Banat, I. M. | bioRxiv Science

bioRxiv2022

Biological and synthetic surfactant exposure increase anti-microbial gene occurrence in a freshwater mixed microbial biofilm environment

Aquatic habitats are particularly susceptible to chemical pollution from domestic, agricultural, and industrial sources. Antimicrobials are commonly used in medical and industrial environments to reduce harmful bacteria and biofilms. This has led to the rapid increase in the prevalence of antimicrobial resistant (AMR) genes. Alternate remedies to fight pathogenic bacteria and biofilms are in development including synthetic and biological surfactants such as sodium dodecyl sulphate (SDS) and rhamnolipids respectively. In the aquatic environment these surfactants are present as pollutants with potential to affect biofilm formation and AMR gene occurrence; however, there is limited research showing the actual environmental impact of such exposure. We tested the effects of rhamnolipid and SDS on natural aquatic biofilms in a freshwater stream in Northern Ireland. We grew biofilms on contaminant exposure substrata deployed within the stream over four weeks, and then carried out shotgun sequencing to determine microbial community composition, through 16s rRNA analyses (64,678 classifiable reads identified), and AMR gene occurrence (81 instances of AMR genes over 9 AMR gene classes) through a metagenomic analysis. There were no significant changes in community composition within all systems; however, biofilm exposed to rhamnolipid had a greater number of unique taxa as compared to our SDS treatments and controls. AMR gene prevalence was higher in surfactant-treated biofilms, with biofilm exposed to rhamnolipids having the highest presence of AMR genes and classes compared to the control or SDS treatments, in which genes encoding for rifampin resistance were detected. Our results suggest that the presence of rhamnolipid, and to a lesser extent SDS, encourages an increase in the prevalence of AMR genes in biofilms produced in mixed use water bodies.

microbiology↗

bioRxiv2021

Identification of the Park Grass Experiment soil metaproteome

The Park Grass Experiment, is an international reference soil with an impressive repository of temperate grassland (meta)data, however, it still lacks documentation of its soil metaproteome. The identification of these proteins is crucial to our understanding of soil ecology and their role in major biogeochemical processes. However, protein extraction can be fraught with technical difficulties including co-extraction of humic material and lack of a compatible databases to identify proteins. To address these issues, we used two compatible soil protein extraction techniques on Park Grass soil, one that removed humic material, namely a modified freeze-dry, heat/thaw/phenol/chloroform (HTPC) method and another which co-extracted humic material, namely an established surfactant method. Proteins were identified by matching mass spectra against a tailored Park Grass metagenome database. We identified a broad range of proteins from Park Grass soil, mainly in "protein metabolism", "membrane transport", "carbohydrate metabolism", "respiration" and "ribosome associated" categories, enabling reconstitution of specific processes active in grassland soil. The soil microbiome was dominated by Proteobacteria, Actinobacteria, Acidobacteria and Firmicutes at phyla level and Bradyrhizobium, Rhizobium, Acidobacteria, Streptomyces and Pseudolabrys at genus level. Further functional enrichment analysis enabled us to identify many proteins in regulatory and signalling networks of key biogeochemical cycles such as the nitrogen cycle. The combined extraction methods connected previous Park Grass metadata with the metaproteome, biogeochemistry and soil ecology. This could provide a base on which future targeted studies of important soil processes and their regulation can be built. HighlightsO_LIParallel protein extraction methods identified 1266 proteins from Park Grass soil C_LIO_LIProteome was enriched in ribosomal and respiration proteins for the surfactant extraction method and nitrogen associated proteins for the modified phenol/chloroform method C_LIO_LIIdentification of regulatory and signalling proteins in key biogeochemical cycles C_LIO_LILinks metaproteome to microbiome, biogeochemical cycles and Park Grass metadata C_LIO_LIProvides baseline for future targeted studies C_LI

biochemistry↗