A lysogen or lysogenic bacterium is a bacterial cell which can produce and transfer the ability to produce a
phage
A bacteriophage (), also known informally as a ''phage'' (), is a duplodnaviria virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν ('), meaning "to devour". Bacter ...
. A prophage is either integrated into the host
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
's
chromosome
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
or more rarely exists as a stable
plasmid within the host cell. The prophage expresses gene(s) that repress the phage's
lytic
The lytic cycle ( ) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bacter ...
action, until this repression is disrupted (see
lytic cycle
The lytic cycle ( ) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bacteri ...
). Currently a variety of studies are being conducted to see whether other genes are active during lysogeny, examples of which include phage-encoded
tRNA
Transfer RNA (abbreviated tRNA and formerly referred to as sRNA, for soluble RNA) is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes), that serves as the physical link between the mRNA and the amino ...
and virulence genes.
History
Theories about Lysogeny dominated the field of microbiology between 1920-29. However, Lysogenic Bacterium were first brought to light by studies conducted in 1921 that explored the mechanisms between phages and bacteria.
Lysogenic Conversion
Lysogenic conversion is a process that occurs between a bacterium and a phage that is often beneficial for the bacteria. In lysogenic conversion, the phage inserts specific characteristics into the bacterial genes causing the bacteria to have better survival. Lysogenic conversion has been known to convert non-pathogenic bacteria into pathogenic bacteria that is capable of producing harmful toxins.
[{{cite journal , last1=Feiner , first1=Ron , last2=Argov , first2=Tal , last3=Rabinovich , first3=Lev , last4=Sigal , first4=Nadejda , last5=Borovok , first5=Ilya , last6=Herskovits , first6=Anat A. , title=A new perspective on lysogeny: prophages as active regulatory switches of bacteria , journal=Nature Reviews Microbiology , date=16 September 2015 , volume=13 , issue=10 , pages=641–650 , doi=10.1038/nrmicro3527, pmid=26373372 ]
Types
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Lambda phage
''Enterobacteria phage λ'' (lambda phage, coliphage λ, officially ''Escherichia virus Lambda'') is a bacterial virus, or bacteriophage, that infects the bacterial species ''Escherichia coli'' (''E. coli''). It was discovered by Esther Leder ...
See also
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lysogenic cycle
Lysogeny, or the lysogenic cycle, is one of two cycles of viral reproduction (the lytic cycle being the other). Lysogeny is characterized by integration of the bacteriophage nucleic acid into the host bacterium's genome or formation of a circu ...
References
Bacteriophages