Transfer and Expression of a Multiple Antibiotic Resistance Plasmid in Marine Bacteria |
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Authors: | Subramanian Chandrasekaran Balakrishnan Venkatesh Damodharan Lalithakumari |
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Institution: | (1) Environmental Biotechnology Programme, Centre for Advanced Studies in Botany, University of Madras, Guindy Campus, Madras 600 025, India , IN |
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Abstract: | Conjugal transfer of a multiresistance plasmid from Pseudomonas fluorescens to halophilic and halotolerant bacteria was studied under in vitro and in situ conditions. Mating conducted in broth as well
as on plates yielded a plasmid transfer frequency of as high as 10−3. Among these two, plate mating facilitated conjugal transfer of plasmid, because the cell-to-cell contact is more in plate
mating. When P. fluorescens was incubated in seawater, the organism progressively lost its colony forming activity within 15 days. Microscopic examination
revealed the presence of very short rods, indicating that the cells have become viable but nonculturable (VNC). Mating conducted
in natural seawater without any added nutrients revealed that the conjugal transfer is influenced by the physical state of
the donor and the recipients as well as the availability of nutrients. But a plasmid transfer frequency of 10−7 was obtained even after the donor cells have become VNC suggesting that the nonculturable state and nutrient deprived condition
may not limit plasmid transfer. The results suggest that the terrestrial bacteria entering into the seawaters with antibiotic
resistance plasmids may be responsible for the prevalence of resistance genes in the marine environment.
Received: 4 May 1998 / Accepted: 18 June 1998 |
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