Genetic supression analysis of an asgA missense mutant in Myxococcus xanthus /
The A-signal is an extracellular cell density signal required
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| Format: | Thesis eBook |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1997.
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| Subjects: | |
| Online Access: | Link to OAK Trust copy |
| Summary: | The A-signal is an extracellular cell density signal required for multicellular development in Myxococcus xanthus. Three unlinked loci, asga, asgb, and asgc, encode regulatory proteins that are thought to function in a pathway leading to the production of A-signal. This project is concerned with asga, which encodes a protein similar to those found in two- component signal transduction systems. AsgA is unusual in that it consists entirely of a receiver domain followed by a transmitter domain, without any membrane-spanning regions or input and output domains. Our goal is to identify genes encoding products that interact with AsgA or that are otherwise important for Asignal production or sensing. To identify these genes, we have initiated a genetic suppression analysis of an asga missense mutant. Wfm, isolated forty-two independent pseudorevertants containing mutations that suppress the asgA473 mutation. We used a DNA fragment containing the wild type asga sequence disrupted with the gene for kanamycin resistance to transform each pseudorevertant. This gene replacement experiment allowed us to distinguish strains containing mutations that bypass the need for AsgA from those that do not. Strains containing bypass mutations are still able to develop after such a replacement; those containing reversions and interaction suppressors cannot. Data from the gene replacement experiments suggest that nineteen pseudorevertants contain bypass mutations. We then determined the percent linkage of the suppressing mutation in each pseudorevertant to a Tn5 80% linked to the original asgA473 allele. All kanamycin- resistant transductants of pseudorevertants containing mutations that are unlinked to asga should develop because asgA473 has replaced itself at the given frequency. However, if the suppressing mutation is linked to the original asga gene, the number of kanamycin-resistant transductants unable to develop will be proportional to the percent linkage experiments suggests that seven of the pseudorevertants contain reversions while sixteen contain interaction suppressors. Each pseudorevertant was also assayed for production of A-signal. Only four pseudorevertant strains were found to produce significant levels of A-signal. Direct and viable spore counts were done to compare sporulation levels of each pseudorevertant to wild type levels. |
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| Item Description: | Vita. "Major subject: Microbiology". |
| Physical Description: | viii, 50 leaves : illustrations ; 28 cm. Also available online. Issued also on microfiche from Lange Micrographics. |
| Bibliography: | Includes bibliographical references: pages 43-49. |