The Effect of Culture Media Composition and Microorganism Species Affiliation on the Biological Destruction of White Phosphorus
Authors: Anton Z. Mindubaev, Edward V. Babynin, Elena K. Badeeva, Salima T. Minzanova, Lubov’ G. Mironova
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The presented study compared the growth of Aspergillus niger strain AM1 in culture media varying in composition but containing P4 as the sole source of phosphorus. Of the ten media, two in which Aspergillus grew the fastest were selected. These media were concluded to be optimal for growth. Comparing the compositions of the media and the growth rate of Aspergillus in them, we found a key component that is a favorable factor for the growth of AM1 and the biodegradation of white phosphorus. This component was sodium nitrate (NaNO3). It has also been shown that copper sulphate (CuSO4) has no effect on the growth of Aspergillus in media with white phosphorus, regardless of the composition of these media. This result is in harmony with our previous findings. Furthermore, in the present work, attempts to increase the concentration of white phosphorus in the culture medium to values above 1 % are described for the first time. For this purpose, we added the following solvents to the culture media: dimethyl sulfoxide (DMSO) and diesel, in which white phosphorus dissolves relatively well. Apparently, the presence of these substances adversely affects the growth of Aspergill. Therefore, the problem of further increasing the concentration of P4 remains an unanswered.
White phosphorus, reacts with ions of divalent copper even at room temperature. and the Pridham-Gottlieb medium, which we have chosen for our purposes, contains copper sulfate in its composition. The addition of an emulsion of white phosphorus led to the formation of a black precipitate, which is evidence that a chemical reaction took place. Thus, the growth of microorganisms occurred in the presence of not so much white phosphorus as the products of its chemical transformations, and the experiments were not completely clean. Therefore, in the present study, we carried out further modification of the Pridham-Gottlieb nutrient medium, excluding from it not only phosphates as a source of phosphorus, but also copper sulfate. In addition, we compared the white phosphorus resistance of our A. niger strains AM1 and AM2, with three strains from the All-Russian Collection of Microorganisms (ARCM) (strains FW-650, FW-2664 and FW-2731), as well as four different bacterial species. Though highest resistance was observed in strain AM1, the three strains of A. niger, sent from ARCM, also showed a higher resistance to white phosphorus than the bacteria. It was shown that exclusion of copper sulfate from the composition of the nutrient medium with white phosphorus does not prevent the growth of fungi. In addition, white phosphorus does not react with the formation of a precipitate and remains for a longer period under these conditions. This fact is a serious argument in favor of biodegradation and has practical applicability in the method of microbial detoxification of white phosphorus. However, a higher resistance of AM1 in comparison to the ARCM strains was only observed in a medium with copper. Apparently, strain AM1 is most resistant to the toxic products from the reaction of white phosphorus with Cu2+.
Our previous studies demonstrated for the first time the presence of genotoxic properties in white phosphorus. This in no doubt makes white phosphorus even more dangerous to handle. However, our initial studies were carried out on prokaryotes (Salmonella typhimurium). Since the genetic apparatus of prokaryotes is differently arranged than in eukaryotes (including humans), the results of the studies on Salmonella is not completely transferable to humans. In addition to the gene mutations studied by the Ames test and the SOS-lux test, which have a common nature in all living organisms, there are genomic rearrangements that should be studied in eukaryotes. For this purpose, an Allium test is used on onion rootlets (Allium cepa L.). In this work, we present the first report on the negative effect of white phosphorus on the cell cycle of eukaryotes by the Allium test method. It turned out that white phosphorus, even at very low concentrations of 0.01 %, exponentially increases the number of chromosomal aberrations.