The missing link in linear alkylbenzenesulfonate surfactant degradation: 4-sulfoacetophenone as a transient intermediate in the degradation of 3-(4-sulfophenyl)butyrate by Comamonas testosteroni KF-1

Comparative analysis of microbial community under acclimation of linear alkylbenzene sulfonate (LAS) surfactants and degradation mechanisms of functional strains

Linear alkylbenzene sulfonate (LAS) is one of the most widely used anionic surfactants and a common toxic pollutant in wastewater. This study employed high throughput sequencing to explore the microbial community structure within activated sludge exposed to a high concentration of LAS. Genera such as Pseudomonas, Aeromonas, Thauera and Klebsiella exhibited a significant positive correlation with LAS concentrations. Furthermore, Comamonas and Klebsiella were significantly enriched under the stress of LAS. Moreover, bacterial strains with LAS-degrading capability were isolated and characterized to elucidate the degradation pathways. The Klebsiella pneumoniae isolate L1 could effectively transform more than 60 % of 25 mg/L of LAS within 72 h. Chemical analyses revealed that L1 utilized the LAS sulfonyl group as a sulfur source to support its growth. Genomic and transcriptomic analyses suggested that strain L1 may uptake LAS through the sulfate ABC transport system and remove sulfonate with sulfate and sulfite reductases.

Composition of "gold juice" using an ancient method based on intestinal microecology

OBJECTIVE

To identify potentially effective bacterial components of gold juice, a traditional Chinese medicine treatment used for fecal microbiota transplantation.

METHODS

Fecal samples were collected from five healthy children (two boys and three girls; mean age, 7.52 ± 2.31 years). The children had no history of antibiotic use or intestinal microecological preparation in the preceding 3 months. Fresh fecal samples were collected from children to prepare gold juice in mid-to-late November, in accordance with traditional Chinese medicine methods, then used within 7 days. Finally, 16S rDNA sequence analysis was used to identify potentially effective bacterial components of gold juice. QIIME software was used for comparisons of microbial species among gold juice, diluent, filtrate, and loess samples.

RESULTS

Microflora of gold juice exhibited considerable changes following "ancient method" processing. Microbial components significantly differed between gold juice and filtrate samples. The gold juice analyzed in our study consisted of microbes that synthesize carbohydrates and amino acids by degrading substances, whereas the filtrate contained probiotic flora, Bacteroides, and Prevotella 9.

CONCLUSIONS

This study of microbial components in gold juice and filtrate provided evidence regarding effective bacterial components in gold juice, which may aid in clinical decisions concerning fecal microbiota transplantation.

Higher alkyl sulfatase activity required by microbial inhabitants to remove anionic surfactants in the contaminated surface waters

Biodegradation of anionic surfactants, like sodium dodecyl sulfate (SDS) are challenged by some bacteria through the function of the enzyme alkyl sulfatases. Therefore, identifying and characterizing bacteria capable of degrading SDS with high alkyl sulfatase enzyme activity are pivotal. In this study, bacteria isolated from surfactant contaminated river water were screened for their potential to degrade SDS. Primary screening carried out by the conventional enrichment culture technique and assessment of SDS-degrading ability through methylene blue active substance assay revealed 12, out of 290, SDS-degrading surface water bacteria with maximum SDS degrading abilities of 46-94% in 24-54 h. The isolates exhibited optimum growth at SDS concentration of 1 g/L, but tolerated up to 15-75 g/L. Eleven isolates were identified as the species of Pseudomonas and one isolate was identified as Aeromonas through 16S rRNA sequencing. Proteolytic activity of alkyl sulfatases in the identified isolates was shown by using native-PAGE analysis. The determined enzyme activities changed in between 1.32 and 2.90 U/mg in the crude extracts. Preliminary experiments showed that the isolates with the alkyl sulfatase enzyme activities ≥2.50 U/mg were strong gratuitous degraders. However, their relative importance in soil, sewage, and wastewater treatment plants remains to be assessed.

Permanent draft genome sequence of Comamonas testosteroni KF-1

Comamonas testosteroni KF-1 is a model organism for the elucidation of the novel biochemical degradation pathways for xenobiotic 4-sulfophenylcarboxylates (SPC) formed during biodegradation of synthetic 4-sulfophenylalkane surfactants (linear alkylbenzenesulfonates, LAS) by bacterial communities. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 6,026,527 bp long chromosome (one sequencing gap) exhibits an average G+C content of 61.79% and is predicted to encode 5,492 protein-coding genes and 114 RNA genes.

Two enzymes of a complete degradation pathway for linear alkylbenzenesulfonate (LAS) surfactants: 4-sulfoacetophenone Baeyer-Villiger monooxygenase and 4-sulfophenylacetate esterase in Comamonas testosteroni KF-1

Complete biodegradation of the surfactant linear alkylbenzenesulfonate (LAS) is accomplished by complex bacterial communities in two steps. First, all LAS congeners are degraded into about 50 sulfophenylcarboxylates (SPC), one of which is 3-(4-sulfophenyl)butyrate (3-C(4)-SPC). Second, these SPCs are mineralized. 3-C(4)-SPC is mineralized by Comamonas testosteroni KF-1 in a process involving 4-sulfoacetophenone (SAP) as a metabolite and an unknown inducible Baeyer-Villiger monooxygenase (BVMO) to yield 4-sulfophenyl acetate (SPAc) from SAP (SAPMO enzyme); hydrolysis of SPAc to 4-sulfophenol and acetate is catalyzed by an unknown inducible esterase (SPAc esterase). Transcriptional analysis showed that one of four candidate genes for BVMOs in the genome of strain KF-1, as well as an SPAc esterase candidate gene directly upstream, was inducibly transcribed during growth with 3-C(4)-SPC. The same genes were identified by enzyme purification and peptide fingerprinting-mass spectrometry when SAPMO was enriched and SPAc esterase purified to homogeneity by protein chromatography. Heterologously overproduced pure SAPMO converted SAP to SPAc and was active with phenylacetone and 4-hydroxyacetophenone but not with cyclohexanone and progesterone. SAPMO showed the highest sequence homology to the archetypal phenylacetone BVMO (57%), followed by steroid BVMO (55%) and 4-hydroxyacetophenone BVMO (30%). Finally, the two pure enzymes added sequentially, SAPMO with NADPH and SAP, and then SPAc esterase, catalyzed the conversion of SAP via SPAc to 4-sulfophenol and acetate in a 1:1:1:1 molar ratio. Hence, the first two enzymes of a complete LAS degradation pathway were identified, giving evidence for the recruitment of members of the very versatile type I BVMO and carboxylester hydrolase enzyme families for the utilization of a xenobiotic compound by bacteria.

Comamonas testosteronan synthase, a bifunctional glycosyltransferase that produces a unique heparosan polysaccharide analog

Glycosaminoglycans (GAGs) are linear hexosamine-containing polysaccharides. These polysaccharides are synthesized by some pathogenic bacteria to form an extracellular coating or capsule. This strategy forms the basis of molecular camouflage since vertebrates possess naturally occurring GAGs that are essential for life. A recent sequence database search identified a putative protein from the opportunistic pathogen Comamonas testosteroni that exhibits similarity with the Pasteurella multocida GAG synthase PmHS1, which is responsible for the synthesis of a heparosan polysaccharide capsule. Initial supportive evidence included glucuronic acid (GlcUA)-containing polysaccharides extracted from C. testosteroni KF-1. We describe here the cloning and analysis of a novel Comamonas GAG synthase, CtTS. The GAG produced by CtTS in vitro consists of the sugars d-GlcUA and N-acetyl-D-glucosamine, but is insensitive to digestion by GAG digesting enzymes, thus has distinct glycosidic linkages from vertebrate GAGs. The backbone structure of the polysaccharide product [-4-D-GlcUA-α1,4-D-GlcNAc-α1-](n) was confirmed by nuclear magnetic resonance. Therefore, this novel GAG, testosteronan, consists of the same sugars as the biomedically relevant GAGs heparosan (N-acetyl-heparosan) and hyaluronan but may have distinct properties useful for future medical applications.

Enantioselective degradation and unidirectional chiral inversion of 2-phenylbutyric acid, an intermediate from linear alkylbenzene, by Xanthobacter flavus PA1

Microbial degradation of the chiral 2-phenylbutyric acid (2-PBA), a metabolite of surfactant linear alkylbenzene sulfonates (LAS), was investigated using both racemic and enantiomer-pure compounds together with quantitative stereoselective analyses. A pure culture of bacteria, identified as Xanthobacter flavus strain PA1 isolated from the mangrove sediment of Hong Kong Mai Po Nature Reserve, was able to utilize the racemic 2-PBA as well as the single enantiomers as the sole source of carbon and energy. In the presence of the racemic compounds, X. flavus PA1 degraded both (R) and (S) forms of enantiomers to completion in a sequential manner in which the (S) enantiomer disappeared much faster than the (R) enantiomer. When the single pure enantiomer was supplied as the sole substrate, a unidirectional chiral inversion involving (S) enantiomer to (R) enantiomer was evident. No major difference was observed in the degradation intermediates with either of the individual enantiomers when used as the growth substrate. Two major degradation intermediates were detected and identified as 3-hydroxy-2-phenylbutanoic acid and 4-methyl-3-phenyloxetan-2-one, using a combination of liquid chromatography-mass spectrometry (LC-MS), and (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy. The biochemical degradation pathway follows an initial oxidation of the alkyl side chain before aromatic ring cleavage. This study reveals new evidence for enantiomeric inversion catalyzed by pure culture of environmental bacteria and emphasizes the significant differences between the two enantiomers in their environmental fates.