Metagenome-Assembled Genome Sequences Recovered from Epilithic River Biofilm in the Tama River, Japan

Draft genome sequences of putatively novel bacteria were assembled from the metagenome of epilithic biofilm samples collected from the Tama River (Tokyo, Japan). The metagenome contains 44,630,724 sequences, 44,792 contigs, and 48% G+C content. Binning resulted in 31 metagenome-assembled genomes (MAGs) with >50% completeness.

Physical properties of epilithic river biofilm as a new lead to perform pollution bioassessments in overseas territories

Chlordecone (CLD) levels measured in the rivers of the French West Indies were among the highest values detected worldwide in freshwater ecosystems, and its contamination is recognised as a severe health, environmental, agricultural, economic, and social issue. In these tropical volcanic islands, rivers show strong originalities as simplified food webs, or numerous amphidromous migrating species, making the bioindication of contaminations a difficult issue. The objective of this study was to search for biological responses to CLD pollution in a spatially fixed and long-lasting component of the rivers in the West Indies: the epilithic biofilm. Physical properties were investigated through complementary analyses: friction, viscosity as well as surface adhesion were analyzed and coupled with measures of biofilm carbon content and exopolymeric substance (EPS) production. Our results have pointed out a mesoscale chemical and physical reactivity of the biofilm that can be correlated with CLD contamination. We were able to demonstrate that epilithic biofilm physical properties can effectively be used to infer freshwater environmental quality of French Antilles rivers. The friction coefficient is reactive to contamination and well correlated to carbon content and EPS production. Monitoring biofilm physical properties could offer many advantages to potential users in terms of effectiveness and ease of use, rather than more complex or time-consuming analyses.

Assessing arsenic bioremediation potential of epilithic biofilms affected by acid-mine drainage

<p>Arsenic is a toxic but naturally abundant metalloid that globally leads to contamination in groundwater and soil, exposing millions of people to cancer and other arsenic-related diseases. In several areas in Northern Italy arsenic in soil and water exceeds law limits (20 mg kg<sup>-1</sup> and 10 mg L<sup>-1</sup>, respectively), due to both the mineralogy of bedrock and former mining activities. The Rio Rosso stream, located in the Anzasca Valley (Piedmont) is heavily affected by an acid mine drainage originated from an abandoned gold mine. Arsenic, together with other heavy metals, is transferred by the stream to the surrounding area. The stream is characterized by the presence of an extensive reddish epilithic biofilm at the opening of the mine and on the whole contaminated waterbed.</p> <p>The aim of this study was to characterize the mechanisms allowing the biotic fraction of this biofilm to cope with extreme arsenic concentrations. The composition and functionality of the microbial communities constituting the epilithic biofilms sampled in the close proximity and downstream the mine were unraveled by 16S rRNA genes and shotgun Illumina sequencing in relation to the extreme physico-chemical parameters. In parallel, autotrophic and heterotrophic microbial populations were characterized <em>in vivo</em> by enrichment cultivation and isolated strains were tested for their ability to perform arsenic redox transformation.</p> <p>Preliminary analyses indicated that the biofilm accumulated arsenic in the order of 6 · 10<sup>3</sup> mg kg<sup>-1</sup>, in contrast to 0.14 mg L<sup>-1</sup>, measured in the surrounding water. The main chemical parameter affecting the composition of the microbial community was the pH, being 2 next to the mine and 6.7 in the downstream sampling point. In both sampling sites iron- and sulfur-cycling microorganisms were retrieved by both cultivation and molecular methods. However, the diversity of the microbial community living next to the mine was significantly lower with respect to the community developed downstream. In the latter, autotrophic <em>Cyanobacteria</em> belonging to the species <em>Tychonema</em> were the dominant taxa. A complete arsenic cycle was shown to occur, with heterotrophic bacteria mainly responsible for arsenate reduction and autotrophic bacteria performing arsenite  oxidation.</p> <p>These observations indicate that the epilithic biofilm living in the Rio Rosso stream represents a peculiar ecosystem where microorganisms cope with metalloid toxicity likely using diverse mechanisms. Such microbial metabolic properties might be exploited in bioremediation strategies applied in arsenic-contaminated environments.</p>