Fluorescence microscopy of N2, daf-2 and phm-2 single mutant, and daf-2;phm-2 double mutant C. elegans strains feeding on GFP-expressing E. coli.

Relationships between introduced and surviving bacteria in worms with decreased intestinal immunity To examine the effect of both increased bacterial delivery to the intestine and decreased immunity, we created a pharynx defective (phm-2) and immunocompromised (dbl-1) double mutant [31, 55]. As before, the dbl-1 single mutant showed a difference in bacterial load compared with N2 (Figure 9A), as well as a decreased lifespan reflecting their diminished immunity (Figure 9B). Bacterial load on day 0 (L4 stage) were markedly (100 fold) higher in the dbl-1;phm-2 double mutants than in the dbl-1 single mutant and N2 wild type worms, and 10 times higher than in the phm-2 single mutant (Figure 9A). As worms grew older, they were ill-appearing; by day 3, they had decreased body movement XL184 research buy and coordination, this website decreased pharyngeal pumping, and showed a dramatic reduction in survival (Figure 9B). The bacterial concentrations did not increase

as much as the phm-2 single mutants, most likely because they were feeding poorly. The early life results indicate that the DBL-1 pathway and the pharynx have additive effects in control of bacterial load, with drastic effects on survival when both are interrupted. Figure 9 Immunocompromised C. elegans are hypersusceptible to bacterial accumulation. Panel A: Number (cfu) of E. coli OP50 within the intestine of N2, dbl-1 and phm-2 single mutant, and dbl-1;phm-2 double mutant C. elegans strains. Panel B: Survival of same strains when grown on lawns of E. coli OP50. Effect

of mitochondrial function on bacterial proliferation and lifespan Finally, we asked whether intestinal bacterial load is affected by genes known to have effects on lifespan that are independent of gut immunity. Ubiquinone (coenzyme Q) biosynthesis, essential in mitochondrial respiration, requires demethoxyubiquinone hydroxylase, encoded by clk-1 [56]. C. elegans clk-1 mutants that generate diminished amounts of reactive Branched chain aminotransferase oxygen species (ROS) and subsequent reduced levels of oxidative damage [57, 58], have prolonged lifespans and resistance to stress induced by UV irradiation, heat, or reactive oxygen [56, 59]. Inactivation of clk-1 results in an average slowing of a number of developmental and physiological processes, including cell cycle, embryogenesis, post-embryonic growth, rhythmic behaviors, and aging [60]. No role in innate immunity has been described so far. As predicted, the clk-1 mutants had a prolonged lifespan compared to N2, when grown on lawns of E. coli OP50 (Figure 10A).We then assessed whether clk-1 affects intestinal bacterial accumulation. We found that the clk-1 mutants had intestinal E.