For both organisms, there was an Selleck MGCD0103 inverse correlation between day 2 bacterial density and survival [for E. coli OP50 (R = 0.83; Figure 6C), and

S. typhimurium SL1344 (R = 0.89; Figure 6D)]. These strong relationships suggest that immune handling of bacterial load in the intestine of early adults is an important causative factor in determining lifespan. We chose day 2 to study, because colonization levels were significantly differed amongst the C. elegans mutants at that time point (Figure 2E). However we also performed correlations between longevity and bacterial counts for other time points (see Additional file 3), as well as calculations based on a Cox Model, which takes into account bacterial accumulation LY2109761 cost over time (see Additional file 4). Both results suggest that there exists a significant relationship between longevity and bacterial load throughout early adulthood. Figure 6 Relationship between C. elegans genotype, colonizing bacterial species, and lifespan. Symbols for the 14 worm genotypes are as indicated in Table 1. Panel A: Relationship of lifespans for worms grown on E. coli OP50 and S. typhimurium SL1344, measured as TD50. Worm survival is strongly correlated with growth on the two organisms (R = 0.98;

p < 0.0001). Panel B: Relationship of intestinal bacterial density for worms grown on E. coli OP50 or S. typhimurium, measured as LY3023414 day 2 log10 cfu. Results show a strong direct correlation for the two bacterial species (R = 0.82; p < 0.001). Panel C: Relationship between lifespan and intestinal bacterial density for C. elegans grown on E. coli OP50 lawns.

There is an inverse correlation between intestinal bacterial density and survival (R = 0.83; p < 0.001). Panel D: Relationship between lifespan and intestinal bacterial density for C. elegans grown on S. typhimurium SL1344 lawns. There is an inverse correlation between intestinal bacterial density and survival (R = 0.89; p < 0.001). Relationships between introduced and surviving bacteria in worms with enhanced intestinal immunity The C. elegans pharynx contains a grinder that breaks up bacterial cells to provide nutrients for the worm [54]. Grinder-defective worms (e.g. due to phm-2 mutation) have shortened very lifespan [24]. We hypothesized that the reduced lifespan was related to increased accumulation of viable bacteria in the worm intestine. When grown on an E. coli OP50 lawn, the number of viable bacterial cells recovered from the intestine of phm-2 mutants was about 102 E. coli cfu/worm at L4 stage (day 0), and increased to 104 cfu/worm by day 4 (L4 + 4), ~10-fold higher than levels observed in N2 worms (Figure 7A). A similar trend was observed when phm-2 mutants were grown on S. typhimurium SL1344 lawns, but colonization reached higher bacterial densities, a difference paralleling the other worm genotypes (Figure 7C). After day 4, bacterial concentrations remain on a plateau (data not shown), similar to the observations for the other genotypes.