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Bacteriophages

Bacteriophages - eaters of bacteria

Since their discovery in the early 20th century, bacteriophages have been one of the most important model systems in biology. In the 1930s and subsequent decades, pioneering virologists utilized these viruses to investigate many aspects of virology, including virus structure, genetics, replication, etc. These relatively simple agents have since been very important in the development of our understanding of all types of viruses, including those which infect humans, but are much more difficult to propagate and study. Phages are still a paradigm for many areas of biology, especially gene expression.

Bacteriophages, like bacteria, are very common in all natural environments and are directly related to the numbers of bacteria present. They are thus very common in soil and have shaped the evolution of bacteria. They are also of industrial and economic importance. e.g:

This video shows plaques (clear areas) produced in a lawn of bacterial cells by the replication of phages and consequent death (lysis) of the bacterial cells. The dark spots on the agar plate are colonies of bacteria which are resistant to the phages:

Virulent vs. Temperate Phages

The "single burst experiment" (Ellis E.L, Delbruck M. 'The growth of bacteriophage' J.Gen.Physiol. 22: 365-384, 1939) revealed the nature of virus replication. You can perform this experiment for yourself online!

 

CoverA Genetic Switch: Phage and Higher Organisms
by Mark Ptashne

A beautiful in-depth examination gives an appreciation for molecular biology at a comfortably sophisticated level. This extended edition includes higher organisms, focusing on how an organism uses its genes to direct its growth. New chapters assess how well the lambda model can explain gene control in eukaryotes, and the elaborations necessary to explain more complex systems.
(Amazon.co.UK)


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