Abstract
BackgroundBenzo[a]anthracene (BAA), also known as “tetraphene” belongs to the polycyclic aromatic hydrocarbons (PAHs) which are considered as an important class of environmental genotoxins. The present work focused on the evaluation of the efficiency of the biodegradation of the BAA by Bacillus amyloliquefaciens using animal bioassays, which include micronucleus (MN) and DNA fragmentation as end point of genotoxicity of the resulting metabolites from BAA biodegradation.ResultsB. amyloliquefaciens was exposed to different doses of γ radiation (0.5, 1.0, 1.5, and 2.0 kGy) kGy. The colonies for the wild strain and its variants obtained after radiation were counted. The final counts for variant 3 (V3), variant 4 (V4), and variant 5 (V5) have been increased from its initial count by (0.3, 0.48, and 0.1 log cycle) respectively at 1 mg/100 ml (BAA). For animal bioassay, male mice were divided into seven groups; control group received vehicle only, groups II and III were injected with 5 and 10 mg/kg b.wt (BAA) respectively, and groups IV, V, VI, and VII were injected with the residues of BAA after biodegradation with wild type, V3, V4, and V5 of B. amyloliquefaciens respectively.ConclusionsResults of the micronucleus test and the DNA fragmentation as end point of genotoxicity of (BAA) indicated that B. amyloliquefaciens have the efficiency in biodegradation of (BAA) to nongenotoxic metabolites where (V3) and (V4) are more efficient than the wild type and (V5). So B. amyloliquefaciens could solve the problem of soil and water contamination by oil spill or industrial petroleum waste by ecofriendly manner.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) are considered as pollutants which consist of two or more fused aromatic rings
The bacterial growth and count The growth of B. amyloliquefaciens wild type and its variants in 1 mg/100 ml BAA as indicated in Table 1 cleared a variation in the O.D., but in all samples the final OD was not higher than the initial OD so in this experiment, it was not recognized which sample can get the highest growth under the effect of BAA, which could be cleared in the bacterial count experiment
Only variant 3 (V3), variant 4 (V4), and variant 5 (V5) were chosen for further evaluation by animal bioassay
Summary
Polycyclic aromatic hydrocarbons (PAHs) are considered as pollutants which consist of two or more fused aromatic rings It formed after incomplete combustion of the organic materials such as fossil fuels, wood, or coal, present in the smoke of cigarette (Li et al 2018). It found in different environment places as fresh water, marine sediment, sand, and in the atmosphere. These environmental pollution has a global concern; this is because almost all PAHs are highly toxic, mutagenic, and carcinogenic to humans, plant, and to microorganisms (Rengarajan et al 2015). The present work focused on the evaluation of the efficiency of the biodegradation of the BAA by Bacillus amyloliquefaciens using animal bioassays, which include micronucleus (MN) and DNA fragmentation as end point of genotoxicity of the resulting metabolites from BAA biodegradation
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