Metabolism of the benzidine-based azo dye Direct Black 38 by human intestinal microbiota.

Benzidine-based azo dyes are proven mutagens and have been linked to bladder cancer. Previous studies have indicated that their initial reduction is the result of the azo reductase activity of the intestinal microbiota. Metabolism of the benzidine-based dye Direct Black 38 was examined by using a semicontinuous culture system that simulates the lumen of the human large intestine. The system was inoculated with freshly voided feces, and an active flora was maintained as evidenced by volatile fatty acid and gas production. Within 7 days after exposure to the dye, the following metabolites were isolated and identified by gas chromatography-mass spectrometry:benzidine, 4-aminobiphenyl, monoacetylbenzidine, and acetylaminobiphenyl. Benzidine reached its peak level after 24 h, accounting for 39.1% of the added dye. Its level began to decline, and by day 7 the predominant metabolite was acetylaminobiphenyl, which accounted for 51.1% of the parent compound. Formation of the deaminated and N-acetylated analogs of benzidine, which have enhanced mutagenicity and lipophilicity, previously has not been attributed to the intestinal microbiota.     

Monoazo and diazo dye decolourisation studies in a methanogenic UASB reactor

Mixed anaerobic bacterial consortia have been show to reduce azo dyes and batch decolourisation tests have also demonstrated that predominantly methanogenic cultures also perform azo bond cleavage. The anaerobic treatment of wool dyeing effluents, which contain acetic acid, could thus be improved with a better knowledge of methanogenic dye degradation. Therefore, the decolourisation of two azo textile dyes, a monoazo dye (Acid Orange 7, AO7) and a diazo dye (Direct Red 254, DR254), was investigated in a methanogenic laboratory-scale Upflow Anaerobic Sludge Blanket (UASB), fed with acetate as primary carbon source. As dye concentration was increased a decrease in total COD removal was observed, but the acetate load removal (90%) remained almost constant. A colour removal level higher than 88% was achieved for both dyes at a HRT of 24h. The identification by HPLC analysis of sulfanilic acid, a dye reduction metabolite, in the treated effluent, confirmed that the decolourisation process was due mainly to azo bond reduction. Although, HPLC chromatograms showed that 1-amino-2-naphthol, the other AO7 cleavage metabolite, was removed, aeration batch assays demonstrated that this could be due to auto-oxidation and not biological mineralization. At a HRT of 8h, a more extensive reductive biotransformation was observed for DR254 (82%) than for AO7 (56%). In order to explain this behaviour, the influence of the dye aggregation process and chemical structure of the dye molecules are discussed in the present work.     

Degradation of Sulphonated Azo Dye Red HE7B by Bacillus sp. and Elucidation of Degradative Pathways

Bacteria capable of degrading the sulfonated azo dye Red HE7B were isolated from textile mill effluent contaminated soil. The most efficient isolate was identified as Bacillus sp. Azo1 and the isolate could successfully decolorize up to 89 % of the dye. The decolorized cultural extract analyzed by HPLC confirmed degradation. Enzymatic analysis showed twofold and fourfold increase in the activity of azoreductase and laccase enzymes, respectively, indicating involvement of both reductive and oxidative enzymes in biodegradation of Red HE7B. Degraded products which were identified by GC/MS analysis included various metabolites like 8-nitroso 1-naphthol, 2-diazonium naphthalene. Mono azo dye intermediate was initially generated from the parent molecule. This mono azo dye was further degraded by the organism, into additional products, depending on the site of cleavage of R–N=N–R molecule. Based on the degradation products identified, three different pathways have been proposed. The mechanism of degradation in two of these pathways is different from that of the previously reported pathway for azo dye degradation. This is the first report of a microbial isolate following multiple pathways for azo dye degradation. Azo dye Red HE7B was observed to be phytotoxic, leading to decrease in root development, shoot length and seedling fresh weight. However, after biotreatment the resulting degradation products were non-phytotoxic.     

Microarray method to monitor 40 intestinal bacterial species in the study of azo dye reduction

Azo dyes are widely used in dye manufacturing, paper printing, textile industries, and as tattoo pigmentation. Since intestinal and skin bacteria can metabolize certain azo dyes to carcinogenic compounds, many researchers have studied the azoreductases of these bacteria. In this study, we used a microarray method to identify the intestinal bacterial species from cultured fecal samples in Brain Heart Infusion (BHI) broth with or without azo dyes that may be involved in azo dye reduction. The microarray was designed to identify 40 bacterial species that are reported in the literature to be predominant in human feces. Results from this study showed 26-30 species are present in the cultured fecal samples. The representative bacteria were then examined for the azo dye reduction activity.     

绒毛栓孔菌菌丝体在无营养条件下对偶氮染料刚果红的脱色作用

【目的】在无营养条件下,利用白腐真菌绒毛栓孔菌(Trametes pubescens)菌丝体对染料进行脱色可减少试验成本,提高染料处理的实用性。【方法】将该菌株液体培养的菌丝体在无营养条件下对染料进行脱色,并对其中脱色效果较好的偶氮染料刚果红的脱色过程进行分析。在此过程中,测定了该菌株分泌的胞外胞内酶活力,优化影响因子如初始pH值、温度、染料浓度和盐度,同时利用气相色谱-质谱联用技术分析无营养条件下偶氮染料刚果红的降解产物。植物毒性试验测定刚果红经绒毛栓孔菌菌丝体脱色前后的毒性变化。【结果】菌丝体对偶氮染料刚果红有较好的脱色效果,在初始pH值为2.0,温度为30°C,染料浓度为80 mg/L,盐度为2.5%(质量体积比)时,150 r/min转速下培养7 d后脱色率可达80.52%。在此过程中,菌丝体可被连续使用2次,且其所分泌的酶系可降解染料。此外,通过气相色谱-质谱联用分析得到刚果红的降解产物为萘胺、联苯胺和叠氮萘。植物毒性试验显示在无营养条件下的绒毛栓孔菌菌丝体对染料有明显的脱毒作用。【结论】研究发现绒毛栓孔菌菌丝体在无营养条件下的偶氮染料废水处理中具有广阔的应用前景。     

Fe(III)-enhanced Azo Reduction by <Emphasis Type="Italic">Shewanella decolorationis</Emphasis> S12

Shewanella decolorationis S12 is capable of high rates of azo dye decolorization and dissimilatory Fe(III) reduction. Under anaerobic conditions, when Fe(III) and azo dye were copresent in S12 cultures, dissimilatory Fe(III) reduction and azo dye biodecolorization occurred simultaneously. Furthermore, the dye decolorization was enhanced by the presence of Fe(III). When 1 mM Fe(III) was added, the methyl red decolorizing efficiency was 72.1% after cultivation for 3 h, whereas the decolorizing efficiency was only 60.5% in Fe(III)-free medium. The decolorizing efficiencies increased as the concentration of Fe(III) was increased from 0 to 6 mM. Enzyme activities, which mediate the dye decolorization and Fe(III) reduction, were not affected by preadaption of cells to Fe(III) and azo dye nor by the addition of chloramphenicol. Both the Fe(III) reductase and the azo reductase were membrane associated. The respiratory electron transport chain inhibitors metyrapone, dicumarol, and stigmatellin showed significantly different effects on Fe(III) reduction than on azo dye decolorization.     

Degradation of azo compounds by ligninase from Phanerochaete chrysosporium: involvement of veratryl alcohol

Phanerochaete chrysosporium decolorized several polyaromatic azo dyes in ligninolytic culture. The oxidation rates of individual dyes depended on their structures. Veratryl alcohol stimulated azo dye oxidation by pure lignin peroxidase (ligninase, LiP) in vitro. Accumulation of compound II of lignin peroxidase, an oxidized form of the enzyme, was observed after short incubations with these azo substrates. When veratryl alcohol was also present, only the native form of lignin peroxidase was observed. Azo dyes acted as inhibitors of veratryl alcohol oxidation. After an azo dye had been degraded, the oxidation rates of veratryl alcohol recovered, confirming that these two compounds competed for ligninase during the catalytic cycle. Veratryl alcohol acts as a third substrate (with H2O2 and the azo dye) in the lignin peroxidase cycle during oxidations of azo dyes.     

肠道微生态与白血病的研究进展

微生物群与人体的健康密切相关,约20%的恶性肿瘤与微生态失调有关。研究显示肠道微生物可以调节造血,其与血液系统疾病的关系逐渐得到研究者的关注,肠道微生物参与白血病的发生发展,影响白血病的治疗效果。较早的暴露于微生物群是儿童白血病的保护性因素,化疗会引起肠道微生物紊乱,肠道微生物可以改变化疗药物的疗效和毒性,其多样性和组成能够预测化疗相关的并发症,通过微生态制剂和粪菌移植可以减少化疗相关的并发症。本文从肠道微生态与白血病及其并发症的关系,以及调节肠道微生态对白血病的影响两个方面的最新进展进行综述。     

肠道菌群与肥胖关系的研究进展

西方化的高脂饮食方式造成了越来越多的肥胖人群。高脂饮食在一定程度上可以改变肠道菌群的结构组成和功能,促进宿主对食物营养的吸收,从而增加体重形成肥胖。高脂饮食诱导的肥胖者肠道菌群的改变会导致宿主能量吸收增加,肠道通透性和炎症增加,而有减肥功能的短链脂肪酸合成能力下降。最近研究发现肠道菌群也可以通过影响中枢神经系统,尤其是下丘脑相关基因的表达来控制食欲,从而调控肥胖的形成。本文系统介绍了最近几年高脂饮食诱导肥胖的研究,总结了一些与肥胖形成有密切关系的肠道菌群以及其在肥胖形成中的作用机制,为进一步研究肠道菌群与肥胖之间的调控作用奠定了基础。最后总结了肠道菌群可以作为一个预防和治疗肥胖的有效靶点,可以通过在食物中添加有益菌或者通过菌群移植来治疗肥胖。     

Microbial decolorization and degradation of synthetic dyes: a review

The synthesis of dyes and pigments used in textiles and other industries generate the hazardous wastes. A dye is used to impart color to materials of which it becomes an integral part. The waste generated during the process and operation of the dyes commonly found to contain the inorganic and organic contaminant leading to the hazard to ecosystem and biodiversity causing impact on the environment. The amount of azo dyes concentration present in wastewater varied from lower to higher concentration that lead to color dye effluent causing toxicity to biological ecosystem. The physico-chemical treatment does not remove the color and dye compound concentration. The decolorization of the dye takes place either by adsorption on the microbial biomass or biodegradation by the cells. Bioremediation takes place by anaerobic and/or aerobic process. The anaerobic process converts dye in toxic amino compounds which on further treatment with aerobic reaction convert the intermediate into CO₂ biomass and inorganics. In the present review the decolorization and degradation of azo dyes by fungi, algae, yeast and bacteria have been cited along with the anaerobic to aerobic treatment processes. The factors affecting decolorization and biodegradation of azo dye compounds such as pH, temperature, dye concentration, effects of CO₂ and Nitrogen, agitation, effect of dye structure, electron donor and enzymes involved in microbial decolorization of azo dyes have been discussed. This paper will have the application for the decolorization and degradation of azo dye compound into environmental friendly compounds.     

The development of gut immune responses and gut microbiota: effects of probiotics in prevention and treatment of allergic disease

The infant's immature intestinal immune system develops as it comes into contact with dietary and microbial antigens in the gut. The evolving indigenous intestinal microbiota have a significant impact on the developing immune system and there is accumulating evidence indicating that an intimate interaction between gut microbiota and host defence mechanisms is mandatory for the development and maintenance of a balance between tolerance to innocuous antigens and capability of mounting an inflammatory response towards potential pathogens. Disturbances in the mucosal immune system are reflected in the composition of the gut microbiota and vice versa. Distinctive alterations in the composition of the gut microbiota appear to precede the manifestation of atopic disease, which suggests a role for the interaction between the intestinal immune system and specific strains of the microbiota in the pathogenesis of allergic disorders. The administration of probiotics, strains of bacteria from the healthy human gut microbiota, have been shown to stimulate antiinflammatory, tolerogenic immune responses, the lack of which has been implied in the development of atopic disorders. Thus probiotics may prove beneficial in the prevention and alleviation of allergic disease.     

Characterization of azo reduction activity in a novel ascomycete yeast strain

Several model azo dyes are reductively cleaved by growing cultures of an ascomycete yeast species, Issatchenkia occidentalis. In liquid media containing 0.2 mM dye and 2% glucose in a mineral salts base, more than 80% of the dyes are removed in 15 h, essentially under microaerophilic conditions. Under anoxic conditions, decolorization does not occur, even in the presence of pregrown cells. Kinetic assays of azo reduction activities in quasi-resting cells demonstrated the following: (i) while the optimum pH depends on dye structure, the optimum pH range was observed in the acidic range; (ii) the maximum decolorizing activity occurs in the late exponential phase; and (iii) the temperature profile approaches the typical bell-shaped curve. These results indirectly suggest the involvement of an enzyme activity in azo dye reduction. The decolorizing activity of I. occidentalis is still observed, although at a lower level, when the cells switch to aerobic respiration at the expense of ethanol after glucose exhaustion in the culture medium. Decolorization ceased when all the ethanol was consumed; this observation, along with other lines of evidence, suggests that azo dye reduction depends on cell growth. Anthraquinone-2-sulfonate, a redox mediator, enhances the reduction rates of the N,N-dimethylaniline-based dyes and reduces those of the 2-naphthol-based dyes, an effect which seems to be compatible with a thermodynamic factor. The dye reduction products were tested as carbon and nitrogen sources. 1-Amino-2-naphthol was used as a carbon and nitrogen source, and N,N-dimethyl-p-phenylenediamine was used only as a nitrogen source. Sulfanilic and metanilic acids did not support growth either as a carbon or nitrogen source.     

Isolation and characterization of Bacillus thuringiensis for acid red 119 dye decolourisation

Studies were carried out to isolate Acid red 119 (AR-119) resistant and decolourising bacteria from dye contaminated soil and water samples. Six morphologically distinct bacterial isolates resistant to 100 ppm AR-119 dye were isolated directly from the soil and waste contaminated with azo dyes. The most efficient isolate, which showed decolourisation zone of 44 mm on 100 ppm AR-119 containing plate was identified as Bacillus thuringiensis SRDD. Gradual adaptation increased the efficiency of the isolate and within 7h of incubation it showed decolourisation up to 1000 ppm of AR-119 dye in liquid medium. Addition of 300 ppm of AR-119 in each step in ongoing dye decolourisation flask gave more than 90% decolourisation of 300 ppm AR-119 in time as short as 1.25 h. The developed B. thuringiensis showed 50-60% decolourisation of 5000 ppm AR-119 in 7d of incubation. This organism was also able to remove more than 98%, 92%, 95% and 95% colour of C.I. Acid brown 14, C.I. Acid black 210, C.I. Acid violet 90 and C.I. Acid yellow 42 azo dyes at 100 ppm concentration in 24h, respectively. When the developed isolate was studied for bioremediation of actual azo dye contaminated waste it removed 70% colour from the waste in 24h. The developed B. thuringiensis exhibited excellent resistance and decolourisation ability to AR-119 and other acid azo dyes.     

Alteration of the Canine Small-Intestinal Lactic Acid Bacterium Microbiota by Feeding of Potential Probiotics

Five potentially probiotic canine fecal lactic acid bacterium (LAB) strains, Lactobacillus fermentum LAB8, Lactobacillus salivarius LAB9, Weissella confusa LAB10, Lactobacillus rhamnosus LAB11, and Lactobacillus mucosae LAB12, were fed to five permanently fistulated beagles for 7 days. The survival of the strains and their potential effects on the indigenous intestinal LAB microbiota were monitored for 17 days. Denaturing gradient gel electrophoresis (DGGE) demonstrated that the five fed LAB strains survived in the upper gastrointestinal tract and modified the dominant preexisting indigenous jejunal LAB microbiota of the dogs. When the LAB supplementation was ceased, DGGE analysis of jejunal chyme showed that all the fed LAB strains were undetectable after 7 days. However, the diversity of the intestinal indigenous microbiota of the dogs, as characterized from jejunal chyme plated on Lactobacillus selective medium without acetic acid, was reduced and did not return to the original level during the study period. In all but one dog, an indigenous Lactobacillus acidophilus strain emerged as the dominant LAB strain. In conclusion, strains LAB8 to LAB12 have potential as probiotic strains for dogs as they survive in and dominate the jejunal LAB microbiota during feeding and have the ability to modify the intestinal microbiota.     

脱色希瓦氏菌(Shewanella decolorationis)S12T的脱色特性

从印染废水活性污泥中分离到一株高效染料脱色菌,经鉴定该菌株为希瓦氏菌属的一个新种,命名为脱色希瓦氏菌(Shewanelladecolorationis)S12T。该菌株在偶氮染料浓度为50mg/L的培养基中培养4h后,染料去除率达到96%,对偶氮染料的最高脱色浓度达到2000mg/L。在浓度为500mg/L的偶氮染料平板上生长4d后,可观察到明显的脱色圈。全波长光谱扫描的结果表明希瓦氏菌S12T以生物降解的方式对偶氮染料进行脱色。希瓦氏菌S12T的脱色酶为组成型的胞内酶。     

氧气对混合菌群脱色降解偶氮染料效果的影响

【背景】偶氮染料及其中间产物具有一定的环境毒性,利用混合菌群降解偶氮染料是一种环境友好型方法,但降解过程中氧气的存在起到至关重要的作用,可以促进或抑制偶氮染料的微生物降解作用。【目的】探讨氧气对偶氮染料微生物脱色液的影响,分析氧气对混合菌群脱色降解偶氮染料效果的影响。【方法】利用混合菌群DDMY1在3种培养条件(好氧、厌氧、兼氧)下,对7种偶氮染料进行脱色降解,探讨偶氮染料脱色液对氧气的响应情况,利用紫外可见分光光度法(ultraviolet visible spectrophotometry,UV-vis)和傅里叶变换红外光谱法(Fourier transform infrared spectroscopy,FTIR)对脱色产物进行分析。【结果】在兼氧和厌氧条件下反应48 h后的染料脱色液,与氧气充分接触后,部分偶氮染料微生物脱色液发生较为明显的复色现象,如活性黑5、直接黑38;UV-vis分析结果表明,这种复色现象是由于脱色液与氧气接触之后产生新物质所致;FTIR分析结果表明,混合菌群对发生复色反应的偶氮染料仍然具有一定脱色降解效果,但是脱色尚不够完全。【结论】兼氧和厌氧条件下,氧气对部分偶氮染料微生物脱色液具有较为明显的影响,从而影响混合菌群对偶氮染料的整体脱色效果,这可为今后研究偶氮染料彻底生物降解提供理论基础。     

A role for IL-22 in the relationship between intestinal helminths,gut microbiota and mucosal immunity

The intestinal tract is home to nematodes as well as commensal bacteria (microbiota), which have coevolved with the mammalian host. The mucosal immune system must balance between an appropriate response to dangerous pathogens and an inappropriate response to commensal microbiota that may breach the epithelial barrier, in order to maintain intestinal homeostasis. IL-22 has been shown to play a critical role in maintaining barrier homeostasis against intestinal pathogens and commensal bacteria. Here we review the advances in our understanding of the role of IL-22 in helminth infections, as well as in response to commensal and pathogenic bacteria of the intestinal tract. We then consider the relationship between intestinal helminths and gut microbiota and hypothesize that this relationship may explain how helminths may improve symptoms of inflammatory bowel diseases. We propose that by inducing an immune response that includes IL-22, intestinal helminths may enhance the mucosal barrier function of the intestinal epithelium. This may restore the mucosal microbiota populations from dysbiosis associated with colitis and improve intestinal homeostasis.     

Convergent dynamics of the juvenile European sea bass gut microbiota induced by poly-β-hydroxybutyrate

Poly-β-hydroxybutyrate (PHB) is a bacterial energy and carbon storage compound which exhibits a controlling effect on the gastrointestinal microbiota. Its beneficial activities for aquaculture have already been shown in terms of increased disease resistance and growth performance in a number of studies. However, the action of PHB on the intestinal microbial community in the treated animals has not yet been studied in depth. In this research, the effects of PHB on the microbiota composition in the intestinal tract of juvenile sea bass were examined. It was found that fish cohabiting in the same tank were on average 87% similar regarding the intestinal microbiota. When subjected to the same treatment and environmental conditions but reared in different tanks, the compositions of the enteric communities diverged. The provision of PHB overruled this tank effect by sustaining a microbial core community in the gut that represented 60% of the total bacterial diversity at the highest PHB level of 10%. The microbial community compositions converged between replicate tanks upon supplementation of PHB and were characterized by high dynamics and increased evenness. The results are discussed in the framework of hypotheses that try to relate the intestinal microbial community composition to the health status of the host organisms.     

Movement and fixation of intestinal microbiota after administration of human feces to germfree mice

Human flora-associated (HFA) mice have been considered a tool for studying the ecology and metabolism of intestinal bacteria in humans, although they have some limitations as a model. Shifts in dominant species of microbiota in HFA mice after the administration of human intestinal microbiota was revealed by 16S rRNA gene sequence and terminal restriction fragment length polymorphism (T-RFLP) analyses. Characteristic terminal restriction fragments (T-RFs) were quantified as the proportion of total peak area of all T-RFs. Only the proportion of the T-RF peak at bp 366, identified as the Gammmaproteobacteria group and the family Coriobacteriaceae, was reduced in this study. Increased T-RFs over time at bp 56, 184, and 196 were affiliated with the Clostridium group. However, most of the isolated bacteria with unique population shifts were phylotypes. The vertical transmission of the intestinal microbiota of the mouse offspring was also investigated by dendrogram analysis derived from the similarity of T-RFLP patterns among samples. As a result, the intestinal microbiota of HFA mice and their offspring reflected the composition of individual human intestinal bacteria with some modifications. Moreover, we revealed that human-derived lactobacilli (HDL), which have been considered difficult to colonize in the HFA mouse intestine in previous studies based on culture methods, could be detected in the HFA mouse intestine by using a lactic acid bacterium-specific primer and HDL-specific primers. Our results indicate that the intestinal microbiota of HFA mice represents a limited sample of bacteria from the human source and are selected by unknown interactions between the host and bacteria.     

Movement and Fixation of Intestinal Microbiota after Administration of Human Feces to Germfree Mice

Human flora-associated (HFA) mice have been considered a tool for studying the ecology and metabolism of intestinal bacteria in humans, although they have some limitations as a model. Shifts in dominant species of microbiota in HFA mice after the administration of human intestinal microbiota was revealed by 16S rRNA gene sequence and terminal restriction fragment length polymorphism (T-RFLP) analyses. Characteristic terminal restriction fragments (T-RFs) were quantified as the proportion of total peak area of all T-RFs. Only the proportion of the T-RF peak at bp 366, identified as the Gammmaproteobacteria group and the family Coriobacteriaceae, was reduced in this study. Increased T-RFs over time at bp 56, 184, and 196 were affiliated with the Clostridium group. However, most of the isolated bacteria with unique population shifts were phylotypes. The vertical transmission of the intestinal microbiota of the mouse offspring was also investigated by dendrogram analysis derived from the similarity of T-RFLP patterns among samples. As a result, the intestinal microbiota of HFA mice and their offspring reflected the composition of individual human intestinal bacteria with some modifications. Moreover, we revealed that human-derived lactobacilli (HDL), which have been considered difficult to colonize in the HFA mouse intestine in previous studies based on culture methods, could be detected in the HFA mouse intestine by using a lactic acid bacterium-specific primer and HDL-specific primers. Our results indicate that the intestinal microbiota of HFA mice represents a limited sample of bacteria from the human source and are selected by unknown interactions between the host and bacteria.