Background:Escherichia coli have an optimum pH range of 6-7 for growth and survival that's why, called neutrophiles. The ΔpH across the cytoplasmic membrane is linked to cellular bioenergetics and metabolism of the body which is the major supplier of the proton motive force, so homeostasis of cellular pH is essential. When challenged by low pH, protons enter the cytoplasm; as a result, mechanisms are required to alleviate the effects of lowered cytoplasmic pH.Materials and Methods:The activities of Succinate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase and glucose-6-phosphate dehydrogenase in acid shocked cells of E. coli DH5 α and E. coli W3110 subjected to pH 3, 4, and 5 by two types of acidification, like external (using 0.1 N HCl), external along with the monensin (1 μM) and cytoplasmic acidification using the sodium benzoate as an acid permeant (20 mM) which is coupled to the electron transport chain by the reducing power, as yet another system possessed by E. coli as an armor against harsh acidic environments.Result:Results showed that an exposure to acidic environment (pH 3, 4 and 5) for a short period of time increased the activities of these dehydrogenases in all types of acidification except cytoplasmic acidification, which shows that higher recycling of reducing power results in pumping out of protons from the cytoplasm through the electron transport chain complexes, thereby restoring the cytoplasmic pH of the bacteria in the range of 7.4-7.8.Conclusion:Study indicates that acid shocked E. coli for a period of 2 h can survive for a sustained period.

Since past three decades new discoveries in plant genetic engineering have shown remarkable potentials for crop improvement. Agrobacterium Ti plasmid based DNA transfer is no longer the only efficient way of introducing agronomically important genes into plants. Recent studies have explored a novel plant genetic engineering tool, Rhizobia sp., as an alternative to Agrobacterium, thereby expanding the choice of bacterial species in agricultural plant biotechnology. Rhizobia sp. serve as an open license source with no major restrictions in plant biotechnology and help broaden the spectrum for plant biotechnologists with respect to the use of gene transfer vehicles in plants. New efficient transgenic plants can be produced by transferring genes of interest using binary vector carrying Rhizobia sp. Studies focusing on the interactions of Rhizobia sp. with their hosts, for stable and transient transformation and expression of genes, could help in the development of an adequate gene transfer vehicle. Along with being biologically beneficial, it may also bring a new means for fast economic development of transgenic plants, thus giving rise to a new era in plant biotechnology, viz. "Rhizobia mediated transformation technology."

The CaCl2 method, commonly used for transformation of Escherichia coli, was modified and used to develop a simpler and easier transformation method for Rhizobia sp. Two species of Rhizobia, Sinorhizobium meliloti MTCC 100 and Mesorhizobium ciceri TAL 620, were transformed with the 13.2 kb binary vector pGA482. At an optical density of 0.4, the transformation efficiencies in Sinorhizobium meliloti MTCC 100 and Mesorhizobium ciceri TAL 620 were 104 and 103, respectively. Competent cells of Sinorhizobium meliloti MTCC 100 were prepared at different growth intervals and transformed by the same vector. A maximum transformation efficiency of 104 was achieved at an optical density of 0.5.