Heterogeneity of ribosomal-RNA operons in Bacillus subtilis.
Item
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Title
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Heterogeneity of ribosomal-RNA operons in Bacillus subtilis.
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Identifier
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AAI8914804
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identifier
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8914804
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Creator
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Widom, Russell Lee.
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Contributor
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Adviser: Rivka Rudner
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Date
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1988
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, General | Biology, Molecular | Biology, Genetics
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Abstract
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The heterogeneity of rRNA operons in Bacillus subtilis was examined on three major levels. Heterogeneity among strains with respect to the number of rRNA gene sets was examined. Some strains of B. subtilis have only 9 instead of 10 gene sets, with specific deletion of either rrnG or rrnW. These deletions occur only where gene sets are found in tandem arrays, with rrnG being clustered next to rrnI and rrnH, and rrnW in a newly discovered tandem with rrnJ. Deletions of these gene sets can occur during plasmid insertion into the chromosome, or spontaneously. Rescue of chromosomal DNA from the site of such spontaneous deletions indicates that homologous recombination between tandem repeats is the most likely mechanism to generate strains lacking rRNA gene sets.;Heterogeneity at the DNA sequence level was studied by sequencing the DNA upstream of rrnJ and comparing it to previously sequenced regions. Analysis shows that B. subtilis rRNA leaders and promoters are heterogeneous whereas the analogous sequences in E. coli can be easily put into 2 highly homologous groups. The B. subtilis rrnJ promoters cloned in E. coli exhibit growth-rate regulation, as expected for ribosomal promoters, indicating that the sequence requirements are conserved between the two organisms.;Heterogeneity of expression was examined by creating rrn-lacZ transcriptional fusions using an insertional plasmid with a promoterless lacZ gene. Measurements of beta-galactosidase activity indicate that the rrn gene sets can be grouped into strong (rrnO,rrnW), intermediate (rrnA,rrnE), and weak (rrnB,rrnD) levels of expression. The same fusions measured during spore formation shows a decrease in activity of all rrn-lacZ fusions, with a plateau at T{dollar}\sb3{dollar} (3 hours after sporulation begins). The strong and intermediate operons mentioned above all reach a similar plateau, and the weak operons reach a similar, lower plateau.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
