Untersuchungen zum Pentose- und Pentitolstoffwechsel bei Staphylococcus xylosus und Staphylococcus saprophyticus

The degradation of pentoses and xylitol, respectively is a meaningful taxonomic parameter for the distinction of the coagulase-negative staphylococci Staphylococcus xylosus and S. saprophyticus. It is, therefore, of interest to learn more about the catabolism of these C₅-sugars and sugar alcohols. The following pathway for the breakdown of pentoses and xylitol has been found in S. xylosus and S. saprophyticus:

inducible uptake of unsubstituted carbohydrates; phosphoenolpyruvate phosphotransferase system (PTS) is not involved in the uptake of pentoses and xylitol.

Isomerization of pentoses and dehydration of xylitol is inducible. Phosphorylation probably occurs on ketopentoses, since activity for D-ribulokinase could be detected in D-ribose grown cells, but neither activity for pentokinases nor D-ribose-5-phosphate-isomerase could be demonstrated.

Therefore, the pathway is analogous to the metabolism of pentoses and pentitol in Enterobacteriaceae, exceptionally for D-ribose, and differs from the degradation of pentitols by Lactobacillaceae. Growth with D-xylose as substrate was inhibited by xylitol due to the inhibition of the enzyme D-xylose-isomerase.

Experiments with mutants should prove the value of pentose/pentitol utilization as a biochemical character for the identification of S. xylosus and S. saprophyticus. It was possible to isolate pentose-negative mutants of S. xylosus which resemble S. saprophyticus in the pentose/pentitol metabolism, but we did not succeed in isolating pentose-positive mutant of S. saprophyticus. This indicates that degradation of xylose and/or arabinose is a characteristic property fo S. xylosus strains. Pentose-negative mutants of S. xylosus lack activity for the isomerization of pentoses but they are still typical S. xylosus as could be shown by DNA-DNA-hybridization studies. DNA-homology values between wild and mutant strains were about 100%, whereas homology values between these mutant strains and a pentose-negative S. saprophyticus wild type were 35–40% corresponding to values obtained between wild types of S. xylosus and S. saprophyticus.