Since anaerobic bacteria cannot take advantage of citrate oxidation through the reactions of the tricarboxylic acid cycle special enzymes are needed for its fermentation. The activity of citrate lyase (the key enzyme of the citrate fermentation pathway) is in most cases strictly controlled by acetylation/deacetylation and configurational changes. In order to efficiently regulate citrate metabolism the activity of various regulatory enzymes, that modulate citrate lyase activity, are in turn under stringent control. Covalent modification by phosphorylation/dephosphorylation and electron transport dependent processes are some of the regulatory mechanisms that are here involved. L-Glutamate, which signals the availability of citrate, plays a central role in the regulation of citrate metabolism by influencing the enzymes that are acting in a complex cascade system.