Azoreductase activity of anaerobic bacteria isolated from human intestinal microflora

Abstract

A plate assay was developed for the detection of anaerobic bacteria that produce azoreductases. With this plate assay, 10 strains of anaerobic bacteria capable of reducing azo dyes were isolated from human feces and identified as Eubacterium hadrum (2 strains), Eubacterium spp. (2 species), Clostridium clostridiiforme, a Butyrivibrio sp., a Bacteroides sp., Clostridium paraputrificum, Clostridium nexile, and a Clostridium sp. The average rate of reduction of Direct Blue 15 dye (a dimethoxybenzidine-based dye) in these strains ranged from 16 to 135 nmol of dye per min per mg of protein. The enzymes were inactivated by oxygen. In seven isolates, a flavin compound (riboflavin, flavin adenine dinucleotide, or flavin mononucleotide) was required for azoreductase activity. In the other three isolates and in Clostridium perfringens, no added flavin was required for activity. Nondenaturing polyacrylamide gel electrophoresis showed that each bacterium expressed only one azoreductase isozyme. At least three types of azoreductase enzyme were produced by the different isolates. All of the azoreductases were produced constitutively and released extracellularly.

Decolorization of diazo-dye Reactive Blue 172 byPseudomonas aeruginosa NBAR12

“…or Bacteroides sp.) that decolorized sulfonated azo dyes during growth on solid or liquid complex media under anaerobic conditions (RAFII et al 1990).…”

Expression and characteristics of the gene encoding azoreductase from Rhodobacter sphaeroides AS1.1737

“…Azoreductase activity has been identified in several bacteria, such as Xenophilus azovorans KF46 [5], Pseudomonas luteola [6], Rhodococcus [7], Shigella dysenteriae Type I [8], Klebsiella pnumoniae RS-13 [9] and Clostridium perfringens [10]. Studies on these strains suggested that some of them require flavin compounds for azoreductase activities, and others do not [11]. Recent reports from the laboratory of Dr. Stolz showed that the addition of quinoid redox mediators to anaerobically incubated cultures of various taxonomically different bacterial species could result in significantly increased reduction rate for azo dye [12,13].…”

Decolourization and biodegradation of N,N′-dimethyl-p-phenylenediamine by Klebsiella pneumoniae RS-13 and Acetobacter liquefaciens S-1

“…Synthetic dyes such as azo dyes, xanthene dyes and anthraquinone dyes are very toxic to living organisms (Gingell and Walker 1971 ;Meyer 1981 ;Manning et al 1985 ;Rafii et al 1990). Azo dyes are a group of compounds characterized by the presence of one or more azo groups (-N N-) in association with one or more aromatic system.…”

“…In fact, although some azo dyes are non-mutagenic, their reductive degradation products, particularly aromatic amines, are mutagenic (Chung et al 1981). Most studies on azo dye biodegradation have focused on bacteria (Horitsu et al 1977 ;Idaka et al 1980Idaka et al , 1982Brown 1981 ;Zimmermann et al 1984 ;Liu and Yang 1989, 1992Ogawa and Yatome 1990 ;Rafii et al 1990 ;So et al 1990 ;Yatome et al 1990Yatome et al , 1991Yatome et al , 1993Cao et al 1993 ;Govindaswami et al 1993 ;Rafii and Cerniglia 1993 ;Hu 1996). With the exception of the study conducted by Cao et al (1993), most studies reported that mutagenic and recalcitrant aromatic amines were produced during the reductive cleavage of azo dyes by bacteria.…”