Characteristics And Application Of Lux Genes From Vibrio Qinghaiensis And Photorhabdus Luminescens

Bioluminescent bacteria had a unique ability to autonomously produce a luminescent signal by lux genes coding luciferase. This research chose Vibrio qinghaiensis Q67 and Photorhabdus luminescens as original strains, aimed to compare the characteristics of lux genes from two different bacteria. Vibrio qinghaiensis Q67 grew in freshwater without Na+, while Photorhabdus luminescens was terranous bacteria, parasitizing in the intestine of insect pathogenic nematode. This test built plasmids pHSG396-P.luxCDABE and pHSG396-Q.luxCDABE, to take E. coli Top10 as host bacteria. Using blue-white selection and electrophoresis analysis, P. harbouring lux genes from Photorhabdus luminescens and Q. harbouring lux genes from Vibrio qinghaiensis Q67 were screened.Light intensity of two bacteria in different growing stages was mesured under the same cultural condition. Results showed that, P. and Q. had similar growth regular, 0-3 h as adjustment phrase, 4-10 h as logarithmic phase, and after 11 h as stationary phase. Two bacteria gave out very weak light at early stage, but light intensity increased with time goiong on. P. reached its luminescent peak 5894 at 12 h, which was the early stationary phase, but the luminescent peak 1848 of Q. was at later logarithmic phase of 10 h. After the stationary stage, light intensity of two bacteria descended identically.Effects of IPTG, pH, Cml, decanal, NaCl and temperature on luminescence were studied. The results showed that 0.1 mg/mL IPTG was the best level to induce two bacteria, while higher level restrained light. Lux genes were prone to be expressed in aicdic condition, pH7 for P. and pH6 for Q. the highest luminescence coming. When Cml absent light intensity of P. reached maxmum, but 25 μg/mL was best for Q. luminescence. The optimal concentration of decanal was 0.1 μL/mL for P. and 1.0 μL/mL for Q. NaCl at 5 mg/mL P. had the max light intensity, while Q. was depressed by every level of NaCl tested. The best temperature of two bacteria was 37 ℃, the highest temperature two bacteria could bear were 40 ℃ for P. and 43 ℃ for Q. At room ?temperature, P. had better stability than Q. in light maintance.Effects of four antibiotics oen two bacteria were tested after 15 min reaction, taking water and milk as solvent. Results showed that, at 15 min, to take water as solution, P. can detect Gentamicin and Tetracycline,for the stong antagonistic action, and Q. can detect Streptomycin, Gentamicin and Tetracycline. To take milk as solution, P. can detect Streptomycin and Tetracycline, for the stong antagonistic action, and Q. can detect Penicillium G and Gentamicin. In detail, for Streptomycin, 1-1000 mg/L had no significant effect on P. while 10000 mg/L depressed P. greatly. All level Streptomycin tested depressed Q.. For Penicillium G, 0.1 and 1 mg/L depressed P. and 100 mg/L above stimulated P. 0.1-10000 mg/L Penicillium G all depressed Q..For Gentamicin, all tested concentration depressed two bacteria, the strongest inhibition level were 0.1mg/L for P. and 1000 mg/L for Q..For Tetracycline, 0.1 mg/L promoted P. 1-10000 mg/L depressed P. And all tested concentration depressed Q. In the milk, four antibiotics varied from 0.1 mg/m L to 1.0 mg/mL. For Streptomycin, intensiy of P. had negative linear correlation with concentration(R2=0.804). All level depressed Q. yet there was no correlation between intensity and concentraion. For Penicillium G, except 0.3 mg/mL stimulated light of P. all level played restrained role(p<0.05), 1.0 mg/mL mostly. All level depressed Q. and 0.5 mg/mL had strongest effect. For Gentamicin, except 0.3 mg/mL had less inhibition, other level had no signifecant inhibitional effect on P. 0.1 mg/mL stimulated Q., and other concentration had negative linear correlation with Q.intensity(R2=0.9807). For Tetracycline, intesity of P. sharply decreased with concentration increasing, while 0.1-0.9 mg/mL all stimulated Q. luminescence and 0.3 mg/mL performed mostly.