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Volume 129,
Issue 2,
1983
Volume 129, Issue 2, 1983
- Pathogenicity And Medical Microbiology
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Virulence For Mice Of A Proteinase-Secreting Strain Of Candida Albicans and A Proteinase-Deficient Mutant
More LessA proteinase-deficient mutant of Candida albicans, M12, was produced by nitrosoguanidine mutagenesis of a proteinase-producing strain, ATCC 28366. The mutant was phenotypically identical to its parent in nearly all biochemical and morphological characteristics except proteinase production. The mutant was considerably less lethal than the parent when inoculated intravenously into mice and lower counts of C. albicans were recovered from the organs of mice infected with the mutant. Both strains were phagocytosed and killed to a similar extent by human and murine polymorphonuclear leukocytes when the yeasts were grown in a medium that did not induce proteinase production. However, in a proteinase-inducing medium, ATCC 28366 was phagocytosed and killed less well than M12. These results indicate that proteinase secretion by C. albicans is one factor determining the virulence of the species, but that other virulence factors are also involved in the pathogenesis of systemic candidosis.
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Insect Pathogenic Properties Of Serratia Marcescens. Passive And Active Resistance To Insect Immunity Studied With Protease-deficient And Phage-Resistant Mutants
More LessMany insects have a cell-free immune system in which small basic proteins called cecropins are the main defence against Gram-negative bacteria. We have earlier shown that an insect pathogenic strain of Serratia marcescens was resistant to insect immunity and that certain mutants resistant to phage ɸJ become sensitive to cecropins. We have found that protease-deficient mutants with and without resistance to ɸJ appear to be deficient in the mechanism of protease induction. Three different protease fractions exist and for two of the enzymes we describe a partial purification and characterization. The proteases show pronounced autodegradation which increases with the purity. Both enzymes are only partly affected by EDTA and they are highly toxic to Drosophila melanogaster. All three enzymes destroy cecropins in immune haemolymph from Cecropia pupae. However, in vivo experiments with different mutants indicate that in Serratia, passive resistance to insect immunity is more important for virulence in Drosophila than the production of proteases which can destroy cecropins.
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- Physiology And Growth
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A Minimal Medium For The Cultivation Of Infective Trypanosoma Cruzi Epimastigotes
More LessSUMMARY: In a culture medium containing bovine liver catalase, but lacking exogenous free amino acids, only two vitamins (choline and folic acid) were found to be essential for the continuous in vitro multiplication of seven different infective strains of Trypanosoma cruzi. The provision of additional vitamins or sugars had no stimulatory effect under these culture conditions. These, and previous studies, have allowed the design of a trypanosomal minimal medium composed only of bovine liver catalase, choline, folic acid, glucose and inorganic salts. This was able to support the continuous cultivation of T. cruzi for more than 12 consecutive passages (i.e. about 160 d of culture). By several criteria, namely morphological features as seen by electron microscopy, infectivity for vertebrate and invertebrate hosts, glucose utilization and protein biosynthesis, this medium (which is the simplest so far described) proved to be nutritionally adequate for Trypanosoma spp. In addition, the medium appeared to be relatively specific for T. cruzi, as it did not support the growth of T. rangeli and American isolates of leishmania.
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Growth Defects Of Escherichia Coli Cells Which Contain The Gene Of An α-Amylase from Bacillus coagulans on a Multicopy Plasmid
More LessAn α-amylase gene from Bacillus coagulans has previously been cloned in Escherichia coli and shown to direct the synthesis of an enzymically active protein of 60000 Dal ( Cornelis et al., 1982 ). In one particular E. coli host, strain HB101, amylase was found to accumulate in the periplasmic space. To study the processing and the location of the amylase, plasmid pAMY2 was introduced into E. coli 188 which is a strain constitutive for alkaline phosphatase, a periplasmic marker, and for β-galactosidase, a cytoplasmic marker. Abnormally large amounts of both a-amylase and β-galactosidase were found in the culture fluid of cells grown in rich medium. Furthermore a severe growth defect was found when cells containing pAMY2 were grown in maltose and glycerol media, while the ability to grow on glucose remained normal. This defect could be reversed by two types of spontaneous mutations. Mutations in the first class are located on the plasmid and correspond to the insertional inactivation of the amylase gene by IS1. Mutations in the second class are located on the host chromosome. These results suggest that the synthesis and export of B. coagulans α-amylase is deleterious to E. coli, especially in media containing maltose or glycerol as sole carbon source.
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Catabolite Effects On Enzyme Induction And Substrate Utilization In Rhizobium leguminosarum
More LessThe catabolism of l-histidine and p-hydroxybenzoate in Rhizobium leguminosarum 3841 is inducible. Glucose or succinate have relatively little effect on the induction of histidase whereas they produce about 50% repression of the p-hydroxybenzoate catabolic system. When grown in the presence of a mixture of carbon sources, e.g. glucose plus histidine, or succinate plus p-hydroxybenzoate, the cells co-utilize both substrates. However, consumption of histidine and p-hydroxybenzoate (which support slower growth rates than glucose or succinate) is substantially reduced in comparison with that of glucose or succinate.
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The Interrelation Of Phototaxis, Membrane Potential And K+/Na+ Gradient In Halobacterium Halobium
More LessThe attractant effect of green light and the repellent effect of blue light on Halobacterium halobium were studied. It was found that addition of CN− and dicyclohexylcarbodiimide, which block the redox chain and H+-ATPase, respectively, increased both the amplitude of light-dependent changes of membrane potential (∆ψ), monitored by the distribution of tetraphenyl-phosphonium, and the sensitivity of the green-light taxis. A direct proportionality between ∆ψ and the green-light sensitivity was revealed. The sensitivity of the green-light taxis was decreased by glucose, histidine and Na+/K+ gradient, i.e. factors reducing the light-dependent changes of protonic potential. These factors did not affect the blue-light taxis. The uncoupler carbonyl cyanide m-chlorophenylhydrazone appears to repel H. halobium cells. These data are in agreement with the assumption that the green-light taxis is governed by a sensing of protonic potential, whereas the blue-light taxis is mediated by a specific photoreceptor.
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The Influence Of Ionic Strength, Ph And A Protein Layer On The Interaction between Streptococcus Mutans And Glass Surfaces
More LessThe initial interaction between Streptococcus mutans and hard surfaces has been investigated using a rotating disc technique. The deposition to clean and BSA-coated glass of two strains of S. mutans, FA-1 (serotype b) and KPSK2 (serotype c), which exhibit different surface properties, was studied. Organisms were harvested from cultures grown in a chemostat at a dilution rate of 0·06 h−1 and suspended in NaCl solutions of defined ionic strengths and pH values. The deposition of both strains showed a strong dependence on electrolyte concentration, particularly at low ionic strengths, which was inversely related to the zeta potentials of the organisms. Similarly, the ionic strength at which maximum deposition was first noted (critical coagulation concentration) for the two strains correlated with their relative potentials. Deposition was insensitive to changes in pH at an electrolyte concentration of 0·05 m. The maximum observed deposition did not approach values predicted by theory, suggesting that a further barrier to deposition, other than electrostatic repulsion, might exist. Under all experimental conditions, some of the deposited bacteria were observed to be oscillating, suggesting that they were held at a distance from the collector surface. The cells did not, however, appear to be deposited in a secondary minimum predicted by DLVO theory hence it may be that long-range polymer interactions are also involved in the deposition of these organisms.
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Alteration Of Susceptibility To Edta, Polymyxin B And Gentamicin In Pseudomonas Aeruginosa By Divalent Cation Regulation Of Outer Membrane Protein H1
More LessInduction of outer membrane protein H1 in Pseudomonas aeruginosa results in decreased susceptibility to aminoglycosides, polymyxin B, and EDTA. We have previously shown that protein H1 can become the major cellular protein in cells grown in low (0·02 mm) Mg2+. The induction of protein H1 was prevented by supplementation of low Mg2+ medium with Mg2+, Ca2+, Mn2+, or Sr2+ (each at 0·5 mm), but not with Zn2+, Ba2+, Sn2+, Al3+ or Na+ (each at 0·5 mm). Only cells grown in the presence of those cations which failed to prevent H1 induction were resistant to the cationic antibiotics, polymyxin B and gentamicin, and to chelators of divalent cations. Cells grown in Ca2+, but not in Mg2+, were susceptible to outer membrane permeabilization by the Ca2+ specific chelator EGTA, whereas both were susceptible to EDTA. In agreement with this, cells grown in Mg2+, Ca2+, Mn2+, or Zn2+ showed enhanced levels of these cations respectively as their major cell envelope-associated cation. When cells were shifted from low to high Mg2+ medium, the time course of the decrease in the levels of protein H1 correlated well with the increase in sensitivity to EDTA and polymyxin B. These results support the hypothesis that protein H1 acts to replace divalent cations at a critical outer membrane site attacked by cationic antibiotics and chelators of divalent cations, and suggest that only a small proportion of the total divalent cation-binding sites in the outer membrane are susceptible to attack by these agents.
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- Short Communication
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A Conditional Aerial Mycelium-Negative Mutant Of Streptomyces Fradiae with Deficient Ornithine Carbamoyltransferase Activity
More LessA mutant defective in ornithine carbamoyltransferase activity and having a concomitant aerial mycelium-negative phenotype was isolated from Streptomyces fradiae. The aerial mycelium formation of the mutant could be restored by replacing l-arginine with l-citrulline in the minimal medium. The possibility that the ornithine cycle is connected with the regulation of aerial mycelium formation is discussed.
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- Taxonomy
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Numerical Analysis Of Total Fatty Acid Profiles In The Identification Of Coryneform, Nocardioform And Some Other Bacteria
More LessFatty acid profiles of 202 coryneform and nocardioform bacteria were recorded by gas chromatography. Strains were grouped according to their profiles using mean linkage cluster analysis and similarity measures based on the correlation coefficient, the angular separation between vectors in a multidimensional space and the degree of overlap between superimposed traces. Comparisons using both real and hypothetical data showed the last of these measures to be the most effective. Strains were divided into two major groups, depending on whether they contained predominantly straight chain or iso- and anteiso-branched acids. The first group was divided into two subgroups according to the relative proportions of the characteristic acids present; one subgroup had six clusters containing the rhodococci, nocardiae, mycobacteria and caseobacters, and the other had two containing the xanthobacters and true corynebacteria. The second group was divided into one subgroup containing strains of Arthrobacter simplex, Arthrobacter tumescens and Arthrobacter duodecadis, and one having three clusters. One cluster from this latter subgroup contained cellulomonads, one contained brevibacteria and curtobacteria and one contained arthrobacters, oerskoviae and kurthiae. Identification to generic level by fatty acid composition alone may not be feasible, but fatty acid analysis coupled with morphological examination may be sufficient to identify Corynebacterium, Arthrobacter, Cellulomonas, Oerskovia, Brevibacterium, Caseobacter, Kurthia and the A. simplex/tumescens taxon. Distinction is not easy between Curtobacterium, Microbacterium and the diaminobutyric acid-containing coryneforms and between Rhodococcus, Mycobacterium and Nocardia.
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Aminopeptidase Activity Of Leptospira Strains
More LessA total of 15 cultures of Leptospira were examined for aminopeptidase activity using 22 aminoacyl-β-naphthylamide substrates. Activity was demonstrated in each of the cultures. Extracts from serovars of Leptospira interrogans preferentially hydrolysed the same range of substrates. The level of hydrolysis of the preferred substrates for the seven strains of L. interrogans was distinctively higher than that demonstrated for the six Leptospira biflexa strains. Extracts from cultures of Leptospira illini and Leptospira parva sp. nov. exhibited profiles different to those demonstrated for the other 13 leptospiral cultures examined.
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Determination Of Fatty Acids And Carbohydrate Monomers In Micro-Organisms By Means Of Glass Capillary Gas Chromatography: Analysis Of Mycobacterium gordonae and Mycobacterium scrofulaceum
Trifluoroacetylated whole-cell methanolysates of four strains each of Mycobacterium gordonae and Mycobacterium scrofulaceum were analysed by gas chromatography, using a glass capillary column. The major chromatographic peaks were identified by mass spectrometry as derivatives of fatty acids and carbohydrates. In addition, two predominant peaks, present in chromatograms representing M. scrofulaceum, were identified as 2-octadecanol and 2-eicosanol. These secondary alcohols were not found in any of the strains of M. gordonae studied. The amount of tuberculostearic acid in the latter species was less than 1 % of that in M. scrofulaceum.
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