An Azospirillum brasilense Tn5 mutant with modified stress response and impaired in flocculation |
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Authors: | Galindo Blaha Carlos Alfredo Schrank Irene Silveira |
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Institution: | (1) Programa de Pós-Graduação em Genética e Biologia Molecular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil;(2) Departamento de Biologia Molecular e Biotecnologia, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Campus do Vale, Porto Alegre, CEP 91591-970, CP 15005, Brazil |
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Abstract: | The analysis of an A. brasilense Tn5 mutant shows significant phenotypic differences compared to the wild type isogenic strain. The transposon was located disrupting
an open reading frame of 840 bp (ORF280) which exhibits similarity to the universal stress protein (USP) family. The USP family
encompasses proteins that are expressed as a response to cell growth arrest. The mutant revealed a pleiotrophic phenotype
with respect to different stress conditions. The ORF mutation results in an increased sensitivity of cells to carbon starvation
and heat-shock treatment. However, the mutant strain displays a higher tolerance to oxidative stress agents. In contrast to
the isogenic parent strain, colonies of the mutant are weakly stained by Congo red added to solid media and are impaired in
flocculation. Scanning electron micrographs revealed that the mutant lacks part of the surface material present as a thick
layer of exopolysaccharides on the surface of the wild type cells. The pleiotrophic phenotype revealed for this mutant and
the similarity of the C-terminal region of ORF280 to UspA from E. coli indicates that the A. brasilense ORF280 may be a Usp-like protein.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | Azospirillum Flocculation Stress response USP family |
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