Plasmid transfer and susceptibility to antibiotics in the halophilic phototrophs Rhodovibrio salinarum and Rhodothalassium salexigens

The present study defines a series of genetic procedures to be used for mol ecular studies in photosynthetic halophilic species such as Rhodovibrio sal inarum and Rhodovibrio salinarum and Rhodothalassium salexigens. In both sp ecies, the minimal inhibitory concentrations for the antibiotics tetracycli ne, rifampicin, chloramphenicol. spectinomycin. streptomycin. and kanamycin were determined. In addition. conjugal transfer of IncP and IncQ plasmids from Escherichia coli was demonstrated and the resistance markers expressed in these halophiles were determined. Finally, Rth. salexigens growth depen dence on variable salt concentrations was measured: maximal growth rates we re seen at 6% and 4% NaCl under phototrophic and chemotrophic conditions, r espectively. To the best of our knowledge, this is the first report analyzi ng the genetic properties of two representative species of halophilic purpl e non-sulfur phototrophs. (C) 2001 Federation or European Microbiological S ocieties. Published by Elsevier Science B.V. All rights reserved.