Influence of hydrocarbons and derivatives on the polar lipid fatty acids of an Acinetobacter isolate

Biodegradation of free phytol by bacterial communities isolated from marine sediments under aerobic and denitrifying conditions

Biodegradation of (E)-phytol [3,7,11, 15-tetramethylhexadec-2(E)-en-1-ol] by two bacterial communities isolated from recent marine sediments under aerobic and denitrifying conditions was studied at 20 degrees C. This isoprenoid alcohol is metabolized efficiently by these two bacterial communities via 6,10, 14-trimethylpentadecan-2-one and (E)-phytenic acid. The first step in both aerobic and anaerobic bacterial degradation of (E)-phytol involves the transient production of (E)-phytenal, which in turn can be abiotically converted to 6,10,14-trimethylpentadecan-2-one. Most of the isoprenoid metabolites identified in vitro could be detected in a fresh sediment core collected at the same site as the sediments used for the incubations. Since (E)-phytenal is less sensitive to abiotic degradation at the temperature of the sediments (15 degrees C), the major part of (E)-phytol appeared to be biodegraded in situ via (E)-phytenic acid. (Z)- and (E)-phytenic acids are present in particularly large quantities in the upper section of the core, and their concentrations quickly decrease with depth in the core. This degradation (which takes place without significant production of phytanic acid) is attributed to the involvement of alternating beta-decarboxymethylation and beta-oxidation reaction sequences induced by denitrifiers. Despite the low nitrate concentration of marine sediments, denitrifying bacteria seem to play a significant role in the mineralization of (E)-phytol.

Production of wax esters during aerobic growth of marine bacteria on isoprenoid compounds

This paper describes the production of isoprenoid wax esters during the aerobic degradation of 6,10,14-trimethylpentadecan-2-one and phytol by four bacteria (Acinetobacter sp. strain PHY9, Pseudomonas nautica [IP85/617], Marinobacter sp. strain CAB [DSMZ 11874], and Marinobacter hydrocarbonoclasticus [ATCC 49840]) isolated from the marine environment. Different pathways are proposed to explain the formation of these compounds. In the case of 6,10, 14-trimethylpentadecan-2-one, these esters result from the condensation of some acidic and alcoholic metabolites produced during the biodegradation, while phytol constitutes the alcohol moiety of most of the esters produced during growth on this isoprenoid alcohol. The amount of these esters formed increased considerably in N-limited cultures, in which the ammonium concentration corresponds to conditions often found in marine sediments. This suggests that the bacterial formation of isoprenoid wax esters might be favored in such environments. Although conflicting evidence exists regarding the stability of these esters in sediments, it seems likely that, under some conditions, bacterial esterification can enhance the preservation potential of labile compounds such as phytol.

Aerobic and anaerobic metabolism of 6,10,14-trimethylpentadecan-2-one by a denitrifying bacterium isolated from marine sediments

This report describes the metabolism of 6,10,14-trimethylpentadecan-2-one by a denitrifying bacterium (Marinobacter sp. strain CAB) isolated from marine sediments. Under aerobic and denitrifying conditions, this strain efficiently degraded this ubiquitous isoprenoid ketone. Several bacterial metabolites, 4,8,12-trimethyl-tridecan-1-ol, 4,8,12-trimethyltridecanal, 4,8,12-trimethyltridecanoic acid, Z-3,7-dimethylocten-2-oic acid, Z-3,7,11-trimethyldodecen-2-oic acid, and 6,10,14-trimethylpentadecan-2-ol, were formally identified, and different pathways were proposed to explain the formation of such isoprenoid compounds.

Incorporation of chlorinated alkanes into fatty acids of hydrocarbon-utilizing mycobacteria

The cellular fatty acid composition of Mycobacterium vaccae JOB5 and Mycobacterium convolutum R22 was examined after growth on n-alkanes and compared with the fatty acids of the organisms after growth on 1-chlorohexadecane and 1-chlorooctadecane. Growth on n-alkanes resulted in normal fatty acid profiles. Mass spectral analyses indicated that, after growth on the terminally chlorinated n-alkanes, 75 to 86% of the fatty acids in M. convolutum and ca. 55% of the fatty acids in M. vaccae contained chlorine. Neither organism could utilize chloroacetate or 3-chloropropionate as sole source of carbon and energy. When these compounds were added to a growth medium with n-hexadecane as substrate, there was no evidence that chlorinated fatty acids were produced. Terminally chlorinated n-alkanes can be added to the list of n-alkanes, alkenes, and cyclohexylalkane derivatives that can be directly incorporated into cellular fatty acids of hydrocarbon-utilizing organisms.

Cellular fatty acids derived from normal alkanes by Candida rugosa

In an attempt to examine the specific metabolic relationship between the alkane substrates and lipid products the pattern of formation of cellular lipid, especially fatty acids, has been studied in the course of incubation of cells of C. rugosa with n-alkanes in mineral medium. C18:2, C18:1, C16:1 and C16:0 fatty acids were the major products formed, irrespective of the odd or even chain length of the alkane used as substrate. These unsaturated fatty acids reached a maximum in the stationary phase. In the case of cells grown on odd-chain n-alkanes (from C11 to C19), the proportion of odd-chain cellular fatty acids were markedly high, reaching 77--88% in the n-pentadecane and heptadecane-grown cells. The resulting acids are then metabolized by beta-oxidation or inserted directly or after elongation with C2-units into the cellular fatty acids. The total lipid content of n-alkane (n-C10-C20) grown cells in the stationary phase was 16.3--19.0% of th dry cell weight, which was about three times as much as that of glucose-grown cells. The chain length of alkane substrates had a significant effect on the lipid content. Ergosterol production from n-hexadecane was twice higher than that from glucose.

Regulation of fatty acid biosynthesis by hydrocarbon substrates in Mycobacterium convolutum

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 microgram of lipid into the fatty acids, whereas acetate- or propane-grown cells incorporated 280 and 255 pmol of acetate per microgram 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 micrometer. Cells that were grown on C14 through C16 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. Hexadecane- or pentadecane-grown cells were found to have 5 to 10 times more intracellular free fatty acid than cells grown on acetate, propane, or ethane.

Whole-cell and membrane lipids of the methylotrophic bacterium Methylosinus trichosporium

The lipid composition of the methylotrophic bacterium Methylosinus trichosporium was examined. Whole-cell lipid distribution was 39.1% neutral lipids, 34.5% polar lipids, and 26.4% poly-beta-hydroxybutyric acid. Membrane lipids were 83% phospholipids, with phosphatidylethanolamine and phosphatidylglycerol accounting for over 94% of the total. All the phospholipids had similar fatty acid compositions, with 18:1 accounting for about 87% of the total and most of the rest consisting of 16:1. Similarities between the lipid composition of this bacterium and other bacteria are discussed.