Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “BACTERIOLYSIS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed1996

Differentiation-associated antimicrobial functions in human colon adenocarcinoma cell lines.

We report that the enterocytic cells of the HT-29 glc-/+ cell subpopulation strongly expressed two antimicrobial enzymes: the lysozyme and alpha1-antitrypsin. Moreover, we found that 20 to 30% of these cells expressed positive immunoreactivity using the mAbs directed against the gut porcine PR-39 and cecropin P1 antimicrobial peptides, but did not express immunreactivity against the human antimicrobial polymorphonucleated neutrophil-associated HNP 1-3 defensin and the Xenopus skin magainin. The HT-29 glc-/+ cell subpopulation develops bacteriolytic activity against the enterovirulent diffusely adhering C1845 Escherichia coli characterized by dramatic alterations of the bacterial cell, suggesting lysis, and bacterial death. In contrast, no expression of immunoreactivity against the antimicrobial peptides and no C1845 bacterial alteration were found in the cultured human embryonic undifferentiated INT407 cells and the colon adenocarcinoma T84 crypt cells. The development of the bacterial alteration and the expression of the antimicrobial components were examined as a function of the cell differentiation using the Caco-2 cell line which spontaneously differentiates in culture. We found that the bacterial alteration and the expression of the PR-39 immunoreactivity are differentiation-associated events. Altogether, our results suggest that in the intestine the enterocytes could develop antimicrobial defenses participating in the protection of the gut epithelium against enterovirulent microorganisms.

Bacterial Adhesion↗
PubMed1998

The entericidin locus of Escherichia coli and its implications for programmed bacterial cell death.

Antidote/toxin gene pairs known as "addiction modules" can maintain plasmids in bacterial populations by means of post-segregational killing. However, several chromosome-encoded addiction modules may provide an entirely distinct function in the programmed cell death of moribund subpopulations under starvation conditions. We now report a novel chromosomal bacteriolytic module of Escherichia coli called the entericidin locus, which is activated in stationary phase under high osmolarity conditions by sigmaS and simultaneously repressed by the osmoregulatory EnvZ/OmpR signal transduction pathway. The entericidin locus encodes tandem paralogous genes (ecnAB) and directs the synthesis of two small cell-envelope lipoproteins. An attenuator precedes ecnA and an ompR-sensitive sigmaS promoter governs expression of ecnB. The entericidin A lipoprotein is an antidote to the bacteriolytic lipoprotein entericidin B. The entericidins are predicted to adopt amphipathic alpha-helical structures and to reciprocally modulate membrane stability. The entericidin locus is not present on any known plasmids, but is conserved in the homologous region of the Citrobacter freundii chromosome. Although the cloned C. freundii entericidin locus is expressed in E. coli independently of ompR, it carries an additional ompR-like gene called ecnR. The organization of the entericidin locus as a chromosomal antidote/toxin gene pair, which is regulated by both positive and negative osmotic signals during starvation, is consistent with an emerging paradigm of programmed bacterial cell death.

Amino Acid Sequence↗
PubMed1999

Bacteriophage lambda: the untold story.

The study of bacteriophage lambda has provided key insights into fundamental biological processes. This review recalls some highlights in the history of lambda research, and relates how simple (but elegant) experiments yielded major scientific breakthroughs. What we know about recombination, gene regulation, and protein folding, for example, derives in large part from bacteriophage lambda genetics. Lambda not only represents a model system of scientific logic in a technology-driven age, but continues to reveal new principles of molecular biology.

Bacteriolysis↗
PubMed2000

Genomic sequence and analysis of the atypical temperate bacteriophage N15.

N15 is a temperate bacteriophage that forms stable lysogens in Escherichia coli. While its virion is morphologically very similar to phage lambda and its close relatives, it is unusual in that the prophage form replicates autonomously as a linear DNA molecule with closed hairpin telomeres. Here, we describe the genomic architecture of N15, and its global pattern of gene expression, which reveal that N15 contains several plasmid-derived genes that are expressed in N15 lysogens. The tel site, at which processing occurs to form the prophage ends is close to the center of the genome in a similar location to that occupied by the attachment site, attP, in lambda and its relatives and defines the boundary between the left and right arms. The left arm contains a long cluster of structural genes that are closely related to those of the lambda-like phages, but also includes homologs of umuD', which encodes a DNA polymerase accessory protein, and the plasmid partition genes, sopA and sopB. The right arm likewise contains a mixture of apparently phage- and plasmid-derived genes including genes encoding plasmid replication functions, a phage repressor, a transcription antitermination system, as well as phage host cell lysis genes and two putative DNA methylases. The unique structure of the N15 genome suggests that the large global population of bacteriophages may exhibit a much greater diversity of genomic architectures than was previously recognized.

Bacteriolysis↗
PubMed1999

Bacterial lysis by phage--a theoretical model.

The similarity to materials corrosion is invoked to develop a model for phage-infected bacterial lysis based on the statistics of extremes. The importance of cell size, envelope thickness and lysozyme eclipse time on the final probability distribution of lysis is considered. Experiments are suggested to test the model.

Animals↗
PubMed1998

Hepatitis C virus E1 protein induces modification of membrane permeability in E. coli cells.

The E1 gene of hepatitis C virus (HCV) has been cloned and expressed in BL21(DE3)pLys Escherichia coli strain by pET3a vector to analyze changes in membrane permeability produced by this protein. We showed that the expression of E1 (aa 192-383), as well as of two C-terminal fragments (aa 331-383 and aa 341-383) corresponding to the transmembrane (TM) region of this protein, induced a rapid lysis of cells. On the contrary, the expression of a mutant of E1 (aa 192-340), lacking the last 40 amino acids, did not cause cell lysis. The analysis of permeability changes revealed that modification of membrane permeability to several compounds were observed only in clones expressing E1 and C-terminal fragments, while the synthesis of the C-terminal-deleted mutant had little or no effect on permeability. These findings demonstrate that the TM domain of E1 protein has membrane-active properties that may be involved in some aspects of virus-cell interaction.

Bacteriolysis↗
PubMed1998

Accessory genes in the darA operon of bacteriophage P1 affect antirestriction function, generalized transduction, head morphogenesis, and host cell lysis.

Bacteriophage P1 mutants with the 8.86-kb region between the invertible C-segment and the residential IS1 element deleted from their genome are still able to grow vegetatively and to lysogenize stably, but they show several phenotypic changes. These include the formation of minute plaques due to delayed cell lysis, the abundant production of small-headed particles, a lack of specific internal head proteins, sensitivity to type I host restriction systems, and altered properties to mediate generalized transduction. In the wild-type P1 genome, the accessory genes encoding the functions responsible for these characters are localized in the darA operon that is transcribed late during phage production. We determined the relevant DNA sequence that is located between the C-segment and the IS1 element and contains the cin gene for C-inversion and the accessory genes in the darA operon. The darA operon carries eight open reading frames that could encode polypeptides containing >100 amino acids. Genetic studies indicate that some of these open reading frames, in particular those residing in the 5' part of the darA operon, are responsible for the phenotypic traits identified. The study may contribute to a better comprehension of phage morphogenesis, of the mobilization of host DNA into phage particles mediating generalized transduction, of the defense against type I restriction systems, and of the control of host lysis.

Bacteriolysis↗
PubMed1999

Complete genomic sequence of the lytic bacteriophage DT1 of Streptococcus thermophilus.

Streptococcus thermophilus lytic bacteriophage DT1, isolated from a mozzarella whey, was characterized at the microbiological and molecular levels. Phage DT1 had an isometric head of 60 nm and a noncontractile tail of 260 x 8 nm, two major structural proteins of 26 and 32 kDa, and a linear double-stranded DNA genome with cohesive ends at its extremities. The host range of phage DT1 was limited to 5 of the 21 S. thermophilus strains tested. Using S. thermophilus SMQ-301 as a host, phage DT1 had a burst size of 276 +/- 36 and a latent period of 25 min. The genome of phage DT1 contained 34,820 bp with a GC content of 39.1%. Forty-six open reading frames (ORFs) of more than 40 codons were found and putative functions were assigned to 20 ORFs, mostly in the late region of phage DT1. Comparative genomic analysis of DT1 with the completely sequenced S. thermophilus temperate phage O1205 revealed two large homologous regions interspersed by two heterologous segments. The homologous regions consisted of the early replication genes, the late morphogenesis genes, and the lysis cassette. The divergent segments contained the DNA packaging machinery, the major structural proteins, and remnants of a lysogeny module.

Amino Acid Sequence↗
PubMed1999

Gene 61.3 of bacteriophage T4 is the spackle gene.

The bacteriophage T4 e gene encodes lysozyme (e-lysozyme), which releases progeny phage after normal infection of Escherichia coli cells. A mutation in the spackle gene suppresses the defect in e-lysozyme (Emrich, 1968). The spackle gene was mapped between genes 41 and 61, but its precise location has not previously been determined. In the current study, we constructed an amber mutant of gene 61.3, amST14, by site-directed mutagenesis. The gene 61.3 mutant shares phenotypes with spackle mutants: The amST14 mutant forms large plaques with sharp edges and exhibits truncated lysis inhibition, and furthermore, the mutation can suppress the defect in e-lysozyme activity. In addition, cloned gene 61.3 can rescue (by homologous recombination) as well as complement the S12 mutation in the spackle gene. These results strongly suggest that gene 61.3 is the spackle gene. Indeed, the S12 mutant has one base deletion of five in a consecutive A tract in the gene 61.3 coding region, substituting an unrelated 6-amino acid sequence for the 9 C-terminal amino acids in the gene 61.3 protein. The gene 61.3 protein is predicted to localize in the periplasmic space after cleavage of a signal sequence.

Amino Acid Sequence↗
PubMed1999

Regulation of bacteriophage lambda development by guanosine 5'-diphosphate-3'-diphosphate.

On infection of its host, Escherichia coli, bacteriophage lambda can follow one of two alternative developmental pathways: lytic or lysogenic. Here we demonstrate that the "lysis-versus-lysogenization" decision is influenced by guanosine tetraphosphate (ppGpp), a nucleotide that is synthesized in E. coli cells in response to amino acid or carbon source starvation. We found that the efficiency of lysogenization is the highest at ppGpp concentrations somewhat higher than the basal level; too low and too high levels of ppGpp result in less efficient lysogenization. Maintenance of the already integrated lambda prophage and phage lytic development were not significantly influenced in the host lacking ppGpp. We found that the level of HflB/FtsH protease, responsible for degradation of the CII protein, an activator of "lysogenic" promoters, depends on ppGpp concentration. The highest levels of HflB/FtsH was found in bacteria lacking ppGpp and in cells bearing increased concentrations of this nucleotide. Using lacZ fusions, we investigated the influence of ppGpp on activities of lambda promoters important at the stage of the lysis-versus-lysogenization decision. We found that each promoter is regulated differentially in response to the abundance of ppGpp. Moreover, our results suggest that the cAMP level may influence ppGpp concentration in cells. The mechanism of the ppGpp-mediated control of lambda development at the stage of the lysis-versus-lysogenization decision may be explained on the basis of differential influence of guanosine tetraphosphate on activities of p(L), p(R), p(E), p(I), and p(aQ) promoters and by dependence of HflB/FtsH protease level on ppGpp concentration.

ATP-Dependent Proteases↗
PubMed1977

Lysosomal enzymes of phagocytic cells as humoral mediators of inflammation: modulation of their release by cyclic nucleotides.

The origin of lysosomes in phagocytic cells is described. Studies on their characterization by both morphological and biochemical methods are summarized. Lysosomal enzymes of both polymorphonuclear leukocytes and macrophages can be released by exocytosis in response to a variety of inflammatory stimuli. This response is modulated by cyclic nucleotides. In the polymorphonuclear leukocyte cAMP inhibits enzyme release while cGMP enhances release; the effects of the cyclic nucleotides are less clear in the macrophage. The possible involvement of microtubules and microfilaments in the release process is discussed.

Bacteriolysis↗
PubMed1996

Bacterial lysozymes.

Lysozymes are found in many bacteria that are surrounded by a murein-(peptidoglycan) containing cell wall. Their physiological function for the bacteria is still a matter of debate. On the one hand they can autolyse the cell, on the other hand they may have an essential role during enlargement and division of the cell wall by the controlled splitting of bonds in the murein sacculus. Both beta-1.4-N,6-O-diacetylmuramidase and beta-1.4-N-acetylmuramidases have been described in bacteria. In some cases a modular design of the enzyme has been demonstrated with a catalytic domain and a substrate (murein)-binding and recognition domain consisting of repeated motifs.

Bacteria↗