Please use this identifier to cite or link to this item: https://une.intersearch.com.au/unejspui/handle/1959.11/926
Title: Mutants with Enhanced Nitrogenase Activity in Hydroponic 'Azospirillum brasilense'-Wheat Associations
Contributor(s): Pereg, Lily  (author); Gilchrist, K (author); Kennedy, IR (author)
Publication Date: 2000
Handle Link: https://hdl.handle.net/1959.11/926
Abstract: The effect of a mutation affecting flocculation, differentiation into cyst-like forms, and root colonization on nitrogenase expression by 'Azospirillum brasilense' is described.The gene flcA of strain Sp7 restored these phenotypes in spontaneous mutants of both strains Sp7 and Sp245. Employing both constitutive pLA-lacZ and nifH-lacZ reporter fusions expressed in situ, the colony morphology, colonization pattern, and potential for nitrogenase activity of spontaneous mutants and flcA Tn5-induced mutants were established.The results of this study show that the ability of Sp7 and Sp245 mutant strains to remain in a vegetative form improved their ability to express nitrogenase activity in association with wheat in a hydroponic system. Restoring the cyst formation and colonization pattern to the spontaneous mutant Sp7-S reduced nitrogenase activity rates in association with plants to that of the wild-type Sp7.Although Tn5-induced flcA mutants showed higher potentials for nitrogenase expression than Sp7, their potentials were lower than that of Sp7-S, indicating that other factors in this strain contribute to its exceptional nitrogenase activity rates on plants. The lack of lateral flagella is not one of these factors, as Sp7-PM23, a spontaneous mutant impaired in swarming and lateral-flagellum production but not in flocculation, showed wild-type nitrogenase activity and expression. The results also suggest factors of importance in evolving an effective symbiosis between 'Azospirillum' and wheat, such as increasing the availability of microaerobic niches along the root, increased supply of carbon sources by the plant, and the retention of the bacterial cells in vegetative form for faster metabolism.
Publication Type: Journal Article
Source of Publication: Applied and Environmental Microbiology, 66(5), p. 2175-2184
Publisher: American Society for Microbiology
Place of Publication: United States of America
ISSN: 0099-2240
Field of Research (FOR): 060405 Gene Expression (incl Microarray and other genome-wide approaches)
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
Other Links: http://aem.asm.org/cgi/content/abstract/66/5/2175
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