Mineralization of 4-aminobenzenesulfonate (4-ABS) by Agrobacterium sp. strain PNS-1

Enhanced degradation of 4-aminobenzenesulfonate by a co-culture of Afipia sp. 624S and Diaphorobacter sp. 624L

Two strains, Afipia sp. 624S and Diaphorobacter sp. 624L, were isolated from an enrichment culture with 4-aminobenzenesulfonate (4-ABS) as the only carbon source. Strain 624S utilized 4-ABS as the only source of carbon and energy and degraded 3.8 mM 4-ABS in 2 weeks, releasing a small amount of sulfate ions. On the other hand, strain 624L did not utilize 4-ABS. Additionally, a co-culture of strains 624S and 624L resulted in the enhanced degradation of 4-ABS, and no sulfite was accumulated in the degradation of 4-ABS. When incubated in 50 mM Tris-HCl buffer (pH 8.0) containing 2.2 mM sodium sulfite, strain 624S exhibited no sulfite oxidation; however, strain 624L completely oxidized the sulfite after 2 days. Furthermore, when manganase, which has the ability to oxidize sulfite, was added to the medium, the degradation rate of 4-ABS was increased in comparison with the non-addition control. These results indicate that the sulfite oxidation might stimulate the degradation of 4-ABS by strain 624S, suggesting syntrophic interaction between strains 624S and 624L based on sulfite oxidation.

Impact of sludge treatments on the extractability and fate of acetyl sulfamethoxazole residues in amended soils

Sludge recycled in agriculture may bring antibiotics into cropped soils. The nature, total amount, and availability of the antibiotics in soil partly depend on the sludge treatments. Our paper compares the fate of N-acetyl sulfamethoxazole (AC-SMX) residues between soils incubated with the same sludge but submitted to different processes before being added in soil. The fate of ¹⁴C-AC-SMX residues was studied in mixtures of soil and sludges at different treatment levels: 1) activated and 2) centrifuged sludges, both enriched with ¹⁴C-AC-SMX, and 3) limed and 4) heat-dried sludges obtained by treating the previously contaminated centrifuged sludge. The evolution of the extractability of ¹⁴C residues (CaCl₂, methanol) and their mineralization were followed during 119 days. More than 80% of the initial ¹⁴C-activity was no longer extractable after 14 days, except in soil with limed sludge. Liming and drying the centrifuged sludge decreased the mineralized ¹⁴C fraction from 5.7-6.4% to 1.2-1.8% and consequently, the corresponding soils contained more ¹⁴C residues after 119 days. Although ¹⁴C residues were more CaCl₂-extractable in soil with limed sludge, they seemed to be poorly bioavailable for biodegradation. For all solid sludges, the mineralization rate of ¹⁴C-AC-SMX residues was strongly correlated to that of sludge organic carbon, with a coefficient three times lower for the limed and dried sludges than for the centrifuged sludge after 14 days.

Starvation- and xenobiotic-related transcriptomic responses of the sulfanilic acid-degrading bacterium, Novosphingobium resinovorum SA1

Novosphingobium resinovorum SA1 was the first single isolate capable of degrading sulfanilic acid, a widely used representative of sulfonated aromatic compounds. The genome of the strain was recently sequenced, and here, we present whole-cell transcriptome analyses of cells exposed to sulfanilic acid as compared to cells grown on glucose. The comparison of the transcript profiles suggested that the primary impact of sulfanilic acid on the cell transcriptome was a starvation-like effect. The genes of the peripheral, central, and common pathways of sulfanilic acid biodegradation had distinct transcript profiles. The peripheral genes located on a plasmid had very high basal expressions which were hardly upregulated by sulfanilic acid. The genomic context and the codon usage preference of these genes suggested that they were acquired by horizontal gene transfer. The genes of the central pathways were remarkably inducible by sulfanilic acid indicating the presence of a substrate-specific regulatory system in the cells. Surprisingly, the genes of the common part of the metabolic pathway had low and sulfanilic acid-independent transcript levels. The approach applied resulted in the identification of the genes of proteins involved in auxiliary processes such as electron transfer, substrate and iron transports, sulfite oxidases, and sulfite transporters. The whole transcriptome analysis revealed that the cells exposed to xenobiotics had multiple responses including general starvation-like, substrate-specific, and substrate-related effects. From the results, we propose that the genes of the peripheral, central, and common parts of the pathway have been evolved independently.

Aerobic degradation of sulfanilic acid using activated sludge

This paper evaluates the aerobic degradation of sulfanilic acid (SA) by an acclimatized activated sludge. The sludge was enriched for over three months with SA (>500 mg/L) as the sole carbon and energy source and dissolved oxygen (DO, >5mg/L) as the primary electron acceptor. Effects of aeration rate (0-1.74 L/min), DO concentration (0-7 mg/L) and initial SA concentration (104-1085 mg/L) on SA biodegradation were quantified. A modified Haldane substrate inhibition model was used to obtain kinetic parameters of SA biodegradation and oxygen uptake rate (OUR). Positive linear correlations were obtained between OUR and SA degradation rate (R(2)≥ 0.91). Over time, the culture consumed more oxygen per SA degraded, signifying a gradual improvement in SA mineralization (mass ratio of O(2): SA at day 30, 60 and 120 were 0.44, 0.51 and 0.78, respectively). The concomitant release of near stoichiometric quantity of sulphate (3.2 mmol SO(4)(2-) released from 3.3 mmol SA) and the high chemical oxygen demand (COD) removal efficacy (97.1%) indicated that the enriched microbial consortia could drive the overall SA oxidation close to a complete mineralization. In contrast to other pure-culture systems, the ammonium released from the SA oxidation was predominately converted into nitrate, revealing the presence of ammonium-oxidizing bacteria (AOB) in the mixed culture. No apparent inhibitory effect of SA on the nitrification was noted. This work also indicates that aerobic SA biodegradation could be monitored by real-time DO measurement.

Isolation and Characterization of a Sulfanilic Acid Degrading Bacterial Strain

Sulfanilic acid is a representative intermediate of some sulfonated azo dyes. A bacterial strain isolated from the river in Wenzhou, could utilize sulfanilic acid as the solo carbon source and energy source. Based on its morphological, physiological and biochemical characteristics as well as 16SrRNA sequences the bacterial strain was identified as Ochrobactrum anthrop. Effective biodegradation of sulfanilic acid occurred at pH ranging from 6 to 8. The optimum growth temperature and pH for the bacterial strain to utilize sulfanilic acid are 30°C and 7.0 respectively. Its most favorable sulfanilic acid concentration is 300mg/L.

Biodegradation of crystal violet by Agrobacterium radiobacter

Agrobacterium radiobacter MTCC 8161 completely decolorized the Crystal Violet with 8 hr (10 mg/L) at static anoxic conditions. The decreased decolorization capability by A. radiobacter was observed, when the Crystal Violet concentration was increased from 10 to 100 mg/L. Semi-synthetic medium containing 1% yeast extract and 0.1% NH4C1 has shown 100% decolorization of Crystal Violet within 5 hr. A complete degradation of Crystal Violet by A. radiobacter was observed up to 7 cycles of repeated addition (10 mg/L). When the effect of increasing inoculum concentration on decolorization of Crystal Violet (100 mg/L) was studied, maximum decolorization was observed with 15% inoculum concentration. A significant increase in the activities of laccase (184%) and aminopyrine N-demethylase (300%) in cells obtained after decolorization indicated the involvement of these enzymes in decolorization process. The intermediates formed during the degradation of Crystal Violet were analyzed by gas chromatography and mass spectroscopy (GC/MS). It was detected the presence of N,N,N',N"-tetramethylpararosaniline, [N, N-dimethylaminophenyl] [N-methylaminophenyl] benzophenone, N, N-dimethylaminobenzaldehyde, 4-methyl amino phenol and phenol. We proposed the hypothetical metabolic pathway of Crystal Violet biodegradation by A. radiobacter. Phytotoxicity and microbial toxicity study showed that Crystal Violet biodegradation metabolites were less toxic to bacteria (A. radiobacter, P. aurugenosa and A. vinelandii) contributing to soil fertility and for four kinds of plants (Sorghum bicolor Vigna radiata, Lens culinaris and Triticum aestivum) which are most sensitive, fast growing and commonly used in Indian agriculture.

Biodegradation of 4-aminobenzenesulfonate by a novel Pannonibacter sp. W1 isolated from activated sludge

4-Aminobenzenesulfonate (4-ABS) is a representative intermediate of some sulfonated azo dyes. A novel Pannonibacter sp. strain W1 capable of degrading 4-ABS as sole carbon as well as energy, nitrogen and sulfur source was isolated and identified from the activated sludge of a municipal wastewater treatment plant. Strain W1 was able to completely degrade 4-ABS with initial concentrations of 200-2500 mg L(-1) within 40 h. Haldane inhibition model was used to fit the special degradation rate at different initial concentrations, and the parameters micro(max), K(s) and K(i) were determined to be 227.977 mg (gh)(-1), 84.306 mg L(-1) and 1270.675 mg L(-1), respectively. Elements N and S of 4-ABS were released in respective forms of ammonia and sulfate while degrading 4-ABS by strain W1, accounting for 77.6% and 92.2% of theoretical values, respectively. Relatively low recoveries of dissolved N and S were probably owing to the fact that part of the released ammonia and sulfate were utilized by strain W1 for cell growth. It was found that the reduction of total organic carbon (TOC) was proportional to the degradation of 4-ABS and 84.4% TOC removal rate, corresponding to a 4-ABS degradation rate of 94.7%, was achieved at the end of the test. Additionally, HPLC and UV analyses indicated that there were no other aromatic intermediates detectable, suggesting the achievement of a complete mineralization of 4-ABS with strain W1.

Biodegradation of nicotine by a newly isolated Agrobacterium sp. strain S33

AIMS

To isolate and characterize bacteria capable of degrading nicotine from the rhizospheric soil of a tobacco plant and to use them to degrade the nicotine in tobacco solid waste.

METHODS AND RESULTS

A bacterium, strain S33, was newly isolated from the rhizospheric soil of a tobacco plant, and identified as Agrobacterium sp. based on morphology, physiological tests, Biolog MicroLog3 4.20 system and 16S rRNA gene sequence. Using nicotine as the sole source of carbon and nitrogen in the medium, it grew optimally with 1.0 g l(-1) of nicotine at 30 degrees C and pH 7.0, and nicotine was completely degraded within 6 h. The resting cells prepared from the glucose-ammonium medium or LB medium could not degrade nicotine within 10 h, while those prepared from the nicotine medium could completely degrade 3 g l(-1) of nicotine in 1.5 h at a maximal rate of 1.23 g nicotine h(-1) g(-1) dry cell. Using the medium containing nicotine, glucose and ammonium simultaneously to cultivate strain S33, the resting cells could degrade 98.87% of nicotine in tobacco solid waste with the concentration as 30 mg nicotine g(-1) dry weight tobacco solid waste within 7 h at a maximal rate of 0.46 g nicotine h(-1) g(-1) dry cell.

CONCLUSIONS

This is the first report that Agrobacterium sp. has the ability to degrade nicotine. Agrobacterium sp. S33 could use nicotine as the sole source of carbon and nitrogen. The use of resting cells of the strain S33 prepared from the nicotine-glucose-ammonium medium was an effective method to degrade nicotine and detoxify tobacco solid waste.

SIGNIFICANCE AND IMPACT OF THE STUDY

Nicotine in tobacco wastes is both toxic and harmful to human health and the environment. This study showed that Agrobacterium sp. S33 may be suitable for the disposal of tobacco wastes and reducing the nicotine content in tobacco leaves.

Environmental fate of endocrine-disrupting dimethyl phthalate esters (DMPE) under sulfate-reducing condition

Dimethyl phthalate esters (DMPE) can easily be released into the environment from plastic products. As endocrine disruptors, DMPE mimic estrogenic activities in animals and humans. The metabolites of DMPE are suspected to cause even more serious health problems. Among the common sterilization techniques adopted in the study of DMPE degradation, the average loss of the parent DMPE compounds after autoclaving was as high as 21.26%. In contrast, the loss after 0.2 microm filtration was significantly lower at 2.28%. It is suggested that filtration should be used over autoclaving for sterilizing DMPE. The environmental fate of DMPE under sulfate-reducing condition was simulated and studied in microcosm system. It was observed that dimethyl phthalate (DMP), dimethyl isophthalate (DMI) and dimethyl terephthalate (DMT) could not be mineralized over an extended period of 6 months, but with the transformation to the respective monomethyl phthalate and/or phthalic acid. The dominant species of microorganisms utilizing individual DMPE isomer as the sole carbon source were isolated and identified as facultative anaerobe Thauera sp., Xanthobacter sp. and Agrobacterium sp. for DMP, DMI and DMT, respectively. This study illustrates that the detrimental DMPE and their natural metabolites may accumulate in the sulfate-reducing environment. Accordingly, proper surveillance program should be devised to monitor both the parent compounds and degradation intermediates of DMPE in order to protect the aquatic ecosystem and human health.