Lysis

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

Triggering of autolytic cell wall degradation in Escherichia coli by beta-lactam antibiotics.

Abstract: A biochemical method was developed to quantitatively compare the effectiveness of beta-lactams in triggering murein degradation (autolysin activity) in Escherichia coli. Bacteria prelabeled in their cell walls with radioactive diaminopimelic acid in growth medium were exposed for 10 min to the antibiotics at the appropriate minimal growth inhibitory concentrations and at multiples of these values, and the rate of cell wall degradation was followed during subsequent penicillin-binding protein (PBP)-1 were the most effective triggers of autolytic wall degradation; beta-lactams selective for PBP-2 were the poorest; and antibiotics preferentially binding to PBP-3 showed intermediate activities. The relative effectiveness of beta-lactams in autolysin triggering was found to parallel the effectiveness of the same drugs in causing rapid loss of viability, culture lysis, and spheroplast formation. Autolysin triggering was suppressed by inhibitors of protein and ribonucleic acid biosynthesis but not by inhibitors of deoxyribonucleic acid synthesis. The beta-lactam-induced cell wall degradation did not seem to involve a direct stimulation of enzyme activity or synthesis of new enzyme molecules, and murein sacculi isolated from cells that had been preexposed to a triggering dose of beta-lactam treatment exhibited the same sensitivity to crude, homologous autolysins as sacculi prepared from untreated control bacteria. On the basis of these observations, mechanisms are considered for the triggering of E. coli autolysins and for the role of autolytic activity in bacterial spheroplast formation, lysis, and death.

Comparative acid tolerances and inhibitor sensitivities of isolated F-ATPases of oral lactic acid bacteria.

Abstract: pH activity profiles and inhibitor sensitivities were compared for membrane ATPases isolated from three oral lactic acid bacteria, Lactobacillus casei ATCC 4646, Streptococcus mutans GS-5, and Streptococcus sanguis NCTC 10904, with, respectively, high, moderate, and low levels of acid tolerance. Membranes containing F1F0 ATPases were isolated by means of salt lysis of cells treated with muralytic enzymes. Membrane-free F1F0 complexes were then isolated from membranes by detergent extraction with Triton X-100 or octylglucoside. Finally, F1 complexes free of the proton-conducting F0 sector were obtained by washing membranes with buffers of low ionic strength. The pH activity profiles of the membrane-associated enzymes reflected the general acid tolerances of the organisms from which they were isolated; for example, pH optima were approximately 5.5, 6.0, and 7.0, respectively, for enzymes from L. casei, S. mutans, and S. sanguis. Roughly similar profiles were found for membrane-free F1F0 complexes, which were stabilized by phospholipids against loss of activity during storage. However, profiles for F1 enzymes were distinctly narrower, indicating that association with F0 and possibly other membrane components enhanced tolerance to both acid and alkaline media. All of the enzymes were found to have similar sensitivities to Al-F complexes, but only F1F0 enzymes were highly sensitive to dicyclohexylcarbodiimide. The procedures described for isolation of membrane-free F1F0 forms of the enzymes from oral lactic acid bacteria will be of use in future studies of the characteristics of the enzymes, especially in studies with liposomes.

A continuous electrical cell lysis device using a low dc voltage for a cell transport and rupture

Abstract: We present a continuous and low voltage cell lysis device in which a width and length of a channel change to generate focused the high electric field strength for cell lysis and the low electric field strength for a transport of samples The previous cell lysis devices acquire the high electric field strength for a cell lysis by applying an ac voltage to a micro-gap between electrodes and require additional pumps or valves for a sample transport However, when we change the width and length of the channel between a pair of external electrodes attached to a dc voltage, we generate both the high electric field strength for a cell lysis and the low electric field strength for an electroosmotic flow The present device therefore performs continuous cell lysis and a sample transport without needing either an additional flow source or an additional process fabricating the electrodes for the micro-gap The experimental study features an orifice whose width and length is 20 times narrower and 175 times shorter than the width and length of a microchannel With an operational voltage of 50 V, the present device generates high electric field strength of 12 kV/cm at the orifice to disrupt cells with 100% lysis rate of red blood cells and low electric field strength of 60 V/cm at the microchannel to generate an electroosmotic flow of 30 ± 9 μm/s In conclusion, the present device is capable of continuous self-pumping cell lysis at a low voltage; thus, it is suitable for a sample pretreatment component of a micro total analysis system or lab-on-a-chip