Growth of MR-1/empty vector, MR-1/phfq, hfq∆ /empty vector, and hfq∆ /phfq on LB agar containing kanamycin (A), in LB liquid containing kanamycin (B), or in modified M1 defined medium containing kanamycin (C). Plates in (A) were photographed after 24 hours of growth following inoculation from frozen click here permanent stocks. Three independent liquid cultures of each strain tracked in (B-D) were inoculated with log phase cultures grown in LB (B and D) or modified M1 medium (C). (D) Analysis of the relationship between viable cell counts (CFU/ml) and culture turbidity (ABS600) in LB cultures. Data

points marked with “#” have CFU/ml/ABS600 values of zero. Error bars in panels (B-D) indicate a 99% confidence interval (P = 0.01). To further characterize the nature of the growth defect in the hfq mutant, we compared the growth of the hfq mutant in aerobic liquid cultures to strains containing one or more wild type copies of the hfq gene (Figure 2B). When exponentially-growing cultures were diluted to late lag ASP2215 cost phase and outgrown beyond stationary phase, we consistently observed that the hfq∆/empty vector culture AG-881 order densities were significantly lower than those of the MR-1/empty vector cultures through exponential phase. In

addition, the terminal cell densities of stationary phase hfq∆/empty vector cultures were significantly lower than the terminal cell densities of MR-1/empty vector cultures (Figure 2B). We also observed delayed growth during exponential phase and lower terminal stationary phase densities in hfq∆/empty vector liquid cultures grown in modified M1, a defined medium (Figure 2C). The growth and terminal

density defects of the hfq mutant in liquid cultures were completely rescued by phfq, as the growth of the hfq∆/phfq strain was indistinguishable from that of MR-1/empty vector in both LB (Figure 2B) and modified M1 (Figure 2C). Finally, extra copies of hfq that result in higher Hfq protein levels (Figure 1C) do PTK6 not appear to alter the growth of S. oneidensis in liquid medium, as growth of MR-1/phfq and hfq∆/phfq cultures was indistinguishable from that of MR-1/empty vector cultures in LB and modified M1 media (Figures 2B and 2C). To determine whether the relationships between spectrophotometric measurements of culture density and cell number were comparable between the strains used in our study, we determined the relationship between ABS600 values and viable cell counts for MR-1/empty vector, MR-1/phfq, hfq∆/empty vector, and hfq∆/phfq at various times during culture outgrowth. In both LB cultures (Figure 2D) and modified M1 cultures (data not shown), the relationship between ABS600 and colony forming units per ml (CFU/ml) was consistent for all four strains throughout exponential phase and until approximately mid-stationary phase.