Chapter 15 : Physiology and Sporulation in Clostridium

Abstract:

Clostridia are anaerobic bacteria, although many species can tolerate oxygen to various extents. They are able to form endospores and are not capable of dissimilatory sulfate reduction. Most of them show a positive Gram reaction. These criteria have been used in the past for classification. However, phylogenetic analyses based on 16S rRNA sequences led to reattribution of many former clostridia to numerous other and also novel genera, such as Blautia, Butyrivibrio, Caloramator, Cellulosilyticum, Dendrosporobacter, Eubacterium, Filifactor, Flavonifractor, Moorella, Oxalophagus, Oxobacter, Paenibacillus, Thermoanaerobacter, Thermoanaerobacterium, Sedimentibacter, Sporohalobacter, Syntrophomonas, Syntrophospora, and Tissierella (J. P.Euzéby, List of prokaryotic names with standing in nomenclature – genus Clostridium, http://www.bacterio.cict.fr/c/clostridium.html). For the genus Clostridium, approximately 180 species have been validly described, rendering it one of the largest bacterial genera. Only a few of these species are pathogenic, however, involving microbes producing very dangerous toxins. On the other hand, a large number of species are used in biotechnological applications (enzyme, bulk chemicals, and biofuels production) and tested for use in cancer therapy. This is due to the enormous metabolic diversity within the clostridia, rendering them the avant-garde of biotechnologically exploited microorganisms. During past years, techniques have been developed that allowed establishment of genetic systems for many clostridia. Thus, the tools are at hand for further elucidation and exploitation. Due to the limited space of this article, many aspects cannot be presented in detail. Thus, the interested reader is referred to recent references for additional information ( 1 – 6 ).