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The aim of this study was to examine the bacterial composition of high latitude soils from the Darwin-Hatherton glacier region of Antarctica. Four soil pits on each of four glacial drift sheets were sampled for chemical and microbial analyses. The four drifts-Hatherton, Britannia, Danum, and Isca-ranged, respectively, from early Holocene (10 ky) to mid-Quaternary (ca 900 ky). Numbers of culturable bacteria were low, with highest levels detected in soils from the younger Hatherton drift. DNA was extracted and 16S rRNA gene clone libraries prepared from samples below the desert pavement for each of the four drift sheets. Between 31 and 262 clones were analysed from each of the Hatherton, Britannia, and Danum drifts. Bacterial sequences were dominated by members of the phyla Deinococcus-Thermus, Actinobacteria, and Bacteroidetes. Culturable bacteria, including some that clustered with soil clones (e.g., members of the genera Arthrobacter, Adhaeribacter, and Pontibacter), belonged to Actinobacteria and Bacteroidetes. The isolated bacteria are ideal model organisms for genomic and phenotypic investigations of those attributes that allow bacteria to survive and/or grow in Antarctic soils because they have close relatives that are not tolerant of these conditions.

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The influence of pH, inoculum size, human urine and prostatic extract on the MICs of ciprofloxacin and trimethoprim for Escherichia coli was investigated. There was no influence by the bacterial inoculum size within wide ranges on either drug. An increase in pH had a variable influence on the MICs of trimethoprim for E. coli but lowered those of ciprofloxacin considerably. Human prostatic extract increased the trimethoprim MIC for E. coli but lowered those of ciprofloxacin as compared to Mueller Hinton broth. Human urine increased the MICs of both drugs for E. coli.