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At least 343 records · Page 19Linked to original sources
PubMed1978

Manipulation of phospholipid composition of membranes with the aid of lipid exchange proteins. Incorporation of phosphatidylcholine into protoplasts of Micrococcus lysodeikticus.

Incubation of Micrococcus lysodeikticus protoplasts with phosphatidylcholine liposomes and rat liver exchange proteins (pH 5.1 supernatant fraction) resulted in replacement of about one half of the bacterial total phospholipids by phosphatidylcholine. Protoplasts modified by phosphatidylcholine showed a decreased rate of oxidation of exogenous substrates (NADH, malate) and decreased ferricyanide reductase activity as compared to the initial protoplasts. At the same time incorporation of phosphatidylcholine had no influence on the level of endogeneous respiration. Protoplasts modified by phosphatidylcholine were osmotically more stable than the initial protoplasts. After osmotic lysis of the phosphatidylcholine protoplasts their NADH (malate) oxidase and ferricyanide reductase activities were restored. Incorporation of phosphatidylcholine into membrane ghosts, obtained by osmotic rupture of the initial protoplasts had only small if any effect on the malate and NADH oxidase and dehydrogenase activities. It is concluded that phosphatidylcholine in incorporated predominantly into the outer part of cytoplasmic membrane and that proteinmediated transfer of phosphatidylcholine results in restoration of the permeability barrier due to repair of local defects in the initial protoplast membrane.

Cell Membrane↗
PubMed1979

The kinetics of ATP-dependent exonuclease V from Micrococcus lysodeikticus. A Michaelian dependence on DNA concentration.

The ATP-dependent exonuclease V from Micrococcus lysodekticus shows a Michaelian relation between steady-state velocity and the concentration of T7 DNA substrate. The Km (expressed as a mass concentration) does not change when the T7 DNA is broken into smaller fragments by a restriction enzyme. This is interpreted to mean that the predominant process by which the exonuclease-V--DNA complex breaks down is digestion of the entire DNA molecule rather than physical dissociation, in accord with the already known processive nature of degradation by this enzyme. The way that the V and Km towards DNA vary with ATP and ADP concentration suggests that enzyme-DNA complex is predominantly formed by reaction of DNA with an enzyme-ATP complex rather than with bare enzyme.

Adenosine Diphosphate↗
PubMed1983

Study of the respiratory chain in Micrococcus luteus (lysodeikticus) by electron-spin-resonance spectroscopy.

Low-temperature electron spin resonance spectroscopy was used to investigate the redox centres of Micrococcus luteus membranes. Three different types of iron-sulphur centres were distinguished. Two of these, a [4Fe-4S]3+-type cluster giving rise to a signal at g = 2.01 in the oxidized state and a [2Fe-2S] cluster with a spectrum at g = 2.03 and 1.93 in the reduced state, were attributable to succinate dehydrogenase. Another, generating signals in the reduced state at g = 2.027, 1.90 and 1.78 was identified as a 'Rieske' iron-sulphur centre. This latter cluster had a mid-point potential (pH 7.0) of +130 mV. In addition, signals characteristic of high-spin ferric haem (g = 6.20), low-spin ferric haem (g = 3.67, 3.36 and 3.01) and Cu2+ (g = 2.18 and 2.02) were also detected. The ferric-haem features, together with the Cu2+ and 'Rieske' centres, were enriched in membrane residues insoluble in Triton X-100, which are known from difference spectroscopy to contain cytochromes b-560, c-550 and a-601 (aa3 oxidase). The signals demonstrated by electron spin resonance for M. luteus membranes showed marked similarities to those documented for the complexes II, III, and IV of mitochondria. However, signals analogous to complex I (NADH-ubiquinone reductase) could not be demonstrated for M. luteus membranes.

Bacterial Proteins↗
PubMed1983

Characterization of succinate dehydrogenase from Micrococcus luteus (lysodeikticus) by electron-spin-resonance spectroscopy.

Low-temperature electron spin resonance spectroscopy has been used to study the biophysical properties of succinate dehydrogenase from the gram-positive bacterium Micrococcus luteus. The paramagnetic redox centres of the enzyme were identified in a succinate-dehydrogenase--antigen complex, which had been purified with the aid of monospecific serum from membranes solubilized with Triton X-100. The centres were characterized in further detail using the membrane-bound and Triton-solubilized forms of the enzyme. These studies distinguished two types of iron-sulphur centres, viz. a [4Fe-4S]3+ cluster displaying a narrow signal at g = 2.01 in the oxidized state (conventionally termed centre S-3) and a [2Fe-2S )0 cluster with an axial signal at g = 2.03 and 1.93 in the reduced state (conventionally termed centre S-1). Centre S-3 had a mid-point redox potential of +10 mV, a comparatively low value for this type of cluster. The behaviour of the g = 1.93 signal of centre S-1 was a complex function of the redox potential, microwave power and temperature of measurement. When measured at low power (i.e. non-saturating conditions), the intensities observed for the g = 1.93 signal poised at various critical potentials in the redox titration were similar. However, the corresponding intensities differed markedly at high power, where conditions were saturating. It is proposed that under saturating conditions the spin-lattice relaxation of the [2Fe-2S] cluster S-1 (mid-point potential +70 mV) is enhanced by centre S-3 between the potential range +10-+70 mV and by an ESR-silent centre, termed centre S-2, with a mid-point potential of -295 mV.

Chemical Precipitation↗
PubMed1984

Synthesis of RNA I by the RNA polymerase from Micrococcus luteus on the Escherichia coli plasmid pBR322.

Incubation of DNA-dependent RNA polymerase from Micrococcus luteus (gram-positive) with the plasmid pBR322 under transcription conditions in vitro leads to the formation of a rather short-chained RNA. This transcript is initiated at the same site on pBR322 as RNA I, a defined Escherichia coli RNA polymerase product. M. luteus RNA polymerase initiates transcription at the RNA I site much more efficiently than the E. coli enzyme, using either a plasmid preparation of pBR322 or an appropriate linear restriction fragment as template. In the latter case, cleavage of the restriction fragment 24 or 71 nucleotides (but not 91 nucleotides) upstream of the initiation site destroys template activity. By sequence analysis it was determined that the 3' terminus of the M. luteus RNA polymerase transcription product is identical with that known for RNA I. Moreover, in agreement with synthesis of RNA I by E. coli RNA polymerase in vitro, termination by the M. luteus enzyme is also a stutter process characterized by the same dependence on the available UTP concentration. These observations lead to the hypothesis that termination by eubacterial RNA polymerases might not be species-specific.

Base Sequence↗
PubMed1985

Biosynthesis of wall teichoic acids in Staphylococcus aureus H, Micrococcus varians and Bacillus subtilis W23. Involvement of lipid intermediates containing the disaccharide N-acetylmannosaminyl N-acetylglucosamine.

The precursors for linkage unit (LU) synthesis in Staphylococcus aureus H were UDP-GlcNAc, UDP-N-acetylmannosamine (ManNAc) and CDP-glycerol and synthesis was stimulated by ATP. Moraprenol-PP-GlcNAc-ManNAc-(glycerol phosphate)1-3 was formed from chemically synthesised moraprenol-PP-GlcNAc, UDP-ManNAc and CDP-glycerol in the presence of Triton X-100. LU intermediates formed under both conditions served as acceptors for ribitol phosphate residues, from CDP-ribitol, which comprise the main chain. The initial transfer of GlcNAc-1-phosphate from UDP-GlcNAc was very sensitive to tunicamycin whereas the subsequent transfer of ManNAc from UDP-ManNAc was not. Poly(GlcNAc-1-phosphate) and LU synthesis in Micrococcus varians, with endogenous lipid acceptor, UDP-GlcNAc and CDP-glycerol, was stimulated by UDP-ManNAc. Synthesis of LU on exogenous moraprenol-PP-GlcNAc, with Triton X-100, was dependent on UDP-ManNAc and CDP-glycerol and the intermediates formed served as substrates for polymer synthesis. Membranes from Bacillus subtilis W23 had much lower levels of LU synthesis, but UDP-ManNAc was again required for optimal synthesis in the presence of UDP-GlcNAc and CDP-glycerol. Conditions for LU synthesis on exogenous moraprenol-PP-GlcNAc were not found in this organism. LU synthesis on endogenous acceptor in the absence of UDP-ManNAc was explained by contamination of membranes with UDP-GlcNAc 2-epimerase. Under appropriate conditions, low levels of this enzyme were sufficient to convert UDP-GlcNAc into a mixture of UDP-Glc-NAc and UDP-ManNAc and account for LU synthesis. The results indicate the formation of prenol-PP-GlcNAc-ManNAc-(glycerol phosphate)1-3 which is involved in the synthesis of wall teichoic acids in S. aureus H, M. varians and B. subtilis W23 and their attachment to peptidoglycan.

Bacillus subtilis↗
PubMed1987

Structural and immunochemical characterization of a ribosomal protein from gram-positive Micrococcus luteus which is functionally homologous to Escherichia coli ribosomal protein S1.

Ribosomes from gram-positive Micrococcus luteus contain an acidic protein (ML-S1). ML-S1 has been purified by chromatography of ribosomes on a poly(U)-Sepharose column and the purified protein has a mobility in sodium dodecyl sulphate/polyacrylamide gels similar to that of ribosomal protein S1 of Escherichia coli (apparent Mr 72,000). Protein ML-S1 reacted with E. coli anti-S1 serum with an immunological partial-identity reaction. ML-S1 also reacted with antibodies raised against two structural domains of E. coli S1 (the N-terminal ribosome-binding domain and central and C-terminal nucleic-acid-binding domain). Weak reaction with antiserum to the nucleic-acid-binding domain of E. coli S1 was observed. ML-S1 was digested with trypsin under mild and exhaustive conditions. Mild digestion resulted in the production of a trypsin-resistant core (ML-S1F1) like E. coli S1. The fragment pattern obtained after exhaustive digestion differed appreciably from that obtained with E. coli S1. ML-S1 bound to poly(U) as strongly as E. coli S1 and also showed appreciable binding to denatured DNA. Addition of ML-S1 to S1-depleted ribosomes from E. coli and M. luteus markedly stimulated the poly(U)-directed polyphenylalanine synthesis. Phage MS2-RNA-dependent translation was also found to be stimulated by ML-S1 although to a much lesser extent than the stimulation by E. coli S1. At a molar excess of ML-S1 to ribosomes the protein showed a similar inhibitory effect to E. coli S1 on polypeptide synthesis. Our data indicate that ML-S1 retained the structural domains important for its function despite certain structural differences from E. coli S1.

Cross Reactions↗
PubMed1988

Ionic-strength-dependent substrate inhibition of the lysis of Micrococcus luteus by hen egg-white lysozyme.

The kinetics of lysis of Micrococcus luteus by hen egg-white lysozyme in dilute buffer media is characterized by pronounced substrate inhibition. This effect occurs within the complete pH range where lysozyme activity is detectable. The electrostatic potential of the negatively charged cell-wall proteoglycan increases with decreasing ionic strength, resulting in an enhanced affinity between proteoglycan and lysozyme and probably favouring multipoint substrate attachment. For the lysozyme-catalyzed hydrolysis of cell-wall proteoglycan three plausible mechanisms of substrate inhibition can be postulated. Two out of the three models fit our experimental data, the simplest of the two providing the most rigorous information on the kinetic parameters Km, V and Ki. Three graphical methods consistent with the chosen model were applied for preliminary parameter estimation and the constants obtained were compared to those from nonlinear least-squares analysis. If substrate inhibition is neglected it is shown that serious bias is imposed upon the parameters.

Catalysis↗
PubMed1989

Synergistic hemolytic reactions between staphylococci and Micrococcus lylae.

The primary culture of a clinical specimen obtained from a dog with an acute squamous eczema revealed three different bacterial species which demonstrated synergistic hemolytic activities on sheep blood agar plates. The three cultures were identified as beta-hemolytic Staphylococcus intermedius, as a coagulase-negative staphylococcal species, producing a delta-like hemolysin and as non-hemolytic Micrococcus lylae. The coagulase-negative staphylococcal species as well as M. lylae produced synergistically with beta-hemolytic S. intermedius zones of complete hemolysis. The occurrence of three different synergistically active bacterial species from one clinical specimen might be of clinical significance.

Animals↗
PubMed1997

Micrococcus luteus cells and cell walls induce anaphylactoid reactions accompanied by early death and serum cytokines in mice primed with muramyl dipeptide.

Micrococcus luteus strains at a dose of 500 microg of whole cells caused anaphylactoid reactions leading to death in some instances within 1 h in C3H/HeN mice primed with muramyl dipeptide (MDP, 100 microg). Tumor necrosis factor (TNF) and interleukin-6 (IL-6) were induced in the serum of half and of all the surviving mice, respectively. Cell wall specimens of M. luteus so far examined also caused anaphylactoid reactions accompanied by early death and one strain induced high levels of TNF and IL-6. Cytoplasmic membranes also induced IL-6. Essentially similar results were obtained with representative M. luteus cells and a cell wall specimen in MDP-primed C3H/HeJ mice. These results indicate that M. luteus has virulence activities that are associated with the induction of septic shock and systemic inflammatory diseases.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1986

Inhibition of Micrococcus luteus DNA gyrase by norfloxacin and 10 other quinolone carboxylic acids.

The ability of norfloxacin, amifloxacin, cinoxacin, ciprofloxacin, flumequine, nalidixic acid, ofloxacin (OFL), oxolinic acid, perfloxacin, pipemidic acid, and rosoxacin to inhibit the in vitro supercoiling activity of Micrococcus luteus DNA gyrase was compared with the ability of each drug to inhibit the growth of the M. luteus strain from which the gyrase was purified. The potency of the quinolones as DNA gyrase inhibitors did not always correlate with antimicrobial potency. For example, OFL was a less potent inhibitor of gyrase than rosoxacin, yet the MIC of OFL was 16-fold lower than that of rosoxacin. Similarly, the MICs of norfloxacin and ciprofloxacin (the most potent of the antibiotics tested in these assays) were several hundredfold lower than the MIC of nalidixic acid (the least potent of these antibiotics), but the inhibition of purified gyrase by these two quinolones was only 8- to 16-fold lower than that of nalidixic acid. These results suggest that factors in addition to inhibition of gyrase supercoiling activity are important in determining the potency of these drugs. Further studies indicated that the uptake of norfloxacin, OFL, and amifloxacin by M. luteus cells may not account for the large differences in MICs observed for these drugs (MICs of 0.8, 2.0, and 128 micrograms/ml, respectively).

Anti-Bacterial Agents↗
PubMed2000

Multiparameter flow cytometric analysis of antibiotic effects on membrane potential, membrane permeability, and bacterial counts of Staphylococcus aureus and Micrococcus luteus.

Although flow cytometry has been used to study antibiotic effects on bacterial membrane potential (MP) and membrane permeability, flow cytometric results are not always well correlated to changes in bacterial counts. Using new, precise techniques, we simultaneously measured MP, membrane permeability, and particle counts of antibiotic-treated and untreated Staphylococcus aureus and Micrococcus luteus cells. MP was calculated from the ratio of red and green fluorescence of diethyloxacarbocyanine [DiOC(2)(3)]. A normalized permeability parameter was calculated from the ratio of far red fluorescence of the nucleic acid dye TO-PRO-3 and green DiOC(2)(3) fluorescence. Bacterial counts were calculated by the addition of polystyrene beads to the sample at a known concentration. Amoxicillin increased permeability within 45 min. At concentrations of <1 microg/ml, some organisms showed increased permeability but normal MP; this population disappeared after 4 h, while bacterial counts increased. At amoxicillin concentrations above 1 microg/ml, MP decreased irreversibly and the particle counts did not increase. Tetracycline and erythromycin caused smaller, dose- and time-dependent decreases in MP. Tetracycline concentrations of <1 microg/ml did not change permeability, while a tetracycline concentration of 4 microg/ml permeabilized 50% of the bacteria; 4 microg of erythromycin per ml permeabilized 20% of the bacteria. Streptomycin decreased MP substantially, with no effect on permeability; chloramphenicol did not change either permeability or MP. Erythromycin pretreatment of bacteria prevented streptomycin and amoxicillin effects. Flow cytometry provides a sensitive means of monitoring the dynamic cellular events that occur in bacteria exposed to antibacterial agents; however, it is probably simplistic to expect that changes in a single cellular parameter will suffice to determine the sensitivities of all species to all drugs.

Anti-Bacterial Agents↗
PubMed1974

Effect of penicillin on the in vivo formation of the D-alanyl-L-alanine peptide cross-linkage in cell walls of Micrococcus luteus.

Penicillin G was found to inhibit the formation of the d-alanyl-l-alanine cross-linkage in intact cells of Micrococcus luteus. This reaction was approximately 50-fold less susceptible to penicillin than the formation of the d-alanyl-l-lysine cross-linkage in the same organism. The presence of two penicillin-susceptible transpeptidation reactions that function in the incorporation of peptidoglycan precursors into the cell wall is proposed.

Alanine↗
PubMed1979

Biochemical properties of penicillin amidohydrolase from Micrococcus luteus.

Some biochemical properties of whole-cell penicillin amidohydrolase from Micrococcus luteus have been studied. This whole-cell enzyme showed its maximal activity at 36 degrees C at pH 7.5. It was found that the activation energy of this enzyme was 8.03 kcal (ca. 33.6 kJ) per mol, and this amidohydrolase showed first-order decay at 36 degrees C. The penicillin amidohydrolase was deactivated rapidly at temperatures above 50 degrees C during storage or preincubation for 24 h. The Michaelis constant, Km, for penicillin G was determined as 2.26 mM, and the substrate inhibition constant, Kis, was 155 mM. The whole-cell penicillin amidohydrolase from M. luteus was capable of hydrolyzing penicillin G, penicillin V, ampicillin, and cephalexin, but not cephalosporin C and cloxacillin. This whole-cell enzyme also had synthetic activity for semisynthetic penicillins or cephalosporins from D-(--)-alpha-phenylglycine methyl ester and 6-alpha-aminopenicillanic acid or 7-amino-3-deacetoxycephalosporanic acid.

Amidohydrolases↗
PubMed1982

Application of halophilic nuclease H of Micrococcus varians subsp. halophilus to commercial production of flavoring agent 5'-GMP.

RNA was degraded at 60 degrees C for 24 h by halophilic nuclease H in supernatants from broth cultures of Micrococcus varians subsp. halophilus containing 12% NaCl. Since contaminating 5'-nucleotidase exhibited almost no activity under these conditions, the 5'-GMP formed could be recovered from the reaction mixture, and the yield was 805 mg from 5 g of RNA.

Exoribonucleases↗
PubMed1993

Biodegradation of a synthetic lubricant by Micrococcus roseus.

A bacterium that was able to utilize Emkarate 1550 (E1550), a synthetic lubricant ester, as the sole source of carbon was isolated. The isolate was tentatively identified as Micrococcus roseus. The components of the E1550 ester, octanoate, decanoate, and 1,1,1-tris(hydroxymethyl)propane (TMP), were detected in the culture medium of cells growing on the ester. The TMP tertiary alcohol accumulated during growth and was not utilized by this isolate. The detection of the components of the ester in the supernatant of cultures indicated that one of the first steps in its degradation was cleavage of the ester bonds. Esterase activity was significantly enhanced in cells grown on E1550 compared with esterase activity measured in cells grown on acetate.

Biodegradation, Environmental↗
PubMed1996

Variacin, a new lanthionine-containing bacteriocin produced by Micrococcus varians: comparison to lacticin 481 of Lactococcus lactis.

A new lanthionine-containing bacteriocin, variacin, displaying a broad host range of inhibition against gram-positive food spoilage bacteria, has been identified from two strains of Micrococcus varians isolated from meat fermentations. The new bacteriocin was purified, and its amino-terminal end and total amino acid composition were determined. The structural gene was isolated and analyzed. Variacin is resistant to heat and pH conditions from 2 to 10. Its primary sequence shows significant homology to lacticin 481 to Lactococcus lactis, which is more pronounced for the probacteriocin than for the leader sequence. Variacin, like lacticin 481, contains lanthionine and beta-methyllanthionine residues, but its leader sequence clearly resembles nonlantibiotic leader sequences. In particular, the prepeptide contains glycine residues at positions -1 and -2 of the processing site.

Alanine↗