FIG. 6.

Assays of resistance to heat (A) and UV irradiation (B) in spores from the ΔhupS::Ωhyg mutant K304 (open circles), its isogenic hupS⁺ parent M145 (filled squares), and the mutant strain complemented by hupS in trans in plasmid pKF287 (filled circles). Spores were exposed to 60°C for different times (A) or to different doses of UV irradiation (B), and the numbers of surviving CFU were determined. Mean values and standard deviations are shown, based on data from at least three independent experiments (for panel B, four experiments with three CFU determinations each per UV dose). The hupS mutant spores were clearly impaired in heat resistance but did not show a statistically significant difference in UV resistance compared to the wild-type parent.