- Volume 141, Issue 1, 1995
Volume 141, Issue 1, 1995
- Pathogenicity And Medical Microbiology
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Congo red binding by Porphyromonas gingivalis is mediated by a 66 kDa outer-membrane protein
More LessSUMMARY:Congo red was bound from solution by strains of Porphyromonas gingivalis including W50, HG189, HG184, NCTC 11834, Bg 381, WPH35, the slower brown pigmenting colonial variant W50/BR1, and the avirulent mutant W50/BE1, and by Porphyromonas endodontalis HG370 and Porphyromonas asaccharolytica B537. SDS-PAGE of whole cells of all species examined displayed a 66 kDa Congo-red-binding component which was also detected in the outer membranes of P. gingivalis W50 grown in the chemostat under both haemin limitation and haemin excess, and which corresponded to a Coomassie-blue-stained band of the same mobility. Pretreatment of haemin-excess batch-grown cells of P. gingivalis W50 with polymyxin B, which binds to lipid A, did not inhibit binding, whilst binding was enhanced in the presence of 2 M ammonium sulphate, suggesting the involvement of non-specific hydrophobic interactions. Binding was also reduced by pretreatment with trypsin and papain, and by 8-anilino-1-naphthalenesulphonic acid, which binds to hydrophobic amino acids. The 66 kDa binding component was sensitive to proteinase K digestion, and loss of Congo red staining of this band correlated with the quantitative reduction in Congo red binding by whole cells. These data, and our previous work, show that Congo red and iron protoporphyrin IX (haemin) are bound to different outer-membrane components, and that Congo red binding may be of little value as a marker to detect virulent strains of P. gingivalis or those expressing haemin-binding proteins.
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Adherence of Candida albicans to human salivary components adsorbed to hydroxylapatite
More LessSUMMARY: Colonization of the oral cavity by Candida albicans involves adherence of yeast cells to oral surfaces. An assay was developed to measure the attachment of C. albicans cells, metabolically labelled with [35 S]methionine, to saliva-coated hydroxylapatite (SHA) beads - a model for the tooth surface. Using this assay approximately 1·26 × 106 C. albicans cells (50·5% of input cells) attached to the SHA beads (12 mg). Different strains of C. albicans adhered to varying degrees to SHA beads, but in general adherence was promoted by growth of cells at 28 °C and by starvation of cells for glucose. Proteins in human whole, or parotid, saliva samples were fractionated by gel filtration (Sephacryl S-200 column) and fractions were adsorbed to hydroxylapatite beads. Fractions that contained proline-rich proteins or statherin promoted attachment of C. albicans ATCC 10261 cells. Neuraminidase treatment of SHA beads, but not of cells, significantly increased yeast cell binding to the SHA beads. Neuraminidase activity in the oral cavity may unmask glycoprotein receptors involved in the adhesion of C. albicans to saliva-coated surfaces.
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Cloning of determinants encoding F1652 fimbriae from porcine septicaemic Escherichia coli confirms their identity as F1C fimbriae
More LessSUMMARY: Cloning of the f1652 operon that encodes F1C-like fimbriae in Escherichia coli indicates that this operon is a member of the S/Foc family. The genetic determinant coding for the F1652 fimbriae was cloned from the chromosome of the porcine E. coli wild-type strain 4787 (O115:K-1 :H51:F165). The cloned F1652 and the wild-type operon expressed a major fimbrial protein subunit of molecular mass 17·2 kDa that was detected by anti-F165 and anti-F1C polyclonal sera. The sequences of the f1652A and f1652FGH genes are reported. Major subunit gene f1652A encodes a mature protein of 156 amino acids. Minor subunit genes F, G and H encode mature proteins of 148, 145 and 276 amino acids, respectively. The amino acid sequences of the four proteins share similarities with those of the known S and F1C fimbrial antigens that are produced by extraintestinal E. coli which is associated with sepsis, urinary tract infections and newborn meningitis. The F1652A protein was identical to the major subunit protein of F1C, with a difference only at the first position. It was also similar, to a lesser extent, to the major subunit proteins of Sfal and Sfall fimbriae. F1652F was identical to FocF and SfaG/SfallG. F1652G was more closely related to FocG than to SfalS/SfallS, and F1652H was more closely related to FocH than to SfalH/SfallH.
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- Physiology And Growth
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The role of peptide metabolism in the growth of Listeria monocytogenes ATCC 23074 at high osmolarity
More LessSUMMARY:The growth of Listeria monocytogenes ATCC 23074 in defined medium is sensitive to high osmolarity when compared with its growth in complex media, such as brain heart infusion (BHI). The two major contributors to this difference in growth rate are the availability in BHI of the osmoprotectant glycine betaine and peptides. Peptone plays two major roles: firstly as a nutritional supplement for protein synthesis, and secondly as a source of amino acids and peptides that serve as a mechanism of maintaining turgor. In the presence of peptone the total amino acid pool at high osmolarity is substantial and even in the presence of glycine betaine the amino acid pool makes a major contribution to turgor maintenance. At high osmolarity there is a general increase in amino acid pools, with particularly substantial pools of glutamate, aspartate, proline, hydroxyproline and glycine. Peptides are also accumulated by cells from the peptone supplied in the medium. Glycine-containing peptides are accumulated in the cytoplasm under all conditions. Specific glycine-and proline-containing peptides stimulate growth at high osmolarity. The peptide prolyl-hydroxyproline accumulates in cells to high levels in response to growth at high osmolarity, and the pools of the derived amino acids also show a dependence on the external osmotic pressure. However, proline only confers significant osmoprotection when supplied as peptides. The significance of these data in the context of the occurrence of L. monocytogenes in foods with high peptide content is discussed.
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Identification and characterization of phosphoenolpyruvate: fructose phosphotransferase systems in three Streptomyces species
SUMMARY:Streptomyces lividans, S. coelicolor and S. griseofuscus were examined for the presence of the enzymes of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). All three species were shown to possess Enzyme I, HPr and fructose-specific Enzyme II (IIFru) activities. In S. lividans and S. coelicolor , all three PTS enzymes were fructose-inducible, but in S. griseofuscus the system was expressed constitutively. These organisms apparently lack the HPr(Ser) kinase and HPr(Ser-P) phosphatase that characterize low-GC Gram-positive bacteria.
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Characterization of cell-cycle-specific events in synchronous cultures of Escherichia coli: a theoretical evaluation
More LessSUMMARY:Synchronous growth studies are often used to assess the presence, timing and duration of periodic phenomena in the bacterial cell cycle. In an effort to evaluate the quality and quantity of information on cycle-specific events that can reasonably be expected from such inquiries, a model was constructed of a synchronous culture of Escherichia coli cells as would be derived from a growing population immobilized on a surface, and applied to the case of one stable and one unstable cellular component. The results indicated that, while the presence of cycle-specific events may be easily detectable, their timing and duration are very difficult to establish in synchronous growth experiments. Furthermore, differences in timing can be misconstrued as differences in duration, and vice versa, when interpretations are based on the qualitative analysis of the data.
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An analysis of the instability kinetics of plasmid pHSG415 during continuous culture of Escherichia coli
More LessSUMMARYThe effect of dilution rate on the instability kinetics of Escherichia coli RV308(pHSG415) during glucose-limited continuous culture is examined. Two nonlinear models are fitted to the data, both of which characterize the plasmid-host system in terms of the rate parameters R (for the plasmid segregation rate) and dμ (for the specific growth rate difference between plasmid-free and plasmid-bearing single cells). In the first model, both R and dμ have constant values with respect to time. In the second, either R or dμ is represented as a time-dependent function. Although both models fit the data equally well, it is demonstrated that the constant rate parameter model gives results which appear to be misleading. A comparison is also made among some of the many plasmid instability models (both mass-balance and segregated) which have appeared in the literature. It is found that all of these give identical trajectories and differ only in the definitions of the rate parameters used.
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Is Escherichia coli growing in glucose-limited chemostat culture able to utilize other sugars without lag?
More LessSUMMARY:It was investigated whether Escherichia coli cultured in a glucose-limited chemostat is able to grow with a series of sugars whose utilization is normally repressed during batch growth with glucose. Cells growing at dilution rates of 0·2, 0·3 and 0·6 h-1 were able to immediately utilize and grow with fructose mannose, maltose and ribose. Galactose was transported instantaneously but growth started only after a considerable lag. Arabinose was the only sugar tested which was neither transported nor utilized immediately. The results give experimental evidence that in vivo catabolite repression by glucose is absent at the very low glucose concentrations present in chemostat culture. Additionally, the results demonstrate that chemostat-grown cells of E. coli are able to substitute glucose as a carbon and energy source by several other sugars with no lag period.
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- Systematics
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DNA markers for differentiating isolates of Paecilomyces lilacinus
More LessSUMMARY: Paecilomyces lilacinus is an agent for the potential biological control of soil nematodes. Arbitrarily primed PCR was used to fingerprint the genomes of 28 isolates of this fungus. Most (72%) of the isolates originated from soil of different regions of Brazil. Fourteen 10-mer oligonucleotide primers of arbitrary sequence revealed 293 scorable binary characters. Distinct genotypes were obtained for each isolate. Cluster analysis showed a high level of variability among these genotypes. The similarity among pairwise comparisons of the isolates varied from 84·3% to 7·6%, with a mean of 63·5%. No clearly defined phenetic groups were identified by cluster or multivariate analyses. No correlation with geographical origin or host was detected. In addition, PCR with four pairs of consensus tRNA gene primers was performed on a subsample of 12 P. lilacinus isolates, three P. farinosus isolates, two P. fumosoroseus isolates, and one isolate of P. amoenoroseus. An inferred phylogeny based on 112 binary characters obtained by tRNA-PCR showed a monophyletic group which contained most of the P. lilacinus isolates. In contrast, three isolates of P. farinosus were not in a monophyletic group under the inferred phylogeny. These results suggest that tRNA fingerprinting could provide a valuable tool which could be used to develop the molecular taxonomy of Paecilomyces, as morphological characteristics of asexual structures cannot entirely resolve species.
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