Fatty acid and hydroxy acid adaptation in three gram-negative hydrocarbon-degrading bacteria in relation to carbon source.

The lipids of three gram-negative bacteria, Acinetobacter calcoaceticus, Marinobacter aquaeolei, and Pseudomonas oleovorans grown on mineral media supplemented with ammonium acetate or hydrocarbons, were isolated, purified, and their structures determined. Three pools of lipids were isolated according to a sequential procedure: unbound lipids extracted with organic solvents, comprising metabolic lipids and the main part of membrane lipids, OH--labile lipids (mainly ester-bound in the lipopolysaccharides, LPS) and H+-labile lipids (mainly amide-bound in the LPS). Unsaturated FA composition gave evidence for an aerobic desaturation pathway for the synthesis of these acids in A. calcoaceticus and M. aquaeolei, a nonclassic route in gram-negative bacteria. Surprisingly, both aerobic and anaerobic pathways are operating in the studied strain of P. oleovorans. The increase of the proportion of saturated FA observed for the strain of P. oleovorans grown on light hydrocarbons would increase the temperature transition of the lipids for maintaining the inner membrane fluidity. An opposite phenomenon occurs in A. calcoaceticus and M. aquaeolei grown on solid or highly viscous C19 hydrocarbons. The increases of FA < C18 when the bacteria were grown on n-nonadecane, or of iso-FA in cultures on isononadecane would decrease the transition temperature of the lipids, to maintain the fluidity of the inner membranes. Moreover, P. oleovorans grown on hydrocarbons greatly decreases the proportion of P-hydroxy acids of LPS, thus likely maintaining the physical properties of the outer membrane. By contrast, no dramatic change in hydroxy acid composition occurred in the other two bacteria.

Botryolins A and B, two tetramethylsqualene triethers from the green microalga Botryococcus braunii.

Two new triterpenoid polyethers with a tetramethylsqualene carbon skeleton, botryolins A and B, have been isolated from the green microalga Botryococcus braunii. Their structures were determined by means of spectral analyses including 2D NMR.

C31-C34 methylated squalenes from a Bolivian strain of Botryococcus braunii.

Three new triterpenes, synthesized by a Bolivian strain of the green microalga Botryococcus braunii, were isolated and their chemical structures determined by 1D and 2D NMR, and mass spectrometry. These compounds are tri-, di-, and mono-methylsqualenes, co-occurring with the previously identified tetramethylsqualene and some C(30)-C(32) botryococcenes. In this strain, methylated squalenes constitute up to 24% of the total hydrocarbons and 4.5% of the dry biomass. The results of a pulse-chase experiment with L-[Me-(13)C] methionine provide evidence for the origin of these compounds via methylation of squalene at positions 3, 7, 18 and 22.

Effects of hydrocarbon structure on fatty acid, fatty alcohol, and beta-hydroxy acid composition in the hydrocarbon-degrading bacterium Marinobacter hydrocarbonoclasticus.

The lipids of the gram-negative bacterium Marinobacter hydrocarbonoclasticus grown in a synthetic seawater medium supplemented with various hydrocarbons as the sole carbon source were isolated, purified, and their structures determined. The hydrocarbons were normal, iso, anteiso, and mid-chain branched alkanes, phenylalkanes, cyclohexylalkanes, and a terminal olefin. According to the sequential procedure used for lipid extraction, three pools were isolated: unbound lipids extracted with organic solvents (corresponding to metabolic lipids and to the main part of membrane lipids), OH- labile lipids [mainly ester-bound in the lipopolysaccharides (LPS)], and H+ labile lipids (mainly amide-bound in the LPS). Each pool contained FA, fatty alcohols, and beta-hydroxy acids. The proportions of these lipids in the unbound lipid pools were 84-98%, 1.1-11.6%, and 0.1-3.6% (w/w), respectively. The chemical structures of the lipids were strongly correlated with those of the hydrocarbons fed; analytical data suggested a metabolism essentially through oxidation into primary alcohol, then into FA and degradation via the beta-oxidation pathway. Sub-terminal oxidation of the hydrocarbon chains, alpha-oxidation of FA or double-bond oxidation in the case of the terminal olefin, were minor, although sometimes substantial, routes of hydrocarbon degradation. Cyclohexyldodecane did not support growth, likely because of the toxicity of cyclohexylacetic acid formed in the oxidation of the alkyl side chain. In the OH- and H+ labile lipid pools, beta-hydroxy acids, the lipophilic moiety of LPS, generally dominated (28-72% and 64-98%, w/w, respectively). The most remarkable feature of these cultures on hydrocarbons was the incorporation in LPS of beta-hydroxy acids with Codd, omega-unsaturated, iso, or anteiso alkyl chains in addition to the specific beta-hydroxy acid of M. hydrocarbonoclasticus, 3-OH-n-12:0. These beta-hydroxy acids were tolerated insofar as their geometry and steric hindrance were close to those of the 3-OH-n-12:0 acid.

Incorporation of 1-chlorooctadecane into FA and beta-hydroxy acids of Marinobacter hydrocarbonoclasticus.

The lipids of the gram-negative marine bacterium Marinobacter hydrocarbonoclasticus, cultivated in synthetic seawater supplemented with 1-chlorooctadecane as sole source of carbon, were isolated, purified, and their structures determined. Three pools of lipids were isolated according to the sequential procedure used: unbound lipids extracted by organic solvents, ester-bound lipids released under alkaline conditions, and amide-bound lipids released by acid hydrolysis. FA isolated from the unbound lipids included omega-chlorinated (21%, w/w, of this fraction; C16 predominant) and nonchlorinated compounds (22%, w/w; C18 predominant). These acids were accompanied by a high proportion of omega-chloro-C18 alcohols (43%, w/w) and a lower amount of omega-chloro-beta-hydroxy-C18, -C16, and -C14 acids (5%, w/w). These data, together with the isolation from the culture medium of gamma-butyrolactone, suggested a metabolism of 1-chlorooctadecane through oxidation into omega-chloro acid and then the classic beta-oxidation pathway. The analysis of the ester-bound and amide-bound lipids revealed that significant amounts of omega-chloro-beta-hydroxy C10-C12 acids were incorporated into the lipopolysaccharides of the bacterium. Incorporation of these omega-chloro-beta-hydroxy acids into the lipopolysaccharides represents a novel route for chloroalkane assimilation in hydrocarbonoclastic gram-negative bacteria. The formation of chlorinated hydroxy acids, like the omega-chloro FA in the cellular lipids, could account for an incomplete mineralization of chloroparaffins in the environment.

Elemental and molecular evidence of soot- and char-derived black carbon inputs to New York City's atmosphere during the 20th century.

Soot black carbon (here expressed as GBC) is present in sediments of Central Park and Prospect Park Lakes, New York City (NYC), and peaks in the middle of the 20th Century at the highest values (1-3% dry weight) ever reported in urban lakes. During that period (approximately 1940-1970), the GBC represents up to 28% of the total organic carbon (OC). Radionuclide-normalized whole core inventories of accumulated GBC are similar in the two lakes which are separated by approximately 15 km, suggesting that emissions of fine soot particles may have accumulated homogeneously over at least the urban center of NYC. The distribution of polycyclic aromatic hydrocarbons (PAHs) in the sediments is decoupled from that of GBC. The highest levels of total PAHs correspond to peak coal use for space heating in NYC in the early 1900s. In contrast, GBC concentrations were highest in the mid 1900s, a period when oil combustion dominated local fossil fuel use and incineration of municipal solid waste (MSW) was common practice in NYC. Decreases in GBC levels observed in more recently deposited sediments are consistent with improvements in particle emissions control systems. Non-soot BC (char) was identified by a high carbon to nitrogen (C/N) ratio that persisted after correction for GBC. This likely tracer of MSW incineration was estimated to contribute an additional '35% of total organic carbon found in the sediments deposited during the peak period of combustion. The temporal trends of soot-BC observed in our lake cores do not agree with published historical reconstructions based on fuel consumption and estimated emission factors.

Lycopanerols I-L, four new tetraterpenoid ethers from Botryococcus braunii.

Four new tetraterpenoid ethers, lycopanerols I-L (5-8), were isolated from a culture of a strain of the green microalga Botryococcus braunii (L race). The structures were determined by means of spectral analyses and chemical degradation. The relative stereochemistry of these ethers was established by ROESY NMR. A biogenetic relationship is proposed between lycopanerols and lycopadiene (1), the acyclic diunsaturated tetraterpene hydrocarbon synthesized by the alga.