![]() All characterized lambdoid phages possess an N protein-mediated transcription antitermination mechanism, with the exception of phage HK022 Linear layout of lambda phage genome with major operons, promoter regions and capsid coding genes. However, it is still not entirely clear whether the L and M proteins are part of the virion. The whole particle consists of 12–14 different proteins with more than 1000 protein molecules total and one DNA molecule located in the phage head. The virus particle consists of a head and a tail that can have tail fibers. The presence of the L and M proteins in the virion is still unclear. Protein names and their copy numbers in the virion particle are shown. This prophage may enter the lytic cycle when the lysogen enters a stressed condition.Īnatomy Bacteriophage lambda virion (schematic). The host is termed a lysogen when a prophage is present. ![]() In this state, the λ DNA is called a prophage and stays resident within the host's genome without apparent harm to the host. However, under certain conditions, the phage DNA may integrate itself into the host cell chromosome in the lysogenic pathway. This is followed by cell lysis, releasing the cell contents, including virions that have been assembled, into the environment. Usually, a " lytic cycle" ensues, where the lambda DNA is replicated and new phage particles are produced within the cell. coli, causing DNA in the head of the phage to be ejected through the tail into the cytoplasm of the bacterial cell. ![]() ![]() During infection, the phage particle recognizes and binds to its host, E. The head contains the phage's double-strand linear DNA genome. The phage particle consists of a head (also known as a capsid), a tail, and tail fibers (see image of virus below). Lambda strains, mutated at specific sites, are unable to lysogenize cells instead, they grow and enter the lytic cycle after superinfecting an already lysogenized cell. The wild type of this virus has a temperate life cycle that allows it to either reside within the genome of its host through lysogeny or enter into a lytic phase, during which it kills and lyses the cell to produce offspring. It was discovered by Esther Lederberg in 1950. Bacteriophage Lambda Structural Model at Atomic Resolution Įnterobacteria phage λ ( lambda phage, coliphage λ, officially Escherichia virus Lambda) is a bacterial virus, or bacteriophage, that infects the bacterial species Escherichia coli ( E. ![]()
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