CONICET | Buscador de Institutos y Recursos Humanos

The climate change is affecting the crop production. Therefore, the challenge for the coming years is the development of a sustainable agriculture. In this context, reducing the use of agrochemical is relevant, since they contribute to greenhouse gas emissions. An environmentally friendly strategy is the application of biological inputs based on plant growth-promoting rhizobacteria (PGPR). For the stimulation of plant growth to be effective, PGPR must be able to persist and compete with the rhizospheric microorganisms.The bacteriocins are proteinaceous compounds that contribute to the bacterial competition among rhizosphere-associated bacteria. Therefore, knowledge of how rhizobacteria regulate bacteriocin production is an important point to investigate.Pseudomonas fluorescens SF39a is a PGPR that produces a bacteriocin like S-type pyocins. In this report, cbrA::mini-Tn5 Km1 mutant derivative of P. fluorescens SF39a which overproduces bacteriocin was obtained. CbrAB is a two-component system present in the family Pseudomonaceae and that regulates several physiological processes. Deletion mutants in other genes (cbrB, crcZ and crc) that participate in this regulatory cascade were also constructed. The production of bacteriocin was increased in cbrB-, crcZ-, like cbrA-, whereas decreased in crc-. In addition, the mutants were affected in protease and pyoverdine production compared with the wild-type strain. Moreover, we studied the ability of mutants to colonize the wheat rhizosphere under greenhouse conditions. The mutants were less competitive than the wild-type strain in the rhizosphere. To our knowledge, this research provides the first evidence that CbrAB-Crc system plays a relevant role in the regulation of the synthesis of bacteriocin and other compounds in P. fluorescens. All this together is essential for the competitiveness of P. fluorescens during the wheat colonization.

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