- Volume 142, Issue 12, 1996
Volume 142, Issue 12, 1996
- Pathogenicity And Medical Microbiology
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Neutrophil depletion increases susceptibility to systemic and vaginal candidiasis in mice, and reveals differences between brain and kidney in mechanisms of host resistance
More LessInfections caused by the yeast Candida albicans represent an increasing threat to debilitated and immunosuppressed patients, and neutropenia is an important risk factor. Monoclonal antibody depletion of neutrophils in mice was used to study the role of these cells in host resistance. Ablation of neutrophils increased susceptibility to both systemic and vaginal challenge. The fungal burden in the kidney increased threefold on day 1, and 100-fold on day 4, and infection was associated with extensive tissue destruction. However, a striking feature of the disseminated disease in neutrophil-depleted animals was the altered pattern of organ involvement. The brain, which is one of the primary target organs in normal mice, was little affected. There was a threefold increase in the number of organisms recovered from the brains of neutrophil-depleted mice on day 4 after infection, but detectable abscesses were rare. In contrast, the heart, which in normal mice shows only minor lesions, developed severe tissue damage following neutrophil depletion. Mice deficient in C5 demonstrated both qualitative and quantitative increases in the severity of infection after neutrophil depletion when compared with C5-sufficient strains. The results are interpreted as reflecting organ-specific differences in the mechanisms of host resistance.
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- Physiology And Growth
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NMR analyses of compatible solutes in a halotolerant Brevibacterium sp.
More LessSummary: Internal solutes in a halotolerant Brevibacterium sp. (strain JCM 6894) were analysed by 1H NMR spectroscopy. At the lower osmolarity of complex medium, the main compatible solutes in the cells were glutamate, glycine betaine and hydroxyproline. At higher external salt concentrations, ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid) levels increased and this became the predominant compatible solute at >1.5 M NaCl or KCl. When Brevibacterium sp. was grown in the absence of yeast extract, glycine betaine levels were reduced to about half and a new solute, glycine, was detected. Irrespective of whether the medium contained yeast extract, Brevibacterium sp. accumulated hydroxyproline, which has not been previously reported as an osmolyte in halophilic eubacteria. Trehalose and glutamate were the main solutes in cells grown in chemically defined medium containing 0–0·5 M NaCl. When grown in the presence of > 1·5 M NaCl, both ectoine and hydroxyectoine became dominant, as was also the case in complex medium. Additional compatible solutes detected were γ-aminobutyrate and proline, neither of which were detected in cells grown in complex medium. Regardless of the medium composition and incubation time, ectoine levels were high at high osmolarity, indicating that the halotolerant nature of Brevibacterium sp. is closely related to its accumulation of ectoine. From its accumulation of compatible solutes, we suggest that Brevibacterium sp. JCM 6894 is a different species from other members of the genus Brevibacterium.
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Allophane increases the protein levels of several cephamycin biosynthetic enzymes in Nocardia lactamdurans
More LessSummary: Addition of allophane, a phosphate-trapping agent, to two different strains of Nocardia lactamdurans exerted a large stimulatory effect on cephamycin biosynthesis. The biosynthesis of cephamycin is inhibited by inorganic phosphate at concentrations above 5 mm and allophane reversed this inhibitory effect. Allophane-supplemented cultures showed increased activities and/or an extended life in the cell of four cephamycin biosynthetic enzymes: isopenicillin N synthase, the two-protein-component 7α-cephem methoxylase (7α-cephem hydroxylase and 7-hydroxycephem methyltransferase) and 3′-hydroxymethylcephem O-carbamoyltransferase. However, the first enzyme of the pathway, lysine 6-aminotransferase, was not stimulated by allophane. Allophane-supplemented cultures showed increased protein levels of (i) α-aminoadipyl-cysteinyl-valine synthetase (the condensing multienzyme that forms the tripeptide intermediate), and (ii) the two proteins involved in the 7α-cephem methoxylase, as shown by immunoblotting with antibodies against each of these proteins. Phosphate repressed the de novo synthesis of these proteins but did not increase their degradation. These results indicated that allophane stimulates expression of the cluster of genes extending from the pcbAB gene (encoding α-aminoadipyl-cysteinyl-valine synthetase) to cmcl-cmcJ (encoding the two-protein methoxylase) and cmcH (encoding the O-carbamoyltransferase).
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- Systematics
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Phylogenetic diversity of intra-amoebal legionellae as revealed by 16S rRNA gene sequence comparison
More LessFollowing a recent phylogenetic analysis of all 39 species of the genus Legionella and related organisms, the name Legionella lytica has been proposed for bacteria previously considered either as Sarcobium lyticum or as ‘Legionella-like amoebal pathogens’ (LLAPs). To investigate the phylogenetic integrity of this newly proposed species, we determined the 16S rRNA gene sequences of 10 LLAPs isolated from various environmental sources. All 10 isolates clustered within a monophyletic group containing all other members of the genus Legionella. Eight of the 10 isolates formed a monophyletic subgroup within the genus which also included the two previously characterized L. lytica strains. Four of these 10 isolates shared a specific and very close relationship with the L. lytica type strain (> 99% sequence similarity). However, although clearly legionellae, the remaining two LLAP strains bore no specific evolutionary relationship to either L. lytica or any other Legionella species (<96% sequence similarity). Both isolates lay on their own relatively deep-rooted branches within the radiation of the Legionella cluster. LLAPs do not therefore, represent a unique species or even a single line of descent within the genus, and investigation of more isolates may reveal them to be as evolutionarily diverse as the other presently recognized Legionella species.
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- Corrigendum
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