Chemically-Induced Mutagenesis

Mutagenic studies in propionic acid bacteria have been carried out mainly with the purpose of increasing the productivity in vitamin (Vorobjeva et al., 1973 Grusina et al., 1973, 1974 Glatz and Anderson, 1988), since the production of this vitamin in many countries is based on the vital functions of propionic acid bacteria. 

The mechanism of action of NTG is complex. NTG specifically interacts with DNA. The fact that lesions induced by NTG are repaired in the same way as those induced by UV light, permits to classify NTG as an UV-mimetic agent. Mutants of Haemophilus influenzae having a defective reparation system and highly sensitive to UV light are also highly sensitive 

In mutagenesis the main condition of success is the development of a sensitive and rapid method of mutant selection. Vitamin B12 production by propionic acid bacteria correlates with acid production. But the method of selection based on picking colonies with the maximal diameter of dissolution zones of calcium carbonate (added to solid medium) did not give positive results, since the size of colonies is not identical while acid production is dependent on the quantity of biomass. Selection based on the intensity of pink color that correlates with vitamin B12 production has a disadvantage in that selection of small mutations is made step by step, when differences in color can hardly be noticed by eye. Another method used was based on direct determination of vitamin B12 in single colonies. This method is labor-intensive and severely limits the testing of large numbers of colonies. 

We (Vorobjeva, 1976) have developed a method based on using a medium containing radioactive cobalt ( °Co ), since cobalt is incorporated in vitamin Bn molecule. Mutagenized cells and control (untreated) cells were plated on solid medium with radioactive cobalt. Plates were incubated under anaerobic conditions for nine days at 25°C. The colonies were weighed and their radioactivity was measured. Radioactivity of colonies was calculated per mg wet weight according to the formula  

The proposed selection method for microorganisms forming cobalt-organic substances has the capacity of testing at least 400-500 colonies per day with high precision. 

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Many plasmids are known to possess three properties (1) increased resistance to the bactericidal effects of UV and chemical mutagens, (2) increased spontaneous mutagenesis, and (3) increased susceptibility to UV and chemically induced mutagenesis. Some plasmids possess all three properties others may possess just one, for example, increased susceptibility to mutagenesis (review Mortelmans and Dousman, 1986). Often the profile of activity depends on the DNA repair status of the host cell (Pinney, 1980). Plasmid pKMIOl carries DNA repair genes and has been widely used in strains used in bacterial mutagenicity tests. 

Ansari RM, Hei TK. Effects of extremely low frequency magnetic fields (EMF) on radiation- and chemical-induced mutagenesis in mammalian cells. Carcinogenesis 2000 453(1) 1221—6. 

Lankas GR, Baxter CS, Christian RT. 1978. Effect of alkane tumor-promoting agents on chemically induced mutagenesis in cultured V79 Chinese hamster cells. J Toxicol Environ Health 4 37-41. 

Shimoi K, Kawabata H, Tomita I (1992) Enhancing effect of heterocyclic amines and P-carbolines on UV or chemically induced mutagenesis in E. coli. Mutat Res 268 287-295... 

Induced mutagenesis in Escherichia coli is an active process involving proteins with DNA replication, repair, and recombination functions. The available evidence suggests that mutations are generated at sites where DNA has been damaged and that they arise via an error-prone repair activity. In an attempt to understand what specific contributions to mutagenesis are made by DNA lesions, we have studied the mutational specificity of some carcinogens, such as benzo[a]pyrene and aflatoxin, whose chemical reactions with DNA are... 

Probst GS, McMahon RE, Hill LE, et al. 1981. Chemically-induced unscheduled DNA synthesis in primary rat hepatocyte cultures A comparison with bacterial mutagenicity using 218 compounds. Environmental Mutagenesis 3 11-32. 

There are two strategies to use insertional mutagenesis for cloning purposes. One is the direct tagging approach. In this case a mutant, for example a spontaneous or chemically induced mutant, has already been identified, but no information on the nature of the mutated gene is available. 

Anderson D, Richardson CR. 1981. Issues relevant to the assessment of chemically induced chromosome damage in vivo and their relationship to chemical mutagenesis. Mutat Res 90 261-272. 

Induction of Morphological and Neoplastic Transformation in Mammalian Cells Cell Culture Models for Chemically Induced Cancer Proceeding through Mutagenesis... 

The Ames test is used to screen a wide variety of chemicals for potential carcinogenicity or as potential cancer chemotherapeutic agents. The test enables a large number of compounds to be screened rapidly by examining their ability to induce mutagenesis in several specially constructed bacterial mutants derived from Salmonella typhimurium. 

P.B., Chiang, S.Y., Row, Y.W., and Swenberg, J.A. (1998) Highly sensitive apurinic/apyrimidinic site assay can detect spontaneous and chemically induced depurination under physiological conditions. Cancer Res., 58, 222-225. Loeb, L.A. and Preston, B.D. (1986) Mutagenesis by apurinic/apyrimidinic sites. Annu. Rev. Genet., 20, 201-230. Xue, L. and Greenberg, M.M. (2007)... 

A Role for Poly(ADP-Ribose) in Radiogenic and Chemically-Induced Malignant Transformation and Mutagenesis... 

At the present time such non-haemolytic and hyaluronidase-negative strains are usually obtained by non-direct chemical and UF-induced mutagenesis, followed by selection or cloning of the hyaluronidase gene in order to transform Streptococcus sp. into non-pathogenic bacteria [33]. Of all the hyaluronan producers, the most appropriate strain is streptococcus of the group C, that is Streptococcus equi because it produces the highest yield of HA [30]. 

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