PROIMI   05436
PLANTA PILOTO DE PROCESOS INDUSTRIALES MICROBIOLOGICOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Genome sequence analysis of bacteria highly tolerant to arsenic, isolated from High Altitude Andean Lakes (HAAL)
Autor/es:
OMAR F. ORDOÑEZ; DANIEL KURTH,; ADRIAN TURJANSKI; MARTIN VÁZQUEZ; M. E. FARÍAS; NESTOR R. CORTEZ
Lugar:
Mar del Plata
Reunión:
Congreso; VIII CONGRESO ARGENTINO DE MICROBIOLOGIA GENERAL -SAMIGE; 2012
Institución organizadora:
Sociedad Argentina de Microbiología General
Resumen:
High Altitude Andean lakes (HAAL) comprise a system of shallow lakes
formed during the tertiary period (1.8-65 million years ago) distributed across the Puna (high plateau)
at altitudes varying from 4,200 m to 6,000 m above sea level (asl). These
aquatic ecosystems present extreme environmental conditions such as high levels
of Ultraviolet Radiation (UVR), a wide range of salinity (from 0.4 to 117 ppm),
large daily temperature fluctuations ranging from 20° C to -40° C, low nutrient
concentrations and the presence of heavy metals and metaloids, mainly arsenic.
The presence of arsenic resistance mechanisms
has been explored in several microbiological studies in arsenic-rich
environments. The most characterized arsenic resistance mechanism is the ars operon located either in plasmids or
chromosomes of prokaryotes. Bacterial As detoxification involves the reduction
of arsenate (As[V]) to arsenite (As[III]) via a cytoplasmic arsenate reductase
(arsC). Later on 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 As tolerant
prokaryotes. HAAL isolates show enhanced resistance compared to other bacteria
carrying the ars operon. This could
be explained by the presence of additional genes related to this function,
including extra copies of the ars
operon or supplementary extrusion pumps.
The aim of this study was to elucidate the
genetic mechanisms of tolerance to high arsenic concentrations, taking
advantage of the available genomes of three UV resistant bacterial strains,
recently isolated from HAAL extreme environments. Moreover, the presence of the
ACR3 gene as a possible resistance
mechanism was assessed by degenerate oligonucleotides.
We studied the strains Acinetobacter sp. Ver3 and Exiguobacterium
sp. N30 and S17, isolated from shallow water (Laguna Verde and Laguna
Negra), and from modern stromatolites (in Laguna Socompa) respectively. Maximal
arsenic concentration was 33.81 mg/L. Genome sequences were obtained using a
whole-genome shotgun strategy with a 454 GS Titanium pyrosequencer at INDEAR,
Argentina. Genomes were annotated and analyzed in the RAST annotation server.
PSI-BLAST and ClustalW were used to compare and align sequences, and
phylogenetic trees were built using Mega5. The effect of As[V] and As[III]
during growth in rich media was also evaluated by different protocols. The
strains Exiguobacterium arantiacum
DSMZ 6208 and Acinetobacter baumannii
DSM 30007 were
used as controls during tolerance profiles measurements.
Organisms with high tolerance to this
metalloid, isolated in pure culture from environments such as HAAL, could be
good candidates for studies of bioremediation of metals and metalloids, a
methodology considered of low cost and environmentally friendly.