Résumé
A systematic analysis of the typeⅢ secretion genes of Aeromonas hydrophila strain AH-1 by constructing ahyR and ahyI mutant revealed that they are under quorum-sensing control. This observation was supported by the down-regulation of the TTSS genes in the presence of lacZ-TTSS gene promoter and the corresponding advanced secretion of AexT in ahyI mutant.
Résumé
The temperature and salinity ranges for growth of twelve strains of marine Bdellovibrio-and-like organisms (BALOs) which affiliated with four different phylogenetic clusters in the family Bacteriovoracaceae and the lytic ability of them to six kinds of common shrimp pathogen vibrios were studied. The morphological characteristics of four representative strains were examined with transmission electron microscope. The results showed that the strains within the same cluster or sub-cluster had identical growth temperature or salinity. The growth temperature ranges of clusters IV, VI, IX and X strains were 20?C～35?C, 15?C～35?C, 15?C～40?C, 10?C～40?C, respectively, and the optimum growth temperature was about 30?C or 35?C. The growth salinity ranges of clusters IV, VI, IX and X strains were 5‰～40‰, 2.5‰～30‰, 5‰～60‰ and 5‰～60‰, and the optimum salinities were about 10‰, 5‰, 20‰ and 20‰, respectively. Three of the six kinds of vibrios tested were lysed by all the BALOs, while the others could only be lysed by some of the BALOs. However, differential lysis to some of the vibrios was also observed among BALOs within the same cluster. The four strains of different clusters all exhibited typical BALOs morphology, hav-ing vibrioid cell with a single polar flagellum.