Martínez-Feliciano, Merylin

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    Metabolic and molecular characterization of an acetate and lactate-degrading microbial consortium
    (2014) Martínez-Feliciano, Merylin; Ríos-Hernández, Luis A.; College of Arts and Sciences - Sciences; Rodríguez Minguela, Carlos; Montalvo Rodríguez, Rafael; Department of Biology; Plaza Delestre, María L.
    Acetate is one of the most important intermediaries in the degradation of organic matter in anaerobic environments where carbon dioxide is the dominant electron acceptor. In these environments, acetate is recycled by acetoclastic methanogens or by syntrophic couples. In this thesis, is described a defined culture capable of acetate and lactate oxidation under methanogenic conditions. Combinations of microbiological and analytical methods as well as molecular techniques were used to characterize this culture. This included the construction of anaerobic microcosms that were subsequently characterized by serial dilutions, gas chromatography, high performance liquid chromatography, PCR, qPCR and sequencing. Our results demonstrate that the bacterial population within our enrichment is limited to a single sulfate reducing bacterium as evidenced by qPCR and DNA sequencing analyses of 16S rRNA genes. Furthermore, the highly purified culture is capable of oxidizing both acetate and lactate in the absence of sulfate when coupled with a methanogen. The qPCR data, using universal 16S rRNA primers of Eubacteria and Archaea, suggest that the methanogenic population comprises nearly is 25 % of the total population of microorganisms and is dominated by hydrogentrophic methanogens belonging to the genera Methanospirillum and Methanobacterium. In contrast, analyses of qPCR data using primers to universal 16S rRNA (Eubacteria), specific Syntrophus genus, and for the cap protein of S. aciditrophicus suggests that the bacterium in the culture belongs to the genus Syntrophus. However, these results are extremely interesting since they suggest either a bacterium belonging to the genus Syntrophus is capable of reducing sulfate (novel organism, yet un-described) or that a true sulfate reducing bacterium shares the same cap protein as SB. Unfortunately at this time we do not know which of these two possibilities is correct. We recommend further characterization of the mixed culture to elucidate these important findings; as future work.