Résumé
A pathogenic bacterial strain X1 was isolated from Siberian sturgeon (Acipenser baerii) suffering with bacterial septicemia. The 50% lethal concentration (LC50) of strain X1 was 5.62?105 CFU/mL, which showed that strain X1 was rather strong virulent to Acipenser baerii. Strain X1 was gram negative and 1.0 ?m～1.2 ?m ? 2.1 ?m～2.4 ?m in size with peritrichous flagella, and had ?-hemolytic activity on rabbit blood agar. By means of ATB expression identification and 16S rDNA sequence analysis, strain X1 was identified as Aeromonas hydrophila (locus number: EU669667), which was the closest relative to Aeromo-nas hydrophila strain ATCC35654 (locus number: X74676.1) with 99% homology. In addition, strain X1 was highly sensitive to cefoperazone and cravit, and intermediately sensitive to ten kinds of antibiotics in-cluding tobramycin, norfloxacin, sulperazone, kanamycin, gentamycin, fortum, vancomycin, neomycina, polymyxin B and lomefloxacin.
Résumé
In the experiment, the production of plagues by Bdellovibrio bacteria in solid medium cultivation, the reproduction of Bdellovibrio bacteria in liquid medium cultivation and the attachment of Bdellovibrio bacteria to carrier were observed, which aimed to study the effects of enrofloxacin on the growth and at-tachment ability of Bdellovibrio bacteria BDF-H16. Results indicated that in solid medium cultivation, the production of plagues by Bdellovibrio bacteria BDF-H16 was inhibited by different concentrations (2 ?g/mL, 5 ?g/mL, 10 ?g/mL, 20 ?g/mL, 50 ?g/mL) of enrofloxacin and the inhibitory effects of enrofloxacin became stronger with the increase of the concentration of enrofloxacin. Similarly, in liquid medium cultivation, the reproduction of Bdellovibrio bacteria BDF-H16 was also obviously inhibited by different concentrations ofenrofloxacin and higher concentrations of enrofloxacin such as 10 ?g/mL, 20 ?g/mL, 50 ?g/mL had stronger inhibitory effects on the reproduction of BDF-H16. However, the growth tendency of Bdellovibrio bacteria BDF-H16 was not inhibited in 10 ?g/mL enrofloxacin. Additionally, when zeolite was added, enrofloxacin had also inhibitory effects on the numbers of Bdellovibrio bacteria BDF-H16 attached to zeolite. With the increase of the concentrations of enrofloxacin, the numbers of Bdellovibrio bacteria BDF-H16 attached to zeolite became smaller and smaller. However, the attachment rate of Bdellovibrio bacteria BDF-H16 to zeo-lite became higher under 2 ?g/mL-20 ?g/mL enrofloxacin. The results above showed that enrofloxacin had inhibitory effects on the plague production and reproduction of Bdellovibrio bacteria BDF-H16, but the at-tachment ability of Bdellovibrio bacteria BDF-H16 was strengthened in liquid medium cultivation with 2 ?g/mL-20 ?g/mL enrofloxacin and zeolite, and adding zeolite helped to reduce the adverse effects of en-rofloxacin on Bdellovibrio bacteria BDF-H16.
Résumé
Six bacterial strains with malachite green decolorization ability were isolated from a sediment of aquaculture pond, and strain M6 was selected by further enrichment culture in nutrition broth with malachite green and decolorization rate comparison. The decolorization rate of strain M6 to malachite green was 97.14% in the conditon of 30?C and 150 r/min, and its morphology was observed by gram stain and electronmicroscopy, its physiological and biochemical characteristic was studied by ATB bacteria identification in-strument for identification of bacteria, and its 16S rDNA sequence was determined following PCR amplifi-cation, the sequence was aligned and the phylogenic tree was instructed with those bacterial strains of high identity with strain M6. In addition, its growth characteristics was also studied. The experimental results showed that strain M6 was gram negative and bacilliform with a flagellum at one end. Its size was 0.45 ?m ?0.84 ?m. Its colony produced on common agar plate appeared as round, light blue, dense, hard to choose; 16S rDNA sequence of strain M6 had high identity of 98%～99% with Pseudomonas sp. located in GenBank and strain M6 had the most close relative relation to Pseudomonas putida OW-16 (Locus number: DQ112328.1). Combined the results of the traditional morphological, physiological, biochemical character-istics and 16S rDNA sequence analysis, strain M6 was identified as Pseudomonas putida (Locus number: EU348741.1). Additionally, its growth curve in the condition of 30?C and 150 r/min was as follows: lag phase was 0～4 h, log phase was 4 h～64 h, stationary phase was 64 h～80 h, decline phase was after 80 h. Its best growth conditions were pH 7 and 30?C,and in the rotational speed of 50 r/min to 250 r/min. Its concen-tration increased with the increase in rotational speed.
Résumé
Bdellovibrio bacteria BDF-H16 was isolated from the gut of Carassius auratus gibelio with Aeromonas sobria.Its shape was ob- served by light microscopy,phase-contrast microscopy,electron microscopy and some of its biological characteristics were also studied.It was demonstrated that BDF-H16 was an gram-negative bacterium and had a bacilliform or arc bacilliform shape with a flagellum at one end.Its size was mostly 0.2?m～0.5?m?0.8?m～1.2?m.It had a wide prey area and could lyse all tested gram-negative bacteria and some gram-positive bacteria.The best lysis conditions to Escherichia coli were 6.75?10~9 cfu/mL of prey bacteria concentration,pH7.0～7.5,28℃.It could grow in the solid culture added 0.85%～5.00% NaCl and was inhibited by enrofloxacin and norfloxacin.