- Volume 105, Issue 2, 1978

A rotating disc method was used to compare the tendencies of two oral streptococci to deposit on to glass and polystyrene surfaces from electrolyte solutions of varying ionic strength. Streptococcus salivarius had a greater tendency to deposit than had Streptococcus mitior under these conditions. In addition to the balance of van der Waals’ forces of attraction and electrostatic forces of repulsion, it is suggested that the adsorption to the glass and polystyrene surfaces of material present in the outer layers of the cell wall could play a significant part in the deposition of S. salivarius.

Reduction of cytochrome c from both horse heart and Candida krusei by FeSO4 has been demonstrated. This reaction was stimulated by nalidixic acid and structurally related compounds, and the effect was more pronounced for the yeast cytochrome. Divalent metal ions other than Fe2+ lessened or abolished the stimulation by these compounds. Fe2+ and other metal ions altered the spectra of nalidixic acid and related compounds indicating the formation of metal chelate complexes. 1,10-Phenanthroline inhibited reduction of cytochrome c by Fe2+. Other divalent metal ions relieved the inhibition, probably by forming chelates with 1, 10-phenanthroline. These results suggest that metal ion chelation may be involved in the molecular mode of action of nalidixic acid and related drugs. The relevance of this artificial election transfer system to bacterial electron transfer in vivo is discussed.

The passive permeation and facilitated diffusion of glycerol in various strains of Escherichia coli have been studied by stopped-flow spectrophotometry. Contrary to the prediction for glycerol entry by simple diffusion, the reciprocal relaxation time (1/𝜏, s−1) for the passive permeation of glycerol in cells grown in the presence of glucose was not constant but decreased as the glycerol concentration increased above 100 mm. This anomaly was not due to refractive index differences or to the presence of residual levels of the glycerol facilitator protein in non-induced cells. Although reciprocal relaxation times for glycerol-induced E. coli exhibited the expected elevation relative to non-induced cells, a similar anomalous decrease of 1/𝜏 (s−1) with increasing glycerol concentration was observed. In addition, at early times after suspension in dilute buffer, the 1/𝜏 (s−1) values obtained for induced or non-induced E. coli swelling in glycerol were considerably greater than for organisms incubated in dilute buffer for longer times. We concluded that either this spectro-photometric technique was not monitoring solely the permeation of glycerol into E. coli, or concentrations of glycerol above 100 mm significantly perturbed the structure of the E. coli cell envelope.

Summary: Sucrose catabolism was studied in Rhodopseudomonas capsulata. Sucrose was hydrolysed by the action of a constitutive cytoplasmic sucrase. The use of a glucose-6-phosphate dehydro-genase-deficient mutant and radiorespirometric experiments demonstrated that both the glucose and the fructose moieties of sucrose were catabolized via the Entner-Doudoroff pathway. This result was confirmed by enzyme analysis and studies on sugar assimilation. All the enzymes of the Entner-Doudoroff pathway were present in bacteria grown on sucrose but fructokinase (EC 2.7.1.4) activity was relatively low. In contrast, phosphoenol-pyruvate: fructose phosphotransferase and 1-phosphofructokinase, the key enzymes for the catabolism of exogenous fructose, were only partially induced. Bacteria grown on sucrose and treated with chloramphenicol were, therefore, not able to assimilate exogenous fructose. We conclude that under these conditions endogenous fructose is catabolized via the Entner-Doudoroff pathway, while exogenous fructose is degraded via fructose 1-phosphate and the Embden-Meyerhof pathway.

During germination, Streptomyces antibioticus arthrospores passed through three stages: darkening, swelling and germ tube emergence. The first stage, darkening, whose main features were a decrease in absorbance and a loss of refractility, only required exogenous divalent cations (Ca2+, Mg2+ or Fe2+) and energy that can be obtained from the spore reserves. This stage was blocked by agents that inhibit ATP formation but not by antibiotics that inhibit macromolecular synthesis. The second stage, swelling, needed an exogenous carbon source and was not blocked by mitomycin C. In this stage, the spores exhibited the highest cytochrome oxidase and catalase activities and respiratory quotient. The last stage, germ tube emergence, required additional carbon and nitrogen sources. Ammonium compounds were superior to nitrate. Dry weight remained constant during the stages of darkening and swelling, with a rapid increase from the moment of germ tube emergence. Optimum pH and temperature for germination were 8.0 and 45 °C, respectively. Heat treatment (55 °C for 10 min) had no effect on germination.

The fine structure of the spore underwent important changes during germination. The wall of the swollen spore became stratified and the inner layer was continuous with the germ tube wall.

Macromolecular synthesis occurred in the sequence RNA, protein and then DNA. Rifampicin, streptomycin and mitomycin C prevented synthesis when added at the start of incubation. The same effect was obtained if the addition was made during germination, except with mitomycin C which inhibited DNA, but not RNA and protein synthesis.

Summary: Blastospores of Candida albicans were readily agglutinated by Concanavalin A (Con A) owing to the specific binding of this lectin to the mannan receptors of the cell surface. When mannan was extracted from the cell wall by neutral buffers, alkali and acid, the agglutination was decreased or lost depending on the degree of extraction. A relatively mild alkali treatment was sufficient to derange the multilayered wall organization and transform it into a uniform, medium-density structure having about the same thickness as the untreated wall. After a more drastic extraction, all the electron-dense components of the wall were lost, the residual, alkali-insoluble wall fabric being completely electron-transparent and of about the same thickness as the inner wall region of untreated cells.

Thiol-reducing agents like mercaptoethanol or dithiothreitol also extracted wall materials, an effect which was enhanced by pronase. After dithiothreitol-pronase treatment, the outer wall layers were removed but the inner wall region was not apparently damaged and some electron-dense components remained. None of these treatments significantly affected blasto-spore agglutination by Con A - this was reduced (but not abolished) only by the sequential action of pronase and helicase, which led to sphaeroplast formation. These sphaeroplasts showed a varied amount of residual wall consisting of evenly distributed, fibrogranular components.

Two main conclusions were drawn from these results: (i) mannan polymers extend throughout the wall of the blastospore of C. albicans; (ii) the layering of the wall, as seen by ordinary fixation and staining for electron microscopy, essentially reflects the distribution of the various alkali-soluble complexes, at different levels, both over and in the rigid, glucan-chitin matrix.

Summary: The tetracycline-resistant Haemophilus influenzae strains lu121 and fr16017, recently isolated in West Germany, each harbour a plasmid; that of the former (pLU121) has a mol. wt of 31.5 × 106 and that of the latter (pFR16017) has a mol. wt of 33 × 106. Conjugation and DNA-DNA hybridization studies have shown that both plasmids are self-transmissible and carry tetracycline-resistance genes. The purified plasmid DNA of H. influenzae strain lu121 transformed a sensitive Escherichia coli strain to tetracycline resistance. The two R factors are closely related to the H. influenzae plasmid specifying ampicillin resistance (pKRE5367). Electron microscope DNA heteroduplex analysis indicated that pLU121 and pFR16017 probably carry the tetracycline-resistance transposon TnD and that pKRE5367 probably carries the ampicillin-resistance transposon TnA. There is more than one integration site for the insertion which probably represents TnD in pFR16017. All three plasmids have a similar plasmid core and could have a common evolutionary origin.

Summary: Erythromycin-resistant mutants mapping to the Mendelian ery-M2 locus of Chlamydomonas reinhardii were cold-sensitive for growth at 15 °C. The phenotypes erythromycin-resistance and cold-sensitivity could not be separated in crosses.

Mutants at the ery-M2 locus were previously found to have chloroplast ribosomes with altered [14C]erythromycin binding capacity ( Mets & Bogorad, 1971 ). When grown at 25 °C, haploid strains containing ery-M2 alleles alone or in combination with other ery r loci had fewer chloroplast ribosomes than the wild type. A further reduction occurred when ery-M2 strains were shifted to 15 °C. Diploids containing both ery-M2 and its wild-type allele contained normal amounts of chloroplast ribosomes at 25 and 15°C, and were cold-resistant and antibiotic-sensitive.

The inability of chloroplast ribosome-deficient ery-M2 strains to grow at 15 °C in the presence of a reduced carbon source indicates that chloroplast protein synthesis is essential for cellular growth even when photosynthesis is not essential.

Summary: The amount of Na2CO3 added to semi-synthetic medium determined the length of the lag phase, the growth rate and the dry weight of three strains of Butyrivibrio fibrisolvens (wv1,nor37,b835). With increasing CO3 2-concentration the molar growth yield of bacteria, from glucose, was increased and, of the fermentation products, formate increased more than the other acids. CO3 2-limited cultures of strain wv1 (Group 2 Butyrivibrio) and strain nor37 (Group 1 Butyrivibrio) incorporated 14CO3 2- into lactate and formate. In nor37, lactate and formate had equal specific activities; in wv1, the formate specific activity was twice that of lactate. Strain wv1 had an active pyruvate synthase and an energy-dependent exchange between CO3 2 -and formate was demonstrated. In strain wv1 butyrate was produced mainly from glucose.

Summary: In contrast to observations by previous workers of an inverse relationship between inoculum size and the length of the lag phase, the lag time of Saccharomyces cerevisiae was found to be independent of inoculum size whether the inocula were derived from an exponential phase, diauxic lag phase or stationary phase parent culture. It is concluded that the lag phase of this organism is dependent on the internal physiological state of the parent culture cells, rather than the need to accumulate diffusible substances in the extracellular medium.

Summary: Regulation of glucose, fructose and sucrose catabolism was studied in Rhodopseudomonas capsulata grown under phototrophic conditions. The sequence of preference for the utilization of the sugar substrates was fructose, glucose, sucrose. The presence of a preferred substrate did not completely suppress the utilization of the less preferred. Glucose-6-phosphate dehydrogenase, the key enzyme of glucose and sucrose catabolism, exhibited sigmoidal substrate saturation curves and was inhibited by phosphoenolpyruvate, whereas 1-phosphofructokinase, the key enzyme of fructose catabolism, exhibited hyperbolic substrate saturation curves and was not inhibited by phosphoenolpyruvate. Since phosphoenolpyruvate is a common intermediate of glucose, fructose and sucrose catabolism, the control of glucose-6-phosphate dehydrogenase may be responsible for the preferential utilization of fructose.

Summary: Cultures of 16 coryneform bacteria were grown to late-exponential stage in nutrient media, washed, and starved in 30 mm-potassium phosphate buffer pH 7.0, with no external energy or carbon source. After 4 weeks starvation, 20 to 98% of each culture was still viable; after 8 weeks, 5 to 70% of each culture was still viable. Little change in cell shape or size was detected in Arthrobacter globiformis, A. nicotianae, Brevibacterium linens, Corynebacterium fascians, Mycobacterium rhodochrous and Nocardia roseum when studied by electron microscopy for up to 56 d, although there was a gradual disappearance of intracellular material. No resting structures were discernible. All organisms showed an immediate decrease in endogenous respiration to less than 1% of that observed during growth. A low basal level of endogenous metabolism equivalent to 0.01 to 0.03% of cellular carbon oxidized to CO2 h-1 was maintained for 56 d. Carbohydrate, intracellular pools, protein, ribonucleic acid and deoxyribonucleic acid were utilized at varying rates by different organisms during this period. All species were effective in maintaining 20 to 70% of their Mg2+ content during a 28 d starvation period in the absence of any external Mg2+. It would appear that the soil coryneform bacteria possess similar survival characteristics in laboratory studies which could explain, in part, their ecological success in natural environments.

Dimethyl sulphoxide (DMSO) was reduced to dimethyl sulphide by a wide variety of microorganisms, including prokaryotes and eukaryotes, aerobes and anaerobes. Dimethyl sulphone was not reduced by any of the organisms tested. Cell-free extracts of Escherichia coli reduced DMSO using reduced pyridine nucleotides as electron donors. Activity was greater in anaerobically grown cells than in those grown aerobically. Two other sulphoxides, methionine sulphoxide and tetramethylene sulphoxide, substantially inhibited DMSO reduction by extracts. Mutants of E. coli, which were unable to reduce biotin sulphoxide to biotin, were tested for their ability to reduce DMSO in whole cells and extracts. These mutants were in four different gene loci, bisA to bisD. DMSO reductase activity of the mutants was generally less than that of the wild-type strain, and activity depended upon the gene locus involved, the growth medium and the growth conditions. Only the bisA mutant had very low activity under all conditions. All of the bis mutants were able to grow using methionine sulphoxide as a sulphur source, indicating that biotin sulphoxide and methionine sulphoxide are reduced by different enzyme systems. DMSO may be reduced by both of these enzyme systems.