To approach this question, we examined worms with mutations in each of several important pathways in presumed C. elegans defenses against intestinal bacteria (see Figure 1). We first studied the p38 MAP kinase pathway by analyzing pmk-1 mutants. PMK-1 is the C. elegans p38 homologue [25–27], and the p38 MAP kinase cascade is involved in immune defenses to Gram-negative and Gram-positive bacteria, as well as pathogenic fungi [28–30]. Similarly, we studied the DBL-1 pathway using the dbl-1 mutant, whose product is

homologous to mammalian transforming growth factor-β (TGF-β), and is implicated in pathogen resistance [31, 32]. All receptors and Smads from the DBL-1 pathway are strongly expressed in the intestine and/or pharynx of C. elegans [33, 34]. We also examined mutants in tol-1, the only Toll-like receptor (TLR) in C. elegans, which is required for the PF299 datasheet full innate immune phenotype to certain Gram-negative bacteria, for the full expression of ABF-2, a defensin-like molecule expressed in the pharynx [35], and for avoiding pathogenic bacteria [36]. The dbl-1 mutants showed both markedly Crenigacestat supplier reduced lifespan and elevated intestinal bacterial loads (Figure 4A and 4B, and Table 1). In contrast, the pmk-1 and tol-1 mutants had significantly reduced lifespans, correlating with significantly elevated concentrations of S. typhimurium

SL1344, although not with intestinal E. coli concentrations. These Sclareol results indicate that across C. elegans genotypes, immunocompromise enhances bacterial loads, but is not sufficient to explain lifespan. Figure 4 Survival and density of colonizing bacteria in the intestine of C. elegans mutants with altered immune function. Panel A: Survival of N2 C. elegans and four mutants with

altered intestinal immune learn more function when grown on lawns of E. coli OP50. Panel B: Intestinal load of E. coli OP50 (dark bars) or S. typhimurium SL1344 (grey bars) within N2 C. elegans and the four mutants with altered intestinal immune function on day 2 (L4 stage + 2 days) of their lifespan. Data represent Mean ± SD from experiments involving 30 worms/group. Significant differences (p < 0.05) compared to N2 worms exposed to E. coli OP50 or S. typhimurium SL1344, indicated by * or **, respectively. Panel C: Survival of daf-2 and dbl-1 single mutants, and the daf-2;dbl-1 double mutant when grown on lawns of E. coli OP50. Panel D: Intestinal density of viable E. coli OP50 in the intestine of the single and daf-2;dbl-1 double mutants. The dbl-1 mutation suppresses both the daf-2 intestinal bacterial proliferation and lifespan phenotypes. Therefore, to examine the interactions between the DBL-1 (TGF-B) and the DAF-2 insulin-signaling pathways, we constructed double mutant worms and analyzed both their longevity and bacterial load.