Although the minimal amount of DNA required to trigger the AIM2 inflammasome is unknown, studies of Francisella have shown that inflammasome components can be recruited to singly lysed bacteria (9). One of the most striking findings from our screen was the observation that, despite a wealth of data suggesting that DNA in the cytosol is sufficient to activate the AIM2 inflammasome (8, 9, 37, 38), a subset of our mutants which lyse and release both plasmid and chromosomal DNA into the cytosol of macrophages do not hyperactivate the inflammasome (Fig. 3). MK-deficient mutants lyse at frequencies similar to those seen with pdhC::Tn, ΔyvcK and yvcJ::Tn mutants but avoid activation of the AIM2 inflammasome. It is possible that during infection with MK mutants, changes in host metabolism activate host cell nucleases that modify or degrade bacterial DNA such that inflammasome signals are destroyed. Alternatively, it is possible that the response to infection with MK mutants leads to changes in signaling or cellular redox balance that inactivate either the AIM2 receptor or downstream signaling components, including caspase-1 itself (19, 39). Finally, although less likely given the ability of sterile transfected DNA to activate the AIM2 inflammasome, it is possible that DNA alone is not sufficient for AIM2 activation during infection and that non-respiring L. monocytogenes mutants lack the metabolic signals required to activate the inflammasome. Bacterial metabolism and regulation of innate immune signaling pathways appear to be intimately linked (19, 40–42). For example, S. Typhimurium metabolic mutants induce mitochondrial reactive oxygen production, resulting in NALP3-inflammasome activation (42). How MK-deficient mutants avoid inflammasome activation despite the release of cytosolic DNA is the subject of ongoing studies.