ABSTRACT
The intracellular milieu of any organism must remain relatively constant with regard to pH, metabolite levels, and ionic composition to ensure an active metabolism. This cytoplasmic homeostasis is essential for the growth and survival of bacteria. K+-transport is believed to play an essential role in maintaining homeostasis by regulating cell turgor and the cytoplasmic pH. Potassium is also required for the activity of several enzymes, therefore it is not surprising that bacteria developed several uptake and efflux systems for potassium. Few experimental data on potassium metabolism in clostridia are available. An early report describes potassium to be an essential factor in the fermentation of maize meal by Clostridium acetobutylicum [1], although the underlying metabolic requirement is still unknown. This chapter will focus on the different known potassium transport systems, in part experimentally characterized in C. acetobutylicum and detected in the complete genomes of C. acetobutylicum, C. perfringens, and C. tetani, as well as those found in the still not completely sequenced genomes of C. thermocellum, C. botulinum, and C. diffcile.
