Biotransformation of 1‐Nitropyrene in Intestinal Anaerobic Bacteria

Abstract

Mutagenic nitroaromatic compounds have recently been found in photocopies, urban atmosphere, automobile exhaust and wastewater. 1-Nitropyrene (I-NP) is readily formed when pyrene, ubiquitous in the environment, is exposed to nitrogen dioxide in the urban atmosphere or in automobile exhaust, and is highly mutagenic, inducing 449 hisr revertants/plate/nmol from Salmonella typhimurium strain T A98 in the absence of 89 fraction in the Salmonella-microsome test. It is possible to swallow sputum or some food containing I-NP and it would come into contact with the normal bacterial flora. We determined the I-NP nitroreductase activity in environmental and laboratory bacterial strains. We found that the mutagenicity of I-NP mixed with the feces of a healthy man or a culture of anaerobic bacteria was decreased. The product proved to be I-aminopyrene (I-AP), based on its fluorescence spectrum, its mass spectrum, and its characteristic thin layer chromatographic and high performance liquid chromatographic patterns. The I-NP nitroreductase activity of aerobic bacteria was low, but crude extracts from the anaerobic bacteria, i.e., Bacteroidesfragilis, B. thetaiotaomicron, B. oulgatus, Fusobacterium mortiferum, F. nucleatum, Clostridium perfringens, C. sporogenes, Bifidobacterium adolescentis, B. bifidum, Eubacterium lentum, E. limosum, andPeptostreptococcus anaerobius, all easily converted I-NP to I-AP and proportionally decreased the mutagenic activity of I-NP.A simple method for identifying chemical mutagens has been developed: the Ames test (I) measures back mutation in several specially constructed mutants of Salmonella typhimurium his-strains. A homogenate of rat liver 89 fraction is added to the Ames test to approximate mammalian metabolism.I-Nitropyrene (l-NP) is a nitroaromatic compound that is highly mutagenic in the Ames test. One nanomol of I-NP induces 484 hisr revertants/plate from S. typhimurium tester strain T A98 in the absence of 89 mix (21). Moreover, 1,8-dinitropyrene induces 72,900 hisr revertants/plate/nmol from strain TA98 (21). I-NP is more mutagenic than representative carcinogens and mutagens; for example, 2-nitronaphthalene and benzo(a)pyrene induce 8.7 and 121 hist revertants/plate/ nmol, respectively (20). I-NP is also carcinogenic in rats (26).I-NP has recently been detected in photocopies, airborne particles, automobile 993

Low temperature acclimation with electrical stimulation enhance the biocathode functioning stability for antibiotics detoxification

“…Aeromonas (33.16 ± 19.82%; P ¼ 0.01) and Vagococcus (22.25 ± 15.67%; P ¼ 0.046) were significantly enriched under 10 C, which was consistent with the cold-adapted ability of them (Rouf and Rigney, 1971;Teixeira et al, 1997). Electrochemically active Aeromonas was capable of reducing nitroaromatics 1-nitropyrene to aromatic amine 1-aminopyrene (Kinouchi et al, 1982;Pham et al, 2003). Vagococcus was capable of biodegrading p-chloronitrobenzene (Bao et al, 2009).…”

“…Firstly, most of the dominant genera (Aeromonas, Raoultella, Enterococcus, Citrobacter, Desulfovibrio and Clostridium) are capable of reducing nitroaromatics to corresponding aromatic amines or biodegradation of nitroraomatics (Vagococcus) (Bao et al, 2009;Howard et al, 1983;Kinouchi et al, 1982;Liang et al, 2014;Spain, 1995). Subsequently, most of the dominant genera were identified with electrochemical activity (Aeromonas, Citrobacter, Lactococcus, Desulfovibrio and Clostridium) (Kumar et al, 2015;Logan, 2009) or dominated in biocathode communities (Raoultella and Enterococcus) Wang et al, 2011).…”

In vitro Intestinal Microflora‐Mediated Metabolism of Biliary Metabolites from 1‐Nitropyrene‐Treated Rats

“…Chemicals. 1-NP and 1-aminopyrene (1-AP) were purchased from Aldrich Chemical Co., Milwaukee, Wis., U.S.A., and purified as previously described (17,19). [G-3H] 1-NP (specific activity 100 mCi/mmol) was obtained by 3H-exchange (methods TR.1) from Amersham Radiochemical Centre, Bucks, England.…”

“…[G-3H] 1-NP (specific activity 100 mCi/mmol) was obtained by 3H-exchange (methods TR.1) from Amersham Radiochemical Centre, Bucks, England. The material was purified by HPLC as previously described (17,19). [G-3H] 1-AP (specific activity 126 mCi/mmol) was synthesized from [G-3H] 1-NP by reduction with Zn and HC1 and was purified by HPLC using system 1.…”

“…In the hindgut and feces the population of obligate/facultative anaerobes reaches 1011 organisms per gram (8,28,29) and these bacteria can modify a wide range of environmental chemicals including food additives, carcinogens and mutagens, either directly or via enterohepatic circulation (9, 38). We measured the 1-NP nitroreductase (NRase) activity of a number of aerobic and anaerobic bacteria in vitro, and found while the activity of aerobic bacteria was low, the activity in anaerobic bacteria, especially those normally associated with the intestinal tract, was high (17,20,33). In addition, we isolated and purified four NRases from Bacteroides fragilis and reported that nitroreduction was a necessary step in metabolic activation of 1-NP (19,20).…”