Autolysis and Cell Wall Degradation in a Choline-Independent Strain of<i>Streptococcus pneumoniae</i>

Severin, Anatoly; Horne, Diane; Tomasz, Alexander

doi:10.1089/mdr.1997.3.391

Cited by 48 publications

(45 citation statements)

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“…The relative impact on competence development of a given function, in this complex interplay of positive and negative inputs, may depend on specific growth conditions and genetic backgrounds. Control of LytA-dependent autolysis is also a complex process (Severin et al, 1997;Lopez et al, 1997). Autolysis has classically been described in stationary-phase cultures, and depends on parameters such as the initial pH of the growth medium and its calcium concentration (Trombe et al 1992).…”

Section: Discussionmentioning

confidence: 99%

“…In order to get further insight into the function of LuxS in these Gram-positive bacteria, we have investigated its role in vitro on the developmental phenotypes classically observed: competence for genetic transformation during exponential growth, and autolysis when the culture reaches stationary phase. Autolysis is mainly dependent on the activity of the muramidase LytA and on cell-wall composition (for reviews, see Severin et al, 1997;Lopez et al, 1997 …”

Section: Introductionmentioning

confidence: 99%

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LuxS impacts on LytA-dependent autolysis and on competence in Streptococcus pneumoniae

et al. 2006

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The ubiquitous protein LuxS with S-ribosylhomocysteinase activity is involved in S-adenosyl methionine detoxification, C-1 unit recycling and the production of autoinducers that allow the cell to sense and respond to cell density. Independent reports describe the impact of LuxS deficiency on Streptococcus pneumoniae virulence in the mouse. In vitro, LuxS deficiency confers discrete phenotypes. A combined approach using genetic dissection and mixed-culture experiments allowed the involvement of LuxS in the developmental physiology of S. pneumoniae to be investigated. Functional LuxS was found to be related on the one hand to down-regulation of competence, and on the other hand to attenuation of autolysis in cultures entering stationary phase. The competence phenotype of luxS mutant bacteria was complemented by media conditioned by competence-defective ComAB0 bacteria, but not by BSA. The autolytic phenotype was complemented by BSA, but not by conditioned supernatants. It is suggested that the impact of LuxS on competence, but not on autolysis, involves cell-cell communication. The phenotype of luxS mutant strains reveals a hierarchy in the competence regulatory networks of S. pneumoniae. INTRODUCTIONLuxS, the S-ribosylhomocysteinase involved in furanosyl borate diester, autoinducer 2 (AI-2) production from Sribosylhomocysteine, is ubiquitous in prokaryotes (Sun et al., 2004). Since its discovery (Bassler et al., 1997) and chemical characterization (Chen et al., 2002), the role of AI-2 in the regulation of light production, biofilm formation and virulence in response to high cell density (quorum sensing) has been elucidated in several Gram-negative bacteria, including Vibrio species (Surette et al., 1999;Miller et al., 2002;Hammer & Bassler, 2003;Henke & Bassler, 2004;Vendeville et al., 2005). In some species, furanone uptake and processing involving the lsrACDBFGE operon has been described Xavier & Bassler, 2005). Bioluminescence activation in Vibrio harveyi by conditioned media represents the test for AI-2 production by a given species and supports the paradigm of AI-2-mediated interspecies cell-cell communication culminating in genetic regulation Xavier & Bassler, 2003). Recent studies give credence to the involvement of LuxS in host-bacterial communication (Maroui & Sela, 2003;Sperandino et al., 2003). However, in Neisseria meningitis, AI-2 production is not related to the regulation of specific genes in vitro (Schauder et al., 2005;Dove et al., 2003). In Streptococcus pneumoniae, the impact of LuxS loss-offunction mutations on experimental virulence and genetic expression has been reported; however, results concerning production of AI-2, active in the 'vibrio test', by pneumococci, are divergent (Joyce et al. 2004;Stroeher et al., 2003). In order to get further insight into the function of LuxS in these Gram-positive bacteria, we have investigated its role in vitro on the developmental phenotypes classically observed: competence for genetic transformation during exponential growth, and autolysis when the cult...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

LuxS impacts on LytA-dependent autolysis and on competence in Streptococcus pneumoniae

et al. 2006

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“…16. Wall teichoic acid was removed by treatment with hydrofluoric acid (16) to obtain peptidoglycan.…”

Section: Methodsmentioning

confidence: 99%

“…Digestion Products-Peptidoglycan (2 mg/ml) was digested with 80 g/ml affinity-purified pneumococcal amidase for 24 h at 37°C as described (16), and the glycan strands were separated from the peptides by size-exclusion chromatography using a Keystone GFS-150 column. The compounds were eluted with water at a flow rate of 0.8 ml/min.…”

Section: Isolation Of Glycan Strands and Analysis Of Their Lysozymementioning

confidence: 99%

The pgdA Gene Encodes for a PeptidoglycanN-Acetylglucosamine Deacetylase in Streptococcus pneumoniae

Vollmer

Tomasz

2000

Journal of Biological Chemistry

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232

125

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Analytical work on the fractionation of the glycan strands of Streptococcus pneumoniae cell wall has led to the observation that an unusually high proportion of hexosamine units (over 80% of the glucosamine and 10% of the muramic acid residues) was not N-acetylated, explaining the resistance of the peptidoglycan to the hydrolytic action of lysozyme, a muramidase that cleaves in the glycan backbone. A gene, pgdA, was identified as encoding for the peptidoglycan N-acetylglucosamine deacetylase A with amino acid sequence similarity to fungal chitin deacetylases and rhizobial NodB chitooligosaccharide deacetylases. Pneumococci in which pgdA was inactivated by insertion duplication mutagenesis produced fully N-acetylated glycan and became hypersensitive to exogenous lysozyme in the stationary phase of growth. The pgdA gene may contribute to pneumococcal virulence by providing protection against host lysozyme, which is known to accumulate in high concentrations at infection sites.The unusual complexity and diversity of the cell surface of Streptococcus pneumoniae is apparent both in the capsular structure and in the underlying cell wall structure of this bacterium, and this complexity and diversity may be related to the multiplicity of interactions of this microbe and its human host. S. pneumoniae is capable of producing at least 90 chemically distinct capsular polysaccharides (1). The cell wall of this microorganism contains a teichoic acid of unusually complex chemistry (2, 3) the components of which include ribitol phosphate, galactosamine, trideoxydiaminohexose, and covalently linked phosphocholine residues (4). The peptidoglycan of S. pneumoniae is also unusual because its stem peptides are cross-linked in both a direct and an indirect manner (5). Furthermore, the proportion of distinct linear and branched muropeptides in the peptidoglycan is clonally related (6). The pneumococcal cell wall is a potential target for components of the first line host defense such as lysozyme. In addition, the peptidoglycan and teichoic acid may represent bacterial ligands recognized by the innate immune system of the host.The recent introduction of high resolution analytical techniques and genetic approaches began to shed light on the determinants and biological functions of the pneumococcal cell wall. In this study we describe the identification of a genetic determinant, pgdA, of the first bacterial peptidoglycan GlcNAc deacetylase. We show that the innate activity of this enzyme is responsible for the high proportion of non-acetylated hexosamine residues in the peptidoglycan that appears to play a role in the resistance of S. pneumoniae to the activity of exogenous lysozyme, an enzyme that is known to accumulate in high concentrations at infection sites. EXPERIMENTAL PROCEDURESBacterial Strains, Plasmids, and Growth Media-Cultures of S. pneumoniae R36A, a non-encapsulated laboratory strain from the Rockefeller University collection, were grown in a casein-based semi-synthetic medium (C ϩ Y) containing 1 mg/ml yeast extract (7) o...

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“…Moreover, choline-deprived S. oralis frequently exhibited septa inserted at oblique angles. Through transformation with S. oralis DNA, Severin et al isolated and partly characterized a pneumococcal transformant (R6Cho Ϫ ) able to grow in the absence of choline (29). Remarkably, however, the R6Cho Ϫ strain did not show the morphological alterations characteristic of S. oralis cells grown in choline-deprived medium.…”

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confidence: 99%

Mutations in thetacFGene of Clinical Strains and Laboratory Transformants ofStreptococcus pneumoniae:Impact on Choline Auxotrophy and Growth Rate

et al. 2008

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The nutritional requirement that Streptococcus pneumoniae has for the aminoalcohol choline as a component of teichoic and lipoteichoic acids appears to be exclusive to this prokaryote. A mutation in the tacF gene, which putatively encodes an integral membrane protein (possibly, a teichoic acid repeat unit transporter), has been recently identified as responsible for generating a choline-independent phenotype of S. pneumoniae (M. Damjanovic, A. S. Kharat, A. Eberhardt, A. Tomasz, and W. Vollmer, J. Bacteriol. 189:7105-7111, 2007). We now report that Streptococcus mitis can grow in choline-free medium, as previously illustrated for Streptococcus oralis. While we confirmed the finding by Damjanovic et al. of the involvement of TacF in the choline dependence of the pneumococcus, the genetic transformation of S. pneumoniae R6 by using S. mitis SK598 DNA and several PCR-amplified tacF fragments suggested that a minimum of two mutations were required to confer improved fitness to choline-independent S. pneumoniae mutants. This conclusion is supported by sequencing results also reported here that indicate that a spontaneous mutant of S. pneumoniae (strain JY2190) able to proliferate in the absence of choline (or analogs) is also a double mutant for the tacF gene. Microscopic observations and competition experiments during the cocultivation of choline-independent strains confirmed that a minimum of two amino acid changes were required to confer improved fitness to choline-independent pneumococcal strains when growing in medium lacking any aminoalcohol. Our results suggest complex relationships among the different regions of the TacF teichoic acid repeat unit transporter.

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Autolysis and Cell Wall Degradation in a Choline-Independent Strain ofStreptococcus pneumoniae

Cited by 48 publications

References 30 publications

LuxS impacts on LytA-dependent autolysis and on competence in Streptococcus pneumoniae

LuxS impacts on LytA-dependent autolysis and on competence in Streptococcus pneumoniae

The pgdA Gene Encodes for a PeptidoglycanN-Acetylglucosamine Deacetylase in Streptococcus pneumoniae

Mutations in thetacFGene of Clinical Strains and Laboratory Transformants ofStreptococcus pneumoniae:Impact on Choline Auxotrophy and Growth Rate

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