Wide diversity of genome size among different strains of Clostridium acetobutylicum

The sizes of the genomes of five strains of Clostridium acetobutylicum were estimated by summing the sizes of macro-restriction fragments produced after cleavage of their DNA with SmaI and ApaI. The five C. acetobutylicum strains fell into three discrete groups. The NCIMB 8052 and NI-4081 strains have 6.5 Mbp genomes and restriction profiles of their DNA were indistinguishable. The sizes of the genomes of the ATCC 824 and DSM 1731 strains were about 4-0 and 3.5 Mbp (minimum values), respectively, and the restriction profiles of their DNA were very similar. One notable difference was the presence of an additional 532 kbp SmaI fragment in the DNA of strain ATCC 824. The NCP 262 strain of C. acetobutylicum has a genome size of 2-85 Mbp. Restriction fragment profiles of DNA from strains belonging to different groups were not obviously similar. Probes made from several cloned ATCC 824 genes hybridized with DNA fragments of different sizes from strains representative of each group. These data add further weight to the considerable body of evidence indicating that the species C. acetobutylicum comprises a heterogeneous collection of strains.