Selection for moderately halophilic bacteria by gradual salinity increases

These studies addressed the question as to whether oceanic water contains halophilic bacteria and so could serve as their medium of dispersal between hypersaline sites. Bacteria were collected by filtration from water of Vineyard Sound, whose shores lack extensive hypersaline sites. Enrichments inoculated by these samples and in which salinity was increased were carried out. A few colonies of extremely halophilic bacteria identified as Halococcus representatives were detected in the initial samples, but these types were not subsequently enriched. Moderately halophilic bacteria were strongly favored in each culture when salinity reached 14 – 15%; they accounted for a majority of each population by the time the salts concentration reached 20%. Nonhalophilic bacteria decreased in numbers and diversity when salts concentrations reached 14 – 15% and were not detectable at higher concentrations. Salinity alone accounted for enrichment of moderate halophiles. The results of these laboratory studies imply that ha...