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The phenotypic adaptation of membrane lipids in seven strains of the food-poisoning bacterium Bacillus cereus, isolated from Bangladeshi rice, is reported in relation to their ability to grow under conditions of low water activity ([a.sub.w]), reduced temperature and the presence of soluble rice starch. The strains have different membrane phospholipid head-group and fatty acyl compositions, and they display individual differences in their responses to both low aw and reduced temperature. The extent of the increase in anionic membrane lipids in response to low [a.sub.w] varies from strain to strain, is solute specific and in one strain does not occur. Growth is Stimulated by the presence of soluble rice starch and results in a large rise in the proportion of diphosphatidylglycerol (DPG) at the expense of phosphatidylglycerol (PG), without any change in the proportion of total anionic phospholipids. Growth at 15 [degrees]C compared with 37 [degrees]C increases the proportions of DPG and phosphatidylethanolamine at the expense of PG. At the lower temperature there are changes in phospholipid fatty acyl composition characteristic of those expected to maintain membrane fluidity, including increases in the amount of total branched fatty acids and the anteiso-/iso-branched ratio, and a decrease in the equivalent chain-length, but there are strain differences in how those changes were achieved. In contrast to some other bacilli, there are persistent large increases in the proportions of unsaturated fatty acyl chains in phospholipids during growth at 15 [degrees]C.

The previously identified second citrate synthase gene of Escherichia coli is actually a 2-methylcitrate synthase with some citrate synthase activity. 2-Methylcitrate synthase catalizes the formation of 2-methylcitrate from propionyl-Co-A and enables E. coli to utilize propionate as a carbon source. The evolutionary relationship between 2-Methylcitrate synthase and citrate synthase is investigated by comparing the two with citrate synthases from other organisms.

Microbiological research shows that the 34-amino-acid polypeptide bacteriocin Nisin penetrates the lipid monolayers of diphosphatidylglycerol more than phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, monogalactosyldiacylglycerol and digalactosyldiacylglycerol lipids. Evidence suggests that nisin resistance in the microorganism Listeria monocytogenes is caused by a reduction in diphosphatidylglycerol in the cytoplasmic membrane.

The Pseudomonas sp. strain SC25A degrades the alcohol ethoxylate (PEG) nonionic surfactant, monoethylene glycol dodecyl ether (MEGDE), by cleaving the dodecyl-ether bond to form dodecanol. Dodecanol is further degraded to form dodecanal and then dodecanoic acid. The dodecanoic acid is used as a substrate in the main metabolic pathways to form CO2. The biodegradation process involves omega-oxidation. The cleavage products of MEGDE are easily assimilated by the bacteria. However, the cleavage of higher ethoxamers produces a PEG fragment containing the ether, needing further degradation.

The fatty acid components and temperature/growth characteristics of a psychrophilic bacterium ACAM 456 obtained from Antarctic sea-ice are presented. The acyl components can be classified into three groups; even-chian, odd-chain and iso-branched odd-chain. ACAM 456 changed its use of the acyl primer molecules to be able to adapt to changes in the environment. The regulation of the odd-chain length fatty acids illustrate an unusual adaptational response.

Substances containing the ether linkage are somewhat resistant to biodegradation but are still degraded by microorganisms. Studies of microbial degradation of ether linkages has shown eight systems used by microorganisms: oxygenases, cytochromes P-450, hydroxyl shift, hydrolysis, anaerobic cleavage of methyl-aryl ethers, oxidative mechanisms, reductive mechanisms and carbon-oxygen lyases.

The Biolog microtitre plate assay accurately identifies the bacteria which are capable of degrading sulfated and sulphonated anionic surfactants. The method estimates the reduction of the tetrazolium dye to determine the sole-carbon-source usage by the bacteria. Application of the method to pure and mixed cultures provides reproducible results without any false-positives. The bacterial cultures are tested directly without the need of intermediate growth of the culture. The bacteria identified are primary and final degraders of the surfactants.

Microcosm experiments help analyze the influence of anionic surfactant sodium dodecyl sulphate (SDS) on the attachment of five Pseudomonas strains, three strains expressing enzymes to hydrolyze SDS and two without the enzymes, to riverine sediment. The addition of SDS stimulates the attachment of bacteria to sediments having biodegradation-competent strains, while SDS addition exerts no influence on the weak attachment of biodegradation-incompetent strains. The stimulation accompanies fast biodegradation of the surfactant producing an intermediate, dodecan-1-ol.

Kinetic studies of the biodegradation of sulphosuccinate by a bacterium, Pseudomonas sp. BS1, exhibiting the capacity to grow on sulphosuccinate as the sole source of carbon and energy reveal that the biodegradation involves a direct desulphonation. Bacterial cultures convert the sulphosuccinate into a sulphite, which undergoes oxidation producing a sulphate. Kinetic data facilitate the evaluation of the sequence of desulphonation and carbon-chain catabolism. Catabolism of the C4 chain is absent during direct desulphonation. The oxidative desulphonation mechanism accounts for the formation of sulphite and oxaloacetate from sulphosuccinate.

Metabolic studies of Pseudomonas aeruginosa reveal that the GDP-mannose dehydrogenase (GMD) enzyme encoded in the algD gene modulates alginate biosynthesis. Overexpression of the algG gene results in an increase in GMD function and GDP-mannuronate levels and a decrease in GDP-mannose levels. A small increase in exopolysaccharide production is found in the mucoid strains.

The biosynthesis of cyclopropane fatty acids (CFA) in Pseudomonas halosaccharolytica was computed by employing radiolabelled S-adenosylmethionine as the precursor incubated in cell-free extracts derived by the break up of bacteria. The CFA activity was deferred by the addition of NaCl or KCl but was stimulated by the addition of glycinebetaine. These observations were compared to those of the 100 mM-phosphate buffer.

The metabolic regulation of alginate biosynthesis by the enzyme GDP-mannose dehydrogenase (GMD) in mucoid and non-mucoid strains of Pseudomonas aeruginosa was described. The mucoid strains contained significantly lower levels of GDP-mannose compared with the isogenic non-mucoid strains. However, the GDP-mannose concentrations in mucoid strains were significantly greater than those of the product of GMD activity, GDP-mannuronate. It was thus demonstrated that GMD regulates alginate biosynthesis in mucoid P. aeruginosa.