Isolation and Identification of Photosynthetic Bacteria (Rhodospirillaceae) from Antarctic Marine and Freshwater Sediments

Sediment samples obtained from three freshwater lakes and off-shore coastal marine waters on Signy Island, South Orkney Islands, Antarctica have been inoculated into selective enrichment media for purple non-sulphur bacteria (Rhodospirillaceae). From the freshwater sediments strains of Rhodopseudomonas sphaeroides (1), Rhodopseudomonas palustris (1), Rhodospirillum fulvum (1), Rhodospirillum molischanum (1) and Rhodomicrobium vannielii (3) have been isolated. The only purple non-sulphur bacteria obtained from Lake 10 (Amos lake) were strains of Rhodomicrobium vannielii which were able to tolerate hydrogen sulphide (up to 0.04% w/v) found in this lake. Growth of all the other isolates is inhibited by the presence of hydrogen sulphide. Marine sediments yielded strains of Rhodopseudomonas palustris and Rhodomicrobium vannielii . All the isolates grow optimally at temperatures between 25 and 30 °C. mean generation times vary between 8 and 10.7 h depending on species. There is no evidence of cold adaptation in any of the strains studied.