- Volume 132, Issue 4, 1986

Cell-surface hydrophobicities of six Candida species were studied by two methods: measurement of the contact angle, and partitioning with aqueous-hydrocarbon (n-octane, n-hexadecane and p-xylene) mixtures. C. tropicalis, C. glabrata and C. krusei adhered better to the hydrocarbons than did C. albicans, C. stellatoidea and C. parapsilosis. Contact angles for the less adherent species were smaller than those for the more adherent species. Thus the two methods gave results that were similar overall and indicated that C. tropicalis, C. glabrata and C. krusei have greater cell-surface hydrophobicities than C. albicans, C. stellatoidea and C. parapsilosis.

The oxidative metabolism (chemiluminescence and H2O2 release) and phagocytic activity of mouse peritoneal macrophages during chronic infections induced by Mycobacterium intracellulare and more acute infections due to Listeria monocytogenes were studied. In M. intracellulare infections, macrophage chemiluminescence in response to phorbol myristate acetate (PMA) was greatest at around 2 weeks, with a 1 week lag phase after infection, while the PMA-triggered H2O2 release was markedly enhanced even 1 d after challenge, and remained high thereafter for up to 10 weeks. The pattern of changes in the phagocytic activity of host macrophages in response to latex beads during this infection resembled the pattern seen with macrophage H2O2 release. In the L. monocytogenes infections, the PMA-triggered chemiluminescence of the host macrophages increased 4 d (in a sublethal infection) and 2 d (in a lethal infection) after bacterial challenge, whereas the PMA-triggered H2O2 release was markedly enhanced as early as 1 d after infection and the elevated level persisted until either the bacteria were eliminated or the animals died. The patterns of changes in phagocytic activity of the host macrophages during L. monocytogenes infection at sublethal and lethal doses differed. In the former, phagocytosis was most active in the early phase of infection, with a peak around day 2, followed by a rapid decrease; in the latter, the phagocytic ability increased more slowly, and remained elevated until the animals died. The results suggest that the macrophages induced by M. intracellulare are in a more activated state than are those induced by L. monocytogenes.

A microbial agent was isolated previously from a case of Viluy encephalomyelitis and named the ‘KPN agent’ after the initials of the patient. Here a detailed characterization of nucleic acids extracted from the purified KPN agent is presented. The agent contains both DNA and RNA, and has its own tRNAs and some other low-M r RNAs, including 5S RNA. These findings, and the isolation of eukaryotic-type ribosomes, suggest that the KPN agent is not a virus, as believed before, but a more complex micro-organism, with protein-synthesizing capacity. The nucleotide sequence of the 5S RNA in the ribosomes of the KPN agent is identical with the sequence of 5S RNA of Acanthamoeba castellanii. The novel protozoan nature of the KPN agent is discussed in relation to other unusual properties of this micro-organism. Some implications of these results for the aetiology of Viluy encephalomyelitis are also discussed.

The effect of the β-lactam antibiotic cephalexin on the spiral conformation of cells of Aquaspirillum spp. was examined by scanning electron microscopy. A. itersonii and A. peregrinum, which are known to have a left-handed spiral shape, elongated and still showed left-handed spirals in medium containing cephalexin. The spiral conformation of the elongated cells is therefore considered to represent the natural condition. The spiral conformations of A. metamorphum and A. psychrophilum grown in ordinary cultures were difficult to determine because they have short cells without a complete spiral. After cephalexin treatment, the cells of these species elongated and displayed spiral forms, right-handed in A. metamorphum and left-handed in A. psychrophilum. This elongation method may be useful for checking and determination of the spiral handedness of short spiral or curved bacteria such as vibrios.

Cells of the fission yeast Schizosaccharomyces pombe, normally sausage-shaped, changed to a round-bottomed flask (RBF)-like morphology during growth in the presence of aculeacin A (Acu), an antifungal antibiotic. The volume of RBF-like cells was comparable to that of the control cells. After being transferred to normal conditions (without Acu at 25°C), the RBF-like cells continued to grow at the cylindrical and/or spherical end(s) and then the septum at the subsequent division of the cells was formed without exception at the boundary plane between the spheroidal and the cylindrical region; it is at this boundary that the nucleus was located before mitosis. Hence the RBF-like cell divided into a spheroidal and a cylindrical sib at the first cell division. At the end of the second cell cycle, the spheroidal and the cylindrical progeny divided into two spheroidal and two cylindrical sibs respectively. The values of the mean length (long/short) and volume (big/small) ratios of paired sibs were larger in order of (a) cylindrical normal, with both mean ratios 1·06; (b) cylindrical control; (c) cylindrical progeny of RBF-like cell; (d) spheroidal progeny of RBF-like cell; and (e) RBF-like cell, whose mean length ratio was 1·25 but whose mean volume ratio was 1·94. That is, the more the morphology deviated from the cylindrical form, the greater was the degree of asymmetry. There was no rule relating the biases to the growth pole in these asymmetries.

The Vibrio alginolyticus prot-T1 mutant was able to produce haloes of clearing on skim milk/peptone agar plates at 42°C whereas proteolysis by the wild-type strain was inhibited at 37°C. The prot-T1 mutant overproduced the three major alkaline proteases with apparent molecular masses of approximately 28000, 22500 and 19500 (proteases 1a, 2 and 3, respectively). Their synthesis was not markedly repressed by incubation at 37°C or by non-aeration. Both treatments inhibited protease synthesis in the wild-type strain, which only produced proteases during the stationary growth phase. The prot-T1 mutant synthesized proteases throughout the exponential and stationary growth phases in peptone medium. High protease activities were induced by glucose or glutamine in stationary phase prot-T1 that were pre-grown in peptone medium. Glucose or glutamine had the opposite effect on protease activities in stationary phase prot-T1 cultures that were pre-grown in minimal medium. Collagenase synthesis was not altered in the prot-T1 mutant and was repressed by growth at 37° or without aeration. The independent control of collagenase synthesis supports the conclusion that there are no regulatory proteins responsible for the overall control of extracellular protease synthesis by temperature, aeration and growth phase in V. alginolyticus.

Studies on the tricarboxylic acid cycle of Rhodomicrobium vannielii Rm5 demonstrated that, unlike other Rhodospirillaceae, this organism has a functionally incomplete cycle, broken at 2-oxoglutarate dehydrogenase, under photoheterotrophic conditions. This enzyme was, however, synthesized when Rm. vannielii was grown under microaerophilic chemoheterotrophic conditions. The citrate synthase exhibited responses to inhibitors characteristic of Gram-negative organisms but, unlike many microbes exhibiting an incomplete cycle, was not inhibited by 2-oxoglutarate. Both NAD- and NADP-linked isocitrate dehydrogenase activity was detectable but the functional roles of these enzymes are unclear. No significant differences in enzyme activities or inhibitor sensitivities of enzymes were detected between heterogeneous cultures and synchronous swarmer cell populations.

Thermograms obtained by differential scanning calorimetry of a range of bacteria of different heat resistances were compared. Equations were derived to calculate the rate at which the numbers of viable organisms in a calorimeter decline as the temperature is raised at a constant rate. Vegetative bacteria scanned at 10°C min-1 showed multi-peaked thermograms with four major peaks (denoted m, n, p and q) occurring in the regions 68–73, 77–84, 89–99 and 105–110°C respectively. Exceptions were that peak m (the largest peak) occurred at 79–82°C in Bacillus stearothermophilus and an additional peak, r, was detected in Escherichia coli at 119°C. At temperatures below the main peak m there were major differences in thermograms between species. There was a direct relationship between the onset of thermal denaturation and the thermoresistance of different organisms. Heat-sensitive organisms displayed thermogram features which were absent in the more heat-resistant types. When samples were cooled to 5°C and re-heated, a small endothermic peak, pr , was observed at the same temperature as p. Peaks p and pr were identified as the melting endotherms of DNA. In all vegetative organisms examined, maximum death rates, computed from published D and z values, occurred at temperatures above the onset of thermal denaturation, i.e. cell death and irreversible denaturation of cell components occurred within the same temperature range.

l(–)Sorbose, a sugar known to cause paramorphogenesis in fungi, was tested for its effect on morphology and release of cell-wall bound β-glucosidase (EC 3.2.1.21) in the cellulolytic fungus Trichoderma reesei QM9414. Sorbose caused an increase in branching and septation in the growing mycelium. Extracellular β-glucosidase activity was enhanced when cellobiose or cellulose growth medium was supplemented with sorbose. In sorbose-supplemented cultures, the β-glucosidase activity associated with the wall fraction was less than half that in unsupplemented cultures. The intracellular activity was also lower in the sorbose-supplemented cultures than in unsupplemented controls. The glucosamine/glucose ratio of wall hydrolysates from sorbose-supplemented cultures was about twice that of control hydrolysates. Since β-glucosidase is closely associated with 1,3-β-glucan in the walls of T. reesei, a decrease in wall glucan content, and the resulting weakened association of the enzyme with the walls, is probably responsible for its increased release into the culture medium in the presence of sorbose.

A strain of Hyphomicrobium that could utilize methyl chloride as the sole carbon and energy source for growth was isolated from industrial sewage. The methylotroph utilized methyl chloride quantitatively with stoichiometric release of chloride ion. A specific growth rate (μ) of 0·09 h-1 was observed with about 1% (v/v) methyl chloride in the gas phase.