Metatranscriptomics analysis of mangroves habitats around Mauritius.

Mangroves are unique but endangered coastal ecosystems that play a vital role in the tropical and subtropical environments. Mauritius has two species of mangroves, Bruguiera gymnorrhiza (L.) Lam. and Rhizophora mucronata Lam., growing along its coast. The mangrove rhizosphere harbours a diverse microbial community and the use of RNA-sequencing can reveal both the taxonomic composition and active biochemical functions of the complex microbial community. Metatranscriptomic study was carried out by comparing the microbial community of rhizosphere microbiomes sediments from the two mangroves species. The study also included a comparison between a natural and a man grown mangrove microbiome. Overall, samples showed predominance by Proteobacteria, Bacteroidetes and Firmicutes, with high abundance of sulphate reducers, nitrogen reducers and methanogens. Significant difference was, however, noted at both taxonomic and functional levels among the mangroves species. The data also indicate that the microbial core involved in methane, nitrogen, and sulphur metabolism consisted mainly of Burkholderiaceae, Planctomycetaceae, Rhodobacteraceae, and Desulfobacteraceae. Also, genes encoding enzymes involved in carbon cycling, the metabolism of nitrogen, methane and sulphur were dominant in the rhizosphere of the natural mangrove ecosystem. To our knowledge, this is a first metatranscriptomic study on the microbiome of mangroves in the Mauritius, and our results provide the first insights in the range of functions and microbial diversity of the local mangrove species.

Early bacterial biofilm colonizers in the coastal waters of Mauritius

Background: The past years have witnessed a growing number of researches in biofilm forming communities due to their environmental and maritime industrial implications. To gain a better understanding of the early bacterial biofilm community, microfiber nets were used as artificial substrates and incubated for a period of 24 h in Mauritian coastal waters. Next-generation sequencing technologies were employed as a tool for identification of early bacterial communities. Different genes associated with quorum sensing and cell motility were further investigated. Results: Proteobacteria were identified as the predominant bacterial microorganisms in the biofilm within the 24 h incubation, of which members affiliated to Gammaproteobacteria, Alphaproteobacteria and Betaproteobacteria were among the most abundant classes. The biofilm community patterns were also driven by phyla such as Firmicutes, Bacteroidetes, Chloroflexi, Actinobacteria and Verrucomicrobia. The functional analysis based on KEGG classification indicated high activities in carbohydrate, lipid and amino acids metabolism. Different genes encoding for luxI, lasI, agrC, flhA, cheA and cheB showed the involvement of microbial members in quorum sensing and cell motility. Conclusion: This study provides both an insight on the early bacterial biofilm forming community and the genes involved in quorum sensing and bacterial cell motility.