MARINE VIBRIOS ALSO POSSESS ARS OPERON: MOLECULAR CHARACTERIZATION OF FOUR ARSINIC RESISTANT VIBRIOS FROM GOA, INDIA

Abstract

Arsenic resistance in bacteria is basically due to a detoxification system encoded by the
ars operon. It has been reported in various grams negative as well as gram positive
genera. The E. coli chromosomal ars operon and E. coli plasmid R773 borne ars
operons were the first ones to be discovered. The ars operon Staphylococcus aureus
plasmid pI 258 which shows only 30% structural homology with the E.coli counterpart is
representative of gram positive ars operons and is known to show functional homology
with the former. Subsequently, the ars operon genes were found in diverse taxa. E.g.
Bacillus, Pseudomonas, Acidiphilium multivorum, Corynebacterium, Streptomyces,
Thiobacillus, Exiguobacterium, Clostidium, Synechocystis and many others. But this
inherent property of arsenic resistance and the presence of ars operon have not yet
been reported among the members of the genus Vibrio. We, in our studies came across
four Vibrios isolated from marine habitats which showed high levels of resistance
towards inorganic arsenic species viz. arsenate (>200mM) and arsenite(3mM). All these
strains were PCR positive for arsC gene encoding arsenate reductase using gene
specific primers. The size of the amplicon ranged from 353-356 bp and revealed 98-
99% homology with the chromosomal ars operon E.coli strain W 3110.