Lysis

About: Lysis is a research topic. Over the lifetime, 6072 publications have been published within this topic receiving 216978 citations.

Structure and composition of resistant layers in bacterial spore coats.

Abstract: SUMMARY: Treatment with mercaptoethanol caused spores of various bacteria to become sensitive to lysis by lysozyme, a spore enzyme and hydrogen peroxide; further treatment with alkali caused greater sensitization to these lytic agents. Alkali removed a protein from the outer coats of mercaptoethanol-treated spores. The protein from Bacillus cereus, B. coagulans and Clostridium sporogenes contained high levels of acidic and basic amino acids; that from B. coagulans contained a high proportion (over 7% of its residues) of tyrosine. Electron microscopy of thin section and freeze-etch samples showed that the alkali-soluble protein contributed to a striking banding pattern containing 57 A spaced fibres on the outer surface of B. coagulans spores. This layer may function as a protection against the enzymes of potential predators.

The response of Escherichia coli to ciprofloxacin and norfloxacin

Abstract: Summary The action of ciprofloxacin and norfloxacin on two strains of Escherichia coli was studied by diverse methods including electronmicroscopy, viable counting and continuous turbidimetric monitoring. During the first few hours of exposure to inhibitory concentrations of the drugs, the opacity of bacterial cultures continued to increase for a period that was inversely proportional to the drug concentration. This change corresponded to the appearance of filamentous bacteria, swollen forms and some lysis. There was subsequently a gradual drop in opacity during which extensive lysis occurred. As judged by viable counts of bacteria washed free of drug, cell death occurred within 30 min of first exposure to the drugs and continued over a 3-h period. Ultrastructure studies demonstrated that lysis was preceded by the formation of vacuoles, predominantly at the poles of the cells. At these sites, breaks in the cell walls eventually occurred, resulting in extrusion of the cytoplasmic contents.

Adsorption of pure and dirty bacterial DNA on clay minerals and their transformation frequency

Abstract: Several studies have investigated the adsorption of pure DNA on soil particles and its transformation ability. However, the presence of not purified (dirty) rather than pure DNA is more common in the extracellular soil environment. For this reason, we have investigated the adsorption and binding of dirty DNA on montmorillonite (M) and kaolinite (K) and their transforming ability in comparison to pure DNA. After lysis of Bacillus subtilis cells, induced by KCl, dirty DNA was characterized by the presence of cellular wall debris (cwd) and other constitutional organic components (coc). The dirty DNA was then divided into two fractions, one with cellular wall debris (DNA +cwd) and the other without cellular wall debris (DNA −cwd). B. subtilis BD 1512 (Cmr) and BD 170 (Cms) were selected as donor and recipient bacteria, respectively, for adsorption and transformation studies. Both cwd and coc seem to facilitate the adsorption of DNA to clay minerals, whereas only cwd promote the DNA binding on clays, protecting also the DNA fragments below 400 bp against nucleases. Both dirty DNA fractions adsorbed and bound on clay minerals were able to transform competent cells.

Phage-Antibiotic Synergy via Delayed Lysis.

Abstract: When phages infect bacteria cultured in the presence of sublethal doses of antibiotics, the sizes of the phage plaques are significantly increased. This phenomenon is known as phage-antibiotic synergy (PAS). In this study, the observation of PAS was extended to a wide variety of bacterium-phage pairs using different classes of antibiotics. PAS was shown in both Gram-positive and Gram-negative bacteria. Cells stressed with β-lactam antibiotics filamented or swelled extensively, resulting in an increase in phage production. PAS was also sometimes observed in the presence of other classes of antibiotics with or without bacterial filamentation. The addition of antibiotics induced recA expression in various bacteria, but a recA deletion mutant strain of Escherichia coli also showed filamentation and PAS in the presence of quinolone antibiotics. The phage adsorption efficiency did not change in the presence of the antibiotics when the cell surfaces were enlarged as they filamented. Increases in the production of phage DNA and mRNAs encoding phage proteins were observed in these cells, with only a limited increase in protein production. The data suggest that PAS is the product of a prolonged period of particle assembly due to delayed lysis. The increase in the cell surface area far exceeded the increase in phage holin production in the filamented host cells, leading to a relatively limited availability of intracellular holins for aggregating and forming holes in the host membrane. Reactive oxygen species (ROS) stress also led to an increased production of phages, while heat stress resulted in only a limited increase in phage production.IMPORTANCE Phage-antibiotic synergy (PAS) has been reported for a decade, but the underlying mechanism has never been vigorously investigated. This study shows the presence of PAS from a variety of phage-bacterium-antibiotic pairings. We show that increased phage production resulted directly from a lysis delay caused by the relative shortage of holin in filamented bacterial hosts in the presence of sublethal concentrations of stress-inducing substances, such as antibiotics and reactive oxygen species (ROS).

Characterization of a New Sigma-K-Dependent Peptidoglycan Hydrolase Gene That Plays a Role in Bacillus subtilis Mother Cell Lysis

Abstract: Bacillus subtilis produces a 30-kDa peptidoglycan hydrolase, CwlH, during the late sporulation phase. Disruption of yqeE led to a complete loss of CwlH formation, indicating the identity of yqeE with cwlH. Northern blot analysis of cwlH revealed a 0.8-kb transcript after 6 to 7.5 h for the wild-type strain but not for the ςF, ςE, ςG, and ςK mutants. Expression of the ςK-dependent cwlH gene depended on gerE. Primer extension analysis also suggested that cwlH is transcribed by EςK RNA polymerase. CwlH produced in Escherichia coli harboring a cwlH plasmid is an N-acetylmuramoyl-l-alanine amidase (EC 3.5.1.28) and exhibited an optimum pH of 7.0 and high-level binding to the B. subtilis cell wall. A cwlC cwlH double mutation led to a lack of mother cell lysis even after 7 days of incubation in DSM medium, but the single mutations led to mother cell lysis after 24 h.