This proposal is to study the spontaneous deletion mutant which occurs in the plague bacterium, Yersinia pestis, and results in loss of the ability of the bacterium to accumulate hemin or Congo red and form dark, pigmented colonies. The deletion involves at least 40 kilobase pairs of chromosomal DNA. The size of the in the mutant will be determined. Several mutants are available; this will be constructed with deleted DNA end fragments from the mutant bacteria, and used to transform wild-type cells to examine the involvement of the end fragments in generating the deletion. The mechanism of deletion will studied using the reporter gene construct. %%% The plague bacterium and several other pathogenic bacteria undergo spontaneous deletion of large portions of chromosomal DNA. The plague bacterial mutants are detected by loss of the ability to form dark-pigmented colonies. Several mutants are available; DNA sequences will be determined to see whether the site of excision is same in all the mutants. The DNA fragments representing the site of cleavage will be added to a reporter gene to be added to wild- type cells, to see whether the mechanism can be more clearly understood.
