Binding of deoxyribonucleic acid by cell walls of transformable and nontransformable streptococci

Antibiotic sensitivity reveals that wall teichoic acids mediate DNA binding during competence in Bacillus subtilis

Despite decades of investigation of genetic transformation in the model Gram-positive bacterium Bacillus subtilis, the factors responsible for exogenous DNA binding at the surface of competent cells remain to be identified. Here, we report that wall teichoic acids (WTAs), cell wall-anchored anionic glycopolymers associated to numerous critical functions in Gram-positive bacteria, are involved in this initial step of transformation. Using a combination of cell wall-targeting antibiotics and fluorescence microscopy, we show that competence-specific WTAs are produced and specifically localized in the competent cells to mediate DNA binding at the proximity of the transformation apparatus. Furthermore, we propose that TuaH, a putative glycosyl transferase induced during competence, modifies competence-induced WTAs in order to promote (directly or indirectly) DNA binding. On the basis of our results and previous knowledge in the field, we propose a model for DNA binding and transport during genetic transformation in B. subtilis.

Natural genetic transformation in bacteria requires DNA binding at the surface of competent cells. Here, Mirouze et al. show that wall teichoic acids are specifically produced or modified during competence in Bacillus subtilis and promote (directly or indirectly) DNA binding at the cell surface.

comYA, a gene similar to comGA of Bacillus subtilis, is essential for competence-factor-dependent DNA transformation in Streptococcus gordonii

Tn4001 mutagenesis identified a new competence gene in Streptococcus gordonii Challis designated comYA. A comYA mutant was completely deficient in transformation and exhibited decreased levels of DNA binding and hydrolysis. The deduced 319-amino-acid ComYA protein exhibited 57% similarity and 33% identity to the ComGA transporter protein of Bacillus subtilis and contained the Walker A-box motif conserved in ATP-binding proteins as well as aspartic acid boxes Asp-1 and Asp-2 present in some components of the general secretory pathway of gram-negative bacteria. comYA appeared to be part of a putative operon encompassing a comGB homolog, designated comYB, together with sequences that could encode ComGC- and ComGD-like peptides designated ComYC and ComYD, respectively, as well as other components. The putative ComYC and ComYD peptides had leader sequences similar to the type IV N-methylphenylalanine pilins of gram-negative bacteria, but unlike other examples in this class, including B. subtilis, they contained an alanine at position -1 of the leader instead of the usual glycine residue. Northern analysis identified a single 6.0-kb comYA-containing transcript strictly dependent on exogenous competence factor for expression in ComA1 cells. An identical pattern of expression was seen in wild-type Challis cells grown under conditions of maximal competence but not in cells that were noncompetent.

Haemophilus influenzae periplasmic protein which binds deoxyribonucleic acid: properties and possible participation in genetic transformation

A protein which binds to either single-stranded or double-stranded deoxyribonucleic acid (DNA) but not to ribonucleic acid has been isolated by osmotic shock treatment of growing cells. This periplasmic protein differs from the principal intracellular binding protein in its greater thermolability and by the absence of salt-induced cooperativity in its interaction with single-stranded DNA. Certain mutant strains of Haemophilus influenzae defective in the DNA suptake steps of genetic transformation were found to be deficient in periplasmic DNA-binding protein, suggesting that this protein participates in the uptake of DNA in transformation.

Cell surface-located deoxyribonucleic acid receptors in transformable pneumococci

We studied deoxyribonucleic acid (DNA) binding in transformable pneumococci. The relevant findings are as follows. (i) At least half of the DNA Molecules adsorbed to competent cells in the growth medium are attached to sites on the protoplast membrane. (ii) Most of the DNA bound to live competent cells in the presence of glucose is not released by moderate shear or by autolysin treatment. In contrast, most of the DNA adsorbed to competent cells in the absence of glucose is shear and autolysin sensitive. (iii) The presence of binding sites resembling in properties the sites in live competent cells can be demonstrated in wall-membrane complexes. Most of these sites are lost during preparation of cell walls and protoplasts. It is suggested that the DNA-binding site is a membrane component (protein?) Stabilized by polysaccharide (cell Wall) material. (IV) Mechanical or enzymatic damage to the cell wall or change in the ionic conditions can induce DNA binding (and surface-nuclease activity) in the incompetent pneumococci. However, such cells still show neither genetic transformation nor extensive nuclease-resistant binding of DNA. It is suggested that both competent and incompetent cells contain a large number of sequestered DNA-binding sites that can be unmasked by several experimental conditions. Induction of the competent state by the competence activator protein may involve an endogenous unmasking process.

Interactions between exogenous deoxyribonucleic acid and membrane vesicles isolated from Bacillus subtilis 168

Membrane vesicles isolated from competent cultures of Bacillus subtilis 168 bound up to 20 mug of double-stranded deoxyribonucleic acid (DNA) per mg of membrane protein in the presence of ethylenediaminetetraacetate. The formation of the DNA-membrane complex was time, temperature, and pH dependent. Eighty per cent of the DNA could be removed from the complex by treatment with deoxyribonuclease I. Nevertheless, the DNA that remained attached to the vesicles appeared to have been attacked by the enzyme, suggesting that all the complexed DNA is located at the outer surface of the vesicles. Pretreatment of DNA with deoxyribonuclease I destroyed its affinity for the vesicles. The extent of binding decreased by the addition of Mg(2+) ions, especially at high DNA concentrations (more than 2 mug/ml). This effect was partially due to membrane-associated Mg(2+)-dependent endonucleolytic activity, which caused double-strand breaks in addition to single-strand nicks, and to exonuclease activity. The endonucleolytic activity was enhanced by heating the membranes at 80 C. DNA-membrane association was not markedly affected by sulfhydryl reagents, but was largely inhibited by formaldehyde. Endogenous competence-stimulating activity did not alter the DNA-binding capacity of the vesicles.

Inhibition of transformation by sodium metaperiodate in Streptococcus sanguis (Wicky): demonstration that deoxyribonucleic acid binding sites contain amino acids

Addition of sodium metaperiodate to competent Streptococcus sanguis (Wicky) cells at 0 or 37 C revealed that the deoxyribonucleic acid binding sites consist of amino acids.

Inhibition of the development of competence in Streptococcus sanguis (Wicky) by reagents that interact with sulfhydryl groups: discernment of the competence process

Reagents that interact with sulfhydryl groups are shown to inhibit competence factor (CF)-induced competence development in Streptococcus sanguis (Wicky) strain WE4 (Wicky 4 Ery(R)). Inhibition is correlated with specific inhibition of either the function or biosynthesis of three competent cell-related proteins and is reversed by either 2-mercaptoethanol or dithiothreitol. Mercuric chloride (5 muM) or N-ethylmaleimide (NEM; 50 muM) inhibited (i) the function but not the biosynthesis or activation of the competent cell-associated autolysin; (ii) the biosynthesis of a competent cell-associated protein of unknown function, demonstrated by polyacrylamide gel electrophoresis of acidified phenol extracts; and (iii) the biosynthesis or activation of distinct deoxyribonucleic acid (DNA)-binding sites. Neither reagent at the indicated concentration interfered with the uptake of CF by cells or with the uptake and expression of DNA by competent cells. Neither reagent inactivated CF or genetic markers coded by the transforming DNA, nor did they inhibit cell growth or viability appreciably. The data reveal that either mercuric chloride or NEM can differentially inhibit induced protein synthesis and, in addition, conclusively show that some autolytic activity is essential for the onset of the competent state.

Effect of D-cycloserine on transformation in group H streptococcus, strain Challis

d-Cycloserine (d-CS), a selective inhibitor of bacterial cell wall biosynthesis, inhibited transformation in group H streptococcus, strain Challis, by preventing the development of the competent state. The incubation of strain Challis cells with d-CS resulted in the production of a substance which inhibited the action of competence factor on these cells. d-CS had an enhancing effect on transformation when deoxyribonucleic acid uptake or phenotypic expression was allowed to occur in its presence.

Peptidoglycan composition and taxonomy of group D, E, and H streptococci, and Streptococcus mutans

The qualitative and quantitative composition of the peptidoglycan from the cell wall of groups D, E, and H streptococci, and Streptococcus mutans, was determined. In group D, S. faecalis and the closely related species S. liquefaciens and S. zymogenes were separated from S. faecium and the closely related species S. durans on the basis of their peptidoglycan composition. A relationship among S. bovis, S. equinus, and some strains of S. mutans was indicated by the presence in each of a similar peptidoglycan containing threonine. Threonine was released from the S. mutans polymer as a threonine-lysine dipeptide. Hydrolysis of the dipeptide at 100 C for 24 hr in 6 n HC1 was required to break the peptide bond. Motile group D streptococci possessed a peptidoglycan of the same composition as S. faecium. Group E and H strains were also similar in the composition of their peptidoglycan. The results demonstrate that peptidoglycan composition can be used to (i) aid in the division of members of an immunological group into subgroups, and (ii) indicate a relationship between members of the same genus which are not related on an immunological basis.