Effects of crude oil on phospholipid fatty acid compositions of marine hydrocarbon degraders: estimation of the bacterial membrane fluidity.

In this study, we investigated, in vitro, the effects of petroleum hydrocarbons on the phospholipid ester-linked fatty acid composition of Corynebacterium sp. Strain 8. The usual ratio of monounsaturated fatty acids E/Z (or trans/cis) was calculated. This ratio led to unexpected results because we found similar values for growths on either a hydrophobic substrate (crude oil) or a soluble carbon source (rich medium). The use of such an indicator seemed limited for monitoring an environmental stress, so we proposed an index based on the homeoviscous adaptation theory. A membrane viscosity index was defined and applied to Corynebacterium sp. Strain 8 (in vitro growth) and to a sedimentary community (in situ experiment). The results allowed us to estimate the membrane fluidity of both an isolated strain and a bacterial community in accordance with the medium hydrophobicity.

Comparison of n-eicosane and phenanthrene removal by pure and mixed cultures of two marine bacteria.

The biotransformation activities of two hydrocarbonoclastic marine bacteria, Corynebacterium sp. and Sphingomonas sp. 2MPII, on n-eicosane and phenanthrene were investigated. During a 56-day experiment, in pure and mixed cultures, Corynebacterium sp. and Sphingomonas sp. 2MPII removed about 70% of the initial n-eicosane and phenanthrene concentrations (1 and 0.4 g L(-1), respectively). In pure cultures, culturable cell abundances increased over time, from 0.8 to 8.6 x 10(-11) CFU L(-1) (Corynebacterium sp.) and from 2.1 to 16 x 10(-11) CFU L(-1) (Sphingomonas sp. 2MPII ) but remained barely constant in mixed cultures. We defined a biotransformation index based on the number of culturable cells rather than the culture protein content, with the biotransformation cell yield (BCY) expressed in grams hydrocarbon CFU(-1) per day to better characterize hydrocarbon removal in pure and mixed cultures. The BCY was markedly higher in mixed than in pure cultures, increasing by a factor of 2-10.7 and 2.3-4.7 for n-eicosane and phenanthrene removal, respectively.

Degradation of phenanthrene, methylphenanthrenes and dibenzothiophene by a Sphingomonas strain 2mpII.

Strain Sphingomonassp. (2MPII), isolated from marine sediment, was able to utilize phenanthrene (P) or 2-methylphenanthrene (2MP) as the sole carbon source. However, 9-methylphenanthrene (9MP) and dibenzothiophene (DBT) were weakly degraded. The degradation rates of 9MP and DBT increased in the presence of 2MP, whilst the degradation rate of 2MP increased in the presence of 9MP. However, the presence of DBT inhibited the degradation of 2MP. DBT sulfone, a DBT metabolite, was not assimilated by the bacteria and its presence also decreased the degradation rate of 2MP.

Influence of n-alkanes and petroleum on fatty acid composition of a hydrocarbonoclastic bacterium: Marinobacter hydrocarbonoclasticus strain 617.

This study concerns the effects of various long-chain n-alkanes, n-alkane mixtures and Arabian Light crude oil on the fatty acid (FA) composition of a sedimentary marine bacteria (Marinobacter hydrocarbonoclasticus strain 617), growing under aerobic conditions. The cultures with n-alkanes, as compared with soluble carbon sources, led to greater amounts of saturated and methyl branched FA (mainly belonging to a delta10 series). We observed the appearance or increase of saturated and unsaturated FA with the same carbon chain length (CCL) as the n-alkane carbon source (maximum for n-alkane CCL corresponding to the 'range' of the de novo synthesized fatty acids). We also observed a strong control of the oddness/evenness of the CCL of the FA by the oddness/evenness of the n-alkane. A n-alkane utilization index, (saturated + branched)/monounsaturated fatty acids (SAFA + BFA/MUFA) enabled discriminating between soluble carbon sources and hydrocarbons.

Enhanced biodegradation of phenanthrene by a marine bacterium in presence of a synthetic surfactant.

The biodegradation of phenanthrene by the marine strain Sphingomonas sp. 2MPII (DSMZ 11572) was enhanced by the solubilizating properties of the nonionic surfactant Tween 80. After 197 h of incubation, 85 +/- 4% of the initial amount of phenanthrene (0.4 g l-1) was biodegraded in presence of Tween 80 (0.5 g l-1) as opposed to 52 +/- 5% without this synthetic surfactant. These results confirm that the activity of the strain 2MPII is limited by the bioavailability of the polycyclic aromatic hydrocarbon (PAH) substrate in the aqueous phase. Tween 80 appears to be efficient in increasing the bioavailability of hydrophobic compounds such as PAHs.

In-vitro study of interaction between photooxidation and biodegradation of 2-methylphenanthrene by Sphingomonas SP. 2MPII.

This work reports a study of interactions between reactions of photooxidation and reactions of bacterial degradation of an alkylated polyaromatic hydrocarbon (2-methylphenanthrene). Bacterial growth was carried out using artificial sunlight as light source. Among the various products detected, the major product was identified as the 2-methylphenanthrene aldehyde. Sunlight allows accelerated elimination of the substrate. This enhancement of the biodegradation rate of 2 methylphenanthrene is due to the use of assimilable photoproducts by the bacterium.

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.

Isolation and characterization of a marine bacterium capable of utilizing 2-methylphenanthrene.

A marine bacterium isolated from a coastal hydrocarbon-polluted sediment has been described and attributed on the basis of its phenotypic and genotypic characteristics to the genus Sphingomonas sp. This strain was capable of using an alkylated phenanthrene 2-methylphenanthrene, as sole source of carbon and energy. In experiments, 2-methylphenanthrene (0.2 g/l) was added as crystals to the culture medium. After 5 days of aerobic growth at 30 degrees C, 70% was degraded and the complete dissipation occurred after 20 days. Furthermore, the strain could degrade various kinds of polyaromatic compounds, but failed to grow on aliphatic hydrocarbons.

Salt requirements in the denitrifying bacterium Pseudomonas nautica 617.

Pseudomonas nautica 617, which was isolated from superficial marine sediment, was found to require sodium for growth. Growth also appeared to be sensitive to the divalent cation, Mg2+, the presence of which, together with that of Na+, was necessary for achieving maximal growth. We investigated cell capacity to resist lysis after washing with either 0.05 M MgCl2 or 0.5 M NaCl, by monitoring suspension optical density changes as well as the release of ultraviolet absorbing material. Mg2+ turned out to play a significant role in stabilizing the structure of the cell envelope. Respiratory activity was also sensitive to ionic environment. With cells washed with 0.05 M MgCl2 and suspended in 0.05 M Tris buffer, the respiration rate, assessed by N2O evolution, was 15% of that measured in artificial sea water. Upon addition of 0.5 M Na+, nitrous oxide production rose to 32% of the reference level. The dinitrification rate was fully restored by further addition of 0.05 M Mg2+. K+ alone had almost no effect, but when added with Na+, the rate of denitrification increased to 45%.

Anaerobic biodegradation of hydrocarbons.

The anaerobic biodegradation of hydrocarbons has long been a subject of controversy but enough data have now been accumulated to support the view that hydrocarbons can be metabolized in the natural environment in the absence of molecular oxygen. For a limited number of molecules, anaerobic hydrocarbon metabolism has been demonstrated under fermentative or denitrifying conditions with samples collected from several different biotopes. However, the micro-organisms responsible for anaerobic metabolism generally still need to be isolated and identified and the biochemical mechanisms of the strictly anaerobic strains which carry out hydrocarbon metabolism are still unknown. Despite this restricted knowledge, the improvement in sampling techniques and in experimental methods is now sufficient to confirm the existence of anaerobic hydrocarbon biodegradation. The importance of such metabolism should stimulate research in this field.

Denitrification by a marine bacterium Pseudomonas nautica strain 617.

A bacterial strain was isolated from a marine sediment highly contaminated by hydrocarbons. From taxonomic tests, it was identified as Pseudomonas nautica. This marine strain was able to grow on nitrate, nitrite and nitrous oxide as an electron acceptor. The terminal product from the denitrification was dinitrogen. Thus, P. nautica was a denitrifier. The kinetics of each step of denitrification was examined in resting cell suspensions. The relative rates of nitrate and nitrite reduction and of nitrite reduction and nitrous oxide production explain, respectively, the presence of accumulated nitrite and that of compound intermediate between nitrite and nitrous oxide.

Influence of oxygen on the microsomal electron transport system in Saccharomyces cerevisiae.

The influence of oxygen on the level of microsomal electron transport chain components has been studied during the growth of Saccharomyces cerevisiae. Enzyme activities and cytochrome content were assayed in microsomal fractions prepared from a protoplast lysate free from mitochondrial contamination. It was found that the cytochrome P-450 and cytochrome b5 content, to get her with the NADPH-cytochrome (P-450)-reductase and NADH-cytochrome (b5)-reductase activities, were increased in the cells as the pO2 of the medium was decreasing. At the same time an increase in the membrane surface of the endoplasmic reticulum can be observed.

Lipid studies on Candida tropicalis grown on alkane.

The lipid composition of whole cells and microsomal fraction of Candida tropicalis grown on alkane, glucose and glycerol have been examined. Small quantitative variations in the total lipid content are detected; the differences observed in both triacylglycerols and phospholipids are related to the substrates used to the growth.

Hydroxylase regulation in Candida tropicalis grown on alkanes.

Candida tropicalis synthesizes a hydroxylase (3 to 5 nmol of product formed per minute per milligram of protein) and a cytochrome P-450 (0.10 to 0.13 nmol per milligram of protein) during growth on n-tetradecane. A three- to four-fold increase in the level of NADPH cytochrome c reductase is also observed in those cells as compared to the level of cells grown on glycerol. The most efficient inducers of the hydroxylase and of cytochrome P-450 are straight-chain alkanes having at least 10 carbon atoms. Alkenes and higher alcohols are also good inducers. There is little or no growth on ramified hydrocarbons such as pristane and on long-chain aldehydes and fatty acids. The partial inhibition of growth on decane is probably due to the denaturation of the microsomal electron carrier systems by the fatty acid formed by hydroxylation of the decane in the yeast.