Calorimetric aspects of the heat activation of spores of Phycomyces blakesleeanus

Verbeke, Marc N.; Cauwelaert, F.H. Van; Jadot, R.

doi:10.1016/0006-291x(81)91198-0

Cited by 7 publications

(4 citation statements)

References 6 publications

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“…The technique has been used to study thermotropic phase changes in membrane lipids (McElhaney, 1982(McElhaney, , 1986), activation and germination of spores (Maeda et al, 1974;Verbeke et al, 1981), and the state of water in bacterial cells (Gonda & Koga, 1973). Verrips & Kwast (1977) examined vegetative cells of Citrobacter freundii by DSC and obtained thermograms consisting of eight unidentified endothermic peaks.…”

Section: ;mentioning

confidence: 99%

Thermal denaturation of whole cells and cell components of Escherichia coli examined by differential scanning calorimetry

Mackey¹,

Miles²,

Parsons³

et al. 1991

Journal of General Microbiology

135

126

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Thermograms of whole cells of Escherichia coli obtained by differential Scanning calorimetry contained ten main peaks (denoted& l, m, , m2, m3, n,p, q, r and s) occurring at temperatures of approximately 25,54,61,71,76,81, 95, 105, 118 and 124 "C, respectively. After cooling to 5 "C and reheating, peaks denoted fr, m, and p r were observed at 23,73 and 94 "C, respectively. By examining thermograms of different cell fractions we have identified the following thermal denaturation events. During primary heating there is a broad endotherm ( f ) beginning below 20 "C and extending to just above 40 "C that is caused by melting of membrane lipids. Superimposed on'this is an exothermic process associated with a change of state of the peptidoglycan. The first irreversible denaturation event occurs just above 47 "C, associated with the onset of denaturation of the 30s ribosomal subunit and soluble cytoplasmic proteins. Ribosome melting is a complex process occurring between 47 and 85 "C and is characterized by peaks m, , m2 and n. Peak m3 at 75-76 "C is of unknown identity but may possibly represent melting of tRNA.Peak p at 95 "C results from melting of a portion of the cellular DNA combined with denaturation of a cell wall component. Peak q at 105 "C is multicomponent and may be caused by melting of a different region of DNA together with denaturation of another cell wall component. The complex events denoted r and s at 118 and 125 "C, respectively, are associated with denaturation of a component of the cell envelope, and possibly also of DNA.Following cooling and reheating there is a broad endotherm with a maximum at 23 "C caused by remelting of membrane lipid and a very broad endotherm extending between 40 and lo0 "C caused by the remelting of ribosomal RNA. Peak p , at 94 "C is caused by the melting of reannealed DNA. Additional features not appearing in whole cells were evident in some cell fractions. These observations should allow us to distinguish events that may lead to loss of viability from those that do not. IntroductionThe inactivation of micro-organisms by heat forms the basis of large sections of the food and pharmaceutical industries. Not surprisingly, the factors affecting microbial heat-resistance and the nature of heat damage are of continuing practical and scientific concern.The mechanisms of thermal inactivation of microorganism have commonly been investigated by using biochemical methods to examine the effect of heat on particular cell structures or processes. Membranes, nucleic acids and certain enzymes have all been identified as cellular sites of heat injury and, in some cases, information is available on the molecular nature of heat damage (Tomlins & Ordal, 1976 Gould, 1989). However, despite this large body of information, we still do not understand precisely how micro-organisms are killed by heat. 1984;Differential scanning calorimetry (DSC) enables denaturation and other thermal processes that occur when samples are heated to be detected and recorded as a time-temperature sequence. The techn...

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Section: ;mentioning

confidence: 99%

Thermal denaturation of whole cells and cell components of Escherichia coli examined by differential scanning calorimetry

Mackey¹,

Miles²,

Parsons³

et al. 1991

Journal of General Microbiology

135

126

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“…Neither glucose nor uncoupling agents affect cAMP content or germination in Phycomyces spores. Whether the calorimetric peaks observed during heat activation [31,84] are related to protein denaturation, remains unknown. Whether the calorimetric peaks observed during heat activation [31,84] are related to protein denaturation, remains unknown.…”

Section: Control Of Ca Mp Concentrationmentioning

confidence: 99%

“…The result is not affected by the presence of cycloheximide [12], azide [22] or anaerobic conditions [30] during treatment. The activation curves can be shifted towards higher temperatures by 2H20 [31] or by pressures up to 5 × 107 Pa [32]. Activation temperatures are lowered by pressures in excess of 10 s Pa or by the addition of certain alcohols [32].…”

Section: Breaking Of Dormancymentioning

confidence: 99%

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Biochemistry of spore germination in Phycomyces

Laere¹

1986

FEMS Microbiology Letters

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The constitutionally dormant spores of Phycomyces blakesleeanus can be activated by heat shock or treatment with several monocarboxylic acids. Activation is followed first by a general stimulation of metabolism, e.g. respiration, protein‐, RNA‐ and cell‐wall synthesis, and subsequently by nuclear division and germ‐tube emergence. Initial germination is not dependent on RNA synthesis and can even start without protein synthesis. The first common effect of different activating treatments is a transient rise in cyclic AMP (cAMP) content, caused by a change in phosphodiesterase activity after heat activation, and by unknown factors during activation by acids. cAMP transiently activates trehalase and glycerol‐3‐phosphatase in the spores. The activation of these enzymes causes a quick turnover of trehalose into glycerol. During the same period, the water status of the cells is altered so dramatically that perhaps this may explain at least part of the stimulation of metabolism in the germinating spore.

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The role of water in the activation ofPhycomyces blakesleeanus sporangiospores

Verbeke

Laere

1986

Experimental Mycology

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Calorimetric aspects of the heat activation of spores of Phycomyces blakesleeanus

Cited by 7 publications

References 6 publications

Thermal denaturation of whole cells and cell components of Escherichia coli examined by differential scanning calorimetry

Thermal denaturation of whole cells and cell components of Escherichia coli examined by differential scanning calorimetry

Biochemistry of spore germination in Phycomyces

The role of water in the activation ofPhycomyces blakesleeanus sporangiospores

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