Functional csdA is needed for effective adaptation and initiation of growth of Clostridium botulinum ATCC 3502 at suboptimal temperature

Abstract

The activity of RNA helicase csdA (cbo2802) after temperature downshift was compared to its activity at optimal growth temperature, and the effect of sense and antisense oriented insertional inactivation of cbo2802 on the growth of ATCC 3502 at suboptimal temperature was evaluated. The relative cbo2802 transcript level was significantly induced for 30min to 5h after cold shock. In contrast, a significant decrease in the relative transcript level of cbo2802 was observed within the same time frame at 37°C. Inactivation of cbo2802 led to an extensive delay in initiation of exponential growth at 20°C but not at 37°C. In addition, the mean minimum growth temperatures of the mutant strains were higher than those of the wild-type strain. During a 24-hour incubation at 37°C, all strains were motile, whereas at 20°C the mutant strains showed severely impaired motility compared to the wild-type strain. This study shows that a functional csdA is needed for effective adaptation and initiation of growth and motility of Clostridium botulinum ATCC 3502 at suboptimal temperature.