Escherichia cell inactivation

Vorobjeva LI, Altukhova EA, Naumova ES and Abilev SK (1993b) Antimutagenic effect of culture liquid obtained in propionic acid fermentation. Microbiology 62 634-638 Vorobjeva LI, Nikitenko GV, Khodzhaev EY and Ponomareva GM (1993c) Cell extracts of propionic acid bacteria reactivate cells of Escherichia coli inactivated by ultraviolet radiation. Microbiology 62 657-661... 

For example, Escherichia coli have six PBP. PBP-la and -lb, which are transpepfidases, are involved in the synthesis of peptidoglycan. PBP-2 is necessary for supporting the rodshaped form of bacteria. Selective inhibition of this enzyme causes production of other non-rod-shaped forms of bacteria, which eventually undergo lysis. PBP-3 is necessary to form the partition during division. Selective inhibition of this enzyme leads to the formation of a fibrous form of bacteria containing many units of rod-shaped bacteria unable to separate one from another, which results in their death. Various beta-lactam antibiotics have a selective affinity to one or a few PBP. Inactivation of certain PBP (PBP-la, -lb, -2, or -3) causes cell death. Unlike these, inactivaition of low-molecular PBP (PBP-4, -5, and -6) is not lethal to bacteria. 

Lincomycin increased the TEM - 2 fl - lactamase activity of Escherichia Coli (E. Coli) K -12 cells carrying plasmid RP4 at a concentration which slightly inhibited cell growth (70). In a control culture, a lactamase activity reached its maximal level in late log phase, where as when lincomycin was present, a - lactamase activity continued to increase into the stationary phase. Lincomycin (100 pgftnl) inhibited both cell growth and protein synthesis by about 35 % but the activity of stimulated o lactamase was 2.5 fold per ml of culture and about 4 - fold per cell after 20 hours of growth. Inactivation oh b lactamase appeared to be faster when lincomycin was present. This was determined by measuring the decrease ip b lactamase activity when phenethyl alcohol was present to prevent maturation of the enzyme. 

Adaptability of Shewanella oneidensis MRl and Escherichia coli in these experiments indicates that microorganisms can continue to metabolize substrate at pressures far beyond those previously reported [34, 35,41], Although an evolutionary component to the adaptation of microbial communities to temperature and salinity is well known [71], whether there might be any evolutionary component for pressure adaptation is still in question. Shewanella MRl belongs to a genus that contains a number of piezophiles however, E. coli clearly does not. Despite this, there is evidence that exposure of E. coli to pressures up to 800 MPa selects a population of cells less sensitive to pressure inactivation [71]. Furthermore, it is well known that the increase in pressure tolerance is also associated with heat tolerance [71]. 

The epimerizalion of the 7a-hydroxyl group can occur either by intra- or interspecies mechanisms [16]. However, it is difficult to quantitatively assess the degree of 7-hydroxy epimerization in vivo because this transformation competes with the irreversible 7-dehydroxylation of bile acids (Section VI). 7a-HSDH activity has been reported in several genera of intestinal bacteria however, the most complete characterization of this enzyme has been carried out with the enzyme isolated from Escherichia coli [37] and Bacteroides sp. [29,38,39] (Table 2). Both enzymes used both free and conjugated bile acids as substrates, showed alkaline pH optima and lower values for dihydroxy than for trihydroxy bile acids. However, cell extracts prepared from Bacteriodes sp. contained both NAD- and NADP-depen-dent 7 -HSDH activities whereas, extracts from E. coli contained only an NAD-de-pendent enzyme activity. Additional studies showed that the two 7a-HSDH activities detected in Bacteriodes sp. differed in molecular weight, differential heat inactivation and Mn " requirement, suggesting the presence of two distinct enzymes [29]. 

Shiga toxin (Shigella toxin). A toxic protein from Shigella dysenteriae, the pathogen of bacillary dysentery (shigellosis). S. t. inhibits protein biosynthesis (translation) in afflicted cells by inactivation of ribosomes. It appears that certain strains of the normally harmless intestinal bacterium Escherichia coli can form shiga-like toxins after attack by phages. 

Metal-chelate complexes are ubiquitous in biology. Bacteria such as Escherichia coli and Salmonella enterica in your gut excrete the chelator enterobactin (Figure 13-4) to scavenge iron that is essential for their growth. Chelates excreted by microbes to gather iron are called siderophores. The iron-enterobactin complex binds to the bacterial cell surface and is taken into the cell. Iron is then released by enzymatic disassembly of the chelate. To fight bacterial infection, your immune system produces a protein called siderocalin to sequester and inactivate enterobactin. ... 

Endotoxin is a term often used synonymously with lipopolysaccharide (LPS), a major component of the Gram-negative bacterial cell wall. Endotoxin has been estimated to make up between 3 and 4% of the dry weight of Escherichia coli K12. The LPS molecule consists of a Lipid A component anchored in the outer membrane. This is attached to a series of saccharide units specific for different strains of Gram-negative bacteria. LPS is extremely heat stable and needs to be heated to 180 °C for three hours to ensure inactivation. When injected into the bloodstream, it activates the alternative complement pathway and produces a pyrogenic reaction. Studies on laboratory animals have shown that it can produce severe reactions when inhaled in microgram quantities. ... 

Foschino R, Galli A, Ponticelli G and Volonterio G (1988) Propionic bacteria activity at different culture conditions. Ann Microbiol 38 207-222 Fraikin GY, Vorobjeva LI, Khodjaev EY, Pinyaskina EV and Ponomareva GM (1995) Protective and reactivating effects of cell extract of a propionic acid bacterium on UV-inactivated Candida guilliermondii and Escherichia coli. Microbiology 64 640-644 Francalanci F, Davis NK, Fuller JQ, Murfitt D and Leadlay PF (1986) The subunit structure of methylmalonyl-CoA mutase from Propionibacterium shermanii. Biochem J 236 489-494... 

Lee, H., Zhou, B., Liang, W Feng, H Martin, S. E., 2009. Inactivation of Escherichia coli cells with sonication, manosonication, thermosonication, and manothermosonication Microbial responses and kinetics modeling. /. Food Eng. 93 354-364. 

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