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PubMed1997

The evolution of bacterial transformation: sex with poor relations.

Bacteria are the only organisms known to actively take up DNA and recombine it into their genomes. While such natural transformation systems may provide many of the same benefits that sexual reproduction provides eukaryotes, there are important differences that critically alter the consequences, especially when recombination's main benefit is reducing the mutation load. Here, analytical and numerical methods are used to study the selection of transformation genes in populations undergoing deleterious mutation. Selection for transformability depends on the shape of the fitness function against mutation. If the fitness function is linear, then transformation would be selectively neutral were it not for the possibility that transforming cells may take up DNA that converts them into nontransformable cells. If the selection includes strong positive (synergistic) epistasis, then transformation can be advantageous in spite of this risk. The effect of low quality DNA (from selectively killed cells) on selection is then studied analytically and found to impose an additional cost. The limited data available for real bacterial populations suggest that the conditions necessary for the evolution of transformation are unlikely to be met, and thus that DNA uptake may have some function other than recombination of deleterious mutations.

Bacteria↗
PubMed2001

Fluoranthene-2,3- and -1,5-diones are novel products from the bacterial transformation of fluoranthene.

Fluoranthene is one of the predominant compounds found in soils and sediments contaminated with polycyclic aromatic hydrocarbons (PAH). Four bacterial strains isolated from PAH-contaminated soils transformed fluoranthene to a number of products during growth on phenanthrene, including the novel metabolites fluoranthene-2,3-dione (F23Q) and fluoranthene-1,5-dione (F15Q). Given the known toxicity and mutagenicity of F23Q, we focused on characterizing this metabolite with respect to its effects on the metabolism of other PAH. The yield of F23Q from fluoranthene ranged from 2% for Sphingomonas yanoikuyae R1 to greater than 20% for Pseudomonas stutzeri P16 and Bacillus cereus P21. None of the strains appeared capable of metabolizing F23Q any further. F23Q strongly inhibited phenanthrene removal by strain R1 but had a negligible to minor effect on phenanthrene degradation by the other organisms. At a concentration of 6.8 microM, F23Q also substantially inhibited the mineralization of benz[a]anthracene, benzo[a]pyrene (BaP), and chrysene by strain R1 as well as BaP mineralization by Pseudomonas saccharophila P15. Inhibition of BaP mineralization by strain P15 was still evident at an F23Q concentration of 0.68 microM. The inhibition of strain R1 by F23Q was explained in part by a cytotoxic effect, but results with strain P15 indicate that other mechanisms of inhibition occur. These findings suggest that quinones such as F23Q and F15Q have the potential to accumulate in PAH-contaminated systems and can inhibit the degradation of other PAH.

Biotransformation↗
PubMed2006

Fate of transforming bacterial genome following incorporation into competent cells of Bacillus subtilis: a continuous length of incorporated DNA.

In contrast to the conventional transformation of Bacillus subtilis using purified DNA, those using DNA in lysed protoplasts have a high transformation efficiency and enable whole-genome transfer into competent B. subtilis [Akamatsu, T. and Taguchi, H., Biosci. Biotechnol. Biochem., 65, 823-829 (2001)]. Here, we examined the length of incorporated continuous DNA by analyzing the cotransfer ratio with selected and unselected markers, on the basis of a new experimental design. The cotransfer ratio of a selected marker with an unselected marker on the opposite side of the genetic map of the B. subtilis chromosome was about 5.6% and could be interpreted as congression (double transformation) ratio. In the wild-type strain, the cotransfer ratio of cysA (113 kb position on 4215 kb of B. subtilis chromosome) with metC (1384 kb) and leuB (2891 kb) was 0.77%, twice the value (5.6% x 5.6%=0.31%) calculated from the congression ratio. Moreover, in a genetic background, the cotransfer ratios of metC with cysA and leuB, and metC with cysA and arg1 (3012 kb) were 2.7% and 7.2%, respectively. These results strongly suggest that the length of continuous DNA incorporated into B. subtilis is most probably greater than 1271 kb. When the DNA from the protoplast lysate was fragmented by mixing, the cotransfer ratios of arg1 with metC, and arg1 with metC and trpC (2374 kb) were 2.8% and 0.16%, respectively. A high cotransfer ratio (2.7-7.2%) could not, therefore, be obtained using the fragmented DNA. Based on these observations, we propose a working hypothesis on the mechanism of the transformation of competent B. subtilis by DNA in protoplast lysates (LP transformation).

Bacillus subtilis↗
PubMed1969

Spontaneously occurring bacterial transformations in mice.

In 1963, it was reported that deoxyribonucleic acid (DNA)-mediated transformations could take place spontaneously between genetically distinguishable pneumococci growing in a living host, the mouse. It was found in the present study that such transformations could be increased in frequency if infected animals were treated with a drug which kills only one of the two infecting strains. The frequency of in vivo transformations was also increased if the infection was prolonged. Interspecific transformation between pneumococci and streptococci without the addition of purified DNA was demonstrated both in vitro and in vivo. These results make it seem more likely that DNA-mediated transformations occur in nature.

Animals↗
PubMed1989

Characterization of new bacterial transformation products of 1,1,1-trichloro-2,2-bis-(4-chlorophenyl) ethane (DDT) by gas chromatography/mass spectrometry.

The microbial transformation of DDT, DDD and DDE was studied in Gram-negative strain B-206 and a number of phenolic metabolites were identified as the trimethylsilyl derivatives in the bacterial extracts by gas chromatography/mass spectrometry. The major metabolites of DDT were DDD, DDE, DDMU, 1,1,1-trichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-chlorophenyl) ethane, 1,1,1-trichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-hydroxyphenyl) ethane, and 1,1,1-trichloro-2,2-bis-(2-hydroxy-4-chlorophenyl) ethane. Conversely, DDD was mainly degraded into DDE, 1,1-dichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-chlorophenyl) ethane and 1,1-dichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-hydroxyphenyl) ethane. Finally, DDE was transformed into DDMU, 1,1-dichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-chlorophenyl) ethylene, 1,1-dichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'hydroxyphenyl) ethylene and 1-chloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-chlorophenyl) ethylene. The phenolic metabolites exhibited [M - TMSCl]+., [M - HCl - TMSCl]+. and/or [M - HCl - TMSCl - Me]+ fragment ions which reflect the presence of an ortho hydroxyl group in these molecules. Other mass spectral features used to determine their structure are presented and a metabolic scheme accounting for their formation is proposed.

Bacteria↗
PubMed1984

Bacterial transformations of and resistances to heavy metals.

Bacteria carry out chemical transformations of heavy metals. These transformations (including oxidation, reduction, methylation, and demethylation) are sometimes byproducts of normal metabolism and confer no known advantage upon the organism responsible. Sometimes, however, the transformations constitute a mechanism of resistance. Many species of bacteria have genes that control resistances to specific toxic heavy metals. These resistances often are determined by extrachromosomal DNA molecules (plasmids). The same mechanisms of resistance occur in bacteria from soil, water, industrial waste, and clinical sources. The mechanism of mercury and organomercurial resistance is the enzymatic detoxification of the mercurials into volatile species (methane, ethane, metallic HgO) which are rapidly lost from the environment. Cadmium and arsenate resistances are due to reduced net accumulation of these toxic materials. Efficient efflux pumps cause the rapid excretion of Cd2+ and AsO4(3-). The mechanisms of arsenite and of antimony resistance, usually found associated with arsenate resistance, are not known. Silver resistance is due to lowered affinity of the cells for Ag+, which can be complexed with extracellular halides, thiols, or organic compounds. Sensitivity is due to binding of Ag+ more effectively to cells than to Cl-.

Antimony↗