Lysogenic bacteria

In a normally growing culture of lysogenic bacteria, the majority of bacteria manage to keep their prophages in a dormant state. In a very small minority of cells, however, the prophage genes express themselves. This results in the multiplieation of the virus, lysis of the cells and liberation of infectious particles into the medium. 

Studies on the transformahon of tissue cultures with DNA-containing vimses have shown that, although complete vims particles cannot be found in the infected, transformed cells, viral DNA is present and is bound to the transformed cell DNA as provirus, analogous to the prophage of lysogenic bacteria. 

Although bacteria have a single essential chromosome, one DNA molecule responsible for their genetic material, they may also contain extrachromosomal DNA. One variety of such DNA is viral DNA. This DNA can become incorporated into the chromosome and reproduced with it (lysogenic bacteria) or can become virulent — produced independently from the chromosome DNA — when it will cause lysis i.e. cell breakdown. The compound cis-[Pt(NH3)2Cl2] causes the change from... 

The effect of platinum in a bacterial cell is to act in a very selective way — on cell division or causing lysis of lysogenic bacteria. It is likely that these changes are due to site specific attack on particular proteins or on particular bases in RNA or in DNA. It is necessary now to describe this attack in detail and to develop new probes for following the site in vivo. This exercise can be followed by a parallel examination of how cis- [Pt (NH3) 2CI2] acts as an anti-tumour agent. Here we only point to some interesting observations. 

The effective compounds of platinum and the dialkylating agents both cause lysis in lysogenic bacteria, section I. 

There is evidence that both classes of anti-tumour agent act by inhibiting DNA synthesis as opposed to RNA or protein synthesis. Many agents which inhibit DNA synthesis cause lysis of lysogenic bacteria-X-rays, ultra-violet light, many carcinogens (3, 90). 

The prophage induction in lysogenic bacteria under the influence of cisplatin45). 

S. Vasilukova, nee Reslova, a young Czechoslovakian microbiologist, and an ex-student of J. Drobnik who contributed much to our microbial experiments, worked with strains of E. coli bacteria that had been previously infected with a bacterial virus (A-bacteriophage). In these lysogenic bacteria, the genetic information of the virus has been incorporated into the cell, but it is repressed so that it is not normally detectable. It replicates during cell division along with the bacterial DNA and so is not lost or diluted out after many divisions. 

It should be pointed out here that all the platinum complexes which are active anticancer agents are also efficient inducers. Those complexes which are not active, do not cause lysis. So far, there is a complete isomorphism between the set of active anticancer complexes and the set of efficient inducers. Earlier, we had believed that a good correlation existed between anticancer active complexes and the filament-forming complexes. After a while, however, exceptions in both classes occurred which decreased our faith in this correlation. The correlation of lytic induction and anticancer activity has held up well. In fact, when R. Adamson at the National Cancer Institute reported the anticancer activity of gallium salts, we tested these and, indeed, they did induce lysis in lysogenic bacteria. 

Without making a definite commitment, let us assume the hypothesis that expression of viral DNA is the causative factor in the cell transformation to a cancer state. There is certainly a significant body of experiments indicating that this is true in many mammals, but solid evidence in humans still eludes us. The viral genome, incorporated in the cellular genome, is completely repressed for long periods compared to most cells division times. As in the case of lysogenic bacteria, a wide variety of chemical and physi-... 

Cochran, P. K., and Paul, J. H. (1998). Seasonal abundance of lysogenic bacteria in a subtropical estuary. Appl. Environ. Microbiol. 64, 2308—2312. 

In a normally growing culture of lysogenic bacteria, the majority of bacteria manage to keep... 

More recently, the fact that many of the chemical agents which cause the induction of prophage are carcinogenic has led to the use of lysogenic bacteria in screening tests for detecting potential carcinogens. 

Induction of Lysogeny. As outlined, the growth of phage from lysogenic bacteria is induced by agents which interact with DNA. 

Most assays with lysogenic cultures are carried out with derivatives of E, coli K-12 carrying prophage However, other lysogenic bacteria, such as 5. typhimurium carrying the prophage P22, have been used ... 

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