Navigation Links
Phage


A phage (also called bacteriophage) (in Greek phageton = food/consumption) is a small virus that infects only bacteria. Like viruses that infect eukaryotes, phages consist of an outer protein hull and the enclosed genetic material (which consists of double-stranded DNA in 95% of the phages known) of 5 to 650 kbp (kilo base pairs) with a length of 24 to 200 nm. The vast majority of phages (95%) have a tail to let them inject their genetic material into the host. Phages were discovered independently by Frederick Twort in 1915 and by Flix d’Herelle in 1917. d'Herelle continued his research and development in Stalin's Soviet Union.

Phages infect only specific bacteria. Some phages are virulent, meaning that upon infecting a cell they immediately begin reproducing, and within a short time lyse (destroy) the cell, releasing new phages. (A famous quote from the microbiologist Mark Mller says: Bacteria don't die, they just phage away.) Some phages (so-called temperate phages) can instead enter a relatively harmless state, either integrating their genetic material into the chromosomal DNA of the host bacterium (much like endogenous retroviruses in animals) or establishing themselves as plasmids. These endogenous phages, referred to as prophages, are then copied with every cell division together with the DNA of the host cell. They do not kill the cell, but monitor (via some proteins they code for) the status of their host. When the host cell shows signs of stress (meaning it might be about to die soon), the endogenous phages become active again and start their reproductive cycle, resulting in the lysis of the host cell. An example is phage λ of E. coli. Sometimes, prophages even provide benefit to the host bacterium while they are dormant, by adding new functions to the bacterial genome, a phenomenon called lysogenic conversion. A famous example is the harmless Vibrio bacteria strain, which is turned into Vibrio cholerae by a phage, causing cholera.

Phages play an important role in molecular biology as cloning vectors to insert DNA into bacteria. Phage therapy has been used since the 1940s in the former Soviet Union as an alternative to antibiotics for treating bacterial infections—because killing bacteria is what phages do best. There is an extensive library of research into specific phages and their therapeutic uses in the Tbilisi Institute in Georgia. The development of bacterial strains that are resistant to multiple drugs has led Western medical researchers to re-evaluate phages as alternatives to the use of antibiotics.

Phage display is a test to screen for protein interactions by integrating multiple genes from a gene bank into phages.

Model bacteriophages

Following is a list of bacteriophages that are extensively studied:

See also


'"/>


(Date:7/11/2014)... This news release is available in German . ... imaging is a method that uses the refraction of ... absorption. The images produced with this method are often ... The scientists in the team of Prof. Franz Pfeiffer ... X-ray imaging and therapy including X-ray phase-contrast imaging. ...
(Date:7/11/2014)... 3, 2014, Shenzhen, China Researchers from Salk Institute ... the first time evaluated the safety and reliability ... successfully developed a new method, TALEN-HDAdV, which could ... stem cell (hiPSC). This study published online in ... theoretical foundation for stem cell-based gene therapy. , ...
(Date:7/11/2014)... 11, 2014 Researchers have pioneered a revolutionary ... new technology, called Virtual Finger, allows scientists to ... neurons and synapses using the flat surface of ... 3D imaging studies orders of magnitude more efficient, ... level across many areas of experimental biology. The ...
Breaking Biology News(10 mins):New simple setup for X-ray phase contrast 2A new genome editing method brings the possibility of gene therapies closer to reality 2Virtual finger enables scientists to navigate and analyze complex 3D images 2
... NY) Many egg donation agencies and private couples routinely ... study finds. From a sample of over 300 ... offered payment in excess of $10,000, a violation of ... (ASRM). Compensation strongly correlated with average ...
... PITTSBURGH, March 24 An experimental vaccine against an ... delay the onset of inflammatory bowel disease (IBD) and in ... the University of Pittsburgh School of Medicine. Their findings are ... journal of the American Association for Cancer Research. People ...
... weather in the Canadian Arctic could create problems for nesting ... have spent over 7,000 days observing birds in the North. ... cold, dry summers that mark the high Arctic. However, warmer ... fog, rain, freezing rain, wet snow and stronger winds. ...
Cached Biology News:Fertility industry offers big money to recruit 'desirable' egg donors at top universities 2Vaccine could delay bowel inflammation and colon cancer, says Pitt research 2Warmer summers could create challenges for nesting Arctic seabirds 2Warmer summers could create challenges for nesting Arctic seabirds 3
Other biology definitionOther Tags