Carbon assimilation and regulation by the phosphotransferase system in Actinobacillus succinogenes.

Abstract

Aims: Actinobacillus succinogenes is a succinate-producing, glucose-fermenting bacterium with phosphoenolpyruvate:sugar phosphotransferase system (PTS)-related genes identified in its genome. This study aimed to investigate the role of PTS in carbon source transport and regulation.

Methods and results: A mutant strain was generated lacking genes encoding the non-sugar-specific PTS components EI (Asuc_0995), Hpr (Asuc_0994), and EIIAGlc (Asuc_0996). Characterization of this mutant revealed a partial role of PTS in glucose transport, while uptake of sucrose, cellobiose, mannose, mannitol, sorbitol, L-ascorbate, and fructose was abolished. PTS disruption also reduced consumption of the non-PTS carbon sources xylose, lactose, maltose, L-arabinose, ribose, and glycerol, indicating a regulatory role for the PTS in alternative carbon catabolism. Adding cAMP to cultures of the PTS-deficient mutant partially restored growth on some of the non-PTS carbon sources, suggesting a role of CRP-cAMP in regulating carbon source catabolism in A. succinogenes. Transcriptome and proteome analyses showed differential expression of carbohydrate transport and metabolism genes in the PTS-deficient strain compared to wild-type on glucose. Bioinformatic analyses predicted that several differentially expressed genes have a putative CRP-cAMP binding site in their upstream DNA regions.

Conclusions: We showed that PTS components encoded by Asuc_0994-0996 are essential for transporting several sugars and partially involved in glucose uptake. Our findings also implicate the CRP-cAMP network in regulating non-PTS carbon catabolism.