Plant Growth Promoting Rhizobacteria (PGPR) were used in many previous studies for increasing plant growth and productivity. Some mechanisms were used to enhance the soil productivity such as mineral phosphate solubilization, siderophore production, biological nitrogen fixation, induced systemic resistance and indole acetic acid (IAA) production. Some of the related researches adopted the phosphate solubilization in organisms which was repressed in the presence of succinate resembling the phenomenon of catabolite repression. In addition, the sugar utilization pattern (monosaccharide, disaccharide, and trisaccharide), organisms showed the characteristics like slow and fast-growing rhizobia respectively. Whole-genome sequencing has been used for identifying unique genes in Fast-growing Rhizobia. Existing literature in PGPR studies has been considered and mechanisms for increasing plant growth and productivity have been identified. The review tries to analyse the mechanism of phosphate solubilization and sugar utilization in fast growing Rhizobia. On the contrary, repression due to various carbon sources such as succinate has been reported, leading to succinate mediated catabolite repression.