- Volume 118, Issue 2, 1980
Volume 118, Issue 2, 1980
- Physiology And Growth
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Action of Uncouplers of Oxidative Phosphorylation as Chemotactic Repellents of Bacillus subtilis
More LessBacillus subtilis alternately swims smoothly and tumbles; when administered repellent it only tumbles, but later resumes normal swimming and tumbling. Repellents of B. subtilis include membrane-active agents like uncouplers of oxidative phosphorylation and local anaesthetics and have previously been found to act in a fundamentally different way compared with attractants. It has been suggested previously that uncouplers act as repellents as a result of their ability to depolarize the membrane and that depolarization might affect flagellar function by causing a flux of Ca2+ into the cell. However, we found that there is no correlation between membrane depolarization and chemotaxis and no detectable flux of Ca2+ following tactic stimulation by uncouplers. Experiments with analogues of the uncoupler pentachlorophenol, all of which are weaker acids than pentachlorophenol, indicated that the anionic form of the uncoupler is the potent form and we propose that it binds to a certain membrane protein to cause release into the cytoplasm of the substance (ion, metabolite or protein) that controls tumbling frequency. Adaptation is assumed to occur when this excess is removed by active transport or metabolism.
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Cell Division in the Yeast Saccharomyces cerevisiae Growing at Different Rates
More LessFlow microfluorometry was employed to examine the cell cycle of Saccharomyces cerevisiae growing at different rates governed by different nitrogen sources. In general, the initiation of budding was indistinguishable from the onset of S phase regardless of growth rate. Although with longer generation times S phase showed some increase in length, most of the increase in generation time resulted from increases in Gl.
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Isolation and Characterization of a Mutant of Pseudomonas aureofaciens ATCC 15926 with an Increased Capacity for Synthesis of Pyrrolnitrin
More LessA mutant having a 30-fold increased ability to synthesize pyrrolnitrin was isolated from Pseudomonas aureofaciens ATCC 15926 after mutagenesis with N-methyl-N′-nitro-N-nitrosoguanidine. The mutant strain also differed from the parent strain in pigmentation and in its inability to catabolize anthranilic acid and the benzene moiety of tryptophan and kynurenine.
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- Short Communication
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The Complexity of Immunogenicity of Neisseria gonorrhoeae in the Guinea Pig Subcutaneous Chamber Model
More LessThe immunogenicity of Neisseria gonorrhoeae in the guinea pig subcutaneous chamber model, assessed by serum bactericidal tests and challenge experiments, is complicated by diversity of immunotypes which may or may not show partial cross-reactions, by the need for antibodies to more than one type-specific antigen for full homologous protection, and possibly by the limited accessibility of the relevant antigens on the cell surface.
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The Characteristics of Extracellular Protein Secretion by Staphylococcus staphylolyticus
More LessThe differential rate of extracellular protein formation by Staphylococcus staphylolyticus, the lysostaphin-producing organism, was biphasic with a low rate of exoprotein secretion during exponential growth and an increased rate during the post-exponential phase of growth. After 20 h, when no further exoprotein was secreted, exoprotein accounted for 5% of the total protein in the culture. The secretion of three extracellular enzymes was monitored and found to represent a constant proportion of total exoprotein at exoprotein concentrations greater than O.1 mg ml−1.
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Discrimination of Micro-organisms Using Direct Probe Mass Spectrometry
More LessDirect probe mass spectrometry of single colonies of different bacteria produced spectra which could be distinguished by calculations based on the intensities of 25 selected ions. Direct probe mass spectrometry has enormous potential as a rapid technique for characterizing micro-organisms.
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Mobilization of the Proteus morganii Chromosome by R Plasmids
More LessR plasmids R702, R711b, R1, D, Rip69, R447b, R471 and R394, belonging to different incompatibility groups, mobilized the Proteus morganii 2815 chromosome. Matings employing plasmids R71 1b or R702 as sex factors with doubly auxotrophic recipients produced recombinants characterized by the obligatory inheritance of ser-1 +, irrespective of the selected marker.
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Loss of Extrachromosomal Resistances in Staphylococcus aureus by Treatment with Guanidine Hydrochloride
More LessThe addition of subinhibitory concentrations (optimal 1.8 mg ml−1) of guanidine hydrochloride to broth cultures of three strains of Staphylococcus aureus was followed by loss of penicillin and cadmium resistance. The proportion of sensitive variants, although variable, was higher than in untreated cultures. The penicillinase plasmid was absent from two cultures sensitive to penicillin and cadmium. The genes for penicillinase production in one culture (13136) were apparently carried by a plasmid of 105 106 daltons.
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Effect of Growth Rate on the Production of Phytohormone-like Substances by an Arthrobacter sp. in Chemostat Culture
More LessGibberellins, auxins and cytokinins were produced by an Arthrobacter sp. grown in ammonium-limited chemostat culture. Differences in the production of the three substances occurred in response to changes in growth rate.
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- Taxonomy
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Numerical Classification of Some Named Strains of Nocardia asteroides and Related Isolates from Soil
More LessOne hundred and forty-nine strains of nocardiae, freshly isolated from soil samples obtained from a number of countries with either tropical or temperate climates, and from rubber pipe seals, were compared with appropriate marker cultures in a numerical phenetic study using 156 unit characters. Marker strains were chosen to represent the Nocardia asteroides complex, other Nocardia species and related taxa in an effort both to classify the new soil isolates and, possibly, clarify the structure of the heterogeneous N. asteroides complex. The data were examined using the simple matching (SSM ) and pattern (DP ) coefficients, and clustering was achieved using both single and average linkage algorithms. Cluster composition was not markedly affected by either of the coefficients or clustering methods. The estimated test error of 7·1 % was rather high and could account for a few apparently anomalous results. The 16 defined clusters, containing 185 of the 197 strains studied, were divided into seven major and nine minor clusters, four of which were further subdivided into two subclusters. Marker strains allowed four clusters to be designated as N. asteroides, seven as Nocardia species and one each as Nocardia carnea, Nocardia farcinica, Nocardia autotrophica, Mycobacterium farcinogenes and Rhodococcus species. Twelve strains formed single member clusters including the type strains of Nocardia aerocolonigenes, Nocardia amarae, Nocardia fukuyae, Nocardia orientalis and Nocardia otitidis-caviarum. The majority of the soil and rubber isolates were recovered in the major clusters labelled N. asteroides, N. carnea and Nocardia species and clusters of soil isolates without marker strains seem to represent new centres of variation. The study highlights the need for additional reproducible tests to help both define and determine the status of defined clusters within the N. asteroides complex which would considerably benefit both the ecological and epidemiological study of these organisms.
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Ribosomal Ribonucleic Acid Similarities in the Classification of Rhodococcus and Related Taxa
More LessDuplexes were prepared between 14C-labelled rRNA from both Rhodococcus equi C7 and Rhodococcus rhodochrous N54 and DNA from 16 actinomycetes representing the genera Rhodococcus, Mycobacterium, Nocardia, Sacccharopolyspora and Streptomyces. The relationships between the organisms were determined by plotting the temperature at which 50 % of the duplex was denatured (Tm (e)) against the percentage of rRNA binding (g 14C-labelled rRNA duplexed per 100 g filter-bound DNA). All of the strains formed stable duplexes but each organism occupied a definite area on the rRNA similarity map. All of the organisms share a close phylogenetic relationship but representatives of the genera Rhodococcus, Mycobacterium, Nocardia and Streptomyces fell into four recognizable clusters on the similarity map. These data support and extend current trends in the classification of Rhodococcus and allied taxa. The guanine plus cytosine content of the DNA from the test strains was within the range 693 to 769 mol %.
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Deoxyribonucleic Acid Base Compositions of Dermatophytes
More LessDNA was extracted and purified from 55 dermatophyte isolates representing 34 species of Trichophyton, Microsporum and Epidermophyton. The base compositions of the chromosomal DNA were determined by CsCl density gradient centrifugation and were found to be in the narrow range of 48·7 to 50·3 mol % G + C. A satellite DNA component assumed to be of mitochondrial origin was present in most strains, with a G + C content ranging from 14·7 to 30·8 mol % G + C. Heterogeneity in microscopic and colonial characteristics was not reflected in differences in the mean G + C content of the chromosomal DNAs. Strains varied in the G + C contents of satellite DNA, but these did not correlate with traditional species concepts.
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