- Volume 104, Issue 1, 1978

β-Hydroxybutyrate dehydrogenase (EC 1.1.1.30) was purified 145-fold from Mycobacterium phlei ATCC354 by ammonium sulphate fractionation and DEAE-cellulose chromatography. The pH optima for oxidation and reduction reactions were 8.4 and 6.8 respectively. The purified enzyme was specific for NAD, NADH, acetoacetate and d( − )-β-hydroxybutyrate. K m values for dl-β-hydroxybutyrate and NAD were 7·4 mm and 0.66 mM respectively. The enzyme was inactivated by mercurial thiol inhibitors and by heat, but could be protected by NADH, Ca2+ and partially by Mn2+. The enzyme did not require metal ions and was insensitive to EDTA, glutathione, dithiothreitol, β-mercaptoethanol and cysteine.

The effects of temperature and growth rate on the fatty acid composition of the extractable lipids of four mesophilic and three psychrotrophic bacteria were examined. Two of the mesophiles (Escherichia coli and Pseudomonas aeruginosa) increased the proportion of unsaturated fatty acids in their lipids with decreasing temperature over their whole growth temperature range. The other mesophiles (Enterobacter aerogenes and Lactobacillus casei) increased the proportion of unsaturated fatty acids with decreasing temperature only over the lower half of their growth temperature ranges. The psychrotrophs Pseudomonas fluorescens and Enterobacter sp. had a constant proportion of unsaturated acids over the lower half of their growth temperature range, while the psychrotrophic Lactobacillus sp. showed no consistent change in its unsaturated fatty acid composition with temperature. All species showed some variation of unsaturated fatty acid composition with growth rate at the highest and lowest growth temperatures, although such variations were small in some species (Ent. aerogenes and Lactobacillus sp.).

Exopolysaccharide formation by Pseudomonas ncibii264 in a single-stage continuous culture was maximal under nitrogen limitation with excess carbohydrate substrate at 30±1 °C and pH 7·0±0·1 Polysaccharide production was not enhanced by phosphate limitation but was dependent on the dilution rate. Steady states were maintained for up to 500 h without deterioration of the culture or the development of mutant strains. The efficiency of conversion of the glucose substrate utilized into exopolysaccharide by the chemostat cultures was as high as 73%.

The pectic enzymes of six strains of pigmented, pectolytic clostridia isolated from potatoes were examined and compared with those strains of Clostridium felsineum and Clostridium aurantibutyricum using cup-plate assays. The organisms could be divided into two groups. Group 1 consisted of the potato isolates and the strain of C. aurantibutyricum; these formed pectic lyase enzymes and pectinesterase but no pectic hydrolase. Group 2 consisted of eight strains of C. felsineum (and one culture labelled Clostridium roseum); these formed pectic lyase and pectic hydrolase but no detectable pectinesterase. Viscometric studies and analyses of degradation products of pectate formed by enzymes of four representative strains from group 1 and two strains from group 2 showed that all these clostridia formed endopectate lyase enzymes; studies of one enzyme preparation showed that the pH optimum was about 9·5. In addition, the group 2 organisms formed endopolygalacturonase and probably also exopolygalacturonase.

The attachment and entry of Trypanosoma dionisii to mouse peritoneal macrophages in vitro were studied. Both occurred to a similar extent whether parasites were alive or heat-killed, and whether macrophages were obtained from normal or immunized mice. Attachment occurred equally at 4 and 37 C, but entry only occurred at the higher temperature. Neither was affected by pretreatment of parasites with active or inactivated complement. Entry, but not attachment, was inhibited by cytochalasin B; both were inhibited by trypsin. Immune mouse plasma (if inactivated) stimulated attachment but not entry (within 24 h). It also stimulated intracellular replication of T. dionisii by multiple fission and subsequent differentiation (probably within macrophages) to small extracellular trypomastigotes. No extracellular parasite and only scanty intracellular forms survived 120 h in cultures containing non-inactivated immune mouse plasma. It was concluded that attachment (in the absence of antibody) occurred to non-specific receptors in the macrophage membrane and was followed by phagocytosis of the parasites rather than their active penetration of the cell.

Equations have been developed for assimilation of methane, methanol, methylamine, dimethylamine, trimethylamine, formaldehyde and formate into cell material by bacteria using the ribulose monophosphate pathway, the ribulose bisphosphate pathway and the serine pathway of carbon assimilation. The equations have been used for predicting the effect on cell yields (Y s, Y o2 and Y co2) of various P/O ratios, systems for substrate oxidation and assimilation pathways. The generalizations relating P/O ratios and cell yields, which have been used previously for such calculations, are not always applicable to methylotrophs. In particular, for the majority of methylotrophs the growth yield is determined by NAD(P)H supply as well as ATP supply, and for some methylotrophs growth yields may be exclusively NAD(P)H-limited. Because of this NAD(P)H limitation, the concept of Y ATP in methylotrophs should be used with extreme caution.

Neocallimastix frontalis zoospores showed chemotaxis to a range of carbohydrates, but not to the common amino acids, purines, pyrimidines or vitamins. Four chemoreceptors were identified: the glucose receptor, sensitive to d-glucose, d-galactose, d-xylose, l-sorbose, d-fucose and 2-deoxy-d-glucose; the sucrose receptor, sensitive to sucrose, d-fructose and raffinose; the mannose receptor, sensitive to d-mannose and d-glucose; and the sorbitol receptor, sensitive to d-sorbitol and d-mannitol. Growth of the vegetative stage of N. frontalis did not occur with d-xylose, l-sorbose, d-fucose, 2-deoxy-d-glucose, raffinose, d-mannose or d-sorbitol. The zoospores were attracted to carbohydrate mixtures representing the soluble carbohydrates found in different barley tissues; the highest response was with those mixtures representing carbohydrates of awn and inflorescence tissue. Chemotaxis also occurred preferentially to the awn and inflorescence tissue carbohydrate combinations rather than to carbohydrate combinations representing other tissues. Germination of the zoospores occurred in medium containing glucose in excess of 10−4 m.

The mean base compositions of DNA from 27 strains of Pseudomonas putrefaciens, P. rubescens and P. piscicida ranged from 43·4 to 53·2 mol % GC with genome sizes from 3·04 × 109 to 4·23 × 109 daltons. On the basis of in vitro DNA-DNA binding, estimated spectrophotometrically from initial renaturation rates, P. putrefaciens strains were heterogeneous in the extent to which they shared similar nucleotide sequences, and were divided into four DNA homology groups. The DNA characteristics of strains in these groups correlated with several biochemical characteristics that facilitated identification of clinical isolates of P. putrefaciens. The two species P. putrefaciens and P. rubescens appear to be synonymous and none of the four groups of P. putrefaciens was related in DNA sequences to P. piscicida. Pseudomonas putrefaciens should therefore be retained as a single species and characteristics for identifying the various groups within the species are listed.

Phenetic data on over 600 heterotrophic bacteria from green leaves of Lolium perenne s24 were collected and analysed using numerical taxonomic methods. Marker strains representing 60 taxa were included in the analyses. At similarity levels of 80 % or above, 74 % of the isolates were recovered in six major and 45 minor phena. Four of the major phena were equated with the taxa Listeria grayi/murrayi, Pseudomonas fluorescens, Staphylococcus saprophyticus and Xanthomonas campestris; the two unidentified phena contained pink, Gram-negative rods with polar flagella. Xanthomonads and pink chromogens formed high populations in May, xanthomonads and pseudomonads in July, xanthomonads in September and listeriae and staphylococci in October. It seems that despite the spatial proximity of leaves, litter and soil, each of these habitats contains independent bacterial communities with specific properties.