PHYSICAL AND GENETIC-MAP OF THE CLOSTRIDIUM-ACETOBUTYLICUM ATCC-824 CHROMOSOME

A physical and genetic map of the Clostridium acetobutylicum ATCC 824 chromosome was constructed. The macrorestriction map for CeuI, EagI, a nd SstII ws created by ordering the 38 restriction sties by one- and t wo-dimensional pulsed-filed gel electrophoresis (PFGE) and by using an original strategy based on the CeuI enzyme and indirect end labelling by hybridization on both sides of the CeuI sites with rrs (16S RNA) a nd 3' rrl (23S RNA) probes. The circular chromosome was estimated to b e 4.15 Mb in size, and the average resolution of the physical map is 1 10 kb. The chromosome contains 11 rrn loci, which are localized on 44% of the chromosome in a divergent transcriptional orientation regardin g the presumed location of the replication origin. In addition to thes e 11 rrn operons, a total of 40 identified genes were mapped by hybrid ization experiments with genes from C. acetobutylicum and from various other clostridia as probes. The genetic map of C. acetobutylicum was compared to that of the three other endospore-forming bacteria charact erized so far: Bacillus subtilis, Clostridium beijerinckii, and Clostr idium perfringens. Paradoxically, the chromosomal backbone of C. aceto butylicum showed more similarity to that of B. subtilis than to those of the clostridia.