Inflammasomes are cytosolic multiprotein complexes that assemble in response to 
a variety of infectious and noxious insults. Inflammasomes play a critical role 
in the initiation of innate immune responses, primarily by serving as platforms 
for the activation of inflammatory caspase proteases. One such caspase, 
CASPASE-1 (CASP1), initiates innate immune responses by cleaving pro-IL-1β and 
pro-IL-18, leading to their activation and release. CASP1 and another 
inflammatory caspase termed CASP11 can also initiate a rapid and inflammatory 
form of cell death termed pyroptosis. Several distinct inflammasomes have been 
described, each of which contains a unique sensor protein of the NLR 
(nucleotide-binding domain, leucine-rich repeat-containing) superfamily or the 
PYHIN (PYRIN and HIN-200 domain-containing) superfamily. Here we describe the 
surprisingly diverse mechanisms by which NLR/PYHIN proteins sense bacteria and 
initiate innate immune responses. We conclude that inflammasomes represent a 
highly adaptable scaffold ideally suited for detecting and initiating rapid 
innate responses to diverse and rapidly evolving bacteria.