Formation of intracytoplasmic lipid inclusions by Rhodococcus opacus strain PD630 |
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Authors: | Hector M Alvarez Frank Mayer Dirk Fabritius A Steinbüchel |
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Institution: | CEIMA, Universidad Nacional de la Patagonia San Juan Bosco, km 4, 9000 Comodoro Rivadavia, Argentina, AR Institut für Mikrobiologie der Georg-August-Universit?t G?ttingen, Grisebachstrasse 8, D-37077 G?ttingen, Germany, DE Institut für Mikrobiologie der Westf?lischen Wilhelms-Universit?t Münster, Correnstrasse 3, D-48149 Münster, Germany Tel. +49–251-83-9821; Fax +49-251-83-8388, DE
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Abstract: | An oleaginous hydrocarbon-degrading Rhodococcus opacus strain (PD630) was isolated from a soil sample. The cells were able to grow on a variety of substrates and to produce large
amounts of three different types of intracellular inclusions during growth on alkanes, phenylalkanes, or non-hydrocarbon substrates.
Electron microscopy revealed large numbers of electron-transparent inclusions with a sphere-like structure. In addition, electron-dense
inclusions representing polyphosphate and electron-transparent inclusions with an elongated disc-shaped morphology occurred
in small amounts. The electron-transparent inclusions of alkane- or gluconate-grown cells were composed of neutral lipids
(98%, w/w), phospholipids (1.2%, w/w), and protein (0.8%, w/w). The major component of the cellular inclusions was triacylglycerols;
minor amounts of diacylglycerols and probably also some free fatty acids were also present. Free fatty acids and/or fatty
acids in acylglycerols in cells of R. opacus amounted up to 76 or 87% of the cellular dry weight in gluconate- or olive-oil-grown cells, respectively. The fatty acid composition
of the inclusions depended on the substrate used for cultivation. In cells cultivated on n-alkanes, the composition of the
fatty acids was related to the substrate, and intermediates of the β-oxidation pathway, such as hexadecanoic or pentadecanoic
acid, were among the acylglycerols. Hexadecanoic acid was also the major fatty acid (up 36% of total fatty acids) occurring
in the lipid inclusions of gluconate-grown cells. This indicated that strain PD630 utilized β-oxidation and de novo fatty
acid biosynthesis for the synthesis of storage lipids. Inclusions isolated from phenyldecane-grown cells contained mainly
the non-modified substrate and phenylalkanoic acids derived from the hydrocarbon oxidation, such as phenyldecanoic acid, phenyloctanoic
acid, and phenylhexanoic acid, and approximately 5% (w/w) of diacylglycerols. The lipid inclusions seemed to have definite
structures, probably with membranes at their surfaces, which allow them to maintain their shape, and with some associated
proteins, probably involved in the inclusion formation.
Received: 22 December 1995 / Accepted: 12 March 1996 |
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Keywords: | Rhodococcus opacus PD630 Alkanes Phenylalkanes Gluconate Lipid inclusions |
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