Isolation and Comparative Physiological Studies of Aerobic PhotoーSynthetic Bacteria from Tropical Sea Area of Australia

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Aerobic heterotrophic bacteria containing bacteriochlorophyll a were isolated from specimens from a wide variety of marine environments on the coast of Australia (on the west cost, Shark Bay, Lake Clifton, Lake Heyward and Perth ; on the east coast, near Townsville and Brisbane ; on the north coast, near Darwin ; on the south coast, near Adelaide and Tasmania Island).The bacteria were found in a high proportion (10 to 30%) of the total hetero-trophic bacterial strains isolated from marine algae, seagrasses, stromatolites, the epiphites on stromatolites, and from seawater and sands ; in some cases they constituted up to 49% of the total. This is much higher than the previous report of 6% from Japan. A high percentage, 13%, was also found in the seawater of Hamelin Pool, at Shark Bay, where the salinity was 66%. The proportion of these bacteria was generally low in seawater and sands, with a few exceptions. There were no bacteriochlorophyll-containing bacteria on sponges or corals. Finally about 300 strains were found to contain bacteriochlorophyll a.The isolated strains were orange or pink, and most had absorption maxima around 800 and 850 to 870 nm, the absorption of bacteriochlorophyll in vivo.The maximum bacteriochlorophyll content was 1 nmol/mg dry wt. of bacterial cells. Most of the bacteria did not grow photoheterotrophically under anaeroーbic conditions in a broth medium containing succinate.Cells and cell extracts grown under aerobic conditions had photochemical activities such as reversible photooxidations of the reaction center and cytochrome(s). Some strains showed denitrifying activity. The optimal salinity for bacterial growth varied between strains.