Regulation of fatty acid biosynthesis by hydrocarbon substrates in Mycobacterium convolutum

Abstract

When Mycobacterium convolutum R22 was grown on the n-alkanes C13 through C16, the predominant fatty acids were of the same chain length as the growth substrate. Cells grown on C13 through C16 n-alkanes incorporated between 15 and 85 pmol of acetate per pg of lipid into the fatty acids, whereas acetate-or propanegrown cells incorporated 280 and 255 pmol of acetate per ,ug of lipid, respectively.In vivo experiments demonstrated that hexadecane, hexadecanoic acid, and hexadecanoylcoenzyme A (CoA) all inhibited de novo fatty acid synthesis. Hexadecanoyl-CoA was the most potent inhibitor. Hexadecane and hexadecanoic acid inhibited acetyl-CoA carboxylase by up to 37 and 39%, respectively, at 1 mM. Hexadecanoyl-CoA inhibited the enzyme activity by 65% at 50 uM. Cells that were grown on C14 through C1s n-alkanes had about 25 times less acetyl-CoA carboxylase activity than did cells grown on acetate or propane, suggesting repressed levels of the enzyme. Hexadecaneor pentadecane-grown cells were found to have 5 to 10 times more intracellular free fatty acid than cells grown on acetate, propane, or ethane.Bacterial and yeast cells growing on longchain n-alkanes (C14 through C18) as sole sources of carbon and energy contain a large proportion of fatty acids that are the same carbon chain length as the hydrocarbon substrate (6, 7, 9a, 14, 20, 23, 25). King and Perry (11) have demonstrated that in hexadecane-grown Mycobacterium vaccae, the predominant fatty acids tetradecanoic, hexadecanoic, and hexadecenoic acids were derived directly from the carbon skeleton of hexadecane. Similarly, n-octadecane served as the immediate precursor for tetradecanoic, hexadecanoic, hexadecenoic, octadecanoic, and octadecenoic acids. Makula and Finnerty (16) demonstrated that Acinetobacter HO1-N accu-

Fatty Acid Composition of Rhodococcus aetherivorans Cells During Phenol Assimilation

“…The predominant fatty acids in n-hexadecane grown cells were C 16:0 (43.1 %), C 16:1 (25.4 %) and C 14:0 (11.8 %) obtained directly from the carbon skeleton of n-hexadecane. The obtained data correlate with the results of studying the cellular fatty acid composition of other representatives of hydrocarbon-oxidizing strains of actinobacteria, in particular Mycobacterium convolutum R22 [26] and Mycobacterium vaccae JOB5 [27], for which it has been demonstrated that the n-alkane substrate was incorporated into the cellular lipids after monoterminal oxidation. The presence in R. aetherivorans UCM Ac-602 cells a small amount of straight-chain unsaturated octadecenoic C 18:1 cis-9 fatty acid and a higher amounts of tetradecanoic C 14:0 , hexadecanoic C 16:0 and hexadecenoic C 16:1 cis-9 fatty acids, which were observed in n-hexadecane grown cells in comparison to those grown on glucose similar to the results obtained for the another strains of the genus Rhodococcus − Rhodococcus sp.…”

Pyrrolocin C and equisetin inhibit bacterial acetyl-CoA carboxylase

“…We used radioisotope tracing to test whether PYRC and EQI would inhibit incorporation of acetate into fatty acids of treated S. aureus. Radiolabeled acetate is a well-established tool to trace de novo fatty acid synthesis [22][23][24]. Upon entering the cell, acetate is converted into acetyl-CoA by acetyl-CoA synthase and utilized by subsequent pathways, including fatty acid biosynthesis.…”

Regiospecific Internal Desaturation of Aliphatic Compounds by a Mutant Rhodococcus Strain

“…As the initial step in utilization of alkanes, a coenzyme A-independent internal cis-desaturation may be involved, where an unsaturated metabolite generated would be then split at the double bond into two shorter chain FAs and ultimately oxidized via ␤-oxidation. This postulated pathway is different from the wellknown subterminal oxidation system that converts alkanes initially to their alkyl alcohols and then to FAs, which are further degraded by a ␤-oxidation system (13), as in yeast (2) and other microorganisms (1). The hyperproduction of unsaturated products by mutant KSM-B-3M suggests that the mutation might occur on the gene encoding a double bond-splitting enzyme, since the mutant strain grows poorly on n-hexadecane but well on FA16, and converts aliphatic substrates mainly to cis-9-unsaturated products having the same chain length.…”