Effect of CTXφ prophage deletion in cholera agent on expression of regulatory genes controlling virulence and biofilm formation

• Published in: Russian journal of genetics 2017-03, Vol.53 (3), p.302-313
• Main Authors: Smirnova, N. I., Agafonov, D. A., Kul’shan’, T. A., Shchelkanova, E. Yu, Krasnov, Ya. M., Lozovsky, Yu. V., Kutyrev, V. V.
• Format: Article
• Language: English
• Subjects: Animal Genetics and Genomics; Biomedical and Life Sciences; Biomedicine; Genetics of Microorganisms; Human Genetics; Microbial Genetics and Genomics
• ISSN: 1022-7954; 1608-3369
• DOI: 10.1134/S1022795417020119

This work represents the results of comparative analysis of the nucleotide sequences in the chromosomal region containing CTXφ prophage in isogenic toxigenic (Tox + ) and nontoxigenic (Tox – ) strains of Vibrio cholerae biovar El Tor. It is shown that spontaneous mutants which have identical Tox – phenotype are formed either owing to the precise elimination of CTX φ prophage from the chromosome (deletion size is 6.9 kb) or owing to imprecise elimination with the additional loss of two other prophages (RS1φ and TLC φ ), which are adjacent to CTX φ prophage (deletion size is 17.4 kb). It is revealed that, in the nontoxigenic mutants, CTX φ deletion initiates simultaneous change in several phenotypic properties, which are associated with virulence or biofilm formation, such as colonizing ability, HA/P production, VPS, and motility. For the first time, it is stated that the cause of the pleiotropic effect of the CTX φ deletion is a cascade decrease in the transcription levels of seven regulatory genes ( toxR, aphA, tcpP, tcpH, toxT, vpsT, vpsR ) which control virulence and biofilm formation processes in the cholera agent.