Prodigiosin found in Serratia marcescens y2 initiates phototoxicity in the cytomembrane

Background: Light can be absorbed by bacterial pigment and affects its growth. Prodigiosin is a red pigment found in various bacterial species. The purpose of this study was to investigate the impacts of light on prodigiosin production, biomass formation, and membrane integrity of Serratia marcescens y2. Results: S. marcescens y2 grew better and produced more intracellular prodigiosin in darkness than in illumination. The pigment leakage ratio from cells was detected more in light than in darkness conditions. Ethidium bromide uptake assay could visually prove the prodigiosin-related loss of membrane integrity under illumination. A higher concentration of malondialdehyde (MDA) was detected in light-treated culture than in darkness. Tests of different light treatments (red, yellow, blue and green) showed that the maximum extracellular pigment and the minimum biomass formation and intracellular pigment were obtained in green light. Conclusions: Prodigiosin could absorb light, and then initiate phototoxicity damage of the cytomembrane.

Cloning, expression and characterization of aerolysin from Aeromonas hydrophila in Escherichia coli.

Aerolysin is a toxin (protein in nature) secreted by the strains of Aeromonas spp. and plays an important role in the virulence of Aeromonas strains. It has also found several applications such as for detection of glycosylphosphatidylinositol (GPI)-anchored proteins etc. A. hydrophila is a ubiquitous Gram-negative bacterium which causes frequent harm to the aquaculture. To obtain a significant amount of recombinant aerolysin in the active form, in this study, we expressed the aerolysin in E. coli under the control of T7 RNase promoter. The coding region (AerA-W) of the aerA gene of A. hydrophila XS91-4-1, excluding partial coding region of the signal peptide was cloned into the vector pET32a and then transformed into E. coli b121. After optimizing the expression conditions, the recombinant protein AerA-W was expressed in a soluble form and purified using His.Bind resin affinity chromatography. Recombinant aerolysin showed hemolytic activity in the agar diffusive hemolysis test. Western blot analysis demonstrated good antigenicity of the recombinant protein.