Acinetobacter calcoaceticus

A strain of Acinetobacter calcoaceticus produces an unusual polysaccharide called emulsan. It is a complex polymer comprising about 15% fatty acyl esters and 20% protein. This structure enables it to act as an emulsifying agent, stabilising hydrocarbon/water emulsions at very low concentrations (0.1-1.0%). This property,... 

Several glyculosonic acids have been identified as components of bacterial polysaccharides. D-/yxo-Hexulosonic acid, as Q -D-pyranosyl residues (23), is a component of the extracellular polysaccharide from a Rhodococcus species. The LPS from Acinetobacter calcoaceticus NCTC 10305 contains - D-g/ycero-D-/a/o-octulosonic acid (24). It is isosteric with 3-deoxy-D-mnnno-octulosonic acid (25), which is a constituent of bacterial LPS and links the polysaccharide part to the lipid A region. It seems possible that D-g/ycero-D-tfl/o-octulosonic acid replaces 3-deoxy-D-/wan o-octulosonic acid in the A. calcoaceticus LPS. 

Hydroxylation of n-octane by cell extracts of Gordonia (Corynebacterium) sp. strain 7E1C (Cardini and Jurtshuk 1968), and of some strains of Acinetobacter calcoaceticus induced with -hexadecane (Asperger et al. 1981). 

Kataoka M, K Honda, S Shimizu (2000) 3,4-Dihydrocoumarin hydrolase with haloperoxidase activity from Acinetobacter calcoaceticus. Eur J Biochem 267 3-10. 

Neidle EL, C Hartnett, LN Ornmston, A Bairoch, M Rekin, S Harayama (1991) Nucleotide sequences of the Acinetobacter calcoaceticus benABC genes for benzoate 1,2-dioxygenase reveal evolutionary relationship among multicomponent oxygenases. J Bacteriol 173 5385-5395. 

Wy ndham RC (1986) Evolved aniline catabolism in Acinetobacter calcoaceticus during continuous culture of river water. Appl Environ Microbiol 51 781-789. 

This pathway is supported by the demonstration of benzyl alcohol dehydrogenase, benzaldehyde dehydrogenase, benzoyl-CoA ligase, and benzoyl-CoA reductase activities in cell extracts (Biegert and Fuchs 1995). The benzyl alcohol dehydrogenase from benzyl alcohol-grown cells was similar in many of its properties to those from the aerobic bacteria Acinetobacter calcoaceticus and Pseudomonas putida (Biegert et al. 1995). 

Freeman, R. Sisson, P. R. Noble, W. C. Lightfoot, N. F. An apparent outbreak of infection with Acinetobacter calcoaceticus reconsidered after investigation by pyrolysis mass spectrometry. Zbl. Bakt. 1997, 285, 234-244. 

A well-studied example of a bioemulsifier is emulsan, a cell surface-exposed molecule that allows Acinetobacter calcoaceticus RAG-1 to attach to crude oil droplets [123]. Upon depletion of the short-chain alkanes utilised by this strain, the emulsan molecules were released from the bacterial surface, thereby allowing the cells to leave the oil droplet and to find a new substrate. Important positive side-effects of this mechanism seem to be that the remaining emulsan hydrophilises the droplet and prevents both the reattachment of A. calcoaceticus RAG-1 and the coalescence of the used oil droplet with other droplets that still contain unexploited alkanes. Bredholt et al. [124] studied the oil-emulsifying activity of Rhodococcus sp. strain 094. When exposed to inducers of crude-oil emulsification, the cells developed a strongly hydrophobic character, which was rapidly lost when crude-oil emulsification started. This indicated that the components responsible for the formation of cell-surface hydrophobi-city acted as emulsion stabilisers after release from the cells. 

Kim, Y.S. Park, C. Inactivation of Acinetobacter calcoaceticus acetate kinase by diethylpyrocarbonate. Biochim. Biophys. Acta, 956, 103-109 (1988)... 

Lorenz, M. G., Reipschlager, K. Wackernagel, W. (1992). Plasmid transformation of naturally competent Acinetobacter calcoaceticus in non-sterile soil extract and groundwater. Archives of Microbiology, 157, 355-60. 

Rosenberg, E., Rosenberg, M., Shoham, Y., Kaplan, N. Sar, N. (1989). Adhesion and desorption during growth of Acinetobacter calcoaceticus on hydrocarbons. In Microbial Mats, ed. Y. Cohen E. Rosenberg, pp. 218-26. Washington, DC ASM Publications. 

Rosenberg, M., Bayer, E. A., Delaria, J. Rosenberg, E. (1982). Role of thin fimbriae in adherence and growth of Acinetobacter calcoaceticus RAG-1 on hexadecane. Applied and Environmental Microbiology, 44, 929-37. 

Similarly, Zosim, Gutnik Rosenberg (1983) have reported uranium binding by emulsan (up to 240 mg uranium (U02 + 2)/mg emulsan), a bioemulsifier produced by Acinetobacter calcoaceticus RAG-1. The intriguing aspect of this system is that in a hexadecane-water solution, the emulsan preferentially binds to the hexadecane-water interface, which effectively concentrates the complexed uranium for easy recovery. 

Similarly, bioemulsifiers, such as emulsan produced by Acinetobacter calcoaceticus, have been shown to aid in removal of metals. Potential for remediation of soils using bacterial exopolymers is indicated by a study which showed that purified exopolymers from 13 bacterial isolates removed cadmium and lead from an aquifer sand with efficiencies ranging from 12 to 91% (Chen et al., 1995). Although such molecules have much larger molecular weights ( 106) than biosurfactants, this study showed that sorption by the aquifer sand was low, suggesting that in a porous medium with a sufficiently. large mean pore size, use of exopolymers may be feasible. 

Battey, A.S. and Schaffner, D.W. (2001) Modelling bacterial spoilage in cold-filled ready to drink beverages by Acinetobacter calcoaceticus and Gluconobacter oxydans Journal of Applied Microbiology 91(2), 237-247. 

Other enzymes capable of halogenation processes include a bacterial esterase from Pseudomonas fluorescens (2316), acid phosphatases from the bacteria Shigella flexneri and Salmonella enterica ser. typhimurium (2317), a lactonohydrolase from Acinetobacter calcoaceticus F46 (2318), and hydroperoxide halolyse from the marine diatom Stephanopyxis turris (2319). The biosynthesis of the ubiquitous methyl halides seems to involve methyl transferase enzymes, which have been isolated and purified in the plant Brassica oleracea (S -adenosyl-L-methionine ... 

Baeyer-ViUiger oxidation involves NADPH and flavin (FAD) as cofactors and was originally proposed by Walsh et al. based on data obtained from cyclohexanone monooxygenase (CHMO) from Acinetobacter calcoaceticus (Fig. 24) [156]. In a first step, enzyme-bound flavin is reduced, followed by the addition of oxygen yielding a hydroperoxide anion. Reaction with the ketone substrate gives a Criegee intermediate, which is then converted into the product under dissociation of water. The cofactor FAD is recovered via oxidation with NADP+. 

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