Inner Membrane Damage Research Articles

Inactivation mechanism of slightly acidic electrolyzed water on Bacillus cereus spores

This study aimed to investigate the inactivation mechanism of Bacillus cereus spores by slightly acidic electrolyzed water (SAEW). Spore inactivation efficacy of SAEW at different available chlorine concentrations (ACC, 20, 60 and 100 mg/L), as well as spore structures change, coat damage, mutagenesis, and inner membrane (IM) properties were examined. The viability of treated spores with lysozyme addition and spore germination induced by germinant was also examined. The results showed that SAEW could reach maximal 5.81 CFU/mL log reduction with ACC of 100 mg/L for 20 min treatment. Scanning and transmission electron photomicrographs indicated that SAEW treatment rendered spore surface ruptured, IM damage and core contents loss. No mutants were generated in survivors of SAEW treated-spores. SAEW significantly weakened spore viability in high salt medium, losing its ability to retain pyridine-2,6-dicarboxylic acid (DPA) at 85 °C. SAEW-treated spores germinated with l-alanine or inosine induction were mostly stained with propidium iodide (PI) but could not recover via lysozyme addition. Furthermore, SAEW treatment inhibited spore germination in the induction of germinant (mixture of l-alanine and inosine or dodecylamine). These findings indicated that SAEW inactivated spore primarily by damaging the spore IM.

Toxic effects of albendazole on adenosine triphosphatase activity and ultrastructure in Eisenia fetida

Veterinary drug may influence soil fauna through manure excretion and subsequent application to agricultural field. The aim of this study is to determine the toxicity of albendozale (ABZ) on the whole earthworm as well as its different regions. Earthworms of Eisenia fetida were exposed to ABZ at 0, 100, 200, 400, and 600 mg kg −1 concentrations; samples were taken at days 2, 7, and 14 exposure for determination of two adenosine triphosphatase (Na +–K +- and Mg 2+-ATPase) activities and survival and growth rate. In addition, the ultrastructure of intestinal epithelium of the earthworms was examined after 14-day exposure. The survival and growth rate were reduced as compared to the control at the two highest concentrations (400 and 600 mg kg −1) after 7- and 14-day exposure. With increasing ABZ concentration, ATPase activities were inhibited significantly in the mid-part after 7 and 14 days and the posterior after 14 days. In particular, the inhibition effect was significant even at the lower treatment levels (100 and 200 mg kg −1) after 14 days. Both ATPase activities, however, were increased significantly in the anterior of earthworms at the highest concentration (600 mg kg −1) after 14 days. Ultrastructure observation in intestine epithelium in three concentrations (control, 100, 600 mg kg −1) revealed that mitochondria and smooth endoplasmic reticulum were damaged with increasing ABZ concentration. Some mitochondria was exhibited the damage of inner membrane at 100 mg kg −1 and vacuolization at 600 mg kg −1, which is consistent with ATPase activities inhibition. The investigation of enzymatic activities in different regions of earthworms and pathological alterations in the intestinal epithelium can provide important information in terms of toxic effects of soil contamination and be used as early warning systems.

How complement kills E. coli. I. Location of the lethal lesion.

We have studied the action of human complement (C) on E. coli membranes. We find, as have others, that C disrupts the outer membrane (OM), allowing the release of periplasmic proteins. In addition, we have found 1) that in the complete absence of lysozyme, C damages the inner membrane (IM), 2) IM damage is different from OM damage in that only small molecules traverse a damaged IM whereas macromolecules traverse damaged OM, 3) IM damage and OM damage occur with identical kinetics and dose response, suggesting that IM and OM damage are closely coupled events, and 4) upon the addition of purified C8 and C9 to the washed cellular intermediate, E. coli C 1-7, both IM and OM are damaged coordinately. These results, taken together, suggest that C damages E. coli membranes by acting at a site contiguous with both membranes. We speculate that C may simultaneously gain access to both membranes by acting at the junctions between IM and OM.