Monique Acquaviva

Biodegradation of hydrocarbons by an extremely halophilic archaebacterium

An archaebacterium (strain EH4) able to biodegrade saturated and aromatic hydrocarbons has been isolated from a sail‐marsh. Maximum growth on eicosane (62% of biodegradation, 10 h generation time) was reached in a medium prepared with a natural hypersaline water collected from a salt‐marsh (3.5 mol/1 NaCl concentration). No growth on hydrocarbons was observed for NaCl concentration lower than 1.8 mol/1.

Effects of petroleum hydrocarbons on the phospholipid fatty acid composition of a consortium composed of marine hydrocarbon-degrading bacteria

Phospholipid ester-linked fatty acids (PLFAs) of a bacteria consortium, reconstituted in vitro from ten marine hydrocarbon-degrading bacteria, were studied. Culture of the consortium with ammonium acetate as the sole carbon source mainly yielded even-numbered PLFAs composed of straight chain saturated (ca. 26%) and monounsaturated (ca. 71%) fatty acids. Growth of the consortium on Blend Arabian Light petroleum (BAL 250) resulted in a complex PLFA profile with the appearance of (1) odd-numbered straight chain PLFAs, mainly 15:0 and 17:0, (2) iso- and anteiso-PLFAs with 15–17 carbon atoms, (3) 10-, 11-, 12- and 13-monomethylated PLFAs with 16–19 carbon atoms and (4) odd-numbered monounsaturated PLFAs, mainly 17:1 Δ9Z and 19:1 Δ10. When petroleum grown cells were transferred into a medium containing ammonium acetate, the consortium exhibited mainly even-numbered PLFAs: this demonstrated the ability of bacterial strains to restore their PLFA compositions after exposure to petroleum hydrocarbons. It, therefore, appears that the PLFA compositions of these bacteria are strongly influenced by the carbon sources so that several potential biomarkers of hydrocarbon-degrading bacterial activities could be recognized. In addition, an hydrocarbon-degrading activity index (HDAI) was derived from the characteristic PLFA profiles of the consortium grown on ammonium acetate and petroleum hydrocarbons. The HDAI may prove to be a tool revealing the development of hydrocarbon-degrading strains in oil-contaminated sediments.

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.

Effect of Sodium Chloride Concentration on Growth and Degradation of Eicosane by the Marine Halotolerant Bacterium Marinobacter hydrocarbonoclasticus

Summary The extremely halotolerant marine species Marinobacter hydrocarbonoclasticus presents an absolute requirement for NA + ions. When grown on acetate or eicosane, lag phase of cultures and generation time of cells increased exponentially at NaCl concentrations ≥1.0M whereas the final biomass did not vary significantly (p≤0.05) when salinity increased from 0.2 to 2.5 M NaCl. The increase in salinity induced morphological changes with increased cell size. Scanning electron microscopy revealed extracellular vesicles on cells grown on eicosane. High salinity did not modify hydrocarbon biodegradation rates (80–90% biodegraded eicosane). This bacterium produced an extracellular emulsifying agent and adhered to hydrocarbon, but did not solubilize it before uptake. Both emulsification and adherence took place during growth on eicosane, achieving contact between cells and hydrocarbon. An increase in external NaCl concentration modified emulsifying activity and adherence ability, but not the biodegradation rates.

Hydrocarbon biodegradation and hydrocarbonoclastic bacterial communities composition grown in seawater as a function of sodium chloride concentration

Bacterial strains have been enriched and isolated from marine sediment of an oil-contaminated area and grown in a culture medium prepared with synthetic seawater (0.4 M NaCl) and containing crude oil (EH1 community) or an hydrocarbon mixture (EH2 community) as sole energy and carbon source. The strains isolated from crude oil were code named EH1 community; those from the mixture EH2 community. Hydrocarbon biodegradation in enrichment culture was maximum for 0.4 M NaCl and decreased for NaCl concentrations above or below this value. However, the effect of NaCl concentration depended somewhat on the nature of the substrate supplied for growth. With 2 M NaCl, the saturated fraction of crude oil was the only one significantly biodegraded (27%). In contrast, the level of biodegradation remains rather high for the standard hydrocarbon mixture: 80–95% for saturated hydrocarbons, 17–34% for aromatics. Few phenotypic differences were noted between strains growing on crude oil (EH1) and/or mixture of hydro-carbons (EH2). The clustering of the strains isolated after enrichment at various NaCl concentrations (from 0 to 2 M NaCl) demonstrated the presence of ecotypes of similar bacterial species. From initial enrichments most of the strains were Gram-negative, aerobic rods, possessing few exoenzymes and using mostly fatty acids and organic acids as carbon and energy sources.

Isolation of alkane‐degrading bacteria from deep‐sea Mediterranean sediments

Aims:  To isolate and identify alkane‐degrading bacteria from deep‐sea superficial sediments sampled at a north‐western Mediterranean station.

Anaerobic oxidation of 1-n-heptadecene by a marine denitrifying bacterium

SummaryA denitrifying bacterium showing typical characteristics of Pseudomonas sp. (Al1) capable of growth on 1-heptadecene as the sole source of carbon and energy has been isolated from a hydrocarbon-polluted marine sediment by using classical enrichment techniques. The generation time for anaerobic growth on 1-heptadecene was 24 h, and the percentage of hydrocarbon degradation under anaerobic conditions ranged from 19 to 23%. The emulsifying capacity was observed and suggested that Al1 cultivated anaerobically on heptadecene produced surface-active agents.

N-alkane biodegradation by a marine bacterium in the presence of an oleophilic nutriment

SummaryHexadecane biodegradation by a marine bacterium has been investigated in the presence of an oleophilic nutriment (INIPOL EAP 22). Hydrocarbon attack was only observed after metabolism of the fatty acids present in the fertilizer. The bacterium used up 95 % fatty acids in the first 24 hours. Hexadecane biodegradation took place after 50 h incubation and reached 40 % after 360 h.

Arabian light 150 asphaltene biotransformation with n-alkanes as co-substrates

The biotransformation of Arabian Light oil asphaltene has been studied with an n-alkane mixture as a co-substrate. The experiments were conducted in synthetic sea water with a hydrocarbonoclastic mixed population of 10 bacterial strains. After a one-month exposure, the mass loss of asphaltenes in the test flasks was partly due to an abiotic process (18 %) and to a biotic process by co-metabolism (5 %). Hydrocarbons previously trapped in the asphaltenic matrix were also released in the evaporation control flasks. Aromatic and polar fractions appeared in both test and control flasks were analysed by GC/FID, GC/MS and FTIR showing qualitative and quantitative differences, involving the identification of aromatic degradation products.

n-Alkane degradation by Marinobacter hydrocarbonoclasticus strain SP 17: long chain β-hydroxy acids as indicators of bacterial activity

Abstract The lipids of the Gram-negative marine bacterium Marinobacter hydrocarbonoclasticus , cultivated in synthetic seawater on a single carbon source, acetate or n -icosane, were isolated, purified and their structures determined. Three different pools of lipids were isolated according to the sequential procedure used: “unbound” lipids extractable by solvents, lipids released under basic conditions (“ester bound”) and lipids released by acid hydrolysis (“amide bound”). Even-carbon-numbered, n -fatty acids were identified in the “unbound” lipids of both the acetate and n -icosane cultures. In addition to these compounds, n -icosane induced the formation of n -icosan-1-ol and n -icos-11-en-1-ol, and also of a series of β-hydroxy acids ranging from C 12 to C 20 . In the “ester bound” lipids of the two cultures, short and long chain fatty acids were identified together with the β-hydroxy C 12:0 acid. This hydroxy acid was, by far, the major compound identified in the “amide bound” lipids of the two cultures. Comparison of the analytical data for the two cultures, and the differences in composition thus observed for the “unbound” pool, suggest the following metabolic pathway for n -icosane: hydroxylation to the C 20 primary alcohol, transformation into the C 20 β-hydroxy acid and subsequent degradation into lower homologues. In sharp contrast, lipids from the “ester bound” and “amide bound” pools were quite unaffected by the change of nutrient. Lipids from Escherichia coli were also examined in the same manner. The results are discussed in terms of geochemical implications, relative to the presence of “unbound” β-hydroxy acids in particulate matter and sediments.