A New Twist on a Classic Paradigm: Illumination of a Genetic Switch in
            <i>Vibrio cholerae</i>
            Phage CTXΦ

Nickels, Bryce E.

doi:10.1128/jb.01150-09

Cited by 7 publications

(9 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, no cleavage products of CI were observed in vitro following incubation at alkaline pH or following P L induction in vivo (Fig. 5A and B), suggesting that induction of the lytic promoter in phage TP901-1 occurs by a mechanism different from that of phage lambda, but may use a mechanism somewhat similar to the switch of Vibrio cholerae phage CTX⌽, where the lysogenic promoter also is controlled by two DNA binding proteins, the phage-encoded RstR and the host-encoded SOS response regulator LexA (20). However, is should be noted that no lexA homologue is found in the genome sequence of the Lactococcus lactis MG1363 strain used in our studies.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the CI Repressor Protein Encoded by the Temperate Lactococcal Phage TP901-1

2010

View full text Add to dashboard Cite

The gene regulatory mechanism determining the developmental pathway of the temperate bacteriophage TP901-1 is regulated by two phage-encoded proteins, CI and MOR. Functional domains of the CI repressor were investigated by introducing linkers of 15 bp at various positions in cI and by limited proteolysis of purified CI protein. We show that insertions of five amino acids at positions in the N-terminal half of CI resulted in mutant proteins that could no longer repress transcription from the lytic promoter, P L . We confirmed that the N-terminal domain of CI contains the DNA binding site, and we showed that this part of the protein is tightly folded, whereas the central part and the C-terminal part of CI seem to contain more flexible structures. Furthermore, insertions at several different positions in the central part of the CI protein reduced the cooperative binding of CI to the operator sites and possibly altered the interaction with MOR.Temperate bacteriophages provide a classical example for studies of the choice between two alternative modes of development. Following infection of a sensitive host, a temperate bacteriophage may choose (i) to enter the lysogenic state, in which the viral genome is silenced and integrated into the host genome to be replicated along with the host DNA when the cell divides, or (ii) to enter the lytic state, in which phage replication in the cell leads to production of new phages, cell lysis, and release of phage progeny (4, 21, 25). The choice made by a temperate phage regarding which life cycle to enter is based on a gene regulatory system named the genetic switch (25).A DNA fragment obtained from the temperate lactococcal phage TP901-1 cloned into a low-copy-number plasmid was shown to exhibit bistable gene expression mimicking the lysislysogeny choice when introduced into Lactococcus lactis. The cloned DNA fragment contains the two divergently oriented early promoters P R and P L and the two promoter proximal genes cI and mor (Fig. 1A). P L is the lytic promoter from which MOR, the modulator of repression, is the first gene to be transcribed, and P R is the promoter for CI repressor synthesis. Furthermore, three CI binding sites, O R , O L , and O D , are present on the DNA fragment, which was fused to the reporter genes lacLM in order to measure the activity of either P R or P L (22). Following transformation of such plasmids (pMAP50 in Fig. 1B) into a lactococcal host, two different stable states are obtained; either P L is repressed by CI (immune state, shown in Fig. 1C) or P L is open (anti-immune state, shown in Fig. 1D). The open state of P L requires a large amount of MOR, which apparently counteracts CI binding to the operator sites (17). Knockout mutations introduced in either cI or mor showed that tight repression of P R in the anti-immune state requires the presence of both MOR and CI, and hence this repression of P R was suggested to occur by binding of both proteins to the DNA (Fig. 1D) (22). The nature and the location of the protein complex on the DNA are unkno...

show abstract

Section: Discussionmentioning

confidence: 99%

Characterization of the CI Repressor Protein Encoded by the Temperate Lactococcal Phage TP901-1

2010

View full text Add to dashboard Cite

show abstract

“…It is well known that the production and life cycles of temperate phages are under the strict control of the host (5)(6)(7)(8). In recent years, it has become increasingly apparent that temperate phages could modulate the functions of host cells.…”

mentioning

confidence: 99%

Role of Filamentous Phage SW1 in Regulating the Lateral Flagella of Shewanella piezotolerans Strain WP3 at Low Temperatures

Jian

Xiao

Wang

2013

Appl Environ Microbiol

View full text Add to dashboard Cite

b Low-temperature ecosystems represent the largest biosphere on Earth, and yet our understanding of the roles of bacteriophages in these systems is limited. Here, the influence of the cold-active filamentous phage SW1 on the phenotype and gene transcription of its host, Shewanella piezotolerans WP3 (WP3), was investigated by construction of a phage-free strain (WP3⌬SW1), which was compared with the wild-type strain. The expression of 49 genes, including 16 lateral flagellar genes, was found to be significantly influenced by SW1 at 4°C, as demonstrated by comparative whole-genome microarray analysis. WP3⌬SW1 was shown to have a higher production of lateral flagella than WP3 and enhanced swarming motility when cultivated on solid agar plates. Besides, SW1 has a remarkable impact on the expression of a variety of host genes in liquid culture, particularly the genes related to the membrane and to the production of lateral flagella. These results suggest that the deep-sea bacterium WP3 might balance the high-energy demands of phage maintenance and swarming motility at low temperatures. The phage SW1 is shown to have a significant influence on the swarming ability of the host and thus may play an important role in adjusting the fitness of the cells in the deep-sea environment. Due to a growing awareness that viruses, especially phages, are the most abundant biological entities on the planet and that they play an irreplaceable role in all types of ecosystems, research into phage-host interactions has garnered much attention. Cold environments, including glaciers, permafrost, and deep seas, cover a large part of the earth, and viruses are abundant and functional in these environments (1-4). Nevertheless, our understanding of phage-host interactions and of the extent to which phages influence the adaptation and evolution of hosts in lowtemperature environments is still incomplete (4).It is well known that the production and life cycles of temperate phages are under the strict control of the host (5-8). In recent years, it has become increasingly apparent that temperate phages could modulate the functions of host cells. In Escherichia coli, phages have been found to influence divergent functions of the lysogenic cell, including replication, transcription, translation, degradation, and proteolysis (9-13). Bacterial viruses can regulate the expression of host genes and decrease the growth rate of E. coli in energy-poor environments, thus increasing the population fitness of E. coli (14). Although they can be cryptic and lose their basic function during evolution, prophages allow bacteria to cope with adverse environments and osmotic, oxidative, and acid stresses, increasing host growth and biofilm formation (15, 16).The filamentous phages are temperate phages whose DNA integrates into the bacterial genome, and they become prophages and replicate with the host (17). In addition, some of the phage DNA can exist in the cytoplasm, such as in a plasmid, and this is called replicative-form (RF) DNA. The release of filamentous vir...

show abstract

“…McLeod and colleagues (16) proposed a model for maintaining CTX lysogen by toxigenic V. cholerae (35). In this context, RstR inhibits transcription from P A by binding to the high-affinity operator, O1, and two weaker operators, O2 and O3, whereas LexA inhibits transcription from P A by binding a single site (SOS box) that overlaps with the O2 operator.…”

Section: Discussionmentioning

confidence: 99%

“…Eventually, due to falling levels of RstR, derepression of both P A and P R occurs. When the levels of LexA return to normal, the switch is reestablished (16,35). The presence of high levels of the antirepressor RstC is expected to delay the reestablishment of CTX lysogeny (this study).…”

Section: Figmentioning

confidence: 99%

“…Genetic switch of the CTX phage lysogen, based on previous work (13,16,35), and role of the antirepressor RstC (this study). Under normal growth conditions, the phage repressor RstR inhibits transcription from the P A promoter by binding to the high-affinity operator, O1, and two weaker operators, O2 and O3, whereas LexA inhibits transcription from P A by binding a single site (SOS box) that overlaps with the O2 operator.…”

Section: Figmentioning

confidence: 99%

See 1 more Smart Citation

RS1 Satellite Phage Promotes Diversity of Toxigenic Vibrio cholerae by Driving CTX Prophage Loss and Elimination of Lysogenic Immunity

et al. 2014

View full text Add to dashboard Cite

bIn El Tor biotype strains of toxigenic Vibrio cholerae, the CTX prophage often resides adjacent to a chromosomally integrated satellite phage genome, RS1, which produces RS1 particles by using CTX prophage-encoded morphogenesis proteins. RS1 encodes RstC, an antirepressor against the CTX repressor RstR, which cooperates with the host-encoded LexA protein to maintain CTX lysogeny. We found that superinfection of toxigenic El Tor strains with RS1, followed by inoculation of the transductants into the adult rabbit intestine, caused elimination of the resident CTX prophage-producing nontoxigenic derivatives at a high frequency. Further studies using recA deletion mutants and a cloned rstC gene showed that the excision event was recA dependent and that introduction of additional copies of the cloned rstC gene instead of infection with RS1 was sufficient to enhance CTX elimination. Our data suggest that once it is excised from the chromosome, the elimination of CTX prophage from host cells is driven by the inability to reestablish CTX lysogeny while RstC is overexpressed. However, with eventual loss of the additional copies of rstC, the nontoxigenic derivatives can act as precursors of new toxigenic strains by acquiring the CTX prophage either through reinfection with CTX or by chitin-induced transformation. These results provide new insights into the role of RS1 in V. cholerae evolution and the emergence of highly pathogenic clones, such as the variant strains associated with recent devastating epidemics of cholera in Asia, sub-Saharan Africa, and Haiti.

show abstract

A New Twist on a Classic Paradigm: Illumination of a Genetic Switch in Vibrio cholerae Phage CTXΦ

Cited by 7 publications

References 11 publications

Characterization of the CI Repressor Protein Encoded by the Temperate Lactococcal Phage TP901-1

Characterization of the CI Repressor Protein Encoded by the Temperate Lactococcal Phage TP901-1

Role of Filamentous Phage SW1 in Regulating the Lateral Flagella of Shewanella piezotolerans Strain WP3 at Low Temperatures

RS1 Satellite Phage Promotes Diversity of Toxigenic Vibrio cholerae by Driving CTX Prophage Loss and Elimination of Lysogenic Immunity

Contact Info

Product

Resources

About