Two-component system CbrA/CbrB controls alginate production in Azotobacter vinelandii

Azotobacter vinelandii, belonging to the Pseudomonadaceae family, is a free-living bacterium that has been considered to be a good source for the production of bacterial polymers such as alginate. In A. vinelandii the synthesis of this polymer is regulated by the Gac/Rsm post-transcriptional regulat...

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Bibliographic Details
Published in:Microbiology (Society for General Microbiology) 2017-07, Vol.163 (7), p.1105-1115
Main Authors: Quiroz-Rocha, Elva, Bonilla-Badía, Fernando, García-Aguilar, Valentina, López-Pliego, Liliana, Serrano-Román, Jade, Cocotl-Yañez, Miguel, Guzmán, Josefina, Ahumada-Manuel, Carlos L, Muriel-Millán, Luis Felipe, Castañeda, Miguel, Espín, Guadalupe, Nuñez, Cinthia
Format: Article
Language:English
Subjects:
Alginates
Azotobacter vinelandii - genetics
Azotobacter vinelandii - metabolism
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Flavoproteins - genetics
Flavoproteins - metabolism
Gene Expression Regulation, Bacterial
Glucuronic Acid - biosynthesis
Hexuronic Acids
Pseudomonas aeruginosa - genetics
Pseudomonas aeruginosa - metabolism
Transcription Factors - genetics
Transcription Factors - metabolism
Transcription, Genetic
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Summary:Azotobacter vinelandii, belonging to the Pseudomonadaceae family, is a free-living bacterium that has been considered to be a good source for the production of bacterial polymers such as alginate. In A. vinelandii the synthesis of this polymer is regulated by the Gac/Rsm post-transcriptional regulatory system, in which the RsmA protein binds to the mRNA of the biosynthetic algD gene, inhibiting translation. In several Pseudomonas spp. the two-component system CbrA/CbrB has been described to control a variety of metabolic and behavioural traits needed for adaptation to changing environmental conditions. In this work, we show that the A. vinelandii CbrA/CbrB two-component system negatively affects alginate synthesis, a function that has not been described in Pseudomonas aeruginosa or any other Pseudomonas species. CbrA/CbrB was found to control the expression of some alginate biosynthetic genes, mainly algD translation. In agreement with this result, the CbrA/CbrB system was necessary for optimal rsmA expression levels. CbrA/CbrB was also required for maximum accumulation of the sigma factor RpoS. This last effect could explain the positive effect of CbrA/CbrB on rsmA expression, as we also showed that one of the promoters driving rsmA transcription was RpoS-dependent. However, although inactivation of rpoS increased alginate production by almost 100 %, a cbrA mutation increased the synthesis of this polymer by up to 500 %, implying the existence of additional CbrA/CbrB regulatory pathways for the control of alginate production. The control exerted by CbrA/CbrB on the expression of the RsmA protein indicates the central role of this system in regulating carbon metabolism in A. vinelandii.
ISSN:1350-0872
1465-2080
DOI:10.1099/mic.0.000457