Physiologische Untersuchungen zur Regulation des Aminosäure-Stoffwechsels von Bacillus licheniformis DSM13

In contrast to his close relatives Bacillus licheniformis is able to grow fermentative under strict anaerobic conditions. Investigations of the anaerobic growth in a defined medium have shown that B. licheniformis DSM13 is able to use both glucose or fructose, but not the chosen pentoses as sole carbon sources. Expression patterns of cells which were grown under aerobic and anaerobic conditions have been compared by DNA microarray analysis. These examinations showed that the genes of the pyruvate formate lyase and the associated activating enzyme are induced under anaerobic conditions. These observations are consistent with the detected increase of formate in culture supernatant. In addition to this, ion chromatography analyses of anaerobically grown cultures showed also an accumulation of 2,3-butanediol, lactate, acetate and glycerol as end-products of fermentation. Besides the availability of oxygen other factors - such as different carbon and nitrogen sources - have an impact on the natural habitat of microorganisms. The investigations in this work have shown that B. licheniformis DSM13 is able to use seven out of 18 proteinogenic amino acids as sole carbon and nitrogen source. A comparison of DNA microarrays, made from cells grown on single L-amino acids, reveals a common group of up-regulated genes. This data could be validated for an assortment of genes via real-time RT-PCR. Ion chromatography analysis was used to investigate the depletion of amino acids from mixtures and products that has been formed during the growth on amino acids. During the growth on a defined medium which imitates the amino acid s composition of soybean protein an accumulation of ammonium, acetate and urea was observed in the culture supernatant. These examinations also displayed an accumulation and consumption of the non-proteinogenic amino acid L-ornithine. Furthermore, first phenotypical characterisations of mutants of a putative methyl citric acid cycle were carried out in B. licheniformis.