Search results for "Lysogenic cycle"
showing 7 items of 7 documents
Bacteriophage-Based Bacterial Wilt Biocontrol for an Environmentally Sustainable Agriculture
2017
Bacterial wilt diseases caused by Ralstonia solanacearum, R. pseudosolanacearum and R. syzygii subsp. indonesiensis (former R. solanacearum species complex) are among the most important plant diseases worldwide, severely affecting a high number of crops and ornamentals. Difficulties of bacterial wilt control by non-biological methods are related to effectiveness, bacterial resistance and environmental impact. Alternatively, a great many biocontrol strategies have been carried out, with the advantage of being environmentally friendly. Advances in bacterial wilt biocontrol include an increasing interest in bacteriophage-based treatments as a promising re-emerging strategy. Bacteriophages agai…
Dynamics of gene regulatory networks and their dependence on network topology and quantitative parameters – the case of phage λ
2019
Background Gene regulatory networks can be modelled in various ways depending on the level of detail required and biological questions addressed. One of the earliest formalisms used for modeling is a Boolean network, although these models cannot describe most temporal aspects of a biological system. Differential equation models have also been used to model gene regulatory networks, but these frameworks tend to be too detailed for large models and many quantitative parameters might not be deducible in practice. Hybrid models bridge the gap between these two model classes – these are useful when concentration changes are important while the information about precise concentrations and binding…
Bacteriophage GIL01 gp7 interacts with host LexA repressor to enhance DNA binding and inhibit RecA-mediated auto-cleavage
2015
The SOS response in Eubacteria is a global response to DNA damage and its activation is increasingly associated with the movement of mobile genetic elements. The temperate phage GIL01 is induced into lytic growth using the host's SOS response to genomic stress. LexA, the SOS transcription factor, represses bacteriophage transcription by binding to a set of SOS boxes in the lysogenic promoter P1. However, LexA is unable to efficiently repress GIL01 transcription unless the small phage-encoded protein gp7 is also present. We found that gp7 forms a stable complex with LexA that enhances LexA binding to phage and cellular SOS sites and interferes with RecA-mediated auto-cleavage of LexA, the ke…
Phage-borne factors and host LexA regulate the lytic switch in phage GIL01.
2011
ABSTRACT The Bacillus thuringiensis temperate phage GIL01 does not integrate into the host chromosome but exists stably as an independent linear replicon within the cell. Similar to that of the lambdoid prophages, the lytic cycle of GIL01 is induced as part of the cellular SOS response to DNA damage. However, no CI-like maintenance repressor has been detected in the phage genome, suggesting that GIL01 uses a novel mechanism to maintain lysogeny. To gain insights into the GIL01 regulatory circuit, we isolated and characterized a set of 17 clear plaque ( cp ) mutants that are unable to lysogenize. Two phage-encoded proteins, gp1 and gp7, are required for stable lysogen formation. Analysis of …
Between a rock and a soft place: the role of viruses in lithification of modern microbial mats.
2021
10 pages; International audience; Stromatolites are geobiological systems formed by complex microbial communities, and fossilized stromatolites provide a record of some of the oldest life on Earth. Microbial mats are precursors of extant stromatolites; however, the mechanisms of transition from mat to stromatolite are controversial and are still not well understood. To fully recognize the profound impact that these ecosystems have had on the evolution of the biosphere requires an understanding of modern lithification mechanisms and how they relate to the geological record. We propose here viral mechanisms in carbonate precipitation, leading to stromatolite formation, whereby viruses directl…
Identification of five novel tectiviruses in Bacillus strains: analysis of a highly variable region generating genetic diversity
2013
Our biosphere is abundant with unique and small genes for which no homologs are known. These genes, often referred to as orphans or ORFans, are commonly found in bacteriophage genomes but their origins remain unclear. We discovered five novel tectivirus-like genetic elements by screening more than five-hundred Bacillus strains. A highly variable region (HVR) of these viruses was shown to harbor ORFans in most of these otherwise well-conserved bacteriophages. Previous studies demonstrated that mutations close to this region dramatically alter bacteriophage gene regulation, suggesting that the acquisition of those ORFans may provide a source of genetic diversity that is then subject to geneti…
Icosahedral dsDNA Bacterial Viruses with an Internal Membrane
2008
The icosahedral double-stranded DNA bacteriophages containing an internal membrane belong to two families, the Tectiviridae and the Corticoviridae. Members of the Tectiviridae have a linear dsDNA genome (e.g., PRD1) and those of the Corticoviridae have a circular genome (the only example being PM2). The DNA is covered by a membrane which is in turn covered by a protein capsid. The infection cycle begins when spikes on the capsid recognize the host cell receptor and the virus starts the delivery of the genome into the cell cytoplasm. The replication of the virus genome occurs in the cytoplasm. The members of the Tectiviridae may be virulent or temperate; PM2 is virulent. Virulent bacteriopha…