A new growth medium for rapid selection and purification of Clostridium proteoclasticum transposon mutants

Clostridium proteoclasticum is commonly associated with the rumen microflora of pasture-fed cattle and sheep and has significant hemicellulose degradation abilities. Genes involved in plant fibre breakdown are commonly identified by producing site-specific mutations. However, the genetics of C. proteoclasticum and other closely-related Butyrivibrio/Pseudobutyrivibrio species is not well-established. Therefore random transposon mutants of C. proteoclasticum were generated by conjugation with Enterococcus faecalis containing Tn916. A new counter-selection agar medium was developed containing L-arabinose and D-raffinose as carbon sources, both of which are utilized by C. proteoclasticum only, and also ciprofloxacin, an antibiotic that suppresses the growth of E. faecalis. With this new medium the enhanced growth and more rapid separation of C. proteoclasticum transposon mutants from the background of E. faecalis cells was made, thereby facilitating the selection of transposon mutants and the identification of their Tn916 insertion sites.