Coliform Bacteria for Bioremediation of Waste Hydrocarbons

Abstract

Raw, domestic sewage of Kuwait City contained about 106 ml−1colony forming units ofEnterobacter hormaecheisubsp.oharae(56.6%),Klebsiellaspp. (36%), andEscherichia coli(7.4%), as characterized by their 16S rRNA-gene sequences. The isolated coliforms grew successfully on a mineral medium with crude oil vapor as a sole source of carbon and energy. Those strains also grew, albeit to different degrees, on individualn-alkanes with carbon chains between C9and C36and on the individual aromatic hydrocarbons, toluene, naphthalene, phenanthrene, and biphenyl as sole sources of carbon and energy. These results imply that coliforms, like other hydrocarbonoclastic microorganisms, oxidize hydrocarbons to the corresponding alcohols and then to aldehydes and fatty acids which are biodegraded byβ-oxidation to acetyl CoA. The latter is a well-known key intermediate in cell material and energy production.E. colicells grown in the presence ofn-hexadecane (but not in its absence) exhibited typical intracellular hydrocarbon inclusions, as revealed by transmission electron microscopy. Raw sewage samples amended with crude oil,n-hexadecane, or phenanthrene lost these hydrocarbons gradually with time. Meanwhile, the numbers of total and individual coliforms, particularlyEnterobacter, increased. It was concluded that coliform bacteria in domestic sewage, probably in other environmental materials too, are effective hydrocarbon-biodegrading microorganisms.