Plasmids from environmental strains isolated from High Altitude Lakes

KURTH, D; ORDOÑEZ, OF; FARIAS, ME

Córdoba

Congreso; XI Congreso Argentino de Microbiologia General SAMIGE; 2015

SAMIGE

High-altitude Andean Lakes (HAAL) are pristine environments with extreme conditions such as high UV radiation, high heavymetal content (mainly arsenic), high salinity, and oligotrophy. Survival in these conditions depends on resistance mechanismsthat might be encoded either in genomes or mobile elements. Several linear plasmids have previously been found inactinomycete strains, and a number of genes have been proposed to function as resistance mechanisms. In this work, wesearched for plasmids in other HAAL strains. We analysed isolates identified as Exiguobacterium,Acinetobacter orPseudomonas, as they were among the most abundant within the HAAL collection. Using standard plasmid extraction protocolsfor Gram(+) and Gram(-) bacteria, small plasmids were isolated from two highly UV-B resistant strains, namely Acinetobactersp. Ver3 and Exiguobacterium sp. S17. For the Exiguobacterium plasmid, a partial sequence was obtained from the draftgenome, and completed and confirmed using PCR. For the Acinetobacter plasmids, restriction fragments were cloned andsequenced, and comparison with the draft genome allowed identifying a full 10kb plasmid and at least one moremegaplasmid. Using a different methodology, namely PFGE, it could be further assessed that the Exiguobacterium strain has infact two more megaplasmids which were not purified with the standard extraction protocol. The sequence of the isolatedmegaplasmids was also determined from restriction analysis, sequencing and comparison to the draft genome. Some of thegenes might be important for survival in the environmental extreme conditions. We present here the sequences obtained andaim to characterize the role of these mobile genetic elements, both in survival to extreme conditions and in putative transfer ofthis information to the HAAL microbial community. Characterization of these genetic elements could also help to develop toolsfor the poorly studied Exiguobacterium genus.