ABSTRACT
Sulfur is essential for microbial growth because it is a constituent of cysteine, methionine, iron-sulfur proteins, coenzyme A, lipoic acid, mycothiol, biotin, thiamine, and tRNA. Cysteine and methionine are the predominant sulfur-containing molecules within the cell. Usually, only oxidized sulfur compounds like sulfate are available for the cell, which have to be reduced to the level of sulfide before incorporation into the organic sulfur compounds (assimilatory reduction). Some organisms use inorganic sulfur compounds for energy metabolism. However, energygenerating metabolic processes involving sulfur, such as dissimilatory reduction and oxidation, have not been reported for Corynebacterium species, and there is also no indication from the genome sequence that such processes exist in C. glutamicum and C. efficiens. In this chapter, the present knowledge on the biosynthesis pathways of the sulfur-containing amino acids cysteine and methionine in C. glutamicum will be summarized, including the sulfur assimilation pathway as derived from genome sequence analysis. In addition, the regulatory mechanisms governing the expression of genes involved in cysteine and methionine biosynthesis will be presented.
