[Show abstract][Hide abstract] ABSTRACT: Sphingomonas sp. strain ATCC 31555 can produce an anionic heteropolysaccharide, welan gum, which shows excellent stability and viscosity retention even at high temperatures. Here we present a 4.0-Mb assembly of its genome sequence. We have annotated 10 coding sequences (CDSs) responsible for the welan gum biosynthesis and 55 CDSs related to monosaccharide metabolism.
Journal of bacteriology 11/2012; 194(21):5989-90. DOI:10.1128/JB.01486-12 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas aeruginosa DQ8, which was isolated from the crude oil polluted soil in the Daqing oilfield of China, can efficiently degrade diesel, crude oil, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs). Here, we present a 6.8-Mb assembly of its genome sequence. We have annotated 23 coding sequences (CDSs) responsible for catabolism of n-alkanes and PAHs.
Journal of bacteriology 11/2012; 194(22):6304-5. DOI:10.1128/JB.01499-12 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas stutzeri T13 is a highly efficient aerobic denitrifying bacterium. Information about the genome of this aerobic denitrifying bacterium has been limited until now. We present the draft genome of P. stutzeriT13. The results could provide fur-ther insight into the aerobic denitrification mechanism in strain T13.
Journal of Bacteriology 10/2012; 194(20):5720. DOI:10.1128/JB.01376-12 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas luteola XLDN4-9 and Pseudomonas stutzeri XLDN-R are two efficient carbazole-degrading pseudomonad strains. Here we present 4.63- and 4.70-Mb assemblies of their genomes. Their annotated key genes for carbazole catabolism are similar, which may provide further insights into the molecular mechanism of carbazole degradation in Pseudomonas.
Journal of bacteriology 10/2012; 194(20):5701-2. DOI:10.1128/JB.01296-12 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas psychrophila HA-4 is a cold-adaptable, sulfamethoxazole-degrading bacterium. The genes related to its cold adaptation mechanism and sulfamethoxazole metabolism were unknown. We present the draft genome of strain HA-4. It could provide further insight into the sulfamethoxazole-degrading mechanism of strain HA-4.
Journal of Bacteriology 10/2012; 194(20):5721. DOI:10.1128/JB.01377-12 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Xanthomonas campestris JX, a soil bacterium, is an industrially productive strain for xanthan gum. Here we present a 5.0-Mb assembly of its genome sequence. We have annotated 12 coding sequences (CDSs) responsible for xanthan gum biosynthesis, 346 CDSs encoding carbohydrate metabolism, and 69 CDSs related to virulence, defense, and plant disease.
Journal of bacteriology 09/2012; 194(17):4755-6. DOI:10.1128/JB.00965-12 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Microbial oxidative degradation is a potential way of removing pollutants such as heterocycles from the environment. During this process, reactive oxygen species or other oxidants are inevitably produced, and may cause damage to DNA, proteins, and membranes, thereby decreasing the degradation rate. Carotenoids can serve as membrane-integrated antioxidants, protecting cells from oxidative stress.
Several genes involved in the carotenoid biosynthetic pathway were cloned and characterized from a carbazole-degrading bacterium Sphingobium yanoikuyae XLDN2-5. In addition, a yellow-pigmented carotenoid synthesized by strain XLDN2-5 was identified as zeaxanthin that was synthesized from β-carotene through β-cryptoxanthin. The amounts of zeaxanthin and hydrogen peroxide produced were significantly and simultaneously enhanced during the biodegradation of heterocycles (carbazole < carbazole + benzothiophene < carbazole + dibenzothiophene). These higher production levels were consistent with the transcriptional increase of the gene encoding phytoene desaturase, one of the key enzymes for carotenoid biosynthesis.
Sphingobium yanoikuyae XLDN2-5 can enhance the synthesis of zeaxanthin, one of the carotenoids, which may modulate membrane fluidity and defense against intracellular oxidative stress. To our knowledge, this is the first report on the positive role of carotenoids in the biodegradation of heterocycles, while elucidating the carotenoid biosynthetic pathway in the Sphingobium genus.
PLoS ONE 06/2012; 7(6):e39522. DOI:10.1371/journal.pone.0039522 · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas putida Idaho is an organic-solvent-tolerant strain which can degrade and adapt to high concentrations of organic solvents. Here, we announce its first draft genome sequence (6,363,067 bp). We annotated 192 coding sequences (CDSs) responsible for aromatic compound metabolism, 40 CDSs encoding phospholipid synthesis, and 212 CDSs related to stress response.
Journal of bacteriology 12/2011; 193(24):7011-2. DOI:10.1128/JB.06200-11 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas putida strain B6-2 can efficiently degrade environmental pollutants/toxicants, such as polycyclic aromatic hydrocarbons and dioxin-like compounds, and has unique tolerance to organic solvents. Here, we present a 6.24-Mb draft genome sequence of B6-2, which could provide further insights into the biodegradative mechanisms of a diverse range of chemical compounds.
Journal of bacteriology 12/2011; 193(23):6789-90. DOI:10.1128/JB.06201-11 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The commercial gelling agent gellan gum is a heteropolysaccharide produced by Sphingomonas elodea ATCC 31461. However, the genes involved in the biosynthesis, regulation, and modification of gellan gum have not been fully characterized. Here we describe the draft genome sequence of stain ATCC 31461 and major findings from its annotation.
Journal of bacteriology 12/2011; 193(24):7015-6. DOI:10.1128/JB.06307-11 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sphingobium yanoikuyae XLDN2-5 is an efficient carbazole-degrading strain. Carbazole-degrading genes are accompanied on both sides by two copies of IS6100 elements. Here, we describe the draft genome sequence of strain XLDN2-5, which may provide important clues as to how it recruited exogenous genes to establish pathways to degrade the xenobiotics.
Journal of bacteriology 11/2011; 193(22):6404-5. DOI:10.1128/JB.06050-11 · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Carbazole is a recalcitrant compound with a dioxin-like structure and possesses mutagenic and toxic activities. Bacteria respond to a xenobiotic by recruiting exogenous genes to establish a pathway to degrade the xenobiotic, which is necessary for their adaptation and survival. Usually, this process is mediated by mobile genetic elements such as plasmids, transposons, and insertion sequences.
The genes encoding the enzymes responsible for the degradation of carbazole to catechol via anthranilate were cloned, sequenced, and characterized from a carbazole-degrading Sphingomonas sp. strain XLDN2-5. The car gene cluster (carRAaBaBbCAc) and fdr gene were accompanied on both sides by two copies of IS6100 elements, and organized as IS6100::ISSsp1-ORF1-carRAaBaBbCAc-ORF8-IS6100-fdr-IS6100. Carbazole was converted by carbazole 1,9a-dioxygenase (CARDO, CarAaAcFdr), meta-cleavage enzyme (CarBaBb), and hydrolase (CarC) to anthranilate and 2-hydroxypenta-2,4-dienoate. The fdr gene encoded a novel ferredoxin reductase whose absence resulted in lower transformation activity of carbazole by CarAa and CarAc. The ant gene cluster (antRAcAdAbAa) which was involved in the conversion of anthranilate to catechol was also sandwiched between two IS6100 elements as IS6100-antRAcAdAbAa-IS6100. Anthranilate 1,2-dioxygenase (ANTDO) was composed of a reductase (AntAa), a ferredoxin (AntAb), and a two-subunit terminal oxygenase (AntAcAd). Reverse transcription-PCR results suggested that carAaBaBbCAc gene cluster, fdr, and antRAcAdAbAa gene cluster were induced when strain XLDN2-5 was exposed to carbazole. Expression of both CARDO and ANTDO in Escherichia coli required the presence of the natural reductases for full enzymatic activity.
We predict that IS6100 might play an important role in the establishment of carbazole-degrading pathway, which endows the host to adapt to novel compounds in the environment. The organization of the car and ant genes in strain XLDN2-5 was unique, which showed strong evolutionary trail of gene recruitment mediated by IS6100 and presented a remarkable example of rearrangements and pathway establishments.
PLoS ONE 04/2010; 5(4):e10018. DOI:10.1371/journal.pone.0010018 · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A biphenyl (BP)-utilizing bacterium, designated B6-2, was isolated from soil and identified as Pseudomonas putida. BP-grown B6-2 cells were capable of transforming dibenzofuran (DBF) via a lateral dioxygenation and meta-cleavage pathway. The ring cleavage product 2-hydroxy-4-(3'-oxo-3'H-benzofuran-2'-yliden)but-2-enoic acid (HOBB) was detected as a major metabolite. B6-2 growing cells could also cometabolically degrade DBF using BP as a primary substrate. A recombinant Escherichia coli strain DH10B (pUC118bphABC) expressing BP dioxygenase, BP-dihydrodiol dehydrogenase, and dihydroxybiphenyl dioxygenase was shown to be capable of transforming DBF to HOBB. Using purified HOBB that was produced by the recombinant as the substrate for B6-2, we newly identified a series of benzofuran derivatives as metabolites. The structures of these metabolites indicate that an unreported HOBB degradation pathway is employed by strain B6-2. In this pathway, HOBB is proposed to be transformed to 2-oxo-4-(3'-oxobenzofuran-2'-yl)butanoic acid and 2-hydroxy-4-(3'-oxobenzofuran-2'-yl)butanoic acid (D4) through two sequential double-bond hydrogenation steps. D4 is suggested to undergo reactions including decarboxylation and oxidation to produce 3-(3'-oxobenzofuran-2'-yl)propanoic acid (D6). 3-Hydroxy-3-(3'-oxobenzofuran-2'-yl)propanoic acid (D7) and 2-(3'-oxobenzofuran-2'-yl)acetic acid (D8) would represent metabolites involved in the processes of beta- and alpha-oxidation of D6, respectively. D7 and D8 are suggested to be transformed to their respective products 3-hydroxy-2,3-dihydrobenzofuran-2-carboxylic acid (D10) and 2-(3'-hydroxy-2',3'-dihydrobenzofuran-2'-yl)acetic acid. D10 is proposed to be transformed to salicylic acid (D14) via 2,3-dihydro-2,3-dihydroxybenzofuran, 2-oxo-2-(2'-hydroxyphenyl)acetic acid and 2-hydroxy-2-(2'-hydroxyphenyl)acetic acid. Further experimental results revealed that B6-2 was capable of growing with D14 as the sole carbon source. Because benzofuran derivatives may have biological, pharmacological, and toxic properties, the elucidation of this new pathway should be significant from both biotechnological and environmental views.
[Show abstract][Hide abstract] ABSTRACT: Benzothiophenes are a toxic and relatively recalcitrant fraction of coal-tar creosote. We investigated the co-metabolic transformation of benzothiophene (BT) and its derivatives by the carbazole (CA) degrader Sphingomonas sp. XLDN2-5, which is not able to grow on benzothiophenes as the sole carbon source. Among the benzothiophenes tested, BT, 2-methylbenzothiophene (2-MBT) and 5-methylbenzothiophene (5-MBT) were co-metabolically converted. For 3-methylbenzothiophene, there was complete inhibition of growth on CA. The common transformation products for BT, 2-MBT and 5-MBT are the corresponding sulfoxides and sulfones. For BT, several high-molecular-mass sulfur-containing aromatic compounds, including benzo[b]naphtho[1,2-d]thiophene, benzo[b]naphtho[1,2-d]thiophene-7-oxide, 6a,11b-dihydrobenzo[b]naphtho[1,2-d]thiophene, 6a,11b-dihydrobenzo[b]naphtho[1,2-d]thiophene-7-oxide, and a new product, 6,12-epithiobenzo[b]naphtho[1,2-d]thiophene, were detected by GC-MS. These high-molecular-mass products are thought to be generated from a Diels-Alder-type reaction. Investigations with a combination of GC and flame ionization detection showed that about 17 % of BT was transformed to benzo[b]naphtho[1,2-d]thiophene. Aerobic transformation of benzothiophenes to sulfoxides and sulfones can reduce their toxicity, and facilitate their biodegradation. However, the formation of the high-molecular-mass products, such as benzo[b]naphtho[1,2-d]thiophene, should be considered in the biodegradation of benzothiophenes.
[Show abstract][Hide abstract] ABSTRACT: Polycyclic aromatic heterocycles, such as carbazole, are environmental contaminants suspected of posing human health risks. In this study, we investigated the degradation of carbazole by immobilized Sphingomonas sp. strain XLDN2-5 cells. Four kinds of polymers were evaluated as immobilization supports for Sphingomonas sp. strain XLDN2-5. After comparison with agar, alginate, and kappa-carrageenan, gellan gum was selected as the optimal immobilization support. Furthermore, Fe(3)O(4) nanoparticles were prepared by a coprecipitation method, and the average particle size was about 20 nm with 49.65-electromagnetic-unit (emu) g(-1) saturation magnetization. When the mixture of gellan gel and the Fe(3)O(4) nanoparticles served as an immobilization support, the magnetically immobilized cells were prepared by an ionotropic method. The biodegradation experiments were carried out by employing free cells, nonmagnetically immobilized cells, and magnetically immobilized cells in aqueous phase. The results showed that the magnetically immobilized cells presented higher carbazole biodegradation activity than nonmagnetically immobilized cells and free cells. The highest biodegradation activity was obtained when the concentration of Fe(3)O(4) nanoparticles was 9 mg ml(-1) and the saturation magnetization of magnetically immobilized cells was 11.08 emu g(-1). Additionally, the recycling experiments demonstrated that the degradation activity of magnetically immobilized cells increased gradually during the eight recycles. These results support developing efficient biocatalysts using magnetically immobilized cells and provide a promising technique for improving biocatalysts used in the biodegradation of not only carbazole, but also other hazardous organic compounds.
[Show abstract][Hide abstract] ABSTRACT: A carbazole-utilizing bacterium was isolated by enrichment from petroleum-contaminated soil. The isolate, designated Sphingomonas sp. strain XLDN2-5, could utilize carbazole (CA) as the sole source of carbon, nitrogen, and energy. Washed cells of strain XLDN2-5 were shown to be capable of degrading dibenzofuran (DBF) and dibenzothiophene (DBT). Examination of metabolites suggested that XLDN2-5 degraded DBF to 2-hydroxy-6-(2-hydroxyphenyl)-6-oxo-2,4-hexadienic acid and subsequently to salicylic acid through the angular dioxygenation pathway. In contrast to DBF, strain XLDN2-5 could transform DBT through the ring cleavage and sulfoxidation pathways. Sphingomonas sp. strain XLDN2-5 could cometabolically degrade DBF and DBT in the growing system using CA as a substrate. After 40 h of incubation, 90% of DBT was transformed, and CA and DBF were completely removed. These results suggested that strain XLDN2-5 might be useful in the bioremediation of environments contaminated by these compounds.