An Ecological Survey of Hydrocarbon-oxidizing Micro-organisms

Abstract

SUMMARY: An ecological survey of the microflora of an upland moorland soil and the underlying shale was made over a 2-year period. Samples were taken at different depths of about 5, 20 and 40 cm. in the soil, and from the underlying shale band in a cave system nearby, and the average total counts of bacteria and fungi were 35 × 106, 3 × 106 and 1 × 106 per g. dry wt respectively. Hydrocarbon-oxidizing organisms occurred in all the samples. The numbers and activity of these organisms were determined in a variety of ways and finally expressed as a function of the total population of each sample. A significantly higher proportion of the population of the 20 cm. soil sample was able to utilize hydrocarbons as sole energy and carbon source, than of any of the other samples. When hydrocarbons were added there was a stimulation in respiration of all samples. Maximum stimulation of respiration occurred in the 20 cm. soil sample. The E h of the 20 cm. soil sample was lower than in any other sample, it also contained a higher level of lipid and hydrocarbons. It is suggested that the higher level of hydrocarbon oxidation in the 20 cm. soil sample is due to the accumulation of hydrocarbons with a resulting adaptation of the microbial populations. More organisms were able to oxidize the longer chain n-aliphatic hydrocarbons than the short chain n-aliphatics, aromatic and alicyclic hydrocarbons. A list of the genera, including fungi, responsible for the oxidation of each hydrocarbon is given: the fungi play an important role in the hydrocarbon-oxidizing activity of each sample.