- Volume 128, Issue 5, 1982
Volume 128, Issue 5, 1982
- Physiology And Growth
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Induction and Differentiation of Heterocysts in the Filamentous Cyanobacterium Cylindrospermum licheniforme
More LessThe fragmentation of Cylindrospermum licheniforme filaments resulted in the induction of a synchronous round of heterocyst differentiation. Young heterocysts (proheterocysts) appeared 12 to 15 h after fragmentation, and 12 to 15% of the cells became heterocysts within 24 h. NH4Cl or NaNO3 prevented the formation of new heterocysts, while differentiation was stimulated twofold by the absence of atmospheric N2. The sequence of appearance of heterocyst-specific characteristics was observed following filament fragmentation. Nitrogenase activity increased rapidly between 13 and 26 h, paralleling the increase in heterocyst frequency. Glycolipids unique to the heterocyst envelope were also synthesized between 13 and 26 h, and activities of 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase increased after 10 h and 90 h respectively. Aged medium induced sporulation in intact filaments within 1 d. but sporulation could occur no earlier than 2 d after filament fragmentation, indicating that the induction of sporulation requires the presence of mature (but not necessarily functional) heterocysts.
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The Role of Surface Stress in the Morphology of Microbes
More LessThe shapes of many prokaryotes can be understood by the assumption that the cell wall expands in response to tension created by the osmotically derived hydrostatic pressure. Different organisms have different shapes because wall growth takes place in different regions. A previous paper ( Koch et al., 1981a ) considered the simplest case of prokaryotic growth, i.e. that of Streptococcus faecium. In the present paper, an elaboration of this theory is applied to two further cases - the more perfectly spherical cocci and the rod-shaped bacteria. These cases are more complex mathematically, because growth over a considerable fraction of the surface must be considered. Such diffuse growth cannot be treated analytically, but can be simulated on a computer or handled by geometric arguments.
The spherical form of the cocci may result from either diffuse growth over their entire external surface, or from zonal growth in which the addition of new material only occurs in the immediate vicinity of the splitting septum. In the zonal model, it must be assumed that the least amount of previously laid down septal peptidoglycan consistent with wall growth is reworked in the formation of the new external wall. For Gram-positive rods, where the body of the rod is truly cylindrical, three kinds of growth zones are required: (1) the inward edge of the ingrowing septum, (2) the junction of septum and nascent pole, and (3) the cylindrical walls. Two modes for cylindrical elongation are possible: (a) new wall is added in one or a few narrow annular zones, or (b) new wall material is added continuously all over the innermost surface and the outer layer is degraded. It is shown that the latter case applies to Bacillus subtilis.
Also summarized in this paper are results, developed in more detail elsewhere, concerning the morphology of fusiform bacteria, Gram-negative rods and the hyphal tips of fungi.
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The Shape of the Hyphal Tips of Fungi
More LessA growing hyphal tip is analogous to a molten glass bubble blown under special conditions. These conditions are that the pressure is constant throughout the tip and that the surface tension is very low at the apex and increases towards infinity with distance from the tip. The biological correlate for low surface tension at the apex of the hypha is that enzymic activity and rate of fusion of vesicles are very high in the immediate vicinity of the apex. A formula is developed to allow the calculation of the rate of synthesis at a point on the tip from its distance from the axis and the slope of the tip at that point.
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Effects of Iodoamphenicol on Ribosome Assembly in Two Strains of Escherichia coli
More LessWhen the growth of Escherichia coli strain 15TP was inhibited by iodoamphenicol, three ‘iodoamphenicol particles’ accumulated with sedimentation coefficients of 25S, 33S and 45S. The 25S and 33S particles differ in sedimentation properties from equivalent ribosome precursor particles detected during pulse-labelling of exponentially growing cells. Inhibition of a mutant, strain 15–28 (defective in ribosome assembly), by iodoamphenicol resulted in the accumulation of 38S iodoamphenicol particles that are different from the particles made by the parent. The results support the contention that assembly of 50S ribosomal subunits by the mutant is altered at an early stage.
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Kinetics of Protein Turnover in Growing Cells of Bacillus megaterium
More LessThe course of protein degradation during growth of a [14C]leucine-labelled population of Bacillus megaterium with a surplus of the non-radioactive amino acid indicated the presence of a labile protein fraction decaying with a half-life of less than 1 h. The half-life of the remaining ‘stable’ fraction was much longer (40 h or more). A nutrient shift-down increased, and a shift-up decreased the relative size of the labile fraction and the rate of degradation of the ‘stable’ fraction. When bacteria were prelabelled in the presence of ethionine, both the size of the labile fraction and the rate of degradation of the ‘stable’ fraction were increased. A shift-up in temperature caused a large increase in the size of the labile fraction while the rate of degradation of ‘stable’ proteins increased only slightly. The rate of degradation of the labile fraction was not changed significantly by any treatment. The results suggest that the main target of regulation of protein turnover by environmental conditions is the relative size of the labile protein fraction.
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Growth of Streptococcus faecalis var. zymogenes on Glycerol: The Effect of Aerobic and Anaerobic Growth in the Presence and Absence of Haematin on Enzyme Synthesis
More LessStreptococcus faecalis var. zymogenes was grown aerobically and anaerobically in the presence and absence of haematin, with glycerol as the carbon and energy source. Aerobic growth was stimulated by the inclusion of haematin in the medium but fumarate had no effect on growth. The bacterium was unable to grow anaerobically on glycerol unless fumarate was present; haematin had no effect on growth. NADH oxidase activity, which catalysed the oxidation of NADH + H+ to form H2O rather than H2O2, was found in the soluble fraction and was induced by aerobic growth but partially repressed when haematin was present in the medium. In contrast, a particulate NADH oxidase, which was sensitive to inhibition by antimycin A and 2-heptyl-4-hydroxyquinoline N-oxide, was induced by aerobic growth in the presence of haematin. NADH peroxidase was massively induced by aerobic growth, whereas more lactate dehydrogenase activity was found in anaerobically grown bacteria. Catalase was formed only during aerobic growth in the presence of haematin.
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Chemical Dissolution of Cellulose Membranes as a Prerequisite for Penetration from Appressoria of Colletotrichum lagenarium
More LessThe relationship between protein synthesis during appressorial formation and the ability of appressoria to form penetration hyphae in nitrocellulose membranes was investigated for the plant pathogenic fungus Colletotrichum lagenarium. Cycloheximide treatment before appressorial pigmentation inhibited the formation both of penetration hyphae and of haloes, the latter resulting from the partial degradation of cellulose membranes; but treatment after appressorial pigmentation did not inhibit halo formation. When spores were transferred to 32 °C before appressoria became pigmented, both pigmentation and penetration were prevented. In the presence of 1 mm-3,4-dihydroxyphenylalanine (DOPA) at 32 °C, pigmentation was restored, but the formation of haloes and penetration hyphae was still prevented. Penetration into cellulose membranes pretreated with cellulase was observed from 20–30 % of appressoria which had been formed in the presence of cycloheximide at 24 °C or in the presence of DOPA at 32 °C. The results suggest that there are two phases of protein synthesis following spore germination, only the first of which is involved in halo formation.
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Autolysis in vitro of the Stipe Cell Wall in Coprinus macrorhizus
More LessCell walls isolated from rapidly elongating stipes of Coprinus macrorhizus basidiocarps lost 55 % of their dry weight during 24 h incubation at 37 °C. Neutral sugars accounted for 73 % of the solubilized products, glucose being the major sugar component. In the carbohydrate fraction solubilized after relatively short periods of autolysis, polymeric (degree of polymerization > 10), dimeric and monomeric components were detected, and the larger components were converted to monosaccharide as the reaction proceeded. Three polysaccharide fractions of the cell wall were highly susceptible to autolytic enzymes, whereas another fraction was not. Chitin appeared to be relatively resistant. Analyses of the cell walls from various stages during stipe elongation revealed a positive relation between the rate of stipe elongation and the initial rate of autolysis, suggesting that the autolytic enzymes are involved in the mechanisms of stipe elongation.
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Some Properties of Glutathione Biosynthesis-deficient Mutants of Escherichia coli B
More LessMutants of Escherichia coli B that contain essentially no detectable glutathione were isolated. These mutants had a very low activity of γ-glutamylcysteine synthetase or glutathione synthetase. No significant differences in growth in minimal medium were observed between the mutants and the parental strain. The mutants lacking γ-glutamylcysteine synthetase activity were more susceptible to toxic compounds than either the parental strain or a glutathione synthetase-deficient strain. The mutants lacking γ-glutamylcysteine synthetase activity were also susceptible to oxygen.
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- Short Communication
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Haemophilus influenzae and Neisseria gonorrhoeae Recognize Different Specificity Determinants in the DNA Uptake Step of Genetic Transformation
More LessCross-transformation and quantitative competition experiments showed that Neisseria gonorrhoeae and Haemophilus influenzae do not interact with each other’s DNA in transformation. These organisms must interact with different recognition sequences during DNA uptake.
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- Taxonomy
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An Electrophoretic Study of Enzymes as a Tool in the Taxonomy of the Dermatophytes
More LessZymogram patterns from 84 strains of dermatophyte fungi were obtained using polyacrylamide gradient gel electrophoresis of total cell protein extracts. The enzymes investigated were α-naphthyl acetate esterase, acid phosphatase, lactate dehydrogenase, malate dehydrogenase, tetrazolium oxidase and catalase. These patterns were used to construct similarity matrices and dendrograms using computerized techniques. The results showed that zymograms allowed some species to be readily recognized despite morphological variation. This was also seen in the dendrograms where, in addition, groupings based on ecological or sexual criteria could be distinguished.
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The Bacillus firmus-Bacillus lentus Complex and pH 7·0 Variants of Some Alkalophilic Strains
More LessVariants capable of growth at pH 7·0 were obtained from 174 alkalophilic strains (optimum pH 9·7) of the genus Bacillus by successive transfer on media with decreasing pH values. Nearly half of the pH 7·0 variants were like strains of the B. firmus-B. lentus complex. The remaining pH 7·0 variants grew at 50 °C and were assigned to two groups closely related to B. lentus.
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- Corrigendum
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