- Volume 63, Issue 3, 1970

Summary: Human foetal kidney cell cultures and agar and broth media were inoculated with Mycoplasma pulmonis (Negroni), a rodent pathogen, and were examined by electron microscopy.

In the tissue cell cultures, abundant extracellular mature mycoplasmas and elementary bodies were seen. The average diameter of elementary bodies was 99 nm. The average long and short axes of mycoplasmas growing on agar measured 800 and 600 nm. respectively.

Whole mounted broth-cultured mycoplasmas consisted of three principal cell types: large pleomorphic cells (up to 1500 nm. in diameter), filamentous forms, and elementary bodies (less than 180 nm. in diameter). Production of elementary bodies by budding from the mature cells was the normal method of multiplication. The life cycle was estimated to be 46 ± 7 h. under optimum conditions. Immunoelectron microscopy demonstrated positive reactions only with specific antisera.

SUMMARY: Microelectrophoresis of spores of the actinomycete genera Micromono- spora, Nocardia, Streptomyces and Thermoactinomyces at various pH values and after various modifying treatments indicated that Micromonospora and Streptomyces spores had amino and carboxyl surface groups. Thermoactinomyces spores and the bacillary or coccoid elements of Nocardia had carboxyl groups but not amino groups; their responses to lipase and sodium dodecyl sulphate suggested presence of lipid. All strains studied showed changes in mobility after treatment with lysozyme.

SUMMARY: Nuclei of different diameters, containing different numbers of chromosomes, are found in all macroscopic plasmodia of the true slime mould Didymium nigripes. The relative proportions of small and large nuclei vary in different plasmodial clones. Over extended periods of time c 6 wild-type clones maintain a constant proportion of small nuclei whereas y2–1, a yellow mutant, does not. Nuclear fusion (syngamy) does not occur prior to plasmodium formation in this isolate; neither is it delayed until the plasmodium has formed. The rate of formation of large nuclei in plasmodia was calculated. When plasmodia with differing nuclear size ratios were fused, the observed shifts in the nuclear size ratio suggested the possibility that parasexual processes could exist in the isolate under study.

SUMMARY: Potassium tellurite (K2TeO3) reduction in the obligate aerobe Rhodotorula mucilaginosa 49 and the facultative anaerobe Saccharomyces cerevisiae 1–434 occurs on localized areas of endoplasmic reticulum. The reduction product is granular and is found in close association with the membranes of specific parts of the endoplasmic reticulum. The site of reduction is the same whether R. mucilaginosa 49 is grown on a respiratory substrate (sodium malate) or a fermentable substrate (glucose).

Increasing concentrations of K2TeO3 increasingly inhibit the growth of Rhodotorula mucilaginosa 49. Its rate of oxygen uptake is not altered when grown in the presence of 0·04 % K2TeO3, but in Saccharomyces cerevisiae 1–434 it decreases under the same conditions. Growth of S. cerevisiae 1–434 is completely inhibited with glycerol as substrate in the presence of K2TeO3.

SUMMARY: A comparative study has been made of the influence of growth environment on the properties of the walls of Bacillus subtilis var. niger organisms, particularly with respect to ability to bind magnesium ions. The medium NaCl concentration and the nature of the growth-limiting substrate, in chemostat cultures, both affected markedly the subsequent affinity and capacity of the bacterial walls for Mg2+ adsorption. These changes correlated with differences in the phosphate content of the walls, which in turn related largely to changes in wall teichoic acid content. Thus it seemed that whenever a constraint to the adsorption of Mg2+ was applied (either by growing the organisms in a Mg2+- limited environment, or in one containing high concentrations of a competing ion), walls were synthesized that had an increased teichoic acid content and an increased affinity for magnesium ions. These results support the thesis that anionic polymers in the walls of Bacillus organisms (i.e. teichoic acids and teichuronic acids) are involved in cation assimilation.

SUMMARY: Fermentation balances determined for different substrates in batch and continuous cultures of Lactobacillus casei revealed two pathways of pyruvate conversion by this organism, a reduction to lactate and the phosphoroclastic cleavage. Pyruvate formed anaerobically from mannitol and citrate was split by the phosphoroclastic enzyme. Lactate was the main fermentation product formed during aerobic growth on mannitol and anaerobic and aerobic growth on glucose. In glucose-limited continuous cultures pyruvate conversion was dependent on the dilution rate. At low dilution rates glucose was fermented exclusively to acetate, ethanol and formate. At high rates only small amounts of acetate, ethanol and formate were formed and lactate production was maximal. Lactate dehydrogenase of L. casei had an absolute requirement for fructose-1,6-diphosphate and manganous ions. The specific activity of lactate dehydrogenase did not differ significantly at different dilution rates. It was concluded that the intracellular level of fructose-1,6-diphosphate controlled the pathway of pyruvate conversion. In batch cultures Y atp values were between 18·2 and 20·9. No evidence for oxidative phosphorylation was found. In continuous cultures Y atp values varied from 18·7 at low dilution rates to 23·5 at high dilution rates. From the dependence of Y atp on the dilution rate, a maintenance coefficient of 1·52 × 10−3 was calculated. The Y atp value corrected for energy of maintenance was 24·3. The possibility that the molar growth yields were erroneously high because of assimilation of growth substrate into intracellular polysaccharides, or because of energy yield from components of the medium other than the added energy source, was excluded.

Summary: Homogeneous continuous-flow culture with some mechanical means for concentrating the biomass in the fermenter is termed a chemostat with feedback. The theory of the system has been reformulated and extended to include concentration of the biomass outside or inside the culture vessel by means such as centrifugation, filtration or gravity sedimentation. An important feature of the general system is the provision of two effluents, one of concentrated biomass and the other of diluted biomass. Experimentally, feedback was realized by filtration of one effluent stream. By this means, steady states were obtained over a wide range of flow rates; the values of biomass and growth-limiting substrate were in good agreement with the theory. The maximum biomass output rate of the chemostat was increased fourfold.

SUMMARY: An examination of three species of methane-utilizing bacteria has shown (Lawrence, Kemp & Quayle, 1970) that the bacteria use one of two pathways of carbon assimilation, the serine pathway (Heptinstall & Quayle, 1970) or the ribose phosphate cycle of formaldehyde fixation (Kemp & Quayle, 1967). The isolation of many new types of methane-utilizing bacteria by Whittenbury, Phillips & Wilkinson (1970) has made possible an extension of these studies, and this paper reports the results of an examination of eight of the new isolates. The examination is based on the distribution of two key enzymes, each of which appears to be specifically involved in one of the assimilation pathways, namely hydroxypyruvate reductase (serine pathway) and hexose phosphate synthetase (ribose phosphate cycle).

SUMMARY: Rode & Foster (1965) showed that the germination of spores of Bacillus megaterium is sometimes affected by hydrocarbons such as n-butane: one type of spore (al),which responds germinatively to l-alanine and inosine, is inhibited by n-butane; a second type of spore (gn), which responds to glucose and KNO3, is not inhibited, but even accelerated a little by the same compound. The study of the biological activity of these kinds of compounds in respect of bacterial spores is useful in elucidating the mechanism of germination. In this communication, the effect of n-butane on the superficial charges of the spores was investigated; differences in electron microscopical morphology have already been shown by Rode (1968): the alanine type spores have a veined surface with a superficial beaded ultrastructure pattern, the glucose type spores have the well-known prominent equatorial ridge and polar knob appearance.

SUMMARY: Earlier studies of the antigenic determinants of Rhizobium were almost entirely concerned with agglutinogens and revealed considerable strain specificity, the recognition of which was enhanced by a distinction between flagellar and somatic antigens (Bushnell & Sarles, 1939; Vincent, 1941, 1942; Kleczkowski & Thornton, 1944; Purchase, Vincent & Ward, 1951; Means, Johnson & Date, 1964). In some cases this specificity depended on complex patterns of shared antigens, in others on complete non-cross reactivity between strains that belonged to the same species. Agglutination could not therefore be depended on for the recognition of species or groups of species of rhizobia. On the other hand, the technique has proved valuable for the definition of serotypes and the labelling of strains used for experimental purposes.