil organic matter (SOM). Monoculture corn lowered pH compared to SSS (5.9 vs. 6.9, respectively) but increased SOM (5.4% vs. 4.6%, respectively). Bacterial indicator microbes were categorized into two groups: SOM dependent and acidophile vs. N adverse and neutrophile. Fungi preferred the CCC rotation, characterized by low pH. Archaeal indicators were mainly ammonia oxidizers with species occupying niches at contrasting pHs. Numerous indicator microbes are involved with N cycling due to the fertilizer-rich environment, prone to aquatic or gaseous losses.