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

2017; Microbiology Society; Volume: 163; Issue: 7 Linguagem: Inglês

10.1099/mic.0.000457

1465-2080

Elva Quiroz‐Rocha, Fernando Bonilla-Badía, Valentina García-Aguilar, Liliana López-Pliego, Jade Serrano-Román, Miguel Cocotl‐Yañez, Josefina Guzmán, Carlos L. Ahumada-Manuel, Luis Felipe Muriel‐Millán, Miguel Castañeda, Guadalupe Espı́n, Cinthia Núñez,

Polyamine Metabolism and Applications

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.