Role of Crc in regulation of PQQ GDH dependent mineral phosphate solubilization phenotype and its repression in Acinetobacter species

Abstract

newlinePlant growth-promoting rhizobacteria (PGPR) are healthful bacteria present in or on the newlineroot rhizosphere of the plant and have been explored as bio-inoculants in the agricultural newlinefields for several decades. Many PGPR strains are routinely employed but their positive newlineresponses to plants are often limited to laboratory or greenhouse and the results are newlineinconsistent in field conditions. The plant roots secrete organic compounds in root exudates newlinethat help microbes for survival in the rhizosphere and they in return promote plant growth. newlineThe compositions of root exudates vary according to the plant species and often comprise newlinecomplex mixtures. Presence of various organic acids and sugars in rhizosphere execute CCR newlinefor preferential utilization of carbon sources. This facilitates the bacterium to compete and newlinesurvive among existing microbial communities. While it is not yet clear how bacteria choose newlinethe substrate in a rhizosphere where CCR could be regulating metabolism, various newlineexperiments have been conducted in vitro with commonly found organic acids present in the newlineroot exudate. Here in this study, we looked for the mechanisms underlying the succinate newlinemediated catabolite repression (SMCR) of the gluconate arbitrated mineral phosphate newlinesolubilization (MPS) in Acinetobacter sp. SK2. newlineAcinetobacter sp. SK2, a potential plant growth promoting rhizobacteria isolated from the newlinerhizosphere of Vigna radiata that solubilized 682 and#956;g/ml of tricalcium phosphate (TCP) and 86 newlineand#956;g/ml of rock phosphate (RP) with concomitant decrease in pH up to 4 due to the production newlineof gluconate. The mechanism of MPS in Acinetobacter sp. SK2 was studied in detail and the newlinerole of enzymes responsible for periplasmic glucose oxidation (membrane glucose newlinedehydrogenase-mGDH) and sGDH (soluble glucose dehydrogenase) was elucidated. newlineGluconate mediated MPS phenotype of Acinetobacter sp. SK2 was post-transcriptionally newlinerepressed by Crc in presence of succinate+glucose. Gluconate production and expression of newlinemGDH and sGDH was found only in glucose but not i