Two-component system CbrA/CbrB controls alginate production in Azotobacter vinelandii
Quiroz-Rocha, Elva and Bonilla-Badía, Fernando and García-Aguilar, Valentina and López-Pliego, Liliana and Serrano-Román, Jade and Cocotl-Yañez, Miguel and Guzmán, Josefina and Ahumada-Manuel, Carlos L. and Muriel-Millán, Luis Felipe and Castañeda, Miguel and Espín, Guadalupe and Nuñez, Cinthia,, 163, 1105-1115 (2017),
doi = https://doi.org/10.1099/mic.0.000457,
publicationName = Microbiology Society,
issn = 1350-0872,
abstract= 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.,
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