Cell structure degradation inEscherichia coliandThermococcussp. strain Tc-1-95 associated with thermal death resulting from brief heat treatment

Abstract

The thermal death mechanism of microorganisms when heated at lethally high temperatures is still not fully understood. In this study, we examined the relationship between thermal death and degradation of the cell structure in the mesophilic bacterium Escherichia coli strain W3110 and the hyperthermophilic archaeon Thermococcus sp. strain Tc-1-95. By heating the microorganisms at lethally high temperatures only briefly (1.5 s duration) in a flow-type apparatus, we studied the microbial cells at very early and critical stages of the thermal death process. For E. coli, it was found that the loss of viability was not associated with thermal damage to the cell envelope. Deformation of the nucleoid was observed. These results suggest that the thermal death of E. coli is attributed to thermal denaturation or degradation of cytoplasmic molecules. On the other hand, the thermal death of Thermococcus sp. strain Tc-1-95 was strongly associated with rupture of the cell envelope. Furthermore, massive deformation of the S-layer with lethal thermal stress was observed. These results demonstrate that the thermal deaths of the two microorganisms investigated proceed via very different mechanisms. The contrast can be attributed to the difference in their cell envelope structures.

In situ microscopic observation of chitin and fungal cells with chitinous cell walls in hydrothermal conditions

“…Thermophily in known fungi is usually not as extreme as prokaryotes 37 , but presence of hyperthermophilic eukaryotes, which may survive brief exposure to temperatures above 190 °C, is inferred in hydrothermal sediment 38 . Inactivation of microorganisms after brief exposure to lethally high temperature occurs via rupture of the cell envelope 39 , and it is likely that the chitinous cell envelope of fungal cells is robust enough to withstand brief exposure to 190 °C.…”

Effect of Turning Frequency on the Survival of Fecal Indicator Microorganisms during Aerobic Composting of Fecal Sludge with Sawdust

“…This drop may be attributed to the fact that the thermal death of different microorganisms occurs through various mechanisms. For E-coli, its thermal destruction occurs by deformation of the nucleoids while for other microorganisms, thermal destruction occurs by rupture of the cell envelope [54]. The different mechanisms for thermal death imply that the rate of death will be different for the different microorganisms.…”

Applications of Microwave Energy in Medicine

“…In Staphylococcus aureus the cell loses D-alanine from the teichoic acidswhich results in the cell's inability to perform certain metabolic processes. Proteins are directly damaged by heating as the bonds holding them together are destroyed; this can damage enzymes and structural proteins that result in a loss of functionality [17][18][19]. Heat can also affect the integrity of many cellular aspects causing the cell to become inactive; in Gram negative bacteria the outer membrane is damaged by heat and becomes sensitive to lysozyme and hydrophobic antibiotics [20].…”