The growth of Pseudomonas oleovorans on n-octane was characterized by the formation of intracellular structures. These inclusions were isolated and characterized. Morphologically, they resembled the poly-p-hydroxybutyrate granules found in Bacillus cereus, as shown by freeze-fracture electron microscopy. The elemental analysis of isolated granules showed, however, that they do not contain poly-4-hydroxybutyric acid. Instead, the analysis was consistent with a C8 polyester, which interpretation was supported by the fatty acid analysis of hydrolyzed granules. From the evidence presented here, we conclude that P. oleovorans forms poly-p-hydroxyoctanoate granules when grown on n-octane. MATERIALS AND METHODS Chemicals. n-Octane (>99% pure) was purchased from J. T. Baker Chemical Co., Phillipsburg, N.J. A standard mixture (4-5436) of fatty acid methyl esters was purchased from Supelco, Inc., Bellefonte, Pa.; stearic methyl ester was purchased from Merck-Schuchardt A. G.; and egg white lysozyme was purchased from Boehringer Mannheim GmbH and Soehne GmbH. Rnase I (EC 3.1.4.22) was purchased from Miles-Seravac Ltd., and DNase I (EC 3.1.4.5) was purchased from Sigma Chemical Co.
Two Pseudomonas strains (PpG777 and PaG158) were derived from the parent isolate Pseudomonas incognita (putida). Strain PpG777 resembles the parental culture in growth on linalool as a source of carbon and slight growth on p-cymene, whereas PaG158 grows well on p-cymene, but not on linalool or other terpenes tested, and has a P. aeruginosa phenotype. Curing studies indicate that linalool metabolism is controlled by an extrachromosomal element whose loss forms a stable strain PaG158 with the p-cymene growth and P. aeruginosa phenotype characters. The plasmid can be transferred by PpG777 to both P. putida and P. aeruginosa strains. Surprisingly, the latter assume the P. putida phenotype. We conclude that the genetic potential to oxidize p-cymene is inherent in PpG777 but expression is repressed. Similarly, this observation implies that support of linalool oxidation effectively conceals the P. aeruginosa character.
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