AUTHOR=Kröber Eileen , Mankowski Anna , Schäfer Hendrik 

TITLE=Microorganisms associated with Sporobolus anglicus, an invasive dimethylsulfoniopropionate producing salt marsh plant, are an unrecognized sink for dimethylsulfide

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.950460

DOI=10.3389/fmicb.2022.950460

ISSN=1664-302X

ABSTRACT=<sec><title>Background</title><p>Saltmarshes are hotspots of organosulfur compound cycling due to production of dimethylsulfoniopropionate (DMSP) by benthic microorganisms, macroalgae, and saltmarsh vegetation. Degradation of DMSP is a source of dimethylsulfide (DMS), an important precursor for formation of secondary organic aerosol. Microorganisms degrading DMS play a role in controlling the amount of DMS available for emission into the atmosphere. Previous work has implicated sediment microbial populations as a major sink for DMS. Here, we show that <italic>Sporobolus anglicus</italic> (previously known as <italic>Spartina anglica</italic>), a widely distributed saltmarsh plant, is colonized by DMS-degrading microorganisms.</p></sec><sec><title>Methods</title><p>Dimethylsulfide degradation potential was assessed by gas chromatography and <sup>13</sup>C-DMS stable isotope probing, microbial community diversity and functional genetic potential in phyllosphere and rhizosphere samples was assessed by high-throughput sequencing of 16S rRNA gene amplicons, cloning and sequencing of methanethiol oxidase genes, and by metagenomic analysis of phyllosphere microbial communities.</p></sec><sec><title>Results</title><p>The DMS degradation potential of microbial communities recovered from phyllosphere and rhizosphere samples was similar. Active DMS-degraders were identified by <sup>13</sup>C-DMS stable isotope probing and included populations related to <italic>Methylophaga</italic> and other <italic>Piscirickettsiaceae</italic> in rhizosphere samples. DMS-degraders in the phyllosphere included <italic>Xanthomonadaceae</italic> and <italic>Halothiobacillaceae</italic>. The diversity in sediment samples of the methanethiol oxidase (<italic>mtoX</italic>) gene, a marker for metabolism of methanethiol during DMS and DMSP degradation, was similar to previously detected saltmarsh <italic>mtoX</italic>, including those of <italic>Methylophaga</italic> and <italic>Methylococcaeae</italic>. Phyllosphere <italic>mtoX</italic> genes were distinct from sediment <italic>mtoX</italic> and did not include close relatives of cultivated bacteria. Microbial diversity in the phyllosphere of <italic>S. anglicus</italic> was distinct compared to those of model plants such as rice, soybean, clover and <italic>Arabidopsis</italic> and showed a dominance of <italic>Gammaproteobacteria</italic> rather than <italic>Alphaproteobacteria</italic>.</p></sec><sec><title>Conclusion</title><p>The potential for microbial DMS degradation in the phyllosphere and rhizosphere of <italic>Sporobolus anglicus</italic> suggest that DMS cycling in saltmarshes is more complex than previously recognised and calls for a more detailed assessment of how aboveground activities affect fluxes of DMS.</p></sec>