Carbon substrate utilization, antibiotic sensitivity, and numerical taxonomy of bacterial isolates from the Great Salt Plains of Oklahoma

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The current work extends the phenotypic characterization of a bacterial culture collection from the Great Salt Plains of Oklahoma. This barren expanse of mud flats is typically crusted with thalassohaline salt evaporites. The initial account of the aerobic heterotrophic bacteria from the Great Salt Plains described 105 halotolerant isolates that represented 47 phylotypes. Extensive phenotypic analyses were performed on 76 isolates representing 37 unique phylotypes. The current report extends these observations for 60 of the isolates by measuring a wider set of phenotypic characteristics. Utilization patterns for 45 carbon substrates were used to assign the isolates into seven coherent phenons, along with several singletons and a group of isolates that did not grow on single carbon substrates. Most of the isolates were able to utilize nearly all of the nitrogen sources tested, with nitrate being the least utilized. Little antibiotic resistance was seen in the collection as a whole; however, certain phenons were enriched for antibiotic-resistant organisms. A total of 81 phenotypic characteristics were used to generate dendrograms. The numerical taxonomy trees essentially agreed with those generated using 16S rRNA gene sequences. The pattern of carbon substrate utilization showed substantial changes at different salinities that may have relevance to the variable salinities microbes experience at the Salt Plains over time.

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