Free-living heterotrophic nitrogen-fixing bacteria isolated from fuel-contaminated antarctic soils

Abstract

Five bacterial isolates enriched from fuel-contaminated Antarctic soils fixed nitrogen in the dark heterotrophically and nonsymbiotically. Two isolates utilized jet fuel vapors and volatile hydrocarbons for growth but not in N-deficient medium. Bacteria such as these may contribute to in situ biodegradation of hydrocarbons in Antarctic soils.

FIG. 1.

Maximum likelihood tree of P. stutzeri strains. GenBank accession numbers of the sequences are shown in square brackets. Bootstrap values were obtained from 284 maximum likelihood replicates. Each bootstrap replicate was a full heuristic search with 10 random additions of sequences. Pseudomonas putida was used as an outgroup.

FIG. 2.

Effect of temperature on exponential growth rate (solid circles) and on relative nitrogenase activity (bars). Growth rate was determined graphically from the mean OD₆₀₀ of duplicate liquid cultures (1). Relative nitrogenase activity was determined for cultures pregrown at 10°C (open bars) or 22°C (stippled bars) and subsequently incubated with acetylene at 4, 10, or 22°C. Acetylene reduction activity was expressed as the percentage of total GC peak area corresponding to the ethylene peak for each injection. Values are the means of duplicate cultures; error bars represent 1 standard deviation.