- Volume 113, Issue 2, 1979

Summary: The cellulolytic system from culture filtrates of Clostridium thermocellum, when partially purified by preparative electrophoresis, showed a single protein band on analytical polyacrylamide gel electrophoresis; however, sodium dodecyl sulphate-polyacrylamide gel electrophoresis indicated that at least five proteins were present. Carbohydrate was present in the purified fraction and it is suggested that the cellulase was present as a complex.

The concentration of guanosine 3′-diphosphate 5′-diphosphate increased exponentially with decreasing growth rate in Anacystis nidulans grown at different light intensities. This is inconsistent with the concept of guanosine 3′-diphosphate 5′-diphosphate as a regulator of transcription in A. nidulans since previous work has shown that in this organism the RNA/DNA ratio remains constant with increasing growth rate, implying a constant rate of transcription from individual cistrons.

A novel method for obtaining complete lysis of coryneform bacteria has been devised. Bacteria in the late-exponential phase of growth are treated with antibiotics which inhibit biosynthesis of the cell wall. Organisms treated in this way show increased sensitivity to lysis by added lytic enzymes. The preparation of DNA from this group of organisms is thus greatly facilitated.

The nutritional requirements of 43 strains of Haemophilus influenzae isolated from clinical and normal flora sources were investigated. Two defined minimal media were developed by modifying the medium of Herriott et al. 1970 : 74 % of the strains could grow on the minimal media and Herriott’s medium; the remaining strains could not grow on any of these media.

The total lipid content of Mycobacterium smegmatis ATCC 607 was the same whether it was grown at 27 or 37 °C. The total phospholipid content, however, increased significantly at 27 °C. Phosphatidylethanolamine increased most markedly with a simultaneous decrease in phosphatidylinositol mannosides. Among individual phosphatidylinositol mannosides, tri- and tetra-acylated dimannophosphoinositides and tetra-acylated hexamannophosphoinositides all decreased at the lower growth temperature. Triacylglycerols and monoacylglycerols increased at the lower temperature but diacylglycerols were unaffected. Unsaturated fatty acids of total phospholipids increased as the temperature was lowered.

Cellulolytic activity of the termite flagellate Trichomitopsis termopsidis was demonstrated in vitro and in vivo. Homogenates of axenically-cultivated flagellates hydrolysed carboxy-methylcellulose enzymically indicating that T. termopsidis does not depend on living extracellular or endosymbiotic bacteria for cellulose digestion. Cellulolytic activity of the flagellate was also determined by comparing the longevities of defaunated termites (Zoo-termopsis) refaunated by feeding with either T. termopsidis or with heat-killed flagellates. The termites refaunated with T. termopsidis greatly outlived members of the other group, supporting the view that cellulose digestion by the intestinal flagellate is responsible for the nutrition of termites.

Concentric circular structures were observed on the newly exposed surface of the wall of Staphylococcus epidermidis and on its isolated cross-wall. These structures were removed by treatment with trichloroacetic acid. Chemical analysis revealed that after treatment with trichloroacetic acid most of the wall phosphorus was extracted but more than half of the N-acetylglucosamine remained associated with the wall. These observations suggest that polysaccharides are likely to be arranged circularly on the surface of the wall.

Summary: Free proline is specifically accumulated in an acr A mutant of Escherichia coli K12 when cultured in a medium containing excess NaCl.

Summary: The NAD-specific glutamate dehydrogenase from Crithidia fasciculata has been purified 135-fold. Its molecular weight was about 380000. The apparent K m values for 2-oxoglutarate, NADH and NH4Cl were 3, 0·17 and 47 mm, respectively, at pH 7·8, and for l-glutamate and NAD, 10 and 1·4 mm, respectively, at pH 8·6. The enzyme was strongly inhibited by ATP and GTP, and by thiol-binding reagents, such as 5,5′-dithiobis(2-nitrobenzoate) and p-chloromercuribenzoate. Several organic acids, such as pyruvic and l-malic acids, were also inhibitory.

Summary: Penetration of Toxoplasma gondii tachyzoites was studied in vitro using murine erythroid cells at different stages of development. Toxoplasma gondii penetrated nucleated erythro-blasts and macroreticulocytes from foetal mouse liver and the circulating erythrocytes of foetal, neonatal or severely anaemic adult mice. Immature reticulocytes were more susceptible to penetration than mature ones, indicating that some change in their membrane properties occurred during maturation. The present results confirmed our previous finding that the major erythrocyte membrane-specific proteins do not prevent erythrocyte penetration since these proteins are known to be present in the reticulocyte membrane.

Summary: Yeast cells of Candida albicans growing at 25 °C in glucose/yeast extract medium cannot germinate by dilution into fresh medium at 37 °C before reaching the stationary phase of growth. However, cells at any stage of growth are able to form germ-tubes giving true hyphae when incubated at 37 °C in the presence of inducers such as serum or N-acetyl-d-glucosamine. Thus, stationary phase cells are not endowed with a specific ‘competence’ to germinate.