Inactivation of the Pta-AckA Pathway Causes Cell Death in Staphylococcus aureus

Abstract

bDuring growth under conditions of glucose and oxygen excess, Staphylococcus aureus predominantly accumulates acetate in the culture medium, suggesting that the phosphotransacetylase-acetate kinase (Pta-AckA) pathway plays a crucial role in bacterial fitness. Previous studies demonstrated that these conditions also induce the S. aureus CidR regulon involved in the control of cell death. Interestingly, the CidR regulon is comprised of only two operons, both encoding pyruvate catabolic enzymes, suggesting an intimate relationship between pyruvate metabolism and cell death. To examine this relationship, we introduced ackA and pta mutations in S. aureus and tested their effects on bacterial growth, carbon and energy metabolism, cid expression, and cell death. Inactivation of the Pta-AckA pathway showed a drastic inhibitory effect on growth and caused accumulation of dead cells in both pta and ackA mutants. Surprisingly, inactivation of the Pta-AckA pathway did not lead to a decrease in the energy status of bacteria, as the intracellular concentrations of ATP, NAD ؉ , and NADH were higher in the mutants. However, inactivation of this pathway increased the rate of glucose consumption, led to a metabolic block at the pyruvate node, and enhanced carbon flux through both glycolysis and the tricarboxylic acid (TCA) cycle. Intriguingly, disruption of the Pta-AckA pathway also induced the CidR regulon, suggesting that activation of alternative pyruvate catabolic pathways could be an important survival strategy for the mutants. Collectively, the results of this study demonstrate the indispensable role of the Pta-AckA pathway in S. aureus for maintaining energy and metabolic homeostasis during overflow metabolism.

Pyruvate-Associated Acid Resistance in Bacteria

“…2B, deleting the ackA-pta operon elevated extracellular levels of pyru- vate by a factor of 126 (P ϭ 0.0079). Similar observations have also been reported previously (32,33). As predicted, deleting the ackApta operon increased AR by a factor of 577 (P ϭ 0.0236) (Fig.…”

Genetics and Physiology of Acetate Metabolism by the Pta-Ack Pathway of Streptococcus mutans

“…3A). Thus, rather than a shortage of ATP, the observed growth inhibition of these mutant strains could be due to metabolic toxicity arising from abnormal levels of metabolites, such as AcP, pyruvate, or acetyl-CoA (15,17). Deletion of the ackA gene of S. aureus resulted in a growth defect but also resulted in increases in the amounts of AcP, pyruvate, and acetyl-CoA (15).…”

“…Thus, rather than a shortage of ATP, the observed growth inhibition of these mutant strains could be due to metabolic toxicity arising from abnormal levels of metabolites, such as AcP, pyruvate, or acetyl-CoA (15,17). Deletion of the ackA gene of S. aureus resulted in a growth defect but also resulted in increases in the amounts of AcP, pyruvate, and acetyl-CoA (15). Therefore, we hypothesize that the accumulation of higher levels of AcP in the ackA single deletion strain or the pta and ackA double deletion strain may inhibit the expression or activity of the PDH complex under the conditions tested, leading to an increase in intracellular pyruvate levels, similar to the findings for S. aureus (15,39).…”

“…A recent study with S. aureus revealed that disruption of the Pta-Ack pathway resulted in growth inhibition, accompanied by a redirection of the carbon flow into multiple metabolic pathways. Notably, there were also changes in the levels of key metabolites, including ATP, NAD ϩ , NADH, and pyruvate (15). Also of interest, loss of the Pta-Ack pathway in S. aureus induced the downregulation of the CidR-regulated alsSD and cidABC operons, which carry genes involved in the control of cell death associated with a metabolic block at the pyruvate node (15).…”

Acetate Dissimilation and Assimilation in Mycobacterium tuberculosis Depend on Carbon Availability

“…To further characterize the role of acetate metabolism in M. tuberculosis, we analyzed the pathway responsible for acetate generation. A pathway commonly used by such bacteria as E. coli, Pseudomonas aeruginosa, and S. aureus (35)(36)(37)(38) involves the pta gene, encoding the phosphotransacetylase, and the ackA gene, encoding the acetate kinase. The genome of M. tuberculosis possesses homologous copies of these two genes.…”