EFFECT OF TEMPERATURE ON MICROORGANISAMS

rate of reaction increase until optimum temperature is reached. . EFFECT ON GROWTH RATE Temperature effects the rate of reaction, cell metabolism, nutritional requirement by the cell and the biomass concentration. 2 fold increase in the rate of reaction with every 10*C rise in temperature. rate of reaction increase until optimum temperature is reached. .

Rate of reaction and temperature are related by Arrhenius equation

The graph plotted between ln k against 1/T gives a straight line

EFFECT UPON GROWTH RATE WHEN THE TEMPERATURE IS INCREASED BEYOND THE UPPER LIMIT If temperature is increased beyond the upper limit of temperature optima the cell will start dying due to alteration in the metabolic process. This change can be represented by the following equation dx/dt = µx - kx where µ = specific growth rate k = specific death rate

EFFECT UPON NUTRITIONAL REQUIREMENT In case of Klebsiella aerogenes the growth yield decreases with increase in temperature if GLUCOSE is used as a carbon source. growth factor requirement can change with temperature. For e.g. Yersinia pestis requires more amino acids and vitamins for growth at 37*C than at 28*C. E.coli requires glutamic acid and nicotine amide to grow at 44*C. Saccharomyces cerevisiae require pantothenic acid and NaCl for growth at 38*C but not at 30*C.

EFFECT UPON PRODUCT FORMATION The overproduction of riboflavin by Ashbya gosipii requires temperature range between 25-28*C . Although the organism grow well at 37*C but the production of riboflavin is very low.

EFFECT ON MICROBIAL COMPOSITION Temperature effect the RNA , protein and lipid composition of bacteria and yeast by following ways; RNA content of yeast and bacteria increases with the decrease in temperature. Protein content of yeast may up or down with change in temperature and nature of growth limiting substrate. Yeast lipid increase their content of unsaturated fatty acid when the temperature is lowered. Antigenic composition of bacteria varies with temperature. For ex. Certain antigens of Y.pestis necessary for virulence are synthesized during the growth at 37*C but not at 28*C.

THANKYOU