Preferential Utilization of Sugars and Their Effect on Phosphate Solubilization in Rhizobium sp RM

Abstract

Rhizobia are a group of bacteria existing symbiotically in and around roots of newlineleguminous plants. Members of Rhizobium species have received extensive importance newlineowing to their ability to form nodules on roots where they carry out nitrogen fixation newlineleading to increment in soil fertility. They have hence, been considered as potent newlinecandidates for biofertilizers. Although benefitting the plants by their nitrogen-fixing trait newlineat lab-scale, they are often found futile in field trials. The complex signalling between the newlineplants and rhizobia in the rhizosphere to establish the symbiotic relation has been a major newlinearea of research over decades. However, metabolism and physiology of these bacteria newlinehave received less attention. The limited understanding of biochemical pathways and newlineresponses to various energy conditions is a barrier in harnessing them as successful newlinebiofertilizers. Another major blind spot with respect to understanding the bacterial newlinephysiology is the phenomenon of carbon catabolite repression that helps bacteria to newlinesurvive in the competitive environment. It is known that rhizobia, unlike E. coli and B. newlinesubtilis, and like pseudomonads, prefer organic acids over sugars, however, the newlinepreference among sugars and the molecular basis underlying it has not been explored. newlineThere are many sugars present in the rhizosphere as a result of plant root exudates. newlineMajority of the plants have glucose (G), fructose (F), arabinose (A) and xylose (X) present newlinein their root exudations. The present study aims to explore the effect of utilization of these newlinesugars on the mineral phosphate solubilization (MPS) trait of Rhizobium sp. RM. Further, newlinesequential uptake of these rhizospheric sugars and involvement of global regulators is newlineinvestigated. We hypothesize that utilization of different sugars by Rhizobium sp. RM newlinereleases various organic acids mediating the MPS phenotype. Additionally, preferential newlineutilization of sugars might be governed at the transporter level, initial steps of sugar newlinemetabolism and /or via the regulation of few regul