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Bacteriophages are among the most common and diverse entities in the biosphere. [2] Bacteriophages are ubiquitous viruses, found wherever bacteria exist. It is estimated there are more than 10 31 bacteriophages on the planet, more than every other organism on Earth, including bacteria, combined. [3]
A prophage is a bacteriophage (often shortened to "phage") genome that is integrated into the circular bacterial chromosome or exists as an extrachromosomal plasmid within the bacterial cell. [1] Integration of prophages into the bacterial host is the characteristic step of the lysogenic cycle of temperate phages.
A bacteriophage found to infect Mycobacterium smegmatis in 1947 was the first documented example of a mycobacteriophage. It was found in cultures of the bacteria originally growing in moist compost. [6] The first bacteriophage that infects M. tuberculosis was discovered in 1954. [7]
The prokaryotic cell is shown with its DNA, in green. 2. The bacteriophage attaches and releases its DNA, shown in red, into the prokaryotic cell. 3. The phage DNA then moves through the cell to the host's DNA. 4. The phage DNA integrates itself into the host cell's DNA, creating prophage. 5. The prophage then remains dormant until the host ...
Global geographical differences in phageome composition have been noted, with further variation found within individuals living in rural and urban locations. [13] For instance, residents in Hong Kong, China were found to have less phages associated with targeting pathogenic bacteria in comparison to those in Yunnan province. [14]
Often these bacteria are found in large numbers. As a consequence, phages are found almost everywhere. [citation needed] As a rule of thumb, many phage biologists expect that phage population densities will exceed bacterial densities by a ratio of 10-to-1 or more (VBR or virus-to-bacterium ratio; see [3] for a summary of
Bacteriophage T7 (or the T7 phage) is a bacteriophage, a virus that infects bacteria. It infects most strains of Escherichia coli and relies on these hosts to propagate. Bacteriophage T7 has a lytic life cycle , meaning that it destroys the cell it infects.
The restriction modification system (RM system) is found in bacteria and archaea, and provides a defense against foreign DNA, such as that borne by bacteriophages.. Bacteria have restriction enzymes, also called restriction endonucleases, which cleave double-stranded DNA at specific points into fragments, which are then degraded further by other endonucleases.