IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Identification of genes and proteins involved in the response to arsenic stress in sequenced strains from High Altitude Andean Lakes (HAAL)
Autor/es:
ORDOÑEZ, OMAR; KURTH, DANIEL; MALDONADO, JAVIER; FERRER, GABRIELA; ALBARRACÍN, VIRGINIA; GORRITI, MARTA F.; THOMPSON, FABIANO; RASCOVAN, NICOLÁS; REVALE, SANTIAGO; VAZQUEZ, MARTIN P.; LANZAROTTI, ESTEBAN; TURJANSKY, ADRIAN; FARIAS, MARIA EUGENIA; CORTEZ, NÉSTOR
Lugar:
Rosario
Reunión:
Congreso; IX Congreso de Microbiología General SAMIGE; 2013
Institución organizadora:
Sociedad Argentina de Microbiología General SAMiGe
Resumen:
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Arsenic (As) is one
of the most important global environmental pollutants and a persistent
bioaccumulative carcinogen. As an ubiquitous toxic metalloid it was released in
the environment mainly by volcanic activity. The ars gene system can be
chromosomal or plasmid-borne and provides arsenic resistance to a variety of
microorganisms . The arsC gene, which codes for an arsenate reductase is
essential for arsenate resistance and transforms arsenate into arsenite, which
is scavenged from the cell by extrusion pumps such as the arsB gene. The less studied
gene acr3 codify for an extrusion pump (ACR3)
which ejects specifically arsenite out of the cell, providing high resistance
towards AsIII to the microorganisms expressing it .
The high
concentration of arsenic present in HAAL is strongly limiting not only for
human life but also for growth of many microorganisms, and favored evolution of
arsenic tolerant bacteria. Maximal arsenic concentration observed in these environments was 33.81
mg/L.
Genomes of several microorganisms isolated from the HAAL
have been sequenced recently. We
present here the identification of genes involved in the response to arsenic
stress in these HAAL genomes and the effect of As [V] and As [III] on bacterial growth.
The strains Acinetobacter sp.
Ver3, Exiguobacterium sp. N30 and
S17, Salinivibrio sp N34, N35 and S10B,
Nesterenkonia sp, and Halorubrum sp. were selected for this
study. Genome sequences were obtained using a whole-genome shotgun strategy
with a 454 GS Titanium pyrosequencer (INDEAR, Argentina) and Ion Torrent-based genome sequencing (UFRJ, Brazil).
Final genome sequences 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.
Genetic
analysis and physiological characterization of resistance to arsenic was
performed and the
presence of the genes encoding the arsenite detoxification machinery (ars genes)
was observed in all sequenced strains. Although these
microorganisms showed high tolerance to As (V), the response to As (III) was
more diverse, as Exiguobacterium sp.
S17 was the only strain able to grow at As concentrations above 5 mM. Two types
of arsenic extrusion pumps were observed: ACR3 and ArsB. ACR3 gene was more widely distributed in the
genomes under study.
HAAL sequenced strains
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. Besides basic knowledge about structure and
molecular mechanisms of metal extrusion pumps, the analysis of
sequenced genomes of microorganisms displaying high tolerance to arsenic, could
give information useful for bioremediation of metals and metalloids, a methodology
considered of low cost and environmentally friendly.