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Biomedical subjects

M Maqueda

Publications and source records attributed to M Maqueda.

At least 55 records · Page 3Linked to original sources
PubMed1991

Purification, characterization, and biological effects of a second bacteriocin from Enterococcus faecalis ssp. liquefaciens S-48 and its mutant strain B-48-28.

Enterococcus faecalis ssp. liquefaciens S-48 (producer of the peptide antibiotic AS-48) and its mutant B-48-28 (AS-48-) secrete the bacteriocin Bc-48. This substance has been purified to homogeneity from culture supernatants of strain B-48-28; it consists of a protein (80 kDa) stable from pH. 5.5 to 9.0 and sensitive to temperatures above 45 degrees C and to proteases. Its inhibitory spectrum is restricted to strains of Enterococcus faecalis. Bc-48 inhibits protein synthesis but does not affect amino acid uptake. A partial reduction of cell viability, together with autolysis, is also observed. Bc-48 differs from peptide AS-48 in both its molecular properties and mode of action.

Bacterial Proteins↗
PubMed1990

Genetic stability of the antagonistic character of Enterococcus faecalis ssp. liquefaciens and the detection of a new inhibitory bacteriocin-like substance.

The inhibitory capacity of strain S-48 of Enterococcus faecalis ssp. liquefaciens was studied. The strain produces a broad-spectrum peptide antibiotic (AS-48) that has been characterized elsewhere. The isolation of mutants from S-48 after mutagenic treatment revealed another inhibitory substance which remained masked in the wild strain. The protein nature and restricted spectrum of this substance points to its being a bacteriocin.

Acridine Orange↗
PubMed1990

Induction of inhibitory agent produced by Enterococcus faecalis.

The effect of treatment with inducing agents, such as mitomycin C, hydrogen peroxide and UV irradiation on the production of two inhibitors by different mutants from Enterococcus faecalis S-48 was studied. With hydrogen peroxide and UV light no increase in either the absolute or the relative amount of antagonistic substances was observed. With mitomycin C, a significant increase in the individual cell capacity for inhibitor production was detected.

Anti-Bacterial Agents↗
PubMed1990

Induction of autolysis in Enterococcus faecalis S-47 by peptide AS-48.

In addition to its bactericidal mode of action, the peptide antibiotic AS-48 exhibits a bacteriolytic effect on Enterococcus faecalis S-47 that is associated with autolysin activation. Bacteriolysis induced by the antibiotic can be modulated by addition of EDTA, divalent cations and autolysin activators (trypsin) or inhibitors (cardiolipin), suggesting that topologic regulation of the autolysins is involved in the process. In addition, inhibitors of protein and RNA synthesis interfere markedly with bacteriolysis, as do ionophores and the ATPase inhibitor DCCD, suggesting the participation of an internal messenger in autolysin activation in the presence of AS-48.

Anti-Bacterial Agents↗
PubMed1990

A transferable plasmid associated with AS-48 production in Enterococcus faecalis.

Enterococcus faecalis S-48 produces a peptide antibiotic, AS-48, and a bacteriocin, Bc-48. We have isolated mutants that lack these inhibitory characteristics. Further analysis of the mutants indicates that a plasmid of 56 kilobases (pMB2) may harbor the genes for AS-48. In conjugation experiments, pMB2 has been transferred into a plasmid-free OG1X strain of E. faecalis. The OG1X(pMB2) transconjugant produces the antibiotic AS-48 in solid medium, and the MIC of AS-48 for this strain is the same as that of the donor strain.

Anti-Bacterial Agents↗
PubMed1989

Bactericidal and bacteriolytic action of peptide antibiotic AS-48 against gram-positive and gram-negative bacteria and other organisms.

A purified peptide antibiotic AS-48 from Streptococcus faecalis spp liquiefaciens S-48 exerted a bactericidal mode of action against most Gram-positive and many Gram-negative bacteria tested. In many Gram-positive bacteria and the two Myxococcus species assayed, a bacteriolytic effect, as a consequence of primary lesions, was also observed. In general, the Gram-negative bacteria were more resistant to AS-48. Escherichia coli protoplasts showed increased sensitivity and those of a resistant yeast. Saccharomyces cerevisiae 3.2, became sensitive. These data suggest that resistance is related to the cell wall structure. AS-48 adsorbed rapidly to cell walls and cytoplasmic membranes of sensitive and resistant cells. Adsorption to cytoplasmic membranes involved complete neutralization of AS-48.

Adsorption↗
PubMed1989

Purification and amino acid composition of peptide antibiotic AS-48 produced by Streptococcus (Enterococcus) faecalis subsp. liquefaciens S-48.

Peptide antibiotic AS-48 was purified to homogeneity by ion-exchange chromatography, gel filtration chromatography, and reversed-phase liquid chromatography. The purified fraction was active against gram-positive and gram-negative bacteria. AS-48 is a basic protein with an isoelectric point of ca. 10.5 and a molecular mass of 7.4 kilodaltons. Its inhibitory activity was markedly affected by sodium dodecyl sulfate and cardiolipin but not by neuraminidase, pectinase, beta-glucosidase, or beta-glucuronidase. Differential scanning calorimetry data suggested that AS-48 molecules lack a compact structure.

Amino Acids↗
PubMed1989

Effect of peptide AS-48 on Enterococcus faecalis subsp. liquefaciens S-47.

The enterococcal peptide AS-48 exerts a concentration-dependent bactericidal effect on Enterococcus faecalis subsp. liquefaciens S-47; cell rescue by cardiolipin and trypsin can be effected only in the first few minutes after antibiotic addition. Gramicidin-exposed cells are protected from killing by AS-48. Long-term and pulse incorporation of radiolabeled substrates into trichloroacetic acid-precipitable material, O2 consumption, and the ability to maintain intracellular potassium levels are impaired shortly after addition of AS-48.

Anti-Bacterial Agents↗
PubMed1989

Bactericidal action of peptide antibiotic AS-48 against Escherichia coli K-12.

Peptide antibiotic AS-48 exerts a bactericidal mode of action on exponential cultures of Escherichia coli K-12 through a multi-hit kinetics interaction. AS-48 causes a parallel and gradual cessation of all biosynthetic pathways monitored (protein, RNA, DNA, and cell wall synthesis), the rate of incorporation of labeled precursors, the rate of O2 consumption, and cell growth. These effects have been attributed to alterations of cytoplasmic membrane functions.

Anti-Bacterial Agents↗
PubMed1987

NADH-peroxidase activity and H2O2 decomposition in a peroxidogenic strain of Streptococcus durans.

Streptococcus durans S-76 can accumulate hydrogen peroxide to high concentrations under aerobic conditions when it is previously grown anaerobically. An NADH-peroxidase enzyme protects this bacterium from the bactericidal effect of H2O2. The relationship between oxygen uptake and H2O2 excretion into the medium has been investigated in cultures containing or lacking glucose under various conditions of incubation. The results obtained suggest that neither oxygen nor H2O2 regulate the cellular levels of NADH-peroxidase whose activity seems to be controlled exclusively by the availability of reduced NADH.

Hydrogen Peroxide↗
PubMed1986

Characterization and partial purification of a broad spectrum antibiotic AS-48 produced by Streptococcus faecalis.

Streptococcus faecalis S-48 produces a broad spectrum antibiotic, active against Gram-positive and Gram-negative bacteria. This substance is produced in solid and liquid media and also in a defined basal medium. It is sensitive to protease, pronase, or trypsin, heating at 70 degrees C, and alkaline pH, but resistant to treatment with lipase, lysozyme, alkaline phosphatase, DNAase, RNAase, acidic or neutral pHs, and also lower temperatures (60 degrees C). Several organic solvents cause precipitation, but not inactivation. This antibiotic has been partially purified by gel filtration and further ion-exchange chromatography. Its molecular weight has been estimated close to 2000. The biological activity of this antagonistic substance against the selected indicator strains, Streptococcus faecalis S-47 and Escherichia coli U-9, is bactericidal. The characterization of this substance, initially classified as a bacteriocin, indicates that it is an antibiotic of peptidic nature. The significance of antibiotic occurrence in group D of the genus Streptococcus is also discussed.

Anti-Bacterial Agents↗
PubMed1986

Partial purification of polypeptides activating catalase in Saccharomyces cerevisiae.

In a previous paper the existence of an activating factor for catalase biosynthesis in Saccharomyces cerevisiae was reported. The partial purification of this factor by ammonium sulphate precipitation and chromatography is described. Several fractions with different molecular weights manifesting catalase activity in repressed cultures of S. cerevisiae were obtained, and are discussed.

Catalase↗
PubMed1985

Biochemical and genetic analysis of an acatalasic rho+ mutant of Saccharomyces cerevisiae.

The previously described acatalasic rho+ strain R-6 has been studied in order to determine the type of mutation responsible for its inability to produce catalase. Induction conditions for catalase activity and temperature influence on the behaviour of this strain were assayed. Furthermore, haploid progeny arising from crosses between R-6 and other strains (rho+, rho- and rho0) was examined for catalase levels. From the data obtained a hypothetical interaction between nuclear and mitochondrial genomes in relation to catalase biosynthesis is discussed.

Acatalasia↗
PubMed1985

Production of bacteriocin-like substances by group D streptococci of human origin.

From ninety enterococci of human origin thirty six strains were selected which produced bacteriocin-like substances. The antagonism between them and the resistance to chloroform, heat and pronase were studied. Four types based on such characteristics were established. These groups were different from those described elsewhere in the literature.

Bacteriocins↗
PubMed1984

Cytoplasmic transformation of Saccharomyces cerevisiae using purified mtDNA.

Transformation of cytoplasmic mutants of Saccharomyces cerevisiae proved to be successful using plasmid or intact mitochondria, but not when mtDNA was used as the transforming principle. The sphaeroplasts of two cytoplasmic mutants, respiratory deficient and erythromycin sensitive cells, were transformed using purified mtDNA from respiratory competent or erythromycin resistant donor strains.

Cytoplasm↗
PubMedDate not supplied

Antagonistic action of the bacterium Bacillus licheniformis M-4 toward the amoeba Naegleria fowleri.

Free-living amoebae belonging to the species Naegleria fowleri are known to be the etiological agents for a form of fulminant meningoencephalitis that is generally fatal (primary amoebic meningoencephalitis). In a broad bacterial screening from soil and water we have isolated three strains (M-4, D-13 and A-12) belonging to the species Bacillus licheniformis that have remarkable amoebicidal activity against Naegleria sp. and also against different Gram-positive and Gram-negative bacteria. Physical-chemical characteristics, partial purification and biological activities of a substance produced by the M-4 strain have been investigated. This substance (m-4) is stable at high temperature (up to 100 degrees C) and extremes of pH (2.5-9.5) and also at -20 degrees C for months. Its production is greatly influenced by oxygenation of the cultures and is probably related to the sporulation process of the bacterium. Scanning electron microscope observations reveal that amoebae are lysed after a few minutes contact with m-4.

Amebicides↗