| Deinococcus radiodurans is very resistant to radiation and many chemicals that damage DNA. High-resolution factorial design models were used to analyze the effects of the nutrient interactions in the tryptone-glucose-yeast extract (TGY) growth medium on biomass formation. Results suggested that the cell mass was mainly provided by tryptone and yeast-extract, but not glucose, in the medium. In vivo analysis showed that cells growing on TGY medium utilized glucose by the pentose phosphate (PP) pathway. Mn could induce the Embden-Meyerhof-Parnas (EMP) pathway in D. radiodurans . The EMP pathway competed with the PP pathway for glucose, resulting in a rapid depletion of glucose in the medium. However, the Mn-induced EMP pathway was a futile pathway, i.e., this pathway did not promote biomass formation.; To confirm the above hypothesis, mutants defective in either the PP or the EMP pathway were generated. The marker enzyme for the PP pathway was the NADP+-dependent glucose-6-phosphate dehydrogenase ( zwf) and the marker enzyme for the EMP pathway was the fructose-1,6-bisphosphate aldolase (fda). Deinococcus radiodurans zwf − and fda− mutants were then tested for their resistance to UV irradiation, H2O2, methylmethanesalfonic acid (MMS) and mitomycin C (MMC).; The futile EMP pathway in D. radiodurans was further studied in vitro. Enzymatic analysis showed that glucose and Mn together could fully induce the aldolase activity in the cell-free extract of D. radiodurans. Glucose or Mn alone could only partially induce the enzyme. The amino acid sequence of the deinococcal aldolase shared significant homology with other known Class II aldolases. However, unlike most microbial aldolase, the deinococcal enzyme required Mn, not Zn, as the cofactor. (Abstract shortened by UMI.)... |
