Temperate phage

Viruses are discussed more fully elsewhere (Chapter 3). However, there are certain groups of viruses, called bacteriophages (phages), which can attack bacteria. This attack involves the injechon of viral DNA into baeterial eells which then proceed to make new virus particles and destroy eells. Some viruses, known as temperate viruses, do not cause this catastrophic event when they infect their host, but can pass genetic material from one cell to another. 

When a temperate phage is mixed with sensitive indicator bacteria and plated as described above, the reaction at each focus of infection is generally a combination of lytic and lysogenic responses. Some bacteria will be lysed and produce phage, others will survive as lysogenic cells, and the plaque becomes visible as a partial area of clearing in the bacterial lawn. It is possible to pick off cells from the central areas of these plaques and demonstrate that they carry prophage. 

The phage lambda (X) ofE. coll is the temperate phage that has been most extensively studied. When any particular strain oiE. coli, say K12, is infected with A, the cells surviving the infection are designated E. coli K 12(A) to indicate that they are carrying the /1-prophage. 

With most temperate phages, if the host simply makes a copy of the viral DNA, lysis does not occur but if complete virion particles are produced, then the host cell lyses. In a lysogenic bacterial culture at any one time, a small fraction of the cells, 0.1 to 0.0001 percent,... 

Temperate bacteriophage, the best known being phage X, have a very different life cycle. Their DNA usually becomes integrated at a specific point into the genome of the bacterium (Chapter 27). Only rarely is an infected cell lysed. The retroviruses that attack mammals and birds have a similar characteristic. 

In this chapter we consider the patterns of gene expression found for A, the best understood of the temperate phages. 

Ohki, K. (1999). A possible role of temperate phage in the regulation of Trichodesmium biomass. In Marine Cyanobacteria (Charpy, L., and Larkum, A. W. D., eds.). Bulletin de I Instimte... 

Ohki, K. (1999). A possible role of temperate phage in the regulation of Trichodesmium biomass. Bulletin... 

When a temperate phage is mixed with sensitive indicator bacteria and plated as described above, the... 

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