Growth models of Thermus aquaticus and Thermus scotoductus

Abstract

BABÁK, L., ŠUPINOVÁ, P., BURDYCHOVÁ, R.: Growth models of Thermus aquaticus and Thermus scotoductus. Acta univ. agric. et silvic. Mendel. Brun., 2012, LX, No. 5, pp. 19-26 Members of the genus Thermus family are signifi ant producers of secondary metabolites, which are very commonly used in industry. Beside the productivity, it is also important to study the growth curve of each strain. The mathematical models which are commonly used to describe behavior of microbial strains under diff erent physical and chemical conditions can reduce measured data. In this study, the mathematical models which describe only the microbial count were used. For analysis, Verhulst model, von Bertalanff y model and Richards model were chosen. During the cultivation of Thermus aquaticus and Thermus scotoductus strains, optical density (OD) and concentration of microorganisms were measured. The mathematical models were fi tted to experimental data. The fi tting was made in program MATLAB. The coeffi cients of models and statistical evaluation of goodness of fi t of models were identifi ed from mathematical analyses. Graphs of individual models were plotted with prediction bounds. 95% confi dence levels were used to statistical evaluation of goodness of fi t of models and prediction bounds. Richards model was evaluted as the most corresponding with experimental data. Similar results were reached using Verhulst model. Von Bertalanff y model was not coresponded with experimental data. growth models, bacterial growth, Thermus aquaticus, Thermus scotoductusThe fi rst discovery of representatives of the genus Thermus have been a stimulus for a detailed study of physiology of thermophilic bacteria. Its discovery was very simple, because the cultivation is very easy. It was used salt synthetic medium that proved suitable for the growth of algae found in hot springs (BROCK, 1978). Representatives of the genus Thermus are Gram-negative aerobic bacteria, however some newly isolated species grow in anaerobic environments where nitrates used as the fi nal electron acceptors. This genus does not form endospores (BALKWILL et al., 2004). The morphology of the organism is largely infl uenced by temperature and growth phase. The organism is usually present in fi bers when the temperature is above 75 °C. The fi bers are formed only in the stationary growth phase culture at 65 to 70 °C (BROCK, 1978).Members of the genus Thermus family are used to produce thermophilic compounds, especially enzymes, such as Taq polymerase (DNA polymerase), serine proteases, glucosidases, pullulanase (ČEJKOVÁ, 2009). Because are these products mostly secondary metabolites, it is necessary to know the growth characteristics of microorganisms that can also be described by mathematical models. Taq is frequently used in polymerase chain reaction (PCR).Mathematical models are used to describe the behavior of microorganisms under diff erent physical or chemical conditions such as temperature, pH and water activity. In order to build these models, growth has to be measur...

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