Showing papers in "Microbiology in 1976"

A Taxonomic Study of the Genus Haemophilus, with the Proposal of a New Species

Abstract: SUMMARY: A collection of 426 Haemophilus strains isolated from people with infectious diseases and from the normal flora of mucous membranes in humans and various animal species was studied in an attempt to revise and improve the taxonomy of the genus Haemophilus. The examinations included the determination of a number of biochemical and physiological properties, of which several had not previously been applied to the taxonomy of haemophili. The resulting data revealed many hitherto unrecognized characters of taxonomic significance, and several of the species can now be more accurately defined. The classification presented is supported by the DNA base composition of a large number of representative strains. A diagnostic key to the different taxa is presented. Haemophilus influenzae and H. parainfluenzae have been subdivided into a number of biotypes. It is possible to demonstrate a relationship between the individual biotypes of H. influenzae and the origin of the strains assigned to them. The results indicate that H. aegyptius, H. parahaemolyticus and H. paraphrohaemolyticus do not merit specific status. Four unnamed taxa of V-factor-dependent haemophili have been recognized. The name Haemophilus segnis is proposed for one of these taxa, which consists mainly of strains isolated from the human oral cavity. It is demonstrated that the name H. ducreyi has been used for different groups of bacteria, and that only one of these groups can legitimately be assigned to the genus Haemophilus. Haemolytic V-factor-dependent strains from swine, previously included in H. parahaemolyticus, are significantly different from strains of human origin and should be named H. pleuropneumoniae. None of the strains from swine and fowls were haemindependent. The relationships of these strains to the species H. suis and H. gallinarum, and to H. parasuis and H. paragallinarum are discussed. Haemophilus piscium is shown not to belong to the genus Haemophilus. The taxonomic position of H. aphrophilus is uncertain and its possible relationship to Actinobacillus actinomycetemcomitans requires further study. The positive correlation found between the ecology of the strains studied and their affiliation with the different taxa is discussed.

Mutants of Escherichia coli K12 unable to use fumarate as an anaerobic electron acceptor.

Abstract: Summary: Mutants of Escherichia coli K12 strain WGAS-GF+/LF+ were selected for their inability to use fumarate as terminal electron acceptor for supporting growth on glycerol or lactate in an atmosphere of H2 plus 5% CO2. Eighty-three mutants were grouped into seven different categories according to their ability to grow on different media and their ability to produce gas during glucose fermentation. Enzymological and genetic studies indicated that the major class (type I), representing nearly 70% of the isolates, lacked fumarate reductase and corresponded to the frdA mutants studied previously (Spencer & Guest, 1973, 1974). Members of a second class (type II) were phenotypically similar to men mutants, blocked in menaquinone biosynthesis. They differed from menA mutants in having lesions in the 44 to 51 min region of the chromosome rather than at 87 min. It was concluded that fumarate reductase and menaquinone are essential for anaerobic growth when fumarate serves as electron acceptor but not when nitrate performs this function. Fumarate reductase and menaquinone are also essential for H2-dependent growth on fumarate. Type III mutants, originally frdB, were designated fnr because they were defective in fumarate and nitrate reduction and impaired in their ability to produce gas. The fnr gene was located at 28·5 min by its cotransducibility with pyrF (5·7 to 9·2%) and trpA (2·7 to 5·7%) and the gene order fnr-qmeA-pyrF-trpA was established. It was not possible to assign specific metabolic lesions to the fnr mutants nor to the remaining classes, which all exhibited pleiotropic phenotypes. Nevertheless, the results demonstrate that functional or organizational relationships exist between the fumarate reductase system, nitrate reduction and hydrogen production.

A taxonomic study of the Aeromonas hydrophila-Aeromonas punctata group.

Abstract: Summary: A total of 203 characters has been determined for 68 strains of Aeromonas belonging to the Aeromonas hydrophila-A. punctata group. The results have been subjected to computer analysis using the coefficient of Jaccard-Sneath and the strains clustered by the method of aggregation according to the variance. The 68 strains can be divided into two well-segregated classes on the basis of 59 variable characters, of which seven are of diagnostic value. The two classes are considered as two separate species. The first one (42 strains) is assigned to the type species of the genus, A. hydrophila, and it appears that the species name, A. punctata, is an illegitimate synonym for A. hydrophila. The second (26 strains) constitutes a new species for which the name A. sobria sp.nov. is proposed. The type strain of this new species has been deposited under the reference CIP7433 (our strain 208).

A morphological and genetic mapping study of bald colony mutants of Streptomyces coelicolor

Abstract: SUMMARY: Twelve bld mutations of Streptomyces coelicolor resulting in a lack of visible aerial mycelium were mapped genetically. The mutants were classified into three groups on the basis of colony morphology, production of antibiotics and morphology on different carbon sources. Four map locations were found for the bld genes and three of these were very near the loci of whi genes, which are also involved in differentiation. Closely linked bld mutations had similar phenotypes.

Carbohydrate metabolism in Agaricus bisporus (Lange) Sing: changes in soluble carbohydrates during growth of mycelium and sporophore.

Abstract: SUMMARY: Changes in the ethanol-soluble carbohydrate content of Agaricus bisporus mycelium and sporophores grown on semi-defined media and commercial compost were studied. The accumulation of mannitol in the sporophore during its growth was not accompanied by an increase in mycelial mannitol. The other major soluble carbohydrate of the sporophore, trehalose, decreased throughout the growth of the sporophore; a parallel decrease was observed in the mycelium. The main accumulation of mannitol was in the pileus and stipe of the sporophore and was accompanied by a decrease in the soluble protein content of these tissues. Before fruiting, glucose and sucrose were present in the mycelial samples in similar quantities to mannitol, but their levels decreased during fruiting. Small quantities of glucose were present in the sporophore. The results are discussed in relation to the possible functions of the soluble carbohydrates.

Two restriction and modification systems in Staphylococcus aureus NCTC8325.

Abstract: SUMMARY: The presence of two distinct host specificities in Staphylococcus aureus strain NCTC8325 was revealed by the isolation of restriction- and modification-deficient mutants. The two host specificity systems, designated S1 and S2, are both active on phage 80μα but are not additive in their restricting activity. Restriction-deficient, modification-proficient mutants were invariably affected in both restriction systems. The functional relationship between these two systems is discussed.

The Effects of Proteins on Bacterial Attachment to Polystyrene

Abstract: Summary: Bovine serum albumin, gelatin, fibrinogen and pepsin impaired the attachment of a marine pseudomonad to polystyrene Petri dishes, apparently through adsorption on the dish surface. Serum albumin also appeared to affect the bacterial surface. The basic proteins protamine and histone did not markedly inhibit attachment. These findings are discussed in relation to comparative experiments using tissue cells.

Analysis of acetate non-utilizing (acu) mutants in Aspergillus nidulans.

Abstract: Genetic analysis of 119 acetate non-utilizing (acu) mutants in Aspergillus nidulans revealed ten new loci affecting acetate metabolism in addition to the three previously recognized on the basis of resistance to fluoroacetate and acetate non-utilization. The enzyme lesions associated with mutations at seven of the acu loci are described. These are: facA (= acuA), acetyl-CoA synthase; acuD, isocitrate lyase; acuE, malate synthase; acuF, phosphoenolpyruvate carboxykinase; acuG, fructose 1,6-diphosphatase; acuK and acuM, malic enzyme. The acu loci have been mapped and are widely distributed over the genome of A. nidulans. Close linkage has only been found between acuA and acuD (less than 1% recombination). There is no evidence for any pleiotropic mutation in that region affecting the expression of both these genes. Poor induction of the enzymes of the glyoxylate cycle, isocitrate lyase and malate synthase in mutants lacking acetyl-CoA synthase, and also in the other two classes of fluoroacetate-resistant mutants, indicates that the inducer, acetate, may be metabolized to a true metabolic inducer, perhaps acetyl-CoA, to effect formation of the enzymes. There is no evidence of any other class of pleiotropic recessive acu mutations affecting the expression of the acuD and acuE genes, which are therefore thought to be subject to negative rather than positive control.

Isolation and composition of an alkali-soluble glucan from the cell walls of Saccharomyces cerevisiae.

Abstract: Summary: An alkali-soluble glucan was obtained from the cell walls of Saccharomyces cerevisiae NCYC1109 and baker's yeast by extraction with cold, dilute sodium hydroxide under nitrogen. The glucan, which represented approximately 20% of the cell wall, precipitated as a gel when the alkaline extract was neutralized. The purified glucan was homogeneous and was shown to be free from contamination by other cell-wall polysaccharides by ultracentrifuging, gel filtration and electro-phoresis. In addition to glucose, the glucan contained traces of mannose and nitrogen, but no hexosamine. Structural analyses revealed the presence of 80-85% (1→3)-β-D linkages, 8-12% (1→6)-β-D linkages and 3-4% branched residues linked through C-1, C-3 and C-6. The molecular weight of the glucan was estimated to be about 250000. Electron-microscopic examination of the cell walls after alkali extraction showed that an amorphous surface layer had been removed revealing numerous bud scar structures.

Induced fusion of fungal protoplasts following treatment with polyethylene glycol.

Abstract: Although protoplast fusion is of current interest because of its possibilities in pure and applied genetics, only a few reports exist on intraspecific fusion between fungal protoplasts and subsequent selection of heterokaryons. Naturally-occurring fusion between protoplasts of Geotrichum candidurn (Ferenczy, Kevei & Zsolt, I 974) and Aspergillz4s nidulans (Ferenczy, Kevei & Szegedi, I 975) has been reported. Binding & Weber (1974) described fusion between protoplasts of Phycomyces blakc~slceanus induced by seawater or calcium ions at high pH, but the frequency of heterokaryon formation was low in all cases. We here report heterokaryon formation, at high frequency, after induced intraspecific fusion between protoplasts of auxotrophs of Penicillium chryosogiwim, P . putulurn, P. roquejortii, A. nidulans, A . niger and Cephalosporium acrernonium, and fusion between protoplasts of P. chrysogenu~?z and P. rzotutunz auxotrophs, using solutions containing polyethylene glycol (PEG) mol.wt. 6000.

Haemagglutinating and Adhesive Properties Associated with the K99 Antigen of Bovine Strains of Escherichia coli

Abstract: The K99 antigen common to some bovine strains of Escherichia coli caused mannose-resistant haemagglutination of sheep erythrocytes and was shown to be responsible for the attachment of K99-positive bacteria to calf brush-border preparations because (i) strains grown at 18 degrees C did not produce K99 antigen, cause haemagglutination, or attach to brush borders; (ii) a K12 (K99+) recombinant strain showed both haemagglutinating activity and attachment to brush borders whereas, before it received the K99 plasmid, the recipient strain was negative in both respects; and (iii) cell-free extracts of K99 antigen showed haemagglutinating activity and inhibited the attachment of K99-positive organisms to brush borders. K99 antigen appears to be a virulence determinant in the pathogenesis of neonatal calf diarrhoea. It is readily demonstrated by haemagglutination and brush-border attachment tests.

Identification of beta-lactamases by analytical isoelectric focusing: correlation with bacterial taxonomy.

Abstract: beta-Lactamases (EC. 3.5.2.6) can be directly compared by analytical isoelectric focusing. Using this technique, 242 strains from five Gram-positive and 16 Gram-negative genera were examined. A preparation of each strain focused as a single group of bands which did not match the pattern of any R factor-associated beta-lactamase. None of the strains was known to carry an R factor and resistance transfer experiments were unsuccessful. The enzymes studied were therefore thought to be chromosomally mediated. The isoelectric points ranged from 3.9 to 8.7 and were not related to the substrate profiles or other biochemical properties. The chromosomal beta-lactamases appeared to be specific for genus, species and sub-species, and strains that produced identical beta-lactamases had identical bacterial characteristics. Correlation of bacteriological differences with differences in beta-lactamase patterns is discussed with particular reference to strains of Escherichia coli and Klebsiella spp. Since beta-lactamases may be universally produced by bacteria, separation of the enzymes by analytical isoelectric focusing could be used in bacterial taxonomy.

Further observations on the association of the colicine V plasmid of Escherichia coli with pathogenicity and with survival in the alimentary tract.

Abstract: Summary A high proportion of invasive strains of Escherichia coli produced colicine V. This property was easily eliminated from 20 of 21 of these strains by ‘curing’ agents, especially sodium lauryl sulphate, indicating that the genes determining it were located on a plasmid (ColV) which was transmitted from ten of the strains by conjugation. Inoculated intramuscularly, the ColV-forms of all 17 strains tested were less pathogenic for chickens than the corresponding ColV+ forms. The pathogenicity of the ColV− forms of four strains was increased, usually to that of the ColV+ form from which they were derived, by implanting other ColV determinants in them. Much higher concentrations of organisms were found in the blood and liver of chickens infected with ColV+ forms than in chickens infected with ColV− forms. Inoculated intraperitoneally, the ColV+ form of one of the strains, BI88, was more pathogenic for mice than the ColV− form; much higher concentrations of organisms were found in the peritoneal fluid and blood of ColV+-inoculated mice than of ColV−-inoculated mice. Inoculated orally and intravenously, ColV+ forms were more pathogenic for colostrum-deprived calves than the corresponding ColV− forms. After mixtures of ColV+ and ColV− organisms of the same strain in ratios of 1:10, 1: 100 or 1:1000 were given orally, they were found in a similar ratio in the contents of the alimentary tract 1 to 2 days later, when the calves were near to death. Many more ColV+ than ColV− organisms were found in the mesenteric lymph nodes, the deeper tissues and the blood; in the urinary and gall bladders, locations remote from the defence mechanisms of the body, the numbers of ColV− organisms sometimes exceeded those of ColV+ organisms. Colicine V, although demonstrated in the blood at death, did not appear adversely to influence the concentration of ColV− organisms in these calves. Several days after mixtures of ColV+ and ColV− organisms of strain BI88 were taken orally by two human beings, the ColV+ organisms became much more numerous in their faeces than the ColV− ones. Similar results were obtained when colVr organisms of BI88 were included in the inoculum or when a strain whose ColV− form was completely colicine V-resistant was studied. A ColE+ form of BI88 ColV− was no more pathogenic for chickens, mice or colostrum-deprived calves than was a ColE− form of this strain, and it did not persist in the faeces of the two human beings for longer than the ColE− form.

Studies on the rumen flagellate Sphaeromonas communis.

Abstract: Summary: The rumen flagellate Sphaeromonas communis showed a significant increase in population density 1 to 2 h after the host sheep commenced feeding, followed by a reduction in numbers to the pre-feeding level after a further 2 to 3 h. The life-history of the organism was shown to consist of a motile flagellate which germinated to produce a vegetative stage comprising a limited rhizoidal system on which up to three reproductive bodies were borne together with (in vitro) other spherical bodies of unknown function; in vivo, the reproductive bodies were stimulated to liberate flagellates by a component of the diet of the host. The vegetative stage strongly resembled that of certain species of aquatic phycomycete fungi, and the flagellates may therefore be zoospores. Flagellates liberated in vivo lost their motility within 2 to 3 h and developed into the reproductive vegetative phase, producing a rapid decrease in numbers of flagellates. Conditions of maximum flagellate production (pH 6.5, 39 °C, presence of CO2, absence of oxygen) approximated to those found in the rumen. The organism was cultured in vitro in an undefined medium in the absence of bacteria and other flagellates.

Mitosis, septation, branching and the duplication cycle in Aspergillus nidulans.

Abstract: Mitosis, septation and branching were studied in undifferentiated mycelia and leading hyphae of Aspergillus nidulans, a mould which forms incomplete septa. After spore germination, nuclei divided synchronously until germ-tube hyphae contained 8 or 16 nuclei; mitosis occurred when the volume of cytoplasm per haploid nucleus was about 60 mum3. Intercompartment development was not synchronized, consequently mitosis in the mycelium as a whole eventually became asynchronous. During the stage of asynchronous compartment development, the nuclei, septa, branches and total length of undifferentiated mycelia all increased exponentially at approximately the same specific rate. Septa were formed in hyphae in groups of up to nine; the mean time required for the formation of a group of septa was about 9 min. The mean interval between successive cycles of septation in a hypha was approximately the same as the organism's doubling time. There was a highly significant correlation coefficient between septation and branch initiation and most intercalary compartments initially formed a single branch. The volume of cytoplasm per nucleus in a diploid strain was approximately double the value observed for a haploid strain. However, the length of the hyphal growth unit was not affected by ploidy. The study suggests that a duplication cycle can be recognized during mycelial growth which is analogous to the cell cycle observed in unicellular micro-organisms.

The Mode of Action of Bacilysin and Anticapsin and Biochemical Properties of Bacilysin-resistant Mutants

Abstract: Bacilysin is hydrolysed to L-alanine and anticapsin by suspensions of a bacilysin-sensitive strain of Staphylococcus aureus but not by those of a resistant strain derived from it. In contrast, it is hydrolysed by extracts of both strains. Anticapsin is a powerful inhibitor of glucosamine synthetase in extracts of both the bacilysin-sensitive and -resistant strains of Staph. aureus. Bacilysin, by comparison, is a relatively poor inhibitor of glucosamine synthetase in crude extracts when its hydrolysis is inhibited by EDTA. A phenylalanine auxotroph of Staph. aureus readily uses L-analyl-L-phenylalanine for growth, but a bacilysin-resistant mutant of this strain does not. It is suggested that the antibacterial activity of bacilysin depends on its transport into the organism, its hydrolysis to anticapsin and on inhibition by the latter of glucosamine synthetase, and that bacilysin-resistant mutants are defective in a transport system.

Identification of the antibiotic determined by the SCP1 plasmid of Streptomyces coelicolor A3(2).

Abstract: SUMMARY: The antibiotic whose biosynthesis is determined by the SCP1 plasmid of Streptomyces coelicolor A3(2) has been characterized as the recently described methylenomycin A (2-methylene-cyclopentan-3-one-4,5-epoxy-4,5-dimethyl-1carboxylic acid).

Differentiation of Claviceps purpurea in Axenic Culture

Abstract: SUMMARY: The growth form of a strain of Claviceps purpurea in axenic culture has been controlled by the amino nitrogen source. Within the pairs asparagine/aspartic acid or glutamine/glutamic acid the amide promoted sphacelial growth of the colony whereas the acid supported differentiation of plectenchymatic sclerotial tissue and synthesis of ergot alkaloids. Sclerotial colonies showed purple pigmentation. The mycelium had a greater lipid content, rich in ricinoleic acid, and sporulation was much less than in sphacelial colonies. Changes in the relative distribution of amino acids between the free and peptidyl components of the cells was most marked with respect to lysine; growth on asparagine resulted in more than half remaining free, whereas less than 10 % remained free on aspartic acid. Lysine supplied exogenously as a nitrogen source did not promote sclerotial differentiation. Frequent transfers to fresh medium of colonies grown on dialysis membrane accentuated the extent of sphacelial or sclerotial growth; four transfers during an 18-day growth period yielded mycelia with an alkaloid content (0.4 %, w/w) similar to that of parasitic ergot sclerotia. Asparagine and glutamine were taken up more rapidly from liquid media than their corresponding acids, but each acid exerted a dominant effect over the amide, in a mixture providing equivalent nitrogen, resulting in differentiation from sphacelial to sclerotial growth analogous to that occurring during parasitism. The apparently greater (w/w) proportion of total amino acids in sphacelial mycelia than in sclerotial mycelia mainly reflected the lower lipid content of these tissues, but this factor was insufficient to account for the persistence of a significant proportion of the total lysine amongst the free amino acids. The promotion of sclerotial growth by aspartic and glutamic acids was not confined solely to the experimental strain of the fungus. Although some isolates failed to differentiate into plectenchymatic mycelia on these nitrogen sources, the extent of their sphacelial growth, as indicated by the degree of sporulation, was always much reduced with respect to that promoted by asparagine.

Proteolytic activation and inactivation of chitin synthetase from Mucor rouxii.

Abstract: Summary: Crude chitin synthetase preparations from the mycelial and yeast forms of Mucor rouxii behaved differently. The mycelial preparations, incubated at 28 °C, lost virtually all chitin synthetase activity in a few hours; by contrast, the activity of enzyme preparations from yeast cells increased several fold during similar incubations. These spontaneous changes were probably caused by endogenous protease(s). Seemingly, the chitin synthetase in yeast preparations was present mainly in a latent, ‘zymogenic’, form that was activated by proteases. In the mycelial preparations, chitin synthetase was present mainly in an active state and was rapidly degraded by endogenous proteolysis. Exogenous proteases accelerated activation and destruction of chitin synthetase; an acid protease from Rhizopus chinensis was the most effective activator. The activation of chitin synthetase was inhibited by a soluble protein in the cell-free extract. Treatment with the detergent Brij 36T stabilized the chitin synthetase of crude preparations against spontaneous changes. Stabilized preparations were rapidly activated by exogenous proteases. The different behaviour of chitin synthetases in crude extracts of mycelium and yeast cells is consistent with, and perhaps partially responsible for, the differences in wall construction between mycelial and yeast forms of M. rouxii.

Actinorhodin is a chromosomally-determined antibiotic in Streptomyces coelicolar A3(2).

Abstract: Streptomyces coelicolar A3(2) synthesizes a second antibiotic, in addition to the plasmid-determined methylenomycin A. It was identified, primarily on the evidence of mass spectroscopy of its diethyl ester, as actinorhodin, which has been described previously in other strains. It inhibited most Gram-positive bacteria tested, but only at a comparatively high concentration. Five independent mutations leading to lack of actinorhodin synthesis were located between cysD and strA on the chromosome.

The Production and Growth Characteristics of Yeast and Mycelial Forms of Candida albicans in Continuous Culture

Abstract: SUMMARY: The growth characteristics of Candida albicans CM145,348 have been examined under aerobic conditions in continuous culture. At different steady states the environment was controlled with respect to the concentrations of dissolved oxygen, carbon and nitrogen, the pH, and the temperature. Dry matter, substrate concentration, yield, specific oxygen uptake, specific carbon dioxide release and respiration quotient were examined as a function of the dilution rate. The morphology depended on the carbon source. Maltose produced a mycelial morphology, whereas with lactate a yeast culture was obtained. With fructose or glucose as a carbon source a mixed morphology of yeast, pseudo-mycelial and mycelial forms was produced. A large number of different growth conditions were examined in batch culture but a mixed morphology was always obtained.

Regulation of the tricarboxylic acid cycle and poly-beta-hydroxybutyrate metabolism in Azotobacter beijerinckii grown under nitrogen or oxygen limitation.

Abstract: Azotobacter beijerinckii was grown in ammonia-free glucose/mineral salts media in chemostat culture under oxygen or nitrogen limitation. Selected enzymes of the tricarboxylic acid cycle and poly-beta-hydroxybutyrate metabolism were monitored in relation to oxygen supply for both steady and transition states. Two dissolved oxygen concentrations were used for the nitrogen-limited steady state to investigate the possible effects of respiratory protection of nitrogenase on these enzymes. The levels of NADH oxidase, isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase increased markedly on relaxation of oxygen limitation while pyruvate dehydrogenase and citrate synthase were relatively unaffected. beta-Ketothiolase and acetoacetyl-CoA reductase levels decreased as oxygen limitation was relaxed. Respiratory activity, as measured by the QO2 value, increased with oxygen supply rate. Imposition of oxygen limitation on a nitrogen-limited culture caused an immediate increase in the NADH/NAD ratio but this rapidly readjusted to its previous steady-state value. These changes are discussed in relation to respiratory protection of nitrogenase and poly-beta-hydroxybutyrate metabolism in A. beijerinckii.

The Influence of Surface Charge on the Attachment of Neisseria gonorrhoeae to Human Cells

Abstract: SUMMARY: Isoelectric focusing showed that Neisseria gonorrhoeae has an overall negative surface charge. Chemical modification of protein amino or carboxyl groups changed the surface charge and thereby altered the ability of the organisms to attach to human amnion cells grown in tissue culture. Attachment of modified and unmodified N. gonorrhoeae was increased by the presence of pili only when the bacteria bore a negative surface charge. Thus an important factor in the pathogenesis of gonorrhoea may be the ability of pili to facilitate attachment of N. gonorrhoeae by overcoming the initial electrostatic repulsive barrier which exists between it and the host cell.

Nitrogen Fixation by Bacteria from the Hindgut of Termites

Abstract: SUMMARY: Anaerobically grown bacteria isolated from the hindgut contents of the termites Coptotermes lacteus (Froggatt), Mastotermes darwiniensis Froggatt and Nasutitermes exitiosus (Hill) were nitrogenase-positive as assayed by acetylene reduction. Nitrogen fixation, confirmed with 15N2, was highest in the isolate from M. darwiniensis. All isolates were identified as Citrobacter freundii (Braak) Werkman & Gillen.

Antimicrobial activities and antagonists of bacilysin and anticapsin.

Abstract: Summary: The dipeptide antibiotic bacilysin is active against a wide range of bacteria and against Candida albicans. Its C-terminal amino acid, anticapsin, is a very poor antibacterial agent. The activities of both substances are strongly dependent on the nature of the culture medium. In a minimal medium the minimum inhibitory concentration for bacilysin with E. coli B is 10-3 μg ml-1. The action of bacilysin is antagonized by a variety of dipeptides and that of anticapsin by a number of amino acids. With several bacteria, bacilysin-resistant mutants are found in unusually large numbers. It is suggested that peptide and amino acid transport systems play a role in these phenomena. The antimicrobial action of bacilysin is also inhibited by glucosamine and N-acetylglucosamine. This antibiotic may therefore interfere with glucosamine synthesis and thus with the synthesis of microbial cell walls.

Urease activity in the rumen of sheep and the isolation of ureolytic bacteria.

Abstract: SUMMARY: Urease activity in the sheep rumen varied with the diet of the sheep, but appeared to be largely or entirely present in the small bacterial fraction. Screening of over 1000 strains of rumen bacteria isolated on different media showed that urease activity was apparently confined to species of Staphylococcus, Lactobacillus casei var. casei and Klebsiella aerogenes. Consideration of the numbers in which these occurred and their activities suggested that the bacteria could not be responsible for the total rumen urease activity. By enrichment culture a ureolytic strain of Streptococcus faecium was isolated. This had a higher urease activity than the other bacteria and occurred in higher numbers in the rumen. It could live with other bacteria in the rumen of a gnotobiotic lamb in numbers, and with a urease activity, comparable with those in the normal sheep rumen. The other properties of the bacterium also suggested that it would grow and produce urease in the rumen, but was unlikely to retain its urease activity after isolation. It was concluded that this bacterium was the main source of rumen urease in roughage-fed, and probably other, sheep.

Amino-acid pool composition of Saccharomyces cerevisiae as a function of growth rate and amino-acid nitrogen source.

Abstract: SUMMARY: The composition of the amino-acid pool of Saccharomyces cerevisiae is markedly influenced by the amino-acid nitrogen source. The yeast tends to accumulate the amino acid supplied and those closely related to it metabolically. A relatively high concentration of glutamic acid is maintained in the pools of all cultures irrespective of the nitrogen source, reflecting the central role of glutamic acid in nitrogen metabolism. The total amino-acid pool concentration increases as a function of growth rate, although differences exist in the behaviour of individual amino acids.

Thin-layer chromatographic analysis of mycolic acid and other long-chain components in whole-organism methanolysates of coryneform and related taxa.

Abstract: Acid methanolysates of strains representing 58 coryneform taxa were examined for mycolic acids and other long-chain constituents by thin-layer chromatography. Mycolic esters were detected in the methanolysates of true corynebacteria but not in those from plant pathogenic bacteria, Corynebacterium haemolyticum, Corynebacterium pyogenes or from representatives of the genera Arthrobacter, Cellulomonas, Curtobacterium, Kurthia or Oerskovia. Thin-layer chromatography of whole-organism methanolysates provides a simple method for distinguishing true corynebacteria from coryneforms which do not contain mycolic acids, and from nocardiae and mycobacteria which produce mycolic acids of different mobility. At present the mycolic esters of true corynebacteria cannot be clearly separated from those of some rhodochrous strains.

Chemistry and Architecture of the Mycelial Wall of Agaricus bisporus

Abstract: Summary A purified wall fraction was prepared from the mycelium of Agaricus bisporus. The isolated wall consisted of 43% (w/w) chitin, 14% KOH-soluble glucan, 27% β-glucan, 16% protein and 1–5% lipid. Traces of mannose and xylose were detected by gas chromatography. The architecture of the wall was investigated with sequential enzyme digestion and electron microscopy. The outer wall surface is covered by a mucilage that is removed by the isolation procedure. The wall fraction could be completely degraded by extraction in warm I M-KOH followed by digestion with a mixed β-glucanase and then chitinase. The outer layer of KOH-soluble glucan is amorphous and of variable thickness. Incubation with glucanase did not change the dimensions of the wall but was necessary before the inner wall was susceptible to attack by chitinase, indicating that β-glucan does not constitute a separate wall layer but is a matrix associated with the fibrillar chitin. The inner layer presents an even, compact, fibrillar side as the inside surface of the wall, but is looser and uneven outwardly where it interdigitates with the irregular inner surface of the KOH-soluble glucan. Silver hexamide staining showed cystine-containing protein throughout the wall.

Free Mycolic Acids as Criteria in the Classification of Nocardia and the ‘rhodochrous’ Complex

Abstract: SUMMARY: The methyl esters of free mycolic acids from representative strains of Nocardia asteroides, N. brasiliensis, N. caviae and the ‘rhodochrous’ complex were subjected to detailed mass spectral analysis. The anhydromycolic esters of the Nocardia strains consisted of homologous series containing from zero to three double bonds, with the main components of the parent mycolic acids centred on C52 to C54 (range C46 to C58). The anhydromycolates from one rhodochrous strain, Nocardia opaca, had a molecular weight range similar to the nocardiae (C46 to C57) but the remaining rhodochrous strains gave an homologous series of anhydromycolates containing from zero to two double bonds, with the main components of the parent mycolic acids centred on C38, C42, C44 or C46 (total range from C34 to C50). The mycolic acids from the rhodochrous strains with chain lengths centred around C40 form a group intermediate in size between corynomycolic acids (centred around C50) and nocardomycolic acids (centred around C50). These data weaken the case for retaining the ‘rhodochrous’ complex in the genus Mycobacterium, and also show that many rhodochrous strains can be distinguished from true nocardiae and corynebacteria. These results confirm the value of lipid characters in the classification of these organisms.