RESUMEN
AIMS: The aim of this study was to characterize the inhibitory mechanism in teak (Tectona grandis) bark and to determine its effectiveness against Listeria monocytogenes and methicillin resistant Staphylococcus aureus (MRSA). METHODS AND RESULTS: Methanol extracts of teak bark were inhibitory to L. monocytogenes and MRSA by means of disc diffusion. Gas chromatography-mass spectrometry, and (1)H and (13)C nuclear mass resonance analyses revealed that the inhibitory compound had a molecular weight of 174, and a structure of 5-hydroxy-1,4-naphthalenedione (Juglone). CONCLUSIONS: 5-hydroxy-1,4-naphthalenedione (Juglone) inhibited L. monocytogenes and MRSA. SIGNIFICANCE AND IMPACT OF THE STUDY: A compound in an extract of teak bark was inhibitory to L. monocytogenes and MRSA.
Asunto(s)
Antibacterianos/farmacología , Listeria monocytogenes/efectos de los fármacos , Naftoquinonas/aislamiento & purificación , Pigmentos Biológicos/aislamiento & purificación , Staphylococcus aureus/efectos de los fármacos , Verbenaceae , Cromatografía de Gases y Espectrometría de Masas , Espectroscopía de Resonancia Magnética , Metanol , Resistencia a la Meticilina/genética , Peso Molecular , Naftoquinonas/química , Pigmentos Biológicos/química , Corteza de la Planta/química , Extractos Vegetales/química , Extractos Vegetales/farmacología , Staphylococcus aureus/genética , Verbenaceae/químicaRESUMEN
AIMS: The aim of this study was to improve the selective isolation of Listeria monocytogenes from smoked haddock fillets. METHODS AND RESULTS: Listeria selective agar (LSA)--Oxford formulation was supplemented with 25 microg x ml(-1) of colistin sulphate and 30 microg x ml(-1) of nalidixic acid. Inocula from four smoked haddock fillets produced colonies (approx. 2-13 bacteria x g(-1)), identified as L. monocytogenes, on LSA supplemented with antimicrobial compounds (MLSA). Moreover, there was only negligible evidence of bacteria which were not L. monocytogenes on MLSA. In contrast, LSA supported dense bacterial growth, which was not equated with L. monocytogenes. SIGNIFICANCE AND IMPACT OF THE STUDY: The modified medium permitted the recovery of L. monocytogenes from smoked haddock fillets and reduced the growth of contaminating bacteria.
Asunto(s)
Técnicas Bacteriológicas , Peces/microbiología , Microbiología de Alimentos , Listeria monocytogenes/aislamiento & purificación , Animales , Recuento de Colonia Microbiana , Medios de Cultivo , Tecnología de Alimentos/métodos , Humanos , Listeria monocytogenes/patogenicidad , Listeriosis/etiologíaRESUMEN
The Escherichia coli FtsK protein targets the septum, is essential for cell division and may play a role in DNA partitioning. Computer modelling suggests that the first 180 amino acids of the protein are embedded in the cytoplasmic membrane by up to six transmembrane domains. We demonstrate, using gene fusions, that the N-terminus contains four transmembrane helices that link two periplasmic domains. The first periplasmic domain contains an HEXXH amino acid sequence characteristic of zinc metalloproteases. We show by mutation analysis that the conserved glutamic acid of the HEXXH sequence is essential for FtsK function during septation.
Asunto(s)
Membrana Celular/metabolismo , Escherichia coli , Proteínas de la Membrana/química , Proteínas de la Membrana/metabolismo , Fosfatasa Alcalina/genética , Fosfatasa Alcalina/metabolismo , Secuencias de Aminoácidos , Sustitución de Aminoácidos , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Transporte Biológico , División Celular , Membrana Celular/química , Simulación por Computador , Secuencia Conservada/genética , Escherichia coli/química , Escherichia coli/citología , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli , Proteínas de la Membrana/genética , Mutación , Estructura Terciaria de Proteína , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Temperatura , beta-Galactosidasa/genética , beta-Galactosidasa/metabolismoRESUMEN
Duplication of the Escherichia coli bacterial cell culminates in the formation of a division septum that splits the progenitor cell into two identical daughter cells. Invagination of the cell envelope is brought about by the co-ordinated interplay of a family of septation-specific proteins that act locally at mid-cell at a specific time in the cell cycle. The majority of the genes known to be required for septum formation are found within the large mra cluster located at 2 min on the E. coli genetic map (nucleotides 89552-107474). Examination of the controls exerted on the mra operon shows that E. coli uses an extraordinary range of strategies to co-ordinate the expression of the cell division genes with respect to each other and to the cell cycle.
Asunto(s)
División Celular/genética , Escherichia coli/genética , Proteínas Bacterianas/genética , Escherichia coli/crecimiento & desarrollo , Regulación Bacteriana de la Expresión Génica , Genes Bacterianos/genética , Estadios del Ciclo de Vida , Operón , Regiones Promotoras Genéticas , Transcripción GenéticaRESUMEN
A mutation in a newly discovered Escherichia coli cell division gene, ftsK, causes a temperature-sensitive late-stage block in division but does not affect chromosome replication or segregation. This defect is specifically suppressed by deletion of dacA, coding for the peptidoglycan DD-carboxypeptidase, PBP 5. FtsK is a large polypeptide (147 kDa) consisting of an N-terminal domain with several predicted membrane-spanning regions, a proline-glutamine-rich domain, and a C-terminal domain with a nucleotide-binding consensus sequence. FtsK has extensive sequence identity with a family of proteins from a wide variety of prokaryotes and plasmids. The plasmid proteins are required for intercellular DNA transfer, and one of the bacterial proteins (the SpoIIIE protein of Bacillus subtilis) has also been implicated in intracellular chromosomal DNA transfer.
Asunto(s)
Proteínas Bacterianas , Escherichia coli/crecimiento & desarrollo , Escherichia coli/genética , Genes Bacterianos , Hexosiltransferasas , Proteínas de la Membrana/genética , Peptidil Transferasas , Secuencia de Aminoácidos , Secuencia de Bases , Sitios de Unión , Proteínas Portadoras/genética , División Celular/genética , Mapeo Cromosómico , Secuencia de Consenso , Escherichia coli/citología , Proteínas de Escherichia coli , Prueba de Complementación Genética , Datos de Secuencia Molecular , Muramoilpentapéptido Carboxipeptidasa/genética , Mutación , Proteínas de Unión a las Penicilinas , Peptidoglicano/biosíntesis , Fenotipo , Estructura Secundaria de Proteína , Recombinación Genética , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Supresión GenéticaRESUMEN
A 490-bp DNA segment spanning the junction between the ftsA and ftsZ genes inhibits cell division when present in high copy number. We show that this segment contains an antisense promoter and an antisense transcription terminator which define a new gene, stfZ.
Asunto(s)
Proteínas Bacterianas/biosíntesis , Proteínas del Citoesqueleto , ADN sin Sentido , Proteínas de Escherichia coli , Escherichia coli/genética , Genes Bacterianos , Regiones Promotoras Genéticas , Transcripción Genética , Secuencia de Aminoácidos , Proteínas Bacterianas/genética , Secuencia de Bases , División Celular/genética , Escherichia coli/citología , Datos de Secuencia Molecular , Mapeo RestrictivoRESUMEN
Elevated levels of FtsA protein block cell division at a very early stage, similar to that caused by inhibition of the action of FtsZ. In contrast, overexpression of FtsA and FtsZ together does not block division. A specific ratio of FtsA to FtsZ protein, therefore, is required for cell division.
Asunto(s)
Proteínas Bacterianas/metabolismo , Proteínas del Citoesqueleto , Proteínas de Escherichia coli , Escherichia coli/fisiología , División Celular/fisiología , Escherichia coli/citologíaRESUMEN
The rodA(Sui) mutation allows cell division to take place at 42 degrees C in ftsI23 mutant cells, which produce a thermolabile penicillin-binding protein 3 (PBP3, the septation-specific peptidoglycan transpeptidase). We show here that the mutation in rodA is a single-base change from a glutamine to a chain termination (amber) codon, and that an amber suppressor (supE) present in the strain restores the ability to produce a reduced level of normal RodA protein. The reduced level of RodA is accompanied by an increase in the levels of two other proteins (PBP2 and PBP5) encoded by genes in the rodA operon. We show that an increased level of PBP5 is by itself sufficient to restore cell division to ftsI23 cells at 42 degrees C. Two other treatments were found to restore division capacity to the mutant: an increase in PBP6 (which is a D-alanine carboxypeptidase like PBP5) or suitable concentrations of D-cycloserine. All of the above treatments have the effect of reducing the number of pentapeptide side chains in peptidoglycan and increasing the number of tripeptides. We conclude that the effect of the rodA(Sui) mutation is to indirectly increase the availability of tripeptide side chains, which are used preferentially by PBP3 as acceptors in transpeptidation. A change in the proportions of different kinds of peptide side chain in the peptidoglycan can therefore determine whether cells will divide.
Asunto(s)
Proteínas Bacterianas , Proteínas de Escherichia coli , Escherichia coli/crecimiento & desarrollo , Hexosiltransferasas , Peptidoglicano Glicosiltransferasa , Peptidoglicano/metabolismo , Peptidil Transferasas , Alelos , Secuencia de Bases , Secuencia de Carbohidratos , Proteínas Portadoras/metabolismo , División Celular , Análisis Mutacional de ADN , Escherichia coli/citología , Regulación Bacteriana de la Expresión Génica , Datos de Secuencia Molecular , Muramoilpentapéptido Carboxipeptidasa/metabolismo , Oligonucleótidos , Proteínas de Unión a las Penicilinas , TemperaturaRESUMEN
The essential cell division genes ftsQ and ftsA overlap by 1 bp (A. C. Robinson, D. J. Kenan, G. F. Hatfull, N. F. Sullivan, R. Spiegelberg, and W. D. Donachie. J. Bacteriol. 160:546-555, 1984; Q.-M. Yi, S. Rockenbach, J. E. Ward, and J. F. Lutkenhaus. J. Mol. Biol. 184:399-412, 1985). We have previously shown that ftsA can be expressed from a weak promoter located within the ftsQ gene (Robinson et al., J. Bacteriol. 160:546-555, 1984). We report here the effects on ftsA expression of a series of deletions within ftsQ. We find that two regions upstream of the promoter are important in its expression. When both are present, ftsA is expressed, as is also the case when both are absent. The two regulatory elements (O1 and O2) have 9-bp sequences, of which 8 bp are identical.
Asunto(s)
Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica , Genes Bacterianos , Regiones Promotoras Genéticas , Secuencia de Aminoácidos , Secuencia de Bases , División Celular , Deleción Cromosómica , Clonación Molecular , Datos de Secuencia Molecular , Mapeo Restrictivo , Homología de Secuencia de Ácido NucleicoRESUMEN
The complete Escherichia coli ftsQ coding sequence, together with part of the ftsA coding sequence, has been cloned upstream of the lacZ open reading frame in a lambda-vector (lambda JFL100). Cells which are lysogenic for lambda JFL100 transcribe the cloned lacZ from promoter(s) within the ftsQ and ftsA sequences. The level of beta-galactosidase produced is dependent on growth rate (and/or cell size) and is derepressed in an ftsA-deficient mutant. Transcription during the cell cycle is restricted to the time of cell division.