Sugar uptake and sensitivity to carbon catabolite regulation in Streptomyces peucetius var. caesius

Abstract

Streptomyces peucetius var. caesius produces a family of secondary metabolites called anthracyclines. Production of these compounds is negatively affected in the presence of glucose, galactose, and lactose, but the greatest effect is observed under conditions of excess glucose. Other carbon sources, such as arabinose or glutamate, show either no effect or stimulate production. Among the carbon sources that negatively affect anthracycline production, glucose is consumed in greater concentrations. We determined glucose and galactose transport in S. peucetius var. caesius and in a mutant of this strain whose anthracycline production is insensitive to carbon catabolite repression (CCR). In the original strain, incorporation of glucose and galactose was stimulated when the microorganism was grown in media containing these sugars, although we also observed basal galactose incorporation. Both the induced and the basal incorporation of galactose were suppressed when the microorganism was grown in the presence of glucose. Furthermore, adding glucose directly during the transport assay also inhibited galactose incorporation. In the mutant strain, we observed a reduction in both glucose (48%) and galactose (81%) incorporation compared to the original. Galactose transport in this mutant showed reduced sensitivity to the negative effect of glucose; however, it was still sensitive to inhibition. The deficient transport of these sugars, as well as CCR sensitivity to glucose in this mutant was corrected when the mutant was transformed with the SCO2127 region of the Streptomyces coelicolor genome. Our results support a role for glucose as the most easily utilized carbon source capable of exerting the greatest repression on anthracycline biosynthesis. In consequence, glucose also prevented the repressive effect of galactose by suppressing its incorporation. This suggests the participation of an integral regulatory system, which is initiated by an increase in incorporation of repressive sugars and their metabolism as a prerequisite for establishing the phenomenon of CCR in S. peucetius var. caesius.

A New Piece of an Old Jigsaw: Glucose Kinase Is Activated Posttranslationally in a Glucose Transport-Dependent Manner in <i>Streptomyces coelicolor </i>A3(2)

“…This cysteinerich motif may also play a key role in the functional control of Glk and thus should be targeted for mutational analysis. Recent studies on glucose repression of production of the antibiotic anthracycline in S. peucetius provided evidence that the gene upstream of glkA (SCO2127 in S. coelicolor ) also influences glucose transport [Guzman et al, 2005a[Guzman et al, , 2005b. Hence, it will be of primary interest to elucidate the function of SCO2127.…”

Carbon source regulation of antibiotic production

“…However, a complete reversion of this phenotype is obtained when the mutant is transformed with the sco2127 gene alone. 137,138 Thus, in the recombinant strain, glucose uptake and Glk activity values are reverted back to the level of the original strain or even higher, and the recombinant regains sensitivity to CCR. These results were surprising considering that the sco2127 region does not seem to encode for either a glucose permease 106 or a Glk, 126 and also lacks DNA-binding motifs.…”

“…Its production during logarithmic growth agrees with its predicted involvement in CCR, as SCO2127 expression is closely linked to glucose concentration present in the culture medium. 139 Detection of SCO2127 at the beginning of fermentation may be related to its possible role in carbohydrate transport 138 as the seed cultures were grown in the presence of 50 mM mannitol. On the other hand, cultures grown in 100 mM glucose showed SCO2127 even at later stages of microbial growth coinciding with the presence of 40% of the initial available glucose.…”

Cloning and expression of the sco2127 gene from Streptomyces coelicolor M145

“…A partial reversion of the Dog R phenotype is observed when transforming the mutant with glkA. However, a complete reversion is obtained when transforming the mutant with the sco2127 region alone [8,9]. This result was unexpected since sco2127 does not seem to encode for Glk [5], nor for a glucose permease (GlcP1) [10], and also lacks DNA binding motifs.…”

“…During the last years, our research group has been interested in the study of the sco2127 gene and its role in CCR [8,9]. In S. coelicolor, this region (576 pb) is located upstream of the glkA gene, and no evident function has been conferred to its possible expression product.…”