Lysogeny

Significantly, the RNA viruses or retroviruses, or Retroviridae, are the most widespread of the transforming viruses, affecting nonbacterial species from yeasts to humans. The characteristic enzyme called RNA-dependent DNA polymerase, or reverse transcriptase, is vitally involved. As a matter of record, the end result is what is known as double-stranded DNA, or dsDNA, which in turn can have some far-reaching results that were further spelled out in the Encyclopedia Britannica article. Also noted is that the retroviruses are most usually animal specific that is, they do not ordinarily cross species barriers. 

There are animal viruses, plant viruses, and bacterial viruses called bacteriophages. Animal viruses include mammalian viruses, both human and otherwise, avian viruses, and no doubt reptilian viruses. Additionally, there are insect viruses, from which, oddly enough, plant viruses may have evolved. (Some insects may carry an enormous load of viruses, but remain unaffected, although this is not necessarily the case for humans. Bee stings, for instance, have been correlated with melanoma occurrences, but whether these are attributable to viruses or to the toxins is apparently not known.) There are also fungal viruses and protozoan viruses (affording a potential mode of treatment or cure for malaria). The virus families are referred to as the 

Viridae, and in some the nncleic acid is DNA and in others RNA, with both types occnrring in animals. Large viruses, such as the poxviruses or Poxviridae, may contain enzymes such as RNA polymerase, involved in RNA synthesis. 

Crossovers in fact do occasionally occur between viruses, as in the case of the human influenza virus, where past epidemics and outbreaks have been traced to crossovers or mutations with duck and swine viruses. The notion may, of course, be extended to the AIDS virus and to the Marburg and Ebola viruses. There is the remote prospect, even, that these may be of plant or insect origin. And there are concerns that decimating tropical rain forests may unleash unsuspected and unknown viruses, with adverse consequences. 

In a brief book by former well-known herbalist and author Hanna Kroeger of Boulder, Colorado, titled Free Your Body of Tumors and Cysts, it was stated that tumors are caused by fungi as well as viruses. Among those caused by fungi she lists hard tumors, a tumor formed by the fungus maduromycates as found in India, and prostate cancer. As for the kinds caused by viruses, she lists the following four virus classifications papilloma and papilloma combined with Epstein-Barr, Epstein-Barr with herpes, herpes with another virus, and retroviruses. 

---

The lysis-lysogeny decision depends upon which of the two promoters in the operator region is able to bind polymerase, and that, in turn, depends upon the binding of the Cro and repressor proteins to three binding sites—ORl, OR2, and OR3—in OR. These binding sites are situated in the middle of the operator in such a way that ORl and OR2 overlap the promoter... 

The lytic growth cycle Lysogeny 11 The human immunodeficiency virus... 

The essential features of lysogenic cells and the phenomenon of lysogeny are listed... 

Lysogeny is generally a veiy stable state, but occasionally a cell will lose its prophage and these cured cells are once more susceptible to infection by that particular phage type. 

Lysogeny is an extremely common phenomenon and it seems that most natural isolates of bacteria carry one or more prophages some strains of Staph, aureus have been shown to carry four or five different prophages. 

More recently, the fact that many of the chemical agents whieh eause the induetion of prophage are carcinogenic has led to the use of lysogenie baeteria in sereening tests for deteeting potential carcinogens. 

PRB, Prophage induetion in lysogenie Escherichia coli (+) NT S Heinemann (1971)... 

The Dormant Prophage State of A Is Maintained by a Phage-Encoded Repressor Events That Follow Infection of Escherichia coli by Bacteriophage A Can Lead to Lysis or Lysogeny The N Protein Is an Antiterminator That Results in Extension of Early Transcripts Another Antiterminator, the Q Protein, Is the Key to Late Transcription... 

Events That Follow Infection of Escherichia coli by Bacteriophage A Can Lead to Lysis or Lysogeny... 

The cro protein and the cl protein bind to exactly the same sites on the DNA. Despite this fact, the cl protein is required for lysogeny, whereas the cro protein is required for lysis. These requirements can be shown with mutants. A cl mutant invariably undergoes lysis, whereas a cro mutant can lysogenize but cannot complete the lytic cycle. This remarkable difference in the behavior of cro and cl results from the fact that although they bind to the same sites, they do so with totally different relative affinities (fig. 30.23). Cro binds preferentially to 0R3 and less strongly to 0R, and Or2. 

Segment of the A genome showing the three operators 0RI, 0R2, and OR3 around the Prm and the PR promoters. The cl and cro regulatory proteins bind to these operators with different relative affinities. The net result of these differing affinities is that cl is required for lysogeny and cro is required for the lytic cycle. 

Bacteriophages Bacteriophages (or phages) adsorb to the bacterial host cell and then inject the DNA genome into the cell, leaving the protein capsid outside. Two alternative modes of infection may follow lytic infection or lysogeny (Fig. 1). 

Poblet-lcart, M., Bordons, A., Lonvaud-Runel, A. (1998). Lysogeny of Oenococcus oeni (syn. Leuconostoc oenos) and study of their induced bacteriophages. Curr. Microbiol, 36, 365-369. 

Marie, D., Bmssaard, C. P. D., Thyrhaug, R., Bratbak, G., and VarJot, D. (1999). Enumeration of marine viruses in culture and natural samples by flow cytometry. Appl. Environ. Microbiol. 65, 45—52. McDaniel, L., and Capone, D. G. (1985). A comparison of procedures for the separation of aquatic bacteria from sediments for subsequen direct enumeration. J. Microbiol. Methods 3, 291—302. McDaniel, L., Houchin, L. A., Williamson, S. J., and Pard, J. H. (2002). Lysogeny in marine Synechococcus. Nature 415, 496. 

Ortman, A. C., Lawrence, J. E., and Suttle, C. A. (2002). Lysogeny and lytic viral production during a bloom of the cyanobacterium Synechococcus spp. Microb. Ecol. 43, 225-231. 

Weinbauer, M. G., and Sutde, C. A. (1996). Potential significance of lysogeny to bacteriophage production and bacterial mortality in coastal waters of the Gulf of Mexico. Appl. Environ. Microbiol. 62, 4374-4380. 

Weinbauer, M. G., Brettar, I., and Hofle, M. G. (2003). Lysogeny and virus-induced mortality of bacterioplankton in surface, deep, and anoxic marine waters. Limnol. Oceanogr. 48, 1457—1465. 

---