Chromosome in bacteria

Acquired resistance implies a change in the DNA of the bacteria that results in the appearance of new characteristic features. Such resistance is achieved in two ways mutation of chromosomes in bacteria or acquisition of new pieces of DNA (plasmid) that code for a function of resistance. 

Chromosomes In bacteria, a circular strand of DNA that contains the hereditary information. In eukaryotic cells (higher organisms such as plants), chromosomes consists of linear strands of DNA comprised of tens of thousands of genes. They are found in the nucleus of every cell. 

What conditions give rise to multiforked chromosomes in bacteria ... 

The complete gene complement of any organism, contained in a set of chromosomes in eukaryotes, a single chromosome in bacteria, or a DNA or RNA molecule in viruses the complete set of genes inside the cell or... 

Nitro PAHs have been shown to exhibit a large variety of biological activities. Included in these are the induction of mutations in bacterial (Table I) and eukaryotic cells (9,17,54-57), the neoplastic transformation of cultured mammalian cells (58-59), and the induction of DNA strand breaks (60), DNA repair (61-62), sister chromatid exchanges (63-64), and chromosomal aberrations (65-66). Nitro PAHs have also been demonstrated to bind cellular DNA in bacteria (67-73) and mammalian cells (74-77), to inhibit preferentially the growth of repair-deficient bacteria (78), to have recombinogenic activity in yeast (66,79-80) and to induce tumors in experimental animals (Table II). 

Silver, S. and Walderhaug, M. (1992). Gene regulation of plasmid-determined and chromosome-determined inorganic ion transport in bacteria, Microbiol. Rev., 56, 195-228. 

Under Guideline S2B, the following standard test battery is recommended (1) a test for gene mutation in bacteria, (2) an in vitro test with cytogenetic evaluation of chromosomal damage with mammalian cells or an in vitro mouse lymphoma thymidine kinase (TK) assay, and (3) an in vivo test for chromosomal damage using rodent hematopoietic cells. 

Atrazine was not mutagenic in bacteria and did not cause chromosomal aberrations in cultured rodent cells it did induce DNA strand breaks in stomach, liver, and kidney cells of rats treated orally. ... 

In an in vivo experiment in rats, HCB did not induce dominant lethal mutations. Chromosomal aberrations were not induced in cultured Chinese hamster ovary cells, nor were mutations induced in bacteria. " HCB does not appear to be genotoxic. 

Isophorone does not induce gene mutations in bacteria, chromosomal aberrations in vitro, DNA repair in primary rat hepatocytes, or bone marrow micronuclei in mice. Positive effects were observed only in the absence of an exogenous metabolic system in L5178YTK+/— mouse mutagenesis assays as well as in a sister chromatid exchange assay. The weight of evidence of all mutagenicity data supports the contention that isophorone is not a potent DNA-reactive compound. ... 

In genotoxic assays PNCB induced reverse mutations but not primary damage in bacteria. At toxic doses, it induced chromosomal aberrations, sister chromatid exchange, and repairable DNA breaks in cultured mammalian cells. In vivo it induced DNA damage in mice. ... 

NDPA has exhibited genotoxicity in bacteria Salmonella typhimurium, Escherichia colt) and mammalian cells (mouse lymphoma, Chinese hamster) and caused DNA effects (fragmentation, unscheduled synthesis, repair) in rat hepatocytes and chromosome aberrations in Chinese hamster cells. ... 

Both positive and negative findings have been reported in genotoxic assays of styrene oxide. It has induced gene mutations in bacteria and rodent cells in vitro and caused chromosomal aberrations and sister chromatid exchange both in vivo and in vitro ... 

Electron microscopy shows that DNA consists of either linear or circular structures. The chromosomal DNA in bacteria is a closed circle, a result of covalent joining of the two ends of the double helix (Figure 10.11). Note the presence of supercoils, branch points, intersections, and the generally thin and open structure. The chromosomal DNA in eukaryotic cells, like ours, is believed to be linear. 

HA was found to be mutagenic in bacteria, and it was reported that plant chromosomes break in the presence of HA, but it was found to be noncarcinogenic to mice. However, Gross did cite some A-hydroxy compounds (i.e. HA derivatives) as carcinogens . The mechanism of mutagenesis of HA was found to involve primarily interaction with the pyrimidine bases of the cytidine-guanosine pairs. 

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