Plant Growth Promoting Rhizobacteria (PGPR) involves the use of large array of soil bacteria to improve yield, plant growth and sustainable food production. As free living and symbiotic rhizobacteria, PGPR exert its role by colonizing extracellular and/or intracellular rhizoenvironment in the quest for carbon source. In the past decades, focus has been on developing a biosafety agro base approach void of continuous burden on soil micro flora as a result of agrochemicals application. However, with clear understanding of PGPR mechanisms of action "biocontrol, biofertilization and biostimulation", more hope on the possibility of curbing food insecurity amidst rising population has been strengthened. Seeds or soil application of PGPR inoculants enhances phosphates solubilization, biological nitrogen fixation and secretion of plant hormones (indole acetic acid, gibberellins, cytokinins and ethylene) needed for growth and adaptation in stressed environment. As soil pathogen constantly rival the roles of these organisms, PGPR has developed over time wide spectrum of strategies in the form of systemic resistance, iron, space and nutrient competition, antibiotics synthesis, lytic acid production and hydrogen cyanide for efficient food production. In view of this, the review broadens our scope on the use of PGPR as an efficient microbial consortium for enhanced agrobiology and sustenance especially in the tropics were paucity of data on its use, implementation and application of genetically modified organisms has long prevailed.

Crude oil and its derivatives are among the most potent contaminants of the environment, affecting both the biotic and abiotic components of the ecosystem. The present study was undertaken to evaluate the effects of crude oil contamination on terrestrial and aquatic microorganisms. Eight different concentrations of crude oil (Bonny light) were used to contaminate soil and water samples obtained from pristine environments. Both the control and polluted samples were organized in triplicates and the studies carried out by plate count procedures using nutrient agar and sabouraud dextrose agar for bacteria and fungi respectively. Effect of the crude oil on bacterial and fungal counts was significantly (P<0.05) inhibitory and dose-dependent with 15.0% and 20.0% levels of pollution having the highest impact on the microbial counts. In the control soil samples, bacterial numbers varied between 2.32x10 9 to 2.80x10 9 cfu/g while their numbers varied between 2.00x10 8 to 2.77x10 9 cfu/g in the test samples. For the fungi, numbers varied from 1.02x10 7 to 1.39x10 7 cfu/g in the control soil while it was reported 1.60x10 5 to 1.18x10 7 cfu/g for the test samples. Results showed that both bacteria and fungi were significantly affected by crude oil contamination, among tested microorganisms marine microorganisms demonstrated some tolerance against crude oil contamination.