Abstract:
Two highly lead-resistant bacterial strains designated as M-9 and M-11 were isolated from Zuari estuary of Goa, India, which exhibit resistance up to 0.8 mM and 1.2 mM lead nitrate respectively. These lead-resistant bacterial isolates also tolerate cadmium and mercury as minimum inhibition concentration values for strain M-9 were 0.6 mM and 0.03 mM respectively whereas for strain M-11, the values were 0.6 mM and 0.05 mM respectively. On the basis of biochemical characteristics, 16S rRNA sequence data and fatty acid methyl ester (FAME) profile, these isolates were identified as Pseudomonas stutzeri and Vibrio harveyi respectively. Nested-PCR clearly demonstrated presence of pbrA gene (amplicon size: 750 bp) belonging to P-type ATPase family on chromosomal genome and 5.4 plus or minus 0.7 and 7.9 plus or minus 0.9 fold expression of pbrA gene in Pseudomonas stutzeri strain M-9 and Vibrio harveyi strain M-11 when grown in TMM amended with 0.5 mM lead nitrate revealed efflux mediated lead resistance in both bacterial isolates. PCR amplicons of mdrL gene (1136 bp) and orfA gene (467 bp) also suggested efflux-mediated multiple drug resistance in these leadresistant isolates.
