Sphingobium jiangsuense sp. nov., a 3-phenoxybenzoic acid-degrading bacterium isolated from a wastewater treatment system

Genomic-based taxonomic classification of the order Sphingomonadales

The order Sphingomonadales strains are globally distributed in various biomes and are renowned for their biodegradable and biosynthesis capabilities. At present, it consists of 4 families and 49 genera making it the third largest order within the class Alphaproteobacteria. However, their taxonomy remains complex, especially due to polyphyly in the family Sphingomonadaceae. In this study, we collected 429 Sphingomonadales type strain genomes, reconstructed robust phylogenomic relationships, and proposed delineation thresholds at the genus and family levels based on average amino acid identities (AAI) and evolutionary distances (ED). Based on the maximum-likelihood and Bayesian phylogenomic trees reconstructed by two molecular sets determined by orthologous sequence identity and the Genome Taxonomy Database, the consensus degree values were all higher than 90%, revealing that those phylogenomic trees had similar topological structures. By confirming monophyletic taxa and determining stable nodes, we reclassified the order Sphingomonadales into thirteen families including nine novel ones. AAI calculations indicated that the average intra-family AAI values ranged from 0.62 to 0.84, while inter-family ones were 0.51 to 0.60. ED summaries demonstrated that the average and median intra-family ED values were 0.16 to 0.57, and inter-family ones ranged from 0.50 to 1.22. Comparisons of AAI and ED values calculated by using genomic and phylogenetic analyses supported that those 13 families were significantly separated with p values < 2.2×10-16. Thus, it was speculated that the AAI and ED thresholds for distinguishing different families were <0.6 and >0.5, respectively. Additionally, we reclassified 163 species into new genera with their phylogenetic topologies, according to the previous genus AAI and ED boundaries of 0.7 and 0.4. Our study is the first genomic-based study of the order Sphingomonadales and will promote further insights into the evolution of this order.

Seasonal dynamics of bacterial composition and functions in biological treatment of coking wastewater

Seasonal dynamics of bacterial composition and functions were demonstrated for the biological fluidized-bed bioreactors combined in the anoxic/aerobic1/aerobic2 (AOO) coking wastewater (CWW) treatment sequences. The bacterial composition and functions in the CWW activated sludge samples were revealed by 16S rRNA genes amplicon sequencing. Thiobacillus, Cloacibacterium, Alkaliphilus and Pseudomonas were determined as core genera with seasonal changes. Mutable microbial community composition fluctuated in different seasons in same bioreactor. Distributions of predicted KEGG pathways along four seasons consistently demonstrated enrichment in biodegradation of carbon- and nitrogen-containing compounds. The major contaminants were removed from CWW by biochemical pathway of xenobiotics biodegradation and metabolism. This Level 2 pathway mainly owned the Level 3 pathways of benzoate degradation, drug metabolism-other enzymes, drug metabolism-cytochrome P450, metabolism of xenobiotics by cytochrome P450, and aminobenzoate degradation. The RDA results showed that dissolved oxygen with seasonal fluctuation was the main parameter shaping the microbial community. The observed dynamics within the microbial community composition, coupled with the maintained stability of CWW treatment efficiencies and a consistent profile of microbial functional pathways, underscore the presence of functional redundancy in the AOO bioreactors. The study underscored stable and effective operational performances of bioreactors in the AOO sequences, contributing the knowledge of microbiological basics to the advancement of CWW biological treatment. KEY POINTS: • Seasonal fluctuations of bacterial composition described for the AOO system. • Seasonal distributions of metabolic functions focused on carbon and nitrogen removal. • Functional redundancy was revealed in the AOO microbial community.

Transcriptomic analysis reveals peripheral pathway in 3-phenoxybenzoic acid degradation by Aspergillus oryzae M-4

As a major intermediate metabolite of synthetic pyrethroids, the occurrence of 3-phenoxybenzoic acid hinders the decomposition of the parent pesticide and poses uncertain risks to environmental ecology and living organisms. Strain Aspergillus oryzae M-4 was previously reported to degrade 3-PBA and several substances were identified as downstream transformation products (TPs). But the mechanism underlying the cleavage of ether bond remains largely unclear. Here, we attempted to address such concern through identifying the peripheral TPs and analyzing transcriptomics, coupled with serial batch degradation experiments. Analysis results of chromatographic/mass spectrometry suggested that 3-PBA underwent twice hydroxylation, to yield mono- and dihydroxylated 3-PBA successively. In parallel, a mutual transformation between 3-PBA and 3-phenoxybenzyl alcohol (3-PBOH) also existed. The proposal of peripheral pathway represents an important advance towards fully understanding the whole 3-PBA metabolism in M-4. A specific altered metabolization was found for the first time, that is, resting cells of M-4 skipped the reduction step and initiate hydroxylation directly, by comparison with growing cells. Transcriptome analysis indicated that 3-PBA induced the up-regulation of genes related to energy investment, oxidative stress response, membrane transport and DNA repair. In-depth functional interpretation of differential expression genes suggested that the generation 3-PBOH and hydroxylated 3-PBA may be due to the participation of flavin-dependent monooxygenases (FMOs) and cytochrome P450 (CYP450), respectively. This study provides new insight to reveal the biodegradation mechanism of 3-PBA by A. oryzae M-4.

Highly efficient degradation of cypermethrin by a co-culture of Rhodococcus sp. JQ-L and Comamonas sp. A-3

Cypermethrin is an important synthetic pyrethroid pesticide that widely used to control pests in agriculture. However, extensive use has caused its residue and the metabolite 3-phenoxybenzoic acid (3-PBA) to seriously pollute the environments and agricultural products. In this study, a highly efficient cypermethrin-degrading bacterial consortium was acclimated from long-term pyrethroid-contaminated soil. Two strains, designated JQ-L and A-3, were screened from the consortium, and identified as Rhodococcus sp. and Comamonas sp., respectively. Strain JQ-L transformed 100 mg/L of cypermethrin to 3-PBA within 60 h of incubation; however, 3-PBA could not be further degraded by the strain. Strain A-3 utilized 3-PBA as sole carbon for growth, and completely degraded 100 mg/L of 3-PBA within 15 h of incubation. Co-culture of JQ-L and A-3 completely degraded 100 mg/L of cypermethrin within 24 h of incubation. Furthermore, a complete catabolic pathway of cypermethrin and the metabolite 3-PBA by the co-culture was proposed. This study provided a promising strategy for efficient elimination of cypermethrin residue-contaminated environments and agricultural products.

Description and functional testing of four species of the novel phototrophic genus Chioneia gen. nov., isolated from different East Antarctic environments

Seven Gram-negative, aerobic, non-sporulating, motile strains were isolated from terrestrial (R-67880^T, R-67883, R-36501 and R-36677^T) and aquatic (R-39604, R-39161^T and R-39594^T) East Antarctic environments (i.e. soil and aquatic microbial mats), between 2007 and 2014. Analysis of near-complete 16S rRNA gene sequences revealed that the strains potentially form a novel genus in the family Sphingomonadaceae (Alphaproteobacteria). DNA-DNA reassociation and average nucleotide identity values indicated distinction from close neighbors in the family Sphingomonadaceae and showed that the seven isolates form four different species. The main central pathways present in the strains are the glycolysis, tricarboxylic acid cycle and pentose phosphate pathway. The strains can use only a limited number of carbon sources and mainly depend on ammonia and sulfate as a nitrogen and sulfur source, respectively. The novel strains showed the potential of aerobic anoxygenic phototrophy, based on the presence of bacteriochlorophyll a pigments, which was corroborated by the presence of genes for all building blocks for a type 2 photosynthetic reaction center in the annotated genomes. Based on the results of phenotypic, genomic, phylogenetic and chemotaxonomic analyses, the strains could be assigned four new species in the novel genus Chioneia gen. nov. in the family Sphingomonadaceae, for which the names C. frigida sp. nov. (R-67880^T, R-67883 and R-36501), C. hiemis sp. nov. (R-36677^T), C. brumae sp. nov. (R-39161^T and R-39604) and C. algoris sp. nov. (R-39594^T) are proposed.

Hydroponic approach to assess rhizodegradation by sudangrass (Sorghum x drummondii) reveals pH- and plant age-dependent variability in bacterial degradation of polycyclic aromatic hydrocarbons (PAHs)

Rhizodegradation of polycyclic aromatic hydrocarbons (PAHs) is a product of complex interactions between plant and bacteria. In this study, hydroponic culture of sudangrass was established in order to investigate the effects of the plant on PAHs degradation and vice versa through changes in rhizosphere bacterial community. Results showed a plant-induced variability in PAHs degradation dependent on a characteristic shift in bacterial community, with pH and plant age as driving factors. Moreover, bacterial communities with high diversity seemed to abate the phytotoxic effects of PAHs degradation as observed in the plant's gross health. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and next-generation sequencing revealed that regardless of plant age and culture conditions, the increase or decrease of Sphingobium sp. could dictate the PAHs degradation potential of the bacterial consortium. Overall, this study utilized hydroponic culture of sudangrass to show that plant even of same species can suppress, support, or enhance PAHs degradation of bacteria depending on specific factors.

Efficient biodegradation of 3-phenoxybenzoic acid and pyrethroid pesticides by the novel strain Klebsiella pneumoniae BPBA052

A novel Klebsiella pneumoniae strain (BPBA052) capable of degrading 3-phenoxybenzoic acid (3-PBA) was isolated from soybean rhizosphere soil. The strain was obtained by screening after enrichment, isolation, and purification using 3-PBA as the sole carbon and energy source. It could degrade 96.37% of 3-PBA (100 mg/L) within 72 h, and its growth and 3-PBA degradation followed kinetics models of logistic growth (XBPBA052 = 0.0883 × e0.0947t / [1 − 0.0792 × (1 − 0.0883 × e0.0947t)]; μm = 0.0947 h–1, X0 = 0.0883, and Xm = 1.1145) and first-order degradation (CBPBA052 = 101.8194 × e–0.0403t, k = 0.0403, t1/2 = 17.22 h), respectively. Based on Box–Behnken response surface analysis, the optimal temperature, pH, and 3-PBA concentration for K. pneumoniae BPBA052 were 35.01 °C, 7.77, and 150 mg/L, respectively. Moreover, pyrethroid pesticides (PPs) (such as β-cypermethrin, permethrin, bifenthrin, deltamethrin, and fenvalerate) and 3-PBA metabolites (including phenol, catechol, and protocatechuate) were efficiently utilized by BPBA052. We propose a novel microbial metabolic pathway for 3-PBA, based on metabolite identification; enzyme-degrading activity; and cloning of the phenol hydroxylase, catechol 1,2-dioxygenase, and protocatechuate 3,4-dioxygenase genes. This study provides a fundamental platform for further studies to reveal the mechanism of biodegradation of 3-BPA and show K. pneumoniae BPBA052 as a potential microbial resource for bioremediation of environments polluted with 3-PBA or PPs.

Metaproteomics characterization of the alphaproteobacteria microbiome in different developmental and feeding stages of the poultry red mite Dermanyssus gallinae (De Geer, 1778)

The poultry red mite (PRM), Dermanyssus gallinae (De Geer, 1778), is a worldwide distributed ectoparasite and considered a major pest affecting the laying hen industry in Europe. Based on available information in other ectoparasites, the mite microbiome might participate in several biological processes and the acquisition, maintenance and transmission of pathogens. However, little is known about the role of PRM as a mechanical carrier or a biological vector in the transmission of pathogenic bacteria. Herein, we used a metaproteomics approach to characterize the alphaproteobacteria in the microbiota of PRM, and variations in its profile with ectoparasite development (nymphs vs. adults) and feeding (unfed vs. fed). The results showed that the bacterial community associated with D. gallinae was mainly composed of environmental and commensal bacteria. Putative symbiotic bacteria of the genera Wolbachia, C. Tokpelaia and Sphingomonas were identified, together with potential pathogenic bacteria of the genera Inquilinus, Neorickettsia and Roseomonas. Significant differences in the composition of alphaproteobacterial microbiota were associated with mite development and feeding, suggesting that bacteria have functional implications in metabolic pathways associated with blood feeding. These results support the use of metaproteomics for the characterization of alphaproteobacteria associated with the D. gallinae microbiota that could provide relevant information for the understanding of mite-host interactions and the development of potential control interventions. Research highlights Metaproteomics is a valid approach for microbiome characterization in ectoparasites. Alphaproteobacteria putative bacterial symbionts were identified in D. gallinae. Mite development and feeding were related to variations in bacterial community. Potentially pathogenic bacteria were identified in mite microbiota.

Sphingobium aromaticivastans sp. nov., a novel aniline- and benzene-degrading, and antimicrobial compound producing bacterium

A strictly aerobic, orange-pigmented strain was isolated and designated as UCM-25^T. This strain is capable of degrading aniline and benzene, while is also producing antimicrobial compounds which inhibit the growth of some common pathogenic microbes. A near full-length 16S rRNA gene sequence revealed similarity to Sphingobium chlorophenolicum NBRC 16172^T (98.6%). The level of DNA-DNA hybridization between the new isolate and the related species suggests UCM-25^T to be a new species belonging to the genus Sphingobium. The bacterial cells contained phosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid, phosphatidylcholine, phosphatidylmonomethylethanolamine, phosphatidyldimethylethanolamine, three unidentified polar lipids, and an unidentified aminophospholipid. Ubiquinone Q-10 was the major quinone and spermidine was the major polyamine. The G+C content in the DNA of strain UCM-25^T was 62.9 mol%. Cells contained summed feature 8 (C_18:1ω7c and/or C_18:1ω6c), summed feature 3 (C_16:1ω7c and/or C_16:1ω6c), C_16:0, and C_14:0 2-OH as major fatty acids. Based on the comparison of phenotypic, genotypic, and chemotaxonomic characteristics, strain UCM-25^T represents a new member of the genus Sphingobium, for which the name S. aromaticivastans sp. nov. is proposed. The type strain is UCM-25^T (=KACC 19288^T =DSM 105181^T).

Screening of a beta-cypermethrin-degrading bacterial strain Brevibacillus parabrevis BCP-09 and its biochemical degradation pathway

A novel beta-cypermethrin (Beta-CP)-degrading strain isolated from activated sludge was identified as Brevibacillus parabrevis BCP-09 based on its morphological and physio-biochemical characteristics, and 16S rRNA gene analysis. Strain BCP-09 could effectively degrade Beta-CP at pH 5.0-9.0, 20-40 °C, and 10-500 mg L^-1 Beta-CP. Under optimal conditions (pH 7.41, 38.9 °C, 30.9 mg L^-1 Beta-CP), 75.87% Beta-CP was degraded within 3 days. Beta-CP degradation (half-life, 33.45 h) and strain BCP-09 growth were respectively described using first-order-kinetic and logistic-kinetic models. Seven metabolites were detected by high-performance liquid chromatography and gas chromatography-mass spectrometry- methyl salicylate, catechol, phthalic acid, salicylic acid, 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, 3-phenoxybenzaldehyde, and 3-phenoxybenzoic acid (3-PBA). The major Beta-CP metabolite, 3-PBA was further degraded into phenol, benzoic acid, and 4-methylhexanoic acid. BCP-09 also degraded aromatic compounds such as phenol, catechol, and protocatechuic acid. Beta-CP appears to be mainly degraded into 3-PBA, which is continuously degraded into smaller benzene or chain compounds. Thus, strain BCP-09 could form a complete degradation system for Beta-CP and might be considered a promising strain for application in the bioremediation of environments and agricultural products polluted by Beta-CP.

Isolation of monocrotophos-degrading strain Sphingobiumsp. YW16 and cloning of its TnopdA

The bacterial strain Sphingobium sp. YW16, which is capable of degrading monocrotophos, was isolated from paddy soil in China. Strain YW16 could hydrolyze monocrotophos to dimethylphosphate and N-methylacetoacetamide and utilize dimethylphosphate as the sole carbon source but could not utilize N-methylacetoacetamide. Strain YW16 also had the ability to hydrolyze other organophosphate pesticides. A fragment (7067 bp) that included the organophosphorus hydrolase gene, opdA, was acquired from strain YW16 using the shotgun technique combined with SEFA-PCR. Its sequence illustrated that opdA was included in TnopdA, which consisted of a transpose gene, a putative integrase gene, a putative ATP-binding protein gene, and opdA. Additionally, a conjugal transfer protein gene, traI, was located downstream of TnopdA. The juxtaposition of TnopdA with TraI suggests that opdA may be transferred from strain YW16 to other bacteria through conjugation. OpdA was able to hydrolyze a wide range of organophosphate pesticides, with the hydrolysis efficiency decreasing as follows: methyl parathion > fenitrothion > phoxim > dichlorvos > ethyl parathion > trichlorfon > triazophos > chlorpyrifos > monocrotophos > diazinon. This work provides the first report of opdA in the genus Sphingobium.

Sphingobium soli sp. nov. isolated from rhizosphere soil of a rose

Strain THG-SQA7(T), a Gram-negative, strictly aerobic, non-motile, rod-shaped bacterium was isolated from rhizosphere soil of a rose in PR China. Strain THG-SQA7(T) is closely related to the members of the genus Sphingobium, showing the highest 16S rRNA gene sequence similarities with Sphingobium lactosutens KACC 18100(T) (98.2%) and Sphingobium abikonense KCTC 2864(T) (98.1%). The DNA-DNA relatedness between strain THG-SQA7(T) and S. lactosutens KACC 18100(T) and S. abikonense KCTC 2864(T) was 26.2 ± 0.9 and 28.3 ± 1.2%, respectively. Chemotaxonomic data showed that strain THG-SQA7(T) possesses ubiquinone Q-10 as the predominant respiratory quinone, and C(18:1)ω7c, C(16:0), summed feature 3 (C(16:1)ω7c and/or C(16:1)ω6c) and C(14:0) 2OH as the major fatty acids. The major polar lipids were found to be phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylglycerol, sphingoglycolipid, diphosphatidylglycerol and phosphatidyldimethylethanolamine. Based on these results, together with phenotypic characterization, a novel species, Sphingobium soli sp. nov. is proposed.with the type strain is THG-SQA7(T) (=CCTCC AB 2015125(T) = KCTC 42607(T)).

Sphingobium phenoxybenzoativorans sp. nov., a 2-phenoxybenzoic-acid-degrading bacterium

A Gram-stain-negative, aerobic, yellow-pigmented, rod-shaped bacterium, designated strain SC_3T, was isolated from pesticide-contaminated soil sediment. The strain was able to mineralize 2-phenoxybenzoic acid. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SC_3T formed a monophyletic lineage in the genus Sphingobium, and showed highest similarity to the type strains of Sphingobium abikonense (97.0 %), followed by Sphingobium lactosutens (96.8 %) and Sphingobium cloacae (96.7 %). The DNA-DNA relatedness between strain SC_3T and its closest phylogenetic neighbours was lower than 70 %. The major fatty acids (>5 % of the total) were summed feature 8 (comprising C18:1ω7c/C18:1ω6c), summed feature 3 (comprising C16:1ω7c/C16:1ω6c), C14:0 2-OH, C16:0 and C17:1ω6c. The predominant quinone was ubiquinone Q-10, and the major polyamine was spermidine. The polar lipid profile contained diphosphatidylglycerol (DPG), sphingoglycolipid (SGL), phosphatidylethanolamine (PDME), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylmonomethylethanolamine (PMME), an unknown aminolipid (AL), two unknown lipids (L1, L2) and several unknown phospholipids (PL1-6). The genomic DNA G+C content of strain SC_3T was 62.9 mol%. On the basis of phenotypic, chemotaxonomic, phylogenetic and genotypic data, strain SC_3T represents a novel species of the genus Sphingobium, for which the name Sphingobium phenoxybenzoativorans sp. nov. is proposed. The type strain is SC_3T ( = CCTCC AB 2014349T = KACC 42448T).

A novel angular dioxygenase gene cluster encoding 3-phenoxybenzoate 1',2'-dioxygenase in Sphingobium wenxiniae JZ-1

Sphingobium wenxiniae JZ-1 utilizes a wide range of pyrethroids and their metabolic product, 3-phenoxybenzoate, as sources of carbon and energy. A mutant JZ-1 strain, MJZ-1, defective in the degradation of 3-phenoxybenzoate was obtained by successive streaking on LB agar. Comparison of the draft genomes of strains JZ-1 and MJZ-1 revealed that a 29,366-bp DNA fragment containing a putative angular dioxygenase gene cluster (pbaA1A2B) is missing in strain MJZ-1. PbaA1, PbaA2, and PbaB share 65%, 52%, and 10% identity with the corresponding α and β subunits and the ferredoxin component of dioxin dioxygenase from Sphingomonas wittichii RW1, respectively. Complementation of pbaA1A2B in strain MJZ-1 resulted in the active 3-phenoxybenzoate 1',2'-dioxygenase, but the enzyme activity in Escherichia coli was achieved only through the coexpression of pbaA1A2B and a glutathione reductase (GR)-type reductase gene, pbaC, indicating that the 3-phenoxybenzoate 1',2'-dioxygenase belongs to a type IV Rieske non-heme iron aromatic ring-hydroxylating oxygenase system consisting of a hetero-oligomeric oxygenase, a [2Fe-2S]-type ferredoxin, and a GR-type reductase. The pbaC gene is not located in the immediate vicinity of pbaA1A2B. 3-Phenoxybenzoate 1',2'-dioxygenase catalyzes the hydroxylation in the 1' and 2' positions of the benzene moiety of 3-phenoxybenzoate, yielding 3-hydroxybenzoate and catechol. Transcription of pbaA1A2B and pbaC was induced by 3-phenoxybenzoate, but the transcriptional level of pbaC was far less than that of pbaA1A2B, implying the possibility that PbaC may not be the only reductase that can physiologically transfer electrons to PbaA1A2B in strain JZ-1. Some GR-type reductases from other sphingomonad strains could also transfer electrons to PbaA1A2B, suggesting that PbaA1A2B has a low specificity for reductase.