Inactivation of the Pta-AckA Pathway Impairs Fitness of During Overflow Metabolism

Under conditions of glucose excess, aerobically growing bacteria predominantly direct carbon flux towards acetate fermentation, a phenomenon known as overflow metabolism or the bacterial 'Crabtree effect'. Numerous studies of the major acetate-generating pathway, the Pta-AckA, revealed its important role in bacterial fitness through the control of central metabolism to sustain balanced growth and cellular homeostasis. In this work, we highlight the contribution of the Pta-AckA pathway to fitness of the spore-forming bacterium, We demonstrate that disruption of the Pta-AckA pathway causes a drastic growth reduction in the mutants and alters the metabolic and energy status of the cells. Our results revealed that inactivation of the Pta-AckA pathway increases the glucose consumption rate, affects intracellular ATP, NAD and NADH levels and leads to a metabolic block at the pyruvate and acetyl-CoA nodes. Consequently, accumulation of intracellular acetyl-CoA and pyruvate forces bacteria to direct carbon into the TCA and/or glyoxylate cycles as well as fatty acid and poly(3-hydroxybutyrate) (PHB) biosynthesis pathways. Notably, the presence of phosphate butyryltransferase in partially compensates for the loss of phosphotransacetylase activity. Furthermore, overexpression of the gene not only eliminates the negative impact of the mutation on fitness, but also restores normal growth in the mutant of the non-butyrate-producing bacterium, Taken together, the results of this study demonstrate the importance of the Pta-AckA pathway for fitness by revealing its critical contribution to the maintenance of metabolic homeostasis during aerobic growth under conditions of carbon overflow. , the etiologic agent of anthrax, is a highly pathogenic, spore-forming bacterium that causes acute, life-threatening disease in both humans and livestock. A greater understanding of the metabolic determinants governing fitness of is essential for the development of successful therapeutic and vaccination strategies aimed at lessening the potential impact of this important biodefense pathogen. This study is the first to demonstrate the vital role of the Pta-AckA pathway in preserving energy and metabolic homeostasis in under conditions of carbon overflow, therefore, highlighting this pathway as a potential therapeutic target for drug discovery. Overall, the results of this study provide important insight into understanding the metabolic processes and requirements driving rapid proliferation during vegetative growth.