| Description |
Nitroaromatic compounds are widely distributed in the environment. They are used as drugs, herbicides, pesticides, explosives, dyes and solvents and can be found as contaminants in waste waters, rivers and herbicide- or pesticide-treated soils. Nitroaromatics and products of their complete degradation have relatively high acute toxicity and some may be potential carcinogenic. A few of microorganisms are able to degrade these pollutants. Rhodococci, which are widely occurred in soil and sludge, have been shown to attack various xenobiotic compounds, including nitroaromatics. We have isolated 4 bacterial strains from soil by selective enrichment with nitroaromatic compounds in mineral medium. Two strains (J2J and J3) were isolated by enrichment with 4-nitrocatechol and two strains (J6 and J7) by enrichment with 4-nitroguaiacol. These strains were identified as members of the genus Rhodococcus on the base of a polyphasic taxonomic approach (morphology, biochemical and physiological characterisation, chemotaxonomic analysis, determination of partial sequence of genes for 16S rRNA). The nearest relatives were R. opacus and R. percolatus. The strains were tested for growth on a variety of nitroaromatic compounds such as 4 nitrocatechol (4-NC), 4-nitroguaiacol (4-NG), 5-nitroguaiacol (5-NG), 2-nitrophenol (2 NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP), 2,4-dinitrobenzoic acid (2,4-DNBA), 4,5-dimethoxy-2-nitrobenzoic acid (4,5-dimethoxy-2 NBA) and 2,3-diphluoro-6 nitrophenol (2,3-diP-6 NP). Established degradations were particularly studied. There are some differences in degradation capability of strains but no one were able to degrade 2,4 DNBA, 4,5-dimethoxy-2 NBA and 2,3-diP-6 NP. Strain J3 was able to degrade 4-NC, 5-NG and 3-NP. Strain J6 has the broadest degradation spectrum. This strain was able to degrade 4-NC, 4-NG, 5-NG, 3-NP and 4-NP (all substrates in concentration 0,05 mM). Degradation of some nitroaromatic compounds (4-nitrocatechol, 4-nitroguaiacol and 4 nitrophenol) was monitored by the use of the automatic microbiological system BIOSCREEN C. Degradation of these compounds were tested in concentration range 0,025 mM to 0,1 mM. Degradations of nitroaromatic compounds were confirmed by the use of HPLC.
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