METHANESULFONATE-DEGRADING BACTERIA IN THE ENVIRONMENT: A MOLECULAR APPROACH
The ocean constitutes a large reservoir of sulfur and hence the transfer of sulfur volatile compounds from seawater to the atmosphere represents a key process in the global sulfur cycle. Dimethylsulfide (DMS), produced in the marine environment by the degradation of microalgal and cyanobacterial biomass, is the main component of marine emissions of volatile sulfur, contributing an estimated 98% of the atmospheric DMS. Under the impact of solar radiation and oxidative reactants DMS is oxidized to a variety of products such as sulfur dioxide (SO2), methanesulfonic acid (MSA) and dimethylsulfoxide (DMSO). MSA is one of the main products (estimates between 25 and 70% of the flux of dimethylsulfide = ca. 1010 Kg/year). Due to its hygroscopic nature, MSA takes part in the formation of cloud condensation nuclei (CCN), thus contributing to the regulation of cloud formation and albedo regulation. MSA falls onto lands and oceans in wet and dry precipitations and undergoes microbial degradation.
The degradation of MSA had been previously studied mainly in soil bacteria and genes responsible for these biochemical reactions had been cloned and sequenced. In this work: we looked for the msmA and msmE genes in novel isolated MSA-degrading bacterial strains; we sequenced and analyzed the whole genomes of 3 such strains; we obtained and analyzed metagenomic and amplicon survey sequence information of costal surface seawater before and after enrichment on MSA in order to extend our knowledge on these ecofunctional genetic markers of MSA degradation.
The novel genomes revealed new msm gene clusters in two marine MSA-isolates (Filomicrobium str.s Y and W) while the sequence analysis of the third strain (Rhodococcus str. RD6.2) suggests the presence of completely novel pathways for MSA utilization as source of carbon.
Our results of metagenomic data also show that moderate to high-GC% strains are somehow favoured during enrichment and isolation of MSA-utilizing bacteria, while the majority of msm genes obtained by cultivation-independent methods have low levels of GC%.
With a first degree in Biological Sciences by the Università degli Studi in Milan, Italy, Paolo De Marco has a Ph. D. in Biological Sciences (Environmental Microbiology) from the University of Warwick, UK. As a Post-docs at ICBAS and IBMC, Portugal, Paolo was involved in projects focusing on the degradation of methanesulfonate and other methylotrophic substrates, bioremediation, bacterial physiology and biotechnology. His past lecturing experience includes work at ESB, UCP, Porto and U. “F. Pessoa”, Porto. Paolo is currently a lecturer at Instituto Universitário de Ciências da Saúde (IUCS), Paredes.
[Group Leader: Fernando Tavares, Microbial Diversity and Evolution]
Image credits: Paolo De Marco
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Available from November 27 to December 27, 2015