Ralstonia solanacearum is a rod-shaped phytopathogenic bacterium that causes lethal wilt disease in many plants. On solid agar growth medium, in the early hour of the growth of the bacterial colony, the type IV pili-mediated twitching motility, which is important for its virulence and biofilm formation, is prominently observed under the microscope. In this study, we have done a detailed observation of twitching motility in R. solanacearum colony. In the beginning, twitching motility in microcolonies was observed as a density-dependent phenomenon that influences the shape and sizes of the microcolonies. No such phenomenon was observed in Escherichia coli, where twitching motility is absent. In the early phase of colony growth, twitching motility exhibited by the cells at the peripheral region of the colony was more prominent than the cells towards the centre of the colony. Using a time scale photography and merging those into a video, twitching motility was observed as an intermittent phenomenon that progresses in layers in all directions as finger-like projections at the peripheral region of a bacterial colony. Each layer of bacteria twitches on top of the other and produces a multi-layered film-like appearance. We found that the duration between the emergence of each layer diminishes progressively as the colony becomes older. This study on twitching motility demonstrates distinctly heterogeneity among the cells within a colony regarding their dynamics and the influence of microcolonies on each other regarding colony shape and size.

Antisense technology has been developed as the next generation drug discovery methodology by which unwanted gene expression can be inhibited by targeting mRNA specifically with antisense oligonucleotides. The computational studies of antisense modifications based on phosphorothioate (PS), methoxyethyl (MOE), locked nucleic acids (LNA) may help to design better novel modifications. In the present study, five novel LNA based modifications have been proposed. The conformational search has been done to identify the most stable and alternative stable conformations. The geometry optimization followed by single point energy calculation has been done at B3LYP/6-31G(d,p) level for gas phase and B3LYP/6-311G(d,p) level for the solvent phase for all modifications at monomer as well as base pair level. The electronic properties and the quantum chemical descriptors of the antisense modifications were derived and compared. The local and global reactivity descriptors, such as hardness, chemical potential, electronegativity, electrophilicity index, Fukui function all were calculated at the DFT level for the optimized geometries. A comparison of global reactivity descriptors confirmed that LNA based modifications are the most reactive modifications. They may form a stable duplex when bound to complementary nucleotides, compared to other modifications. Therefore, we are proposing that one of our proposed antisense modifications (A3) may show strong binding to the complementary nucleotide as LNA and may also show reduced toxic effects like MOE. The base pair studies may help us to understand the extent to which our proposed modifications can form standard Watson-Crick base pairing required for oligomer duplexes. This computational approach may be very useful to propose novel modifications prior to undergoing synthesis experimentally in the area of antisense or RNAi technology.