J. Gen. Appl. Microbiol., 53, 221–228 (2007)
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J. Gen. Appl. Microbiol., 53, 221–228 (2007) Full Paper Novosphingobium naphthalenivorans sp. nov., a naphthalene-degrading bacterium isolated from polychlorinated-dioxin-contaminated environments Saori Suzuki and Akira Hiraishi* Department of Ecological Engineering, Toyohashi University of Technology, Toyohashi 441–8580, Japan (Received February 8, 2007; Accepted May 30, 2007) Three strains of strictly aerobic, Gram-negative, naphthalene-degrading bacteria isolated from polychlorinated-dioxin-contaminated soil and sediment were characterized. These isolates grew well with naphthalene as the sole carbon and energy source, degrading it completely within 24 h of incubation. The isolates also degraded dibenzofuran co-metabolically in the presence of naphthalene with the concomitant production of yellow intermediate metabolite(s). A 16S rRNA gene sequence analysis revealed that the isolates affiliated to the genus Novosphingobium with Novosphingobium pentaromativorans and Novosphingobium subarcticum as their nearest phy- logenetic neighbors (97.4–97.5% similarity). The isolates had a genomic DNA G؉C ratio of 64.5–64.6 mol% and formed a genetically coherent group distinguishable from any established species of the genus Novosphingobium at a DNA-DNA hybridization level of less than 46%. The cellular fatty acids were characterized by the predominance of 18 : 1w7c with significant propor- tions of 16 : 0, 16 : 1w7c, 17 : 1w6c and 2-OH 14 : 0. Sphingoglycolipids were present. The major respiratory quinone was ubiquinone-10. Spermidine was detected as the major polyamine. The distinct taxonomic position of the isolates within the Novosphingobium was also demonstrated by physiological and biochemical testing. Based on these phylogenetic and phenotypic data, we propose Novosphingobium naphthalenivorans sp. nov. to accommodate the novel isolates. The type strain is strain TUT562T (DSM 18518T, JCM 13951T, NBRC 102051T). Key Words——naphthalene degradation; Novosphingobium naphthalenivorans; polychlorinated diox- ins; polycyclic aromatic hydrocarbon Introduction Wittich, 1998). Large numbers of aromatic- and PAH- degrading bacteria from polluted environments have Degradation of polycyclic aromatic hydrocarbons been isolated and characterized. The so-called sphin- (PAHs), including polychlorinated dioxins/furans gomonads represent a major group of the aromatic- (PCDD/Fs), by microorganisms has received much at- compound-degrading alphaproteobacteria frequently tention in connection with natural attenuation and isolated from polluted environments (Leys et al., 2004; bioremediation of xenobiotic pollution (Hiraishi, 2003; Pinyakong et al., 2003; Yabuuchi et al., 2001). In par- ticular, members of the genus Novosphingobium, * Address reprint requests to: Dr. Akira Hiraishi, Department which was created to reclassify some species of the of Ecological Engineering, Toyohashi University of Technology, genus Sphingomonas by Takeuchi et al. (2001), are Toyohashi 441–8580, Japan. Tel: +81–532–44–6913 Fax: +81–532–44–6929 aromatic-compound degraders in general (Balkwill et E-mail: [email protected] al., 1997; Fujii et al., 2003; Liu et al., 2005; Sohn et al., 222 SUZUKI and HIRAISHI Vol. 53 2004; Tiirola et al., 2005). with two-layer liquid medium were aerobically incu- Previously, we isolated a number of dibenzofuran- bated on a reciprocal shaker. Growth was monitored degrading aerobic chemoorganotrophic bacteria from by measuring the optical density at 660 nm (OD660), soil and sediment contaminated with different levels of and the concentration of substrate remaining in cul- PCDD/Fs (Futamata et al., 2004). In further studies, tures was measured by reverse-phase HPLC as previ- one of the isolates derived from highly contaminated ously described (Futamata et al., 2004; Hiraishi et al., soil, strain TUT562T, which is phylogenetically affiliated 2002). General cell morphology was studied using an with the genus Novosphingobium, has been found to Olympus phase-contrast microscope and a JEOL grow well with naphthalene as the sole carbon and en- transmission electron microscope. Gram-reaction was ergy source. In this paper, we report the characteristics determined using a Favor G Gram-stain kit (Nissui) ac- of strain TUT562T and 2 additional naphthalene-de- cording to the manufacturer’s instructions. Assimilation grading strains isolated from PCDD/F-contaminated of organic compounds was determined using an API sediment, and propose to classify them as a novel 20E kit (bioMérieux). Fatty acid methyl esters (FAME) species with the name Novosphingobium naph- were extracted according to the standard protocol of thalenivorans. the Microbial Identification System (MIDI; Microbial ID) and analyzed by TechnoSuruga Japan Co. (Shizuoka, Materials and Methods Japan) using a Hewlett Packard model HP6890A gas chromatograph equipped with an FID detector. Respi- Test strains and cultivation. Strain TUT562T was ratory quinones were extracted with an organic solvent previously isolated from farmland soil highly contami- mixture and analyzed by reverse-phase HPLC as de- nated with PCDD/Fs (920 pg-TEQ [toxic equivalent] scribed previously (Hiraishi et al., 1996). Polyamine gϪ1 dry wt) (Futamata et al., 2004). Strains TUT564 patterns and all other phenotypic characteristics were and TUT618 were newly isolated from PCDD/F-conta- determined as described previously (Barrow and minated river sediment (1,000 pg-TEQ gϪ1 dry wt) Feltham, 1993; Takeuchi et al., 2001). (Yoshida et al., 2005) and lake sediment (9.2 pg-TEQ DNA base composition and DNA-DNA hybridization. gϪ1 dry wt) (Hiraishi et al., 2005b), respectively, in this Genomic DNA was extracted and purified by the study. The 2 strains from the aquatic sediments were method of Marmur (1961). DNA base composition was obtained through an enrichment and isolation proce- determined by the HPLC method of Mesbah et al. dure using dibenzofuran-containing liquid medium and (1989). DNA-DNA hybridization studies were per- dibenzofuran-coated agar plates as described previ- formed by the dot-blot hybridization method with alka- ously (Futamata et al., 2004; Kubota et al., 2005). The line phosphatase labeling and chemiluminescence de- type strains of respective Novosphingobium species tection using an Amersham-Pharmacia AlkalPhos kit were obtained from the DSMZ-Deutsche Sammlung as described previously (Kubota et al., 2005). von Mikroorganismen und Zellkulturen, Braunshweig, 16S rRNA gene-based phylogenetic analysis. 16S Germany, the Japan Collection of Microorganisms rRNA genes from the cell lysate were amplified by (JCM), Wako, Japan, and the National Bioresouces PCR with bacterial consensus universal primers Center (NBRC), Kisarazu, Japan (see Table 3). For (Weisburg et al., 1991) as described previously (Hira- preparing pre- and main cultures, the test organisms ishi, 1992). PCR products were sequenced directly were grown aerobically in PBY medium (Futamata et using a Dye Terminator Cycle Sequencing kit and a al., 2004) on a reciprocal shaker at 30°C. These cul- PRISM 3100 DNA sequencer (Applied Biosystems). tures at the mid- to late-exponential phase of growth Sequence data were compiled with the GENETYX- were used for phenotypic and genetic analyses. MAC program (GENETYX Corp.) and compared to Phenotypic testing.All media used for phenotypic those available from the DDBJ/EMBL/GenBank nu- testing was incubated at 30°C unless otherwise indi- cleotide sequence database using the BLAST search cated. Degradation of aromatic compounds including system (Altschul et al., 1997). Multiple alignment of se- PAHs was determined in 20-ml screw-capped test quence, calculation of the corrected evolutionary dis- tubes containing 6 ml of mineral liquid medium supple- tance (Kimura, 1980), and construction of a neighbor- mented with 0.5 ml of an aromatic solution in hep- joining phylogenetic tree (Saitou and Nei, 1987) were tamethylnonane (Hiraishi et al., 2002). The test tubes performed using the CLUSTAL W program (Thompson 2007 Novosphingobium naphthalenivorans sp. nov. 223 et al., 1994). The topology of the tree was evaluated by bootstrapping with 1,000 replicates (Felsenstein, 1985). Alignment positions with gaps were excluded from all calculations. Nucleotide sequence accession numbers. The DDBJ/EMBL/GenBank database accession number for the 16S rRNA gene sequence of strain TUT562T is AB177883. Results and Discussion Degradation of aromatics Strains TUT562T, TUT564, and TUT618 were ob- tained through a screening of aerobic dibenzofuran de- graders from PCDD/F-contaminated environments. On the dibenzofuran-coated nutrient agar plates, all of the isolates formed clear zones with concomitant produc- tion of soluble yellow pigment around colonies. Testing for the degradation of other aromatics on agar plates showed that the isolates also broke down naphthalene but exhibited little or no degradation of biphenyl, p- cresol, dibenzo-p-dioxin or m-xylene. The utilization by the isolates of naphthalene and dibenzofuran as the sole carbon and energy source T were studied in greater detail in the aqueous/nonane Fig. 1. Growth of strain TUT562 by degrading naphtha- lene (a), dibenzofuran (b), and dibenzofuran plus naphthalene. two-phase liquid medium. All of the isolates grew well Symbols: open circles, growth (OD660) with PAH; closed cir- in the liquid medium containing naphthalene as the cles, growth without PAH (control); open triangles, the amount sole carbon and energy source, in which the substrate of naphthalene remaining; closed triangles, the