We have determined the complete primary structure (8031 base pairs) of an infectious clone of cauliflower mosaic virus strain CM1841. The sequence was obtained using the strategy of cloning shotgun restriction fragments in the sequencing vector M13mp7. Comparison of the CM1841 sequence with that published for another caMV strain (Strasbourg) reveals 4.4% changes, mostly nucleotide substitutions with a few small insertions and deletions. The six open reading frames in the sequence of the Strasbourg isolate are also present in CM1841.

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Our study describes the production, purification, and properties of alpha-toxin from Clostridium novyi type A 19402. The bacterium produced maximal amounts of alpha-toxin when grown at 37°C for 72 h in dialysis flask cultures containing brain heart infusion supplemented with 0.75% Tween 80 and 2% glycerol. The alpha-toxin was purified by precipitation with polyethylene glycol 6000, followed by chromatography on Q-Sepharose, phenyl-agarose, and Mono-Q. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the toxin exhibited a single band with an Mr of 200,000. The toxin also exhibited a single immunoprecipitin arc by crossed immunoelectrophoresis with antiserum against crude toxin. It was stable when stored at 4°C and also following exposure to buffers with pHs in the range of 4 to 7. The toxin had a minimum lethal dose in mice of 5 to 10 ng, caused rounding of a variety of cells in tissue culture, and was negative in the rabbit ileal loop assay. The cytotoxic activity was inhibited by agents that affect receptor-mediated processes, and the toxin was less active on a CHO mutant cell line that is defective in endosomal acidification. The analysis of the amino acid composition revealed an unusually high proline content. The N-terminal sequence is Met-Leu-Ile-Thr-Arg-Glu-Gln-Leu-Met-Lys. The Clostridium genus is well known for the numerous and diverse toxins produced by its members. Two Clostridium species, C. difficile and C. sordellii, produce highmolecular-weight toxins that are related (2, 17, 22, 23, 28, 37, 38). The toxins produced by C. difficile are designated toxin