Predominant growth of Alcanivorax during experiments on "oil spill bioremediation" in mesocosms. (1/17)

Mesocosm experiments were performed to study the changes on bacterial community composition following oil spill in marine environment. The analysis of 16S crDNA revealed a shift in the structure of initial bacterial population that was drastically different from that one measured after 15 days. The results showed that, after 15 days, bacteria closely related to the genus Alcanivorax became the dominant group of bacterial community in petroleum-contaminated sea water nitrogen and phosphorus amended. This suggested that these bacteria played the most important role in the process of bioremediation of oil-contaminated marine environments.  (+info)

Analysis of storage lipid accumulation in Alcanivorax borkumensis: Evidence for alternative triacylglycerol biosynthesis routes in bacteria. (2/17)

Marine hydrocarbonoclastic bacteria, like Alcanivorax borkumensis, play a globally important role in bioremediation of petroleum oil contamination in marine ecosystems. Accumulation of storage lipids, serving as endogenous carbon and energy sources during starvation periods, might be a potential adaptation mechanism for coping with nutrient limitation, which is a frequent stress factor challenging those bacteria in their natural marine habitats. Here we report on the analysis of storage lipid biosynthesis in A. borkumensis strain SK2. Triacylglycerols (TAGs) and wax esters (WEs), but not poly(hydroxyalkanoic acids), are the principal storage lipids present in this and other hydrocarbonoclastic bacterial species. Although so far assumed to be a characteristic restricted to gram-positive actinomycetes, substantial accumulation of TAGs corresponding to a fatty acid content of more than 23% of the cellular dry weight is the first characteristic of large-scale de novo TAG biosynthesis in a gram-negative bacterium. The acyltransferase AtfA1 (ABO_2742) exhibiting wax ester synthase/acyl-coenzyme A:diacylglycerol acyltransferase (WS/DGAT) activity plays a key role in both TAG and WE biosynthesis, whereas AtfA2 (ABO_1804) was dispensable for storage lipid formation. However, reduced but still substantial residual TAG levels in atfA1 and atfA2 knockout mutants compellingly indicate the existence of a yet unknown WS/DGAT-independent alternative TAG biosynthesis route. Storage lipids of A. borkumensis were enriched in saturated fatty acids and accumulated as insoluble intracytoplasmic inclusions exhibiting great structural variety. Storage lipid accumulation provided only a slight growth advantage during short-term starvation periods but was not required for maintaining viability and long-term persistence during extended starvation phases.  (+info)

Alcanivorax balearicus sp. nov., isolated from Lake Martel. (3/17)

A bacterial strain designated MACL04(T) was isolated from Lake Martel, a subterraneous saline lake in Mallorca (Spain). The complete 16S rRNA gene sequence of this strain showed nearly 100 % similarity to that of Alcanivorax dieselolei B-5(T). Despite this high similarity, strain MACL04(T) showed phenotypic, chemotaxonomic and molecular differences with respect to A. dieselolei, indicating that strain MACL04(T) represents a separate species. Cells of strain MACL04(T) were motile by means of a single polar or subpolar flagellum and colonies formed on media containing 1 % (v/v) Tween 20 were opaque and mucoid, with blue-green iridescence. The generation time of strain MACL04(T) in this medium was approximately half that of A. dieselolei B-5(T) and strain MACL04(T) did not produce lipases after incubation for 5 days. Strain MACL04(T) did not require NaCl for growth and grew in the presence of up to 15 % (w/v) NaCl. The strain was able to use alkanes as a sole carbon source; however, glucose could also be used, albeit weakly, as a carbon source. Several amino acids and organic acids were used as carbon sources. Strain MACL04(T) produced acid in media containing pyruvate as the sole carbon source. The major fatty acids were C(19 : 0) cyclo omega8c and C(16 : 0). The fatty acid C(16 : 1)omega8c, present in strain MACL04(T), was not detected in the recognized Alcanivorax species. The sequences of the large and short 16S-23S intergenic spacer regions showed similarities of 97.2 and 98.8 % (ungapped) with respect to A. dieselolei B-5(T). Partial sequences of gyrB and alkb genes showed 94.0 % similarity between strain MACL04(T) and A. dieselolei B-5(T). The G+C content of strain MACL04(T) was 62.8 mol%. The data from this polyphasic study indicate that strain MACL04(T) represents a novel species of the genus Alcanivorax, for which the name Alcanivorax balearicus sp. nov. is proposed. The type strain is MACL04(T) (=LMG 22508(T)=CECT 5683(T)).  (+info)

Alcanivorax hongdengensis sp. nov., an alkane-degrading bacterium isolated from surface seawater of the straits of Malacca and Singapore, producing a lipopeptide as its biosurfactant. (4/17)

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Denitrifying activity and homologous enzyme analysis of Alcanivorax dieselolei strain N1203. (5/17)

An Alcanivorax dieselolei strain, termed strain N1203, was isolated from the consortia of ammonia-oxidizing bacteria (AOB) combined with denitrifying bacteria from our previous study and was shown to have ability to reduce nitrate to nitrite to either nitrous oxide or molecular nitrogen. Analysis of 16S rRNA gene sequences established strain N1203 as a member of the species Alcanivorax dieselolei. In addition, the ability of strain N1203 to utilize various organic substrates as the sole carbon source, supplemented with carbohydrates, amino acids, and n-alkane compounds, was investigated, and this strain was found to have a narrow substrate range of growth such as grycerol, succinate, ethanol and n-alkane hydrocarbon. Furthermore, N1203's stepwise denitrifying activity, utilizing succinate and hexadecane as sole carbon sources, was measured. Gene fragments of nirK and qnorB genes, which are involved in denitrifying activities, were obtained, cloned and sequenced. Phylogenetic analysis for these two genes showed that both the nirK and qnorB sequences, although found in separate branches within clusters, formed subclusters branching from uncultured environmental clones. This demonstrated the typical uniqueness of these genes from any cultivated denitrifiers. Thus, strain N1203 is novel type of denitrifying bacteria that demonstrated denitrifying activities when cultivated using succinate as the sole carbon source.  (+info)

Analysis of lipid export in hydrocarbonoclastic bacteria of the genus Alcanivorax: identification of lipid export-negative mutants of Alcanivorax borkumensis SK2 and Alcanivorax jadensis T9. (6/17)

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Kangiella japonica sp. nov., isolated from a marine environment. (7/17)

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Isolation and characterization of a mutant of the marine bacterium Alcanivorax borkumensis SK2 defective in lipid biosynthesis. (8/17)

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