KURTH daniel German
congresos y reuniones científicas
Genome sequence analysis of Acinetobacter sp. Ver3 and Exiguobacterium sp. S17 isolated from High Altitude Andean Lakes
KURTH, D; ORDOÑEZ, OF; ALBARRACIN, V; CORTEZ, N; TURJANSKI, A; VAZQUEZ, M; FARIAS, ME
Conferencia; ISCB Latin America 2012; 2012
The High-Altitude Andean Lakes (HAAL) ecosystems are almost unexplored systems of shallow lakes formed during the Tertiary geological period, distributed in the geographical area called the Puna, at altitudes from 3,000 to 6,000 m above sea level, and isolated from direct human activity. The HAAL ecosystems are unique not only for their geographical characteristics and broad range of extreme environments but also for their abundant biodiversity. The microbial communities that have evolved within these high-altitude aquatic ecosystems tolerate chemical and physical stresses such as wide fluctuations in daily temperatures, hypersalinity, and variable pH and have proved to be adapted to high levels of UV radiation, a low level of nutrient availability, and high concentrations of heavy metals. Here we present and analyze genomic sequences of two bacteria isolated from these extreme environments. They include Acinetobacter sp. Ver3, isolated from Laguna Verde, and Exiguobacterium sp. S17, isolated from Laguna Socompa. Genome sequences were obtained using a whole-genome shotgun (WGS) strategy with a 454 GS Titanium pyrosequencer at INDEAR, Argentina. From the annotated genomes, loaded on RAST annotation server, functional analysis shows remarkable features on these genomes. Particularly Acinetobacter sp. Ver3 shows a high number of genes in the category of Virulence, Disease and Defense, which includes genes conferring resistance to antibiotics and heavy metals. We are most interested in genomic features related to survival of these organisms in the harsh conditions prevailing at the HAAL. We focused our analysis on DNA repair systems, related to UV-B resistance, and arsenic resistance. The high number of antibiotic resistance genes found in these environments is surprising, as no selective pressure due to human contact can be expected. The presence of such genes suggests that new compounds could be isolated from these environments. DNA repair systems were also studied, as all these isolates are highly resistant to UV-B radiation. However, no unique genes were found. The improved resistance could be explained due to more efficient interactions or regulation of common repair systems. Further analysis will be required to associate this phenotype to the presence/absence of particular genes. Finally we performed a detailed analysis of the genes associated to arsenic resistance. The most well characterized arsenic resistance mechanism is the ars operon located on plasmids/chromosomes of prokaryotes. Microbial As detoxification involves the reduction of arsenate (As(V)) to arsenite (As(III)) via a cytoplasmic arsenate reductase (arsC) and further, As(III) will be extruded by a membrane-associated arsB efflux pump. Other genes like arsR, arsD and arsA form part of ars operon along with arsB and arsC in most of the prokaryotes. HAAL isolates show enhanced resistance compared to other bacteria possessing the ars operon. This is explained by the presence of additional genes related to this function, including extra copies of the ars operon (in Acinetobacter sp. Ver3) or supplementary extrusion pumps (in Exiguobacterium S17). The origin of these genes, either by horizontal gene transfer or duplication events, is discussed.