Studies on the sulfur nutrition of Lactobacillus arabinosus.

The sulfur nutrition of microorganisms has been studied by many investigators. Early workers were interested essentially in sulfur compounds used by organisms as sulfur sources. Recent efforts have been directed toward the determination of mechanisms involved in the utilization of sulfur compounds. Results of investigations by Horowitz (1947), Lampen et al. (1947), Teas et al. (1948), Binkley and Hudgins (1953), and Wijesundera and Woods (1953) have led to the following proposed mechanism. Sulfate sulfur is reduced to sulfide, which is converted to organic sulfur, probably in the form of cysteine. At this stage the cysteine can condense with a 4-carbon compound, homoserine, to form the asymmetric thio ether, cystathionine. The cleavage of this compound forms homocysteine, which can then be methylated to form methionine. In this investigation, conditions for the growth of Lactobacilus arabinosus were studied when various sulfur compounds were supplied as sulfur sources. Further, efforts were made to demonstrate the mechanism of sulfur utilization.