Penicillin-binding proteins of Rhodopseudomonas sphaeroides and their membrane localization

Cytoplasmic membranes (CM) prepared from both chemotrophic and phototrophic cells of Rhodopseudomonas sphaeroides possess penicillin-binding proteins (PBPs), as demonstrated by binding of [125]furazlocillin to isolated membranes, the subsequent separation of the constituent PBPs by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and their detection by autoradiography. The major PBP present in CM from R. sphaeroides corresponds in molecular weight to PBP-5, the predominant PBP present in CM of Escherichia coli. In contrast, the outer membrane of R. sphaeroides shows only low-level furazlocillin-binding activity on a per milligram of protein basis compared with chemotrophic CM. The intracytoplasmic membrane (ICM) derived from phototrophic cells contains less than 5% of the furazlocillin-binding activity of the CM. Based on the specific localization of PBPs in the CM, it is possible to provide quantitative estimates of the extent of CM present in preparations of ICM. This method demonstrates that highly purified preparations of ICM contain less than 5% CM. Additionally, the assay for PBPs demonstrates that during ICM remodeling, which occurs upon a shift from phototrophic to chemotrophic growth, there is no significant insertion of PBPs into the ICM over the first two generations after a shift to chemotrophic growth.

Effects of furazlocillin, a beta-lactam antibiotic which binds selectively to penicillin-binding protein 3, on Escherichia coli mutants deficient in other penicillin-binding proteins

Furazlocillin binds selectively to penicillin-binding protein 3 (PBP-3), prevents septation of Escherichia coli, and allows the cells to form long filaments without lysis. The effect of furazlocillin on the morphology, autolysis, and murein synthesis of E. coli mutants deficient in either PBP-1A, PBP-1Bs, or PBP-2 was studied. The results reveal that PBP-1A and PBP-1Bs functions are not equivalent since furazlocillin affects the morphology, autolysis, and murein synthesis of PBP1A- mutants quite differently from that of PBP-1Bs mutants. Different "PBP-2-" mutants were found to respond to furazlocillin in dramatically different ways: strain LS-1 cells formed elongated rods with a central bulge which eventually lysed, whereas SP6 cells formed stable "barbells" in which the two daughter cells were well separated but remained connected by a thick central region.

Evidence for involvement of penicillin-binding protein 3 in murein synthesis during septation but not during cell elongation

Furazlocillin (1 microgram/ml) and piperacillin (5 microgram/ml) bound specifically to penicillin-binding protein 3 (PBP-3) and not to the other major PBPs in intact Escherichia coli cells. The effect of this specific binding to PBP-3 on murein synthesis of elongating and synchronously septating cells was investigated in two thermosensitive division mutants, E. coli BUG6 and E. coli JE10730, the latter possessing a thermolabile PBP-3. Synchronous cell division was induced by shifting the cultures from the nonpermissive temperature (42 degrees C) to 30 degrees C. Both [14C]diaminopimelic acid incorporation into murein of intact cells and [14C]N-acetylglucosamine incorporation into murein of cells permeabilized with ether was inhibited by an average of 42% in septating cells. In filaments growing at the nonpermissive temperature, we detected no inhibition and, frequently, a 10 to 15% stimulation of murein synthesis. The two drugs, at concentrations used in the above experiments, bound exclusively to PBP-3 both in elongating and septating intact cells and in ether-treated cells. These results support the hypothesis that PBP-3 activity is exclusively required for septal murein synthesis.

Genetic characterization of a filament-forming, lipoprotein-deficient mutant of Escherichia coli

The fam-715 allele of Escherichia coli ST715, previously described as a temperature-sensitive filament former with reduced levels of lipoprotein at the nonpermissive temperature (S. V. Torti and J. T. Park, Nature [London] 263: 323--326, 1976), was mapped at 74 min. This mutation appears to be amber. It is recessive and can be complemented by F' plasmids carrying the wild-type allele or by an F' plasmid carrying an amber suppressor. Isotopic labeling experiments as well as map position differentiate the fam-715 allele from lipoprotein structural gene mutations.

A mutant of Escherichia coli defective in penicillin-binding protein 5 and lacking D-alanine carboxypeptidase IA

A mutant of Escherichia coli defective in penicillin-binding protein 5 activity was isolated. The mutation (pfv) was shown to be located at 14.0 min on the E. coli chromosome map. Loss of penicillin-binding protein 5 in the pfv mutant was associated with the loss of D-alanine carboxypeptidase IA activity and increased sensitivity to beta-lactam antibiotics. We conclude that penicillin-binding protein 5 catalyzes the major D-alanine carboxypeptidase IA activity and that the enzyme activity, in vivo, protects E. coli cells from killing by low inhibitory concentrations of beta-lactam antibiotics.

Basis for the observed fluctuation of carboxypeptidase II activity during the cell cycle in BUG 6, a temperature-sensitive division mutant of Escherichia coli

Diaminopimelyl-d-alanyl carboxypeptidase (carboxypeptidase II) is most active at the time of division, whether measured in toluene-treated cells of Escherichia coli K-12 strain D11-1, fractionated by size, or in toluene-treated cells of the temperature-sensitive division mutant, BUG 6 (B. D. Beck and J. T. Park, 1976). The present investigation has now shown that, under conditions that permit division, the increased carboxypeptidase II activity in toluenetreated cells of BUG 6 is probably not due to protein synthesis. Although dividing cells are more permeable than nondividing cells, permeability differences are not sufficient to account for the changes in carboxypeptidase II activity. Thus, in the toluene-treated nondividing cells, carboxypeptidase II is present, but its activity is masked, which suggests the presence of an inhibitor. Another striking difference between nondividing and dividing cells is that carboxypeptidase II is much more readily released from dividing cells by both tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetic acid and toluene treatment. Carboxypeptidase II was partially purified and found to be an 86,000-molecular-weight protein consisting of two 43,000-molecular-weight polypeptides. Tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetic acid treatment of nondividing cells releases less than 10% of the carboxypeptidase II and other periplasmic proteins that are releasable from dividing cells.

Activity of three murein hydrolases during the cell division cycle of Escherichia coli K-12 as measured in toluene-treated cells

The specific activities of three murein hydrolases, carboxypeptidase I, carboxypeptidase II, and amidase were studied with respect to cell division in toluene-treated cells of Escherichia coli K-12. Carboxypeptidase I and amidase activities were constant throughout the division cycle in cells of D11/lac+pro+. Detectable carboxypeptidase II activity varied and was highest at the time of division by a factor of three. Carboxypeptidase II specific activity was also correlated with cell division in BUG 6, a temperature-sensitive mutant (J.N Reeve, D.J. Groves, and D.J. Clark, 1970). Fifteen minutes after shifting BUG 6 from 42 C (nondividing conditions) to 32 C (dividing conditions), there was a rapid resumption of cell division, accompanied by a 10-fold increase in the specific activity of carboxypeptidase II. These results demonstrate a correlation between detectable carboxypeptidase II activity and cell division as reflected by activity in toluene-treated cells. The subcellular location of carboxypeptidase II, a soluble enzyme was found to be periplasmic since it was released by tris(hydroxymethyl)-aminomethane-ethylenediaminetetraacetate treatment and osmotic shock, two methods known to release periplasmic enzymes.

Resistance of Escherichia coli to penicillins: identification of the structural gene for the chromosomal penicillinase

A screening procedure was used to isolate a number of mutants of Escherichia coli K-12 with low penicillinase activity. By co-transduction with purA, three of the mutants were found to map near 82 min. Penicillinase was purified from one mutant and from a transductant with a temperature-sensitive enzyme. Comparison with wild-type penicillinase revealed similarities in the Ouchterlony immunodiffusion test but differences in the catalytic properties. It is concluded that the mutations have occurred in the structural gene of the chromosomal penicillinase (designated ampC). Purified enzyme and a temperature-sensitive mutant were used to investigate whether the penicillinase has a physiological function related to biosynthesis or breakdown of murein. No positive evidence for any such function was obtained.

Properties and purification of N-acetylmuramyl-L-alanine amidase from Staphylococcus aureus H

The principal autolytic enzyme activity of the cell sap of Staphylococcus aureus H has been purified 400-fold. It is an N-acetylmuramyl-l-alanine amidase. This enzyme has a molecular weight of 8 to 10 x 10(5), a pH optimum of 7.3, an ionic strength optimum of 0.16 m and a K(m) of 10(-3)m murein repeating units.

Resistance to penicillin in mutants of a penicillinase-negative organism, Staphylococcus aureus H

Penicillin-resistant mutants of Staphylococcus aureus H were similar to the parent in their response to penicillin though proportionately more penicillin was required for a given effect. The mutants did not inactivate penicillin. Most of the penicillin-binding sites (presumed to be murein transpeptidase molecules) bound penicillin rapidly when exposed to a very low concentration of penicillin (0.1 mug/ml), and yet the mutants retained some functional murein transpeptidase even in the presence of 500 mug of penicillin per ml. An hypothesis based on (i) functional versus nonfunctional transpeptidase molecules and (ii) variations in accessibility to penicillin can explain these findings.

Chemical characterization of a new surface antigenic polysaccharide from a mutant of Staphylococcus aureus

A mutant of Staphylococcus aureus H was isolated by virtue of its inability to agglutinate with antibodies against teichoic acid of S. aureus. Immunological studies revealed that the mutant, S. aureus T, possessed a new surface antigen in addition to having the antigenic determinant of the wild-type strain, the ribitol teichoic acid. The presence of this additional surface component rendered strain T resistant to staphylococcal typing phages, presumably by masking the phage-receptor sites. The polymer was separated from teichoic acid by chromatography on diethylaminoethyl cellulose and was shown to be composed of two amino sugars, N-acetyl-d-fucosamine and N-acetyl-d-mannosamin uronic acid.

Nature and origins of phosphorus compounds in isolated cell walls of Staphylococcus aureus

Preparations of purified cell walls from Staphylococcus aureus were shown to contain small amounts of phospholipid and glycerol teichoic acid. Since these are components of the cell membrane, it is probable that the wall itself contains no lipid, but does retain fragments of membrane because of physical connections between wall and membrane. In walls of S. aureus strain 52A5, which completely lacks ribitol teichoic acid, the only phosphorylated compound identified as a genuine wall component was a phosphorylated derivative of murein that gave rise to muramic acid phosphate on acid hydrolysis. Muramic acid phosphate was also identified in hydrolysates of walls from S. aureus H and strain 52A2.

Staphylococcus aureus H autolytic activity: general properties

Staphylococcus aureus strain H has an autolytic activity which can be found in the cell wall but is most easily obtained from high-speed supernatant fractions of broken-cell preparations. As measured either turbidimetrically or radioactively, this activity is much greater on murein extracted from penicillin-treated cells than on murein extracted from normal cells.

Properties of a novel pleiotropic bacteriophage-resistant mutant of Staphylococcus aureus H

A phage-resistant mutant of Staphylococcus aureus H (Sm(R)), S. aureus 52A5, was previously shown to lack polymeric teichoic acid. This paper characterizes other phenotypic differences between the strains. In broth cultures the mutant cells grew more slowly, were larger, and formed much larger clumps than the parent strain. The clumps of cells appeared to be covalently linked and could only be separated by mild sonic energy-a process which yielded viable cells. Mutant and parent cells autolyzed at equal rates, whereas isolated cell walls of the mutant strain autolyzed faster than the wild type. Nevertheless, the specific activity of the autolytic enzyme in the wild type soluble fraction was much higher than in the mutant. In contrast to the parent, strain 52A5 failed to accumulate nucleotide-bound murein precursors when treated with penicillin. Mutant strains with these characteristics were repeatedly isolated both spontaneously and by chemical mutagenesis. Strain 52A5 was shown to be fully revertible. Thus, it appears to be a pleiotropic mutation, and the possible nature of the defect which causes these varied effects is discussed.

Correlation between growth inhibition and the binding of various penicillins and cephalosporins to Staphylococcus aureus

The concentration of penicillin (or cephalosporin) required to achieve a given rate of binding to Staphylococcus aureus H correlates well with that required for inhibition of growth. This result suggests that the irreversible binding of penicillins and cephalosporins to cells is responsible for their biological activity.