National Institute of Genetic Engineering and Biotechnology
Abstract
Several heavy metal resistant bacterial strains were
isolated from sediment and water samples collected
from the Persian Gulf and enclosed industrial areas.
All the isolated bacteria were identified by 16S rRNA
gene sequencing. Isolated bacteria were tested for the
presence of plasmids using the modified alkaline
lysate method. The method was effective for identification
and characterization of plasmids of different sizes
without the use of highly toxic chemicals. The study
revealed that the frequency of the occurrence of plasmids
in heavy metal resistant bacteria was more than
that in the common bacteria. The study also demonstrated
that about 66% of isolated bacteria carried
large (38-62kb) and/or small sized (4- >2 kb) plasmids.
The highest plasmid incidence (84.6%) was detected
from industrial wastewater bacteria. A slightly higher
incidence of plasmids occurred in bacteria isolated
from marine sediments (55.5%) compared to that of
the marine water (53.8%). The findings suggested that
plasmids are highly ubiquitous and predominant in
most heavy metal resistant bacteria. Removal of lead
and cadmium from solution by some of these bacteria
was very efficient, approximately 120 mg/g dry weightas
high as 90%. The isolates tested, presented distinct
uptake capacities and the best results were obtained
for Delftia tsuruhatensis and Pseudomonas AU3411
respectively
