Antje Sieg

Comparative Systems Biology: Lactic Acid Bacteria

Lactic acid bacteria generally use homolactic fermentation for generation of ATP. Here we studied the role of Arginine and Glutamine metabolism on the general physiology of the lactic acid bacteria Streptococcus pyogenes. A deletion mutant of glnA (glutamine synthetase) has been constructed in the S. pyogenes M49 591 background. The glnA mutant strain shows decreased growth in low glutamine and excess glutamate conditions and no growth at all in low glutamine and low glutamate conditions. An arcA ...

S. pyogenes wildetype, an arcA- and a glnA-deletion mutants were grown in CDM-LAB cultures at pH 6.5 and 7.5 and at a growth rate of 0.05

S. pyogenes was grown in C-limited cultures at pH 6.5 and 7.5 and at a growth rate of 0.05 The glnA mutant strain shows decreased growth in low glutamine and excess glutamate conditions and no growth at all in low glutamine and low glutamate conditions. Preliminary results of glucose-limited chemostat cultures indicate a reversion of the pH dependency of the shift from homolactic to more mixed acid fermentation: wild type - lactate/formate ratio at pH 6.5 = 11.8, at pH 7.5 = 2.8 glnA mutant - ...