Galactosamine inhibition of protein synthesis in Bacteroides thetaiotaomicron

Abstract

Galactosamine does not support growth of Bacteroides thetaiotaomicron. Despite this, galactosamine was more effective than utilizable carbohydrates such as glucose in preventing synthesis of the inducible enzymes alpha-glucosidase and chondroitin lyase. Galactosamine also stopped overall protein synthesis. By contrast glucose and other utilizable carbohydrates increased the rate of protein synthesis. Addition of glucose to bacteria which had been treated with galactosamine restored the ability of the bacteria to synthesize protein and to produce inducible enzymes. Moreover, when B. thetaiotaomicron was incubated with [1-14C]galactosamine for 30 min at 37 degrees C, about one-third of the label which was taken up by the cells comigrated with glucosamine-6-phosphate on a thin-layer chromatogram. Thus galactosamine appears to be phosphorylated by the bacteria. After 2 h incubation of the bacteria with [1-14C]galactosamine, there was a significant increase in the amount of label which could be extracted from acidified extracellular fluid with diethyl ether. This indicates that galactosamine can be metabolized to the level of volatile fatty acids. The rate of uptake of galactosamine and the amount of labeled fatty acids produced from galactosamine were both much lower than the values obtained when glucosamine was the substrate. Thus, although some metabolism of galactosamine occurs, the rate is apparently too slow to enable galactosamine to support growth of B. thetaiotaomicron.

BACTEROIDES OF THE HUMAN LOWER INTESTINAL TRACT

“…Growth yields and maintenance coefficients for colonic Bacteroides growing in continuous culture on polysaccharides have only been determined for one species, B. thetaiotaomicron, and only for two polysaccharides, chondroitin sulfate and arabinogalactan (84,90). In both cases yields were comparable to yields obtained when bacteria were grown on component monosaccharides.…”

“…In both cases yields were comparable to yields obtained when bacteria were grown on component monosaccharides. High specific activities of a particular polysaccharidase are detected only when the organism is grown on the appropriate polysaccharide (85,87,92). Rev.…”

“…Maintenance coefficients were somewhat higher for growth on polysaccharides than for growth on component monosaccharides, but the bacteria were still able Annu. For example, when B. the taiotaomicron is exposed to chondroitin sulfate, a host mucopolysaccharide, synthesis of the degradative enzymes begins within 30 min and the maximum specific activity is reached within 2 hr (87). Microbiol.…”

“…Induction of the synthesis of enzymes such as chondroitin lyase and (X glucosidase does not occur if a more readily fermentable substrate such as glucose is available (91). Whether this is the same phenomenon as catabolite repression, which it resembles superficially, has not been determined.…”

A novel membrane glycoprotein of Escherichia coli

“…COOK et al (1965) have shown the incorporation of 14 C-glucosamine into glycoprotein of smooth endoplasmic reticulum and suggested the biosynthesis of surface membrane glycoprotein. Glucosamine has been used for various purposes in bacterial growth media (IMADA et al 1977, SALYERS et al 1983, ROGERS et al 1988, and PLUMBRIDGE et al 1993. In a separate set of experiments when cells were cultured in basal mineral media containing 14 C-glucosamine in presence of Bacitracin (a general inhibitor of glycosylation; 20 µg/ml), the radiolabelling in the dialyzed TCA supernatant fraction, that contains Gp45, decreased significantly (80%) as compared to the controls with out Bacitracin (data not shown).…”