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H Labischinski

Publications and source records attributed to H Labischinski.

At least 37 records · Page 2Linked to original sources
PubMed1997

Small-angle X-ray scattering analysis of pneumococcal lipoteichoic acid phase structure.

X-Ray-scattering analysis was performed on micelles of lipoteichoic acid from Streptococcus pneumoniae. This lipoteichoic acid differs from poly(glycerophosphate) and poly(glycosylglycerophosphate) lipoteichoic acids by a unique positively charged diacylglyceroglycolipid anchor and a complex structure of the hydrophilic chain which is composed of zwitterionic tetrasaccharide ribitol phosphate repeats each carrying two zwitterionic phosphocholine substituents. The size distribution of the lipoteichoic acid micelles was sufficiently homogenous to determine their size and some related molecular parameters by small-angle scattering analysis. Nearly independent on the ionic strength of the aqueous dispersion, an average micelle contained about 150 lipoteichoic acid molecules arranged in a spherical assembly with a diameter of about 23 nm, whereby the hydrophilic region occupied an outer shell of about 8.5 nm thickness. Taken this as the average chain length of LTA in the micelle and 7.2 repeats per chain, each repeat contributed about 1.2 nm to the thickness of the hydrophilic shell as compared to 2.4 nm for a fully extended chain conformation and 1.1 nm estimated for a more helical arrangement [Klein, R. A., Hartmann, R., Egge, H., Behr, T. & Fischer, W. (1994) Carbohydr. Res. 256, 189-222]. A comparison with the micelle of poly(glycerophosphate) lipoteichoic acid of Staphylococcus aureus suggests that the supramolecular structure is largely independent of the structure of the hydrophilic chain and solely dictated by the small cross-sectional area of the diacylglycerol moiety common to all lipoteichoic acids and lipoglycans of gram-positive bacteria.

Carbohydrate Sequence↗
PubMed1997

Cell wall monoglycine cross-bridges and methicillin hypersusceptibility in a femAB null mutant of methicillin-resistant Staphylococcus aureus.

The femAB operon is involved in the formation of the characteristic pentaglycine side chain of the staphylococcal peptidoglycan. Allele replacement of the femAB operon with the tetracycline resistance determinant tetK in a methicillin-resistant Staphylococcus aureus strain resulted in impaired growth, methicillin hypersusceptibility, and lysostaphin resistance. The usual pentaglycine cross-bridges were replaced by monoglycine bridges exclusively, and cross-linking of the peptidoglycan strands was drastically reduced. Complementation of the femAB null mutant by either femA or femAB resulted in the extension of the cross-bridges to a triglycine or a pentaglycine, respectively. This finding suggests that FemA is responsible for the formation of glycines 2 and 3, and FemB is responsible for formation of glycines 4 and 5, of the pentaglycine side chain of the peptidoglycan precursor. Moreover, it can be deduced that addition of the first glycine must occur by a femAB-independent mechanism.

Amino Acids↗
PubMed1997

Specificities of FemA and FemB for different glycine residues: FemB cannot substitute for FemA in staphylococcal peptidoglycan pentaglycine side chain formation.

The femAB operon codes for two nearly identical approximately 50-kDa proteins involved in the formation of the staphylococcal pentaglycine interpeptide bridge. Sequencing and analysis of the femA region of mutants isolated by chemical mutagenesis and selection for lysostaphin resistance revealed point mutations leading to the expression of truncated FemA proteins. These femA mutants, although still producing an intact FemB, exhibited a phenotype identical as that described for femAB double mutants. Thus, FemA seems to be essential for the addition of glycine residues 2 and 3 only, whereas FemB is involved in the attachment of exclusively glycine residues 4 and 5. Although FemB has 39% identity with FemA, it cannot substitute for FemA. The FemA and FemB proteins seem to be highly specific in regard to the position of the glycine residues that they attach.

Bacterial Proteins↗
PubMed1996

Staphylococcal peptidoglycan interpeptide bridge biosynthesis: a novel antistaphylococcal target?

In staphylococci, crosslinking of the peptide moiety of peptidoglycan is mediated via an additional spacer, the interpeptide bridge, consisting of five glycine residues. The femAB operon, coding for two approximately 50-kDa proteins is known to be involved in pentaglycine bridge formation. Using chemical mutagenesis of the beta-lactam-resistant strain BB270 and genetic, biochemical, and biophysical characterization of mutants selected for loss of beta-lactam resistance and reduced lysostaphin sensitivity it is shown that peptide bridge formation proceeds via three intermediate bridge lengths (cell wall peptides with no, one, three, and five glycine units). To proceed from one intermediate to the next, three genes appear necessary: femX, femA, and femB. The drastic loss of beta-lactam resistance after inactivation of FemA or partial impairment of FemX even beyond the level of the sensitive wild-type strains renders these proteins attractive antistaphylococcal targets.

Amino Acids↗
PubMed1995

FemA of Staphylococcus aureus: isolation and immunodetection.

FemA, a cytoplasmic protein necessary for the expression of methicillin resistance in Staphylococcus aureus and also involved in the biosynthesis of staphylococcal cell walls, was detected and quantified in several S. aureus strains under different growth conditions by Western immunoblot. Two types of antigens were used for the production of polyclonal antibodies against FemA: (i) a synthetic peptide comprising 14 amino acids of its C-terminal sequence; and (ii) FemA isolated by preparative gel electrophoresis and electroelution from an overproducing staphylococcal strain. Immunodetection revealed that all investigated strains, either methicillin-resistant or susceptible, expressed FemA during the exponential growth phase in varying amounts. In the stationary phase, the FemA content was diminished. Strains in which femA was inactivated by insertion of Tn551 into the control region of the femAB operon still expressed about 10% of the protein compared to their parent strains. Tn551 insertion in the middle of the femB gene did not affect the FemA expression. In 40 methicillin-susceptible and 6 resistant clinical isolates of S. aureus, the FemA content or its affinity to the antibodies was reduced compared to laboratory parent strains. In susceptible strains, an additional protein of higher molecular weight, present in large quantities, was also able to bind the FemA antibodies. Such a protein was also present in methicillin-resistant isolates, although it was not as pronounced as in the susceptible strains.

Antibodies, Bacterial↗
PubMed1995

Localization of penicillin-binding proteins to the splitting system of Staphylococcus aureus septa by using a mercury-penicillin V derivative.

Precise localization of penicillin-binding protein (PBP)-antibiotic complexes in a methicillin-sensitive Staphylococcus aureus strain (BB255), its isogenic heterogeneous methicillin-resistant transductant (BB270), and a homogeneous methicillin-resistant strain (Col) was investigated by high-resolution electron microscopy. A mercury-penicillin V (Hg-pen V) derivative was used as a heavy metal-labeled, electron-dense probe for accurately localizing PBPs in situ in single bacterial cells during growth. The most striking feature of thin sections was the presence of an abnormally large (17 to 24 nm in width) splitting system within the thick cross walls or septa of Hg-pen V-treated bacteria of all strains. Untreated control cells possessed a thin, condensed splitting system, 7 to 9 nm in width. A thick splitting system was also distinguishable in unstained thin sections, thereby confirming that the electron contrast of this structure was not attributed to binding of bulky heavy metal stains usually used for electron microscopy. Biochemical analyses demonstrated that Hg-pen V bound to isolated plasma membranes as well as sodium dodecyl sulfate-treated cell walls and that two or more PBPs in each strain bound to this antibiotic. In contrast, the splitting system in penicillin V-treated bacteria was rarely visible after 30 min in the presence of antibiotic. These findings suggest that while most PBPs were associated with the plasma membrane, a proportion of PBPs were located within the fabric of the cell wall, in particular, in the splitting system. Inhibition of one or more high-M(r) PBPs by beta-lactam antibiotics modified the splitting system and cross-wall structure, therefore supporting a role for these PBPs in the synthesis and architectural design of these structures in S. aureus.

Anti-Bacterial Agents↗
PubMed1993

Staphylococcus pasteuri sp. nov., isolated from human, animal, and food specimens.

A new novobiocin-susceptible species of the genus Staphylococcus, Staphylococcus pasteuri, is described on the basis of the results of a study of seven strains isolated from human, animal, and food specimens. DNA relatedness experiments (S1 nuclease method) showed that these strains form a homogeneous genomic species related at DNA homology levels of 2 to 13% to 27 type strains representing known Staphylococcus species. The use of a method based on rRNA gene restriction site polymorphism provides clear-cut distinction between this new species and Staphylococcus warneri, which is the most similar species phenotypically. The type strain of the new species is strain BM9357 (= ATCC 51129).

Amino Acids↗
PubMed1993

Influence of femB on methicillin resistance and peptidoglycan metabolism in Staphylococcus aureus.

The inactivation of FemB by insertion of Tn551 in the central part of the femB open reading frame was shown to increase susceptibility of methicillin-resistant Staphylococcus aureus strains toward beta-lactam antibiotics to the same extent as did inactivation of femA. Strains carrying the methicillin resistance determinant (mec) and expressing PBP 2' were affected to the same extent as were strains selected for in vitro resistance, which did not express PBP 2'. Both femA and femB, which form an operon, are involved in a yet unknown manner in the glycine interpeptide bridge formation of the S. aureus peptidoglycan. FemB inactivation was shown to reduce the glycine content of peptidoglycan by approximately 40%, depending on the S. aureus strain. The reduction of the interpeptide bridge glycine content led to significant reduction in peptidoglycan cross-linking, as measured by gel permeation high-pressure liquid chromatography of muramidase-digested cell walls. Maximum peptide chain length was reduced by approximately 40%. It is shown that the complete pentaglycine interpeptide bridge is important for the sensitivity against beta-lactam antibiotics and for the undisturbed activity of the staphylococcal cell wall-synthesizing and hydrolyzing enzymes, as was also apparent from electron microscopic examinations, which revealed aberrant placement of cross walls and retarded cell separation, leading to a pseudomulticellular phenotype of the cells for both femA and femB mutants.

Amino Acids↗
PubMed1993

Altered muropeptide composition in Staphylococcus aureus strains with an inactivated femA locus.

Tn551 inactivation of femA, a factor involved in methicillin resistance of Staphylococcus aureus, caused the production of peptidoglycan in which the fraction of monoglycyl- and serine-containing muropeptides was increased at the expense of pentaglycyl muropeptides. femA mutants have a specific block in the biosynthesis of pentaglycine cross bridges after the addition of the first glycine residue.

Amino Acid Sequence↗
PubMed1991

Small and medium-angle X-ray analysis of bacterial lipoteichoic acid phase structure.

X-ray scattering analysis was performed on various types of bacterial lipoteichoic acid in solution. The X-ray data show that all samples investigated were characterized by a similar micellar ultrastructure (hydrophilic moiety on the outside) with a fatty acid chain conformation of the disordered, alpha-type at all temperatures between 5 degrees-53 degrees C. The size distribution of Staphylococcus aureus lipoteichoic acid micelles was sufficiently homogeneous to determine their size and some related molecular parameters by detailed small-angle X-ray scattering analysis. Nearly independent of the degree of D-alanine substitution and the ionic strength of the aqueous dispersion, an average micelle contained about 150 lipoteichoic acid molecules arranged in a spherical assembly with a diameter of about 22 nm, whereby the hydrophilic region occupied an outer shell of about 8.5 nm thickness. Based on the average chain length of lipoteichoic acid, it could be estimated that each glycerophosphate residue contributed by about 0.34 nm to the thickness of the hydrophilic shell as compared to a theoretical value of approximately 0.8 nm for a fully extended chain conformation, indicating a highly coiled conformation of the hydrophilic chain. The bearing of these findings on the properties of membrane-associated and secreted lipoteichoic acids is discussed.

Bifidobacterium↗
PubMed1991

Microbiological characterizations by FT-IR spectroscopy.

Infrared signals of microorganisms are highly specific fingerprint-like patterns that can be used for probing the identity of microorganisms. The simplicity and versatility of Fourier-transform infrared spectroscopy (FT-IR) makes it a versatile technique for rapid differentiation, classification, identification and large-scale screening at the subspecies level.

Fourier Analysis↗
PubMed1991

Classification and identification of bacteria by Fourier-transform infrared spectroscopy.

This study describes a computer-based technique for classifying and identifying bacterial samples using Fourier-transform infrared spectroscopy (FT-IR) patterns. Classification schemes were tested for selected series of bacterial strains and species from a variety of different genera. Dissimilarities between bacterial IR spectra were calculated using modified correlation coefficients. Dissimilarity matrices were used for cluster analysis, which yielded dendrograms broadly equated with conventional taxonomic classification schemes. Analyses were performed with selected strains of the taxa Staphylococcus, Streptococcus, Clostridium, Legionella and Escherichia coli in particular, and with a database containing 139 bacterial reference spectra. The latter covered a wide range of Gram-negative and Gram-positive bacteria. Unknown specimens could be identified when included in an established cluster analysis. Thirty-six clinical isolates of Staphylococcus aureus and 24 of Streptococcus faecalis were tested and all were assigned to the correct species cluster. It is concluded that: (1) FT-IR patterns can be used to type bacteria; (2) FT-IR provides data which can be treated such that classifications are similar and/or complementary to conventional classification schemes; and (3) FT-IR can be used as an easy and safe method for the rapid identification of clinical isolates.

Antigens, Bacterial↗
PubMed1991

Somnogenic activity of pseudomurein in rabbits.

Pseudomurein is a major cell wall component of some archaebacteria that chemically differs from but morphologically, functionally, and structurally resembles eubacterial peptidoglycan. Eubacterial cell wall components, e.g., peptidoglycan, induce changes in sleep and body temperature. We now report that intravenous injections of rabbits with a suspension of pseudomurein from Methanobacterium thermoautotrophicum also induce similar central nervous system effects.

Animals↗
PubMed1991

femA, which encodes a factor essential for expression of methicillin resistance, affects glycine content of peptidoglycan in methicillin-resistant and methicillin-susceptible Staphylococcus aureus strains.

femA is a chromosomally encoded factor, occurring naturally in Staphylococcus aureus, which is essential for the expression of high-level methicillin resistance in this organism. The production of a low-affinity penicillin-binding protein, PBP2a or PBP2', which is intimately involved with methicillin resistance in S. aureus, is not influenced by femA. To elucidate a possible physiological function of the 48-kDa protein encoded by femA, several related methicillin-resistant, methicillin-susceptible, and Tn551 insertionally inactivated femA mutants were analyzed for possible changes in cell wall structure and metabolism. Independent of the presence of mec, the methicillin resistance determinant, all femA mutants had a reduced peptidoglycan (PG) glycine content (up to 60% in the molar ratio of glycine/glutamic acid) compared to that of related femA+ parent strains. Additional effects of femA inactivation and the subsequent decrease in PG-associated glycine were (i) reduced digestion of PG by recombinant lysostaphin, (ii) unaltered digestion of PG by Chalaropsis B-muramidase, (iii) reduced cell wall turnover, (iv) reduced whole-cell autolysis, and (v) increased sensitivity towards beta-lactam antibiotics. Also, the PG-associated glycine content of a femA::Tn551 methicillin-susceptible strain was restored concomitantly with the methicillin resistance to a level almost equal to that of its femA+ methicillin-resistant parent strain by introduction of plasmid pBBB31, encoding femA.

Acetylglucosamine↗
PubMed1991

Direct proof of a "more-than-single-layered" peptidoglycan architecture of Escherichia coli W7: a neutron small-angle scattering study.

A neutron small-angle scattering study was performed to determine the thickness and the scattering density profile of isolated peptidoglycan sacculi of Escherichia coli W7 in aqueous suspension (D2O). The maximum thickness (7 +/- 0.5 nm) of the sacculus from the exponential-phase cells was large enough to suggest the existence of a more-than-single-layered architecture. The experimental density profile across the thickness of the sacculus did not allow an unambiguous differentiation between a single-layered architecture characterized by completely extended peptide side chains projecting from the sugar strands or, alternatively, a partially triple layered structure. To resolve this ambiguity, sacculi were labeled with deuterated wall peptides. Comparison of the two experimental profiles indicated that the sacculus is more than single layered across its surface, with about 75 to 80% of its surface single layered and 20 to 25% triple layered.

Escherichia coli↗
PubMed1990

A novel labeling procedure of anteiso-fatty acid-containing lipids in staphylococci for investigating the effect of penicillin on lipid release.

L-[4,5-3H]isoleucine was introduced to label anteiso-fatty acid (AIFA)-containing lipids in Staphylococcus aureus SG 511. After an overnight incubation in peptone broth in the presence of 37 kBq L-[4,5-3H]isoleucine/ml, 8.5-13% of the total radioactivity applied was found to be incorporated into the cells. 22.4-25.6% of the incorporated radioactivity was found in AIFA-containing lipids extracted by chloroform-methanol-water (2:1:0.2, v/v/v) at pH 2. The interphase contained 70-75% of the incorporated radioactivity. Lipoteichoic acid, extracted by phenol-water (80:20, w/v) contained less than 1% of the incorporated radioactivity, as measured after purification by hydrophobic interaction chromatography on octyl sepharose gel. Within 1 h after addition of 10 micrograms/ml penicillin G to exponentially growing cultures of S. aureus, that led to non-lytic death of the cells, 11.9-18.1% of the incorporated L-[4,5-3H]isoleucine label were released. Lipids containing AIFA were excreted to 5.4-8.4% of total incorporated activity; this amount represents more than 1/4 of the labeled cellular lipids.

Fatty Acids↗