Reclassification of Clostridium proteoclasticum as Butyrivibrio proteoclasticus comb. nov., a butyrate-producing ruminal bacterium

Abstract

It is proposed that Clostridium proteoclasticum be reclassified as Butyrivibrio proteoclasticus comb. nov. on the basis of phylogenetic position, DNA G+C content and physiological traits. Phylogenetic analyses based on 16S rRNA gene sequences from an extensive range of taxa within clostridial rRNA subcluster XIVa grouped C. proteoclasticum together with isolates of the genus Butyrivibrio, though this species was genetically distinct from the extant Butyrivibrio species examined. The DNA G+C content of C. proteoclasticum was originally erroneously reported as 28 mol%. However the genome sequence of the type strain of C. proteoclasticum, strain B316(T), and HPLC analysis estimate the DNA G+C content as 40 mol%, which is within the range reported for strains of Butyrivibrio. C. proteoclasticum was distinguishable from other species of the genus Butyrivibrio as the 16S rRNA gene from strain B316(T) shared less than 97 % sequence similarity with sequences from the type strains of Butyrivibrio species. C. proteoclasticum was also able to convert linoleic acid to stearic acid, in contrast to other species of Butyrivibrio. Physiological characteristics, including carbon source utilization, volatile fatty acid production and proteinase activities, were assessed for a panel of representative strains of the genera Butyrivibrio and Pseudobutyrivibrio and C. proteoclasticum. These data, together with the phylogenetic analyses, support the reclassification of Clostridium proteoclasticum as a separate species within the genus Butyrivibrio, Butyrivibrio proteoclasticus comb. nov. (type strain B316(T)=ATCC 51982(T)=DSM 14932(T)).