When the resistant Bacillus spore germinates to resume vegetative growth, from 10 to 20% of the protein of the dormant spore is rapidly degraded to amino acids. These then support much of the protein synthesis in the germinating cell, as the dormant spore lacks many of the enzymes needed for amino acid biosynthesis. The proteins degraded are a group of small acid- soluble spore proteins (SASPs). Their synthesis has only been a group of small acid-soluble spore proteins (SASPs). Their synthesis has only been detected during sporulation, but Southern blot comparisons of DNA from non-sporulating bacterial genera with purified Bacillus SASP sequences shows the presence of SASP-like sequences in their genomes. To date, the sequences for related SASPs have been determined in four Bacillus species and in Thermoactinomyces thalpophilus. Different SASPs have been found in each species. These have shown that large amounts of the SASPs' amino acid sequences are highly conserved both within and across species. The SASPs' genes are monocistronic and are not tightly clustered. Although they are coordinately expressed, each gene is individually regulated. No vegetative function for the genes is known, but the presence of similar sequences in non- sporulating genera suggests there may be one. The proposed research aims to improve our understanding of the basic biological functions of sporulation related molecules, especially those present in non-sporulating genera, and to examine the possible regulatory differences in similar genes of sporulating and non-sporulating bacteria. The evolutionary significance of sequence divergence in these genes will also be examined. The specific goals are to clone and sequence SASP genes similar to those that have been studied in Bacillus species using DNA from non-sporulating genera. The coding and flanking regions of these sequences will be compared with the equivalent regions of the Bacillus sequences. Comparisons of the coding regions will provide information on the conservation of sequence in the structural gene across a wide evolutionary gap, and may indicate if it is possible for these genes to be expressed. Comparison of the flanking regions may indicate that these regions evolve more or less slowly than the structural genes. Similarities and differences in the flanking regions may also indicate similar or different regulatory mechanisms in the different genera. Northern blot analysis of the non-sporulating genera may detect vegetative expression of these genes. There is a possibility that, if they are expressed, a vegetative function for the SASPs may eventually be determined.
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