A Central Role for Carbon-Overflow Pathways in the Modulation of Bacterial Cell Death

Abstract

Similar to developmental programs in eukaryotes, the death of a subpopulation of cells is thought to benefit bacterial biofilm development. However mechanisms that mediate a tight control over cell death are not clearly understood at the population level. Here we reveal that CidR dependent pyruvate oxidase (CidC) and α-acetolactate synthase/decarboxylase (AlsSD) overflow metabolic pathways, which are active during staphylococcal biofilm development, modulate cell death to achieve optimal biofilm biomass. Whereas acetate derived from CidC activity potentiates cell death in cells by a mechanism dependent on intracellular acidification and respiratory inhibition, AlsSD activity effectively counters CidC action by diverting carbon flux towards neutral rather than acidic byproducts and consuming intracellular protons in the process. Furthermore, the physiological features that accompany metabolic activation of cell death bears remarkable similarities to hallmarks of eukaryotic programmed cell death, including the generation of reactive oxygen species and DNA damage. Finally, we demonstrate that the metabolic modulation of cell death not only affects biofilm development but also biofilm-dependent disease outcomes. Given the ubiquity of such carbon overflow pathways in diverse bacterial species, we propose that the metabolic control of cell death may be a fundamental feature of prokaryotic development.

Effects of Low-Dose Amoxicillin on Staphylococcus aureus USA300 Biofilms

“…8C), longer than the doubling time exhibited by the wildtype strain. Previous studies showed that glucose stimulates MRSA cell death (65) and biofilm formation (12,66).…”

SrrAB Modulates Staphylococcus aureus Cell Death through Regulation of cidABC Transcription

“…S1A in the supplemental material). This is most likely due to the inability of acetate (pK a ϭ 4.8) to permeate cells and acidify the cytoplasm under relatively neutral conditions (13). Much to our surprise, however, measurements of acetate production and culture pH revealed that the ⌬srrAB mutant produced nearly identical amounts of acetate compared to that of the wild-type strain (Fig.…”

“…Flow cytometry was performed as previously described (13). Briefly, a BD LSR II flow cytometer (Becton and Dickinson, San Jose, CA) was used to perform analyses using 1-and 3-day-old stationary-phase cultures of S. aureus.…”

“…Given that transcription profiling experiments suggested that the SrrAB regulatory system has a negative effect on cidABC transcription (17) and that medium acidification due to the accumulation of acidic fermentative metabolites can influence cell fate (13), we initially tested the hypothesis that increased cidC-dependent acetate production was responsible for the decreased survival of an S. aureus ⌬srrAB mutant relative to that of the wild-type strain. Thus, we monitored the survival of the wild-type strain and the ⌬srrAB mutant in stationary phase following growth in tryptic soy broth (TSB) supplemented with excess glucose (35 mM) as previously described (13). Indeed, the ⌬srrAB mutant exhibited an increased rate of cell death in the presence of 35 mM glucose compared to that in the wild-type strain, but it demonstrated similar survival in the stationary phase when grown in the presence of 14 mM glucose (Fig.…”

“…Indeed, CidA and LrgA have been shown to associate with the cytoplasmic membrane and to oligomerize into highmolecular-weight complexes (10). More recently, cidC-encoded pyruvate oxidase (12) was shown to potentiate cell death during the stationary phase and biofilm development by promoting cytoplasmic acidification through the production of acetate (13).…”