No abstract

Bacterial swarming is one of the most efficient methods by which bacteria colonize nutrient-rich environments and host tissues. Several mechanisms have been proposed to explain the phenomenon and the associated intricate macroscopic pattern formation, but so far no conclusive evidence has been presented that identifies the factors that control swarming. Vice versa, little is known about how swarming can be controlled. Here, by using a series of complementary genetic and physicochemical experiments and a simple mathematical analysis, we show how the bacterial swarming can be caused by a surface tension driven flow. The opportunistic pathogen, Pseudomonas aeruginosa, is studied, as it is relevant for such bacteria to control and arrest swarming. Moreover, P. aeruginosa bacteria secrete strong surface active components as part of their quorum sensing system. Our results demonstrate that surface tension gradient control can even be the dominant mechanism that drives swarming. It can be quantitatively predicted and can be expected to play a role in a wide variety of bacterial systems. The modeling reveals subtle dependencies on both the wetting conditions and the physical properties of the slime. Based on these dependencies, strategies can be devised to arrest swarming under certain conditions by simple physicochemical means.

Swarming motility is considered to be a social phenomenon that enables groups of bacteria to move coordinately atop solid surfaces. The differentiated swarmer cell population is embedded in an extracellular slime layer, and the phenomenon has previously been linked with biofilm formation and virulence. The gram-negative nitrogen-fixing soil bacterium Rhizobium etli CNPAF512 was previously shown to display swarming behavior on soft agar plates. In a search for novel genetic determinants of swarming, a detailed analysis of the swarming behavior of 700 miniTn5 mutants of R. etli was performed. Twenty-four mutants defective in swarming or displaying abnormal swarming patterns were identified and could be divided into three groups based on their swarming pattern. Fourteen mutants were completely swarming deficient, five mutants showed an atypical swarming pattern with no completely smooth edge and local extrusions, and five mutants displayed an intermediate swarming phenotype. Sequence analysis of the targeted genes indicated that the mutants were likely affected in quorum-sensing, polysaccharide composition or export, motility, and amino acid and polyamines metabolism. Several of the identified mutants displayed a reduced symbiotic nitrogen fixation activity.

Aim: The present study aims to investigate the phytochemical, antimicrobial and acute toxicity assay of methanol extract of Citrus medica L. fruit (CMF) and Citrus hystrix D.C. fruit (CHF). Place and Duration of Study: Fruit samples were collected between February to August 2018, at the Department of Life Sciences, Manipur University. Methodology: Phytochemical studies were conducted using Gas Chromatography-Mass Spectrometry (GC-MS), HR-LC-MS (High Resolution-Liquid Chromatography-Mass Spectrometry), Graphite Furnace-Atomic Absorption Spectrometry (GF-AAS), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) respectively. The standard filtered disc-diffusion method was used for antimicrobial assay. Acute toxicity was performed using 423-OECD guidelines. Results: GC-MS and HR-LC-MS analysis showed presence of Ranitidine, 4-Methylesculetin, Diosmin and Avobenzone in CMF whereas 9-Octadecenamide, Gamma-Sitosterol, n-Hexadecanoic acid, 2-Methoxy-4-Vinylphenol, Rhoifolin, Diosmin and Phytosphingosine in CHF. GF-AAS and ICP-OES study prominently showed Pb content in both the samples. Highest element in CMF was Pb (4.26±0.120 ppm) while in CHF was Cr (4.35±0.70 ppm). Antimicrobial study exhibited highest inhibitory effect of CMF against Staphylococcus aureus and Klebsiella pneumonia while CHF against Escherichia coli, Klebsiella pneumonia and Staphylococcus aureus than Gentamicin (p<0.05). No toxicity behaviour and mortality in mice were observed during acute toxicity study period even at a dose of 5000 mg/kg body weight. Changes in serum constituent level were observed however, no genotoxicity was recorded. Conclusion: We concluded that CMF and CHF cultivation site selection should be the first step to avoid Pb content. The CMF and CHF have many health beneficial constituents. From this study also concluded that CMF and CHF may be a potential source of antiulcer, antimicrobial, antiarthritic, diuretic, antiinflammatory and anticancer effects. However, further study to understand whether changes in serum constituent level for prolonged period usages as medicine or nutraceuticals is highly recommended.