Allan Campbell (biologist)

Allan M. Campbell (born April 27, 1929) is an American microbiologist and geneticist whose pioneering work on Lambda phage has helped advance molecular biology in the late 20th century.

Dr. Campbell has been a professor of biological sciences at Stanford University since 1968, and he was appointed to the Barbara Kimball Browning endowed chair in 1992. Campbell earned his bachelor's degree at the University of California-Berkeley and master's and doctoral degrees from the University of Illinois. He is a member of the National Academy of Sciences and a fellow of the American Academy of Microbiology, the American Association for the Advancement of Science and the American Academy of Arts and Sciences.

Dr. Campbell received the 2004 Abbott-ASM Lifetime Achievement Award from the American Society for Microbiology at the society's 104th general meeting in New Orleans on Monday, May 24, 2004. Campbell delivered the Abbott-ASM Award Lecture and was honored at a dinner ceremony that evening. The award includes a $20,000 cash prize and a commemorative piece.

In honoring Campbell, ASM officials cited his "exceptional insights and achievements in the field of molecular genetics - a career of groundbreaking research that has had a profound influence on several fields, including molecular cloning and gene therapy."

Dr. Campbell's research has concentrated on the genetics of bacteria and their viruses, especially the integration of viral DNA into host chromosomes.

His most prominent discovery was the proposal of the “Campbell model” of virus insertion, where viral DNA is inserted into the host chromosome, becoming covalently bonded to the bacterial DNA, and then remains dormant until activation. Dr. Campbell’s research was focused on a specific bacterial virus, phage lambda, and its host bacterium E. coli, but the model provided insights into how extrachromosomal DNA can be inserted and excised in other organisms.

This model was proposed in the book “Episomes’ published in 1968, which was one of the first comprehensive treatments of plasmid biology.

While study of the regulation of integration and excision of phage lambda in E coli has been a primary focus of his research, Dr. Campbell and research associates also studied regulation and expression of E coli genes linked to the lambda insertion location, including the biotin (bio) and galactose (gal) genes.

Background on phage lambda and lysogeny

Early studies on bacterial viruses began after the discovery by Twort and d’Herelle of ‘filterable agents’ which were able to destroy bacteria. These were demonstrated by creating a lawn of bacteria on appropriate media, mixing with these ‘filterable agents’ and then observing areas of destroyed cells seen as cleared circular areas (plaques) on the lawn. These plaques were interpreted as the result of a single agent infecting a bacterial cell, reproducing in the cell and then bursting open to infect surrounding cells, repeating the process until a clear circular area of destroyed cells becomes visible to the unaided eye. These filterable agents were named bacteriophages (eaters of bacteria) or phage for short.

The 1940s produced the first pictures of bacterial viruses using electron microscopy produced the first photos of bacterial viruses, and research on the mechanism of infection and reproduction dramatically increased. One of the focal points of this research was Cold Spring Harbor Laboratory on Long Island, where a ‘phage group’ led by Salvador Luria, Max Delbrück, Alfred Hershey and others met in the summers for research and training of new investigators.

In 1951 Esther Lederberg discovered lambda phage, which had an unusual characteristic.[1] While lambda could infect and reproduce in some strains of its host bacterium E. coli, other strains seemed immune to infection. However, when the immune strains were mixed with non-immune strains, occasionally lambda phage could be observed infecting the non-immune strains. Further research suggested that the immune strains contained a dormant copy of the lambda genome which protected it from infection, but that dormant copy could be activated into the active viral state to begin a new round of infection. This dormant phase was called the ‘lysogenic’ state and the actively infectious state was called the ‘lytic’ state. The dormant form of the lambda genome was called the ‘prophage’

Study of phage lambda over the next 50 years provided valuable insights into virus life cycles, the regulation and expression of genetic material, and the mechanism of integration and excision of genetic material into chromosomal locations.

Allan Campbell’s contribution to the field with the ‘Campbell model’ of integration and excision marked a huge step forward in the understanding of this process.

References

  1. ↑ http://www.estherlederberg.com/Papers.html#LAMBDAP

External links

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