ADVANCES IN THE SEARCH FOR ELECTROGENIC HALOPHILIC MICROORGANISMS

JUAN IGNACIO SOLCHAGA; JUAN PABLO BUSALMEN; DEBORA NERCESSIAN

Tucumán

Congreso; SAMIGE 2017; 2017

Asociación Argentina de Microbiología General

Electrogenic microorganisms are typically anaerobic and are able to channel their respiratory electrons to a polarized electrode. This capacity is of interest for bio-electrochemical technologies such as microbial fuel cells (MFC).If able to grow at NaCl concentrations ranging from 100 to 390g.l-1, microorganisms are recognised as hyperhalophiles, but so far no microorganisms have been described that meet both characteristics.Hypersaline environments typically present low oxygen solubility and are inhabited by a variety of microaerophilic and anaerobic microorganisms, but life at high salt concentrations is energetically expensive, due to the energy investment in sustaining internal homeostasis. This fact reduces the range of useful combinations between oxidants and reducers that can support cell growth, remaining unknown if polarized electrode can serve to these aims.In order to determine the presence of electrogenic hyperhalophilic microorganisms in the microbial community of Salitral Negro, enrichments were performed on liquid culture medium using fumarate as the only electron acceptor. This community was replicated to minimal media with acetate or lactate as an electron donor, in combination with different oxidizing compounds that would act as acceptors: NaNO3, Na2SO4, Thiosulfate, DMSO and a polarized graphite electrode. DNA extraction was performed on cultures that were positive for growth the gene encoding the 16S subunit of the rRNA was amplified. Amplification products were separated by electrophoresis on denaturing gradient gels (DGGE). DNA bands were extracted and re-amplified for further identification by sequencing. It was observed that the community enriched in fumarate reducers, was composed of both archaea and bacteria indeed capable of respiring NO3-, SO4-2, Thiosulfate and also a graphite electrode polarized to a positive potential. As the electrode was polarized to an oxidation potential a positive current could be recovered, presumably due to the growth of a biofilm using lactate as the electron donor.Work is still in progress to isolate anaerobic microorganisms capable to reduce the different compounds in order to learn more about these communities.