Studies on the mechanism of uptake of hydrocarbon by microorganisms

Abstract

MECHANISM OF HYDROCARBON UPTAKE BY MICROORGANISMS Though considerable work has been done on the various steps in the metabolic transformations of hydrocarbons by microorganisms, the mecha-nism of microbial uptake of these substrates is not clearly understood. Hydrocarbons, in general are practically insoluble in aqueous medium. The mode of uptake of these substrates by microorganisms therefore, is of considerable theoretical interest. Two mechanisms are generally considered in this connection : (I) Uptake through direct attachment of cells to hydrocarbon particles, (II) Uptake from the solubilized/microemulsified/pseudosolubilized hydrocarbon produced during fermentation. The thesis presents studies carried out to examine the above hypotheses and to postulate a generalised mechanism for hydrocarbon uptake by microorganisms. Part I of the thesis presents the state of the art and literature survey on the above subject. Part II describes the contrasting characteris-tics of growth and hydrocarbon uptake by two bacterial strains. Part III describes the isolation, purification and chemical/functional characteri-zation of hydrocarbon pseudosolubilizing and emulsifying factors produced by Pseudomonas cepacia Nl. A. CHARACTERISTICS OF GROWTH AND HYDROCARBON UPTAKE BY TWO STRAINS OF BACTERIA I. Isolation of organisms and growth on hydrocarbons Two organisms, M1 and N1, were isolated from a mixed culture of liquid petroleum gas utilizing microorganisms and identified as Micrococcus luteus M1 and Pseudomonas cepacia N1 through conventional methods and by cellular fatty acid profile analysis using Microbial Identification System. Micrococcus luteus M1 grew very well on n-hexadecane, n-heptadecane, n-octadecane, n-eicosane and pristane but its ability to grow on other n-alkanes, alkenes, alkylbenzenes and aromatic hydrocarbons was poor or negligible. On the other hand Pseudomonas cepacia N1 was able to grow well on various n-alkanes, alkenes, alkylbenzenes and pristane, but not on aromatic hydrocarbons. 2. Effect of EDTA and...