title: Isolation and characterization of Novosphingobium sp. strain MT1, a dominant polychlorophenol-degrading strain in a groundwater bioremediation system.
abstract: A high-rate fluidized-bed bioreactor has been treating polychlorophenol-contaminated groundwater in southern Finland at 5 to 8 degrees C for over 6 years. We examined the microbial diversity of the bioreactor using three 16S ribosomal DNA (rDNA)-based methods: denaturing gradient gel electrophoresis, length heterogeneity-PCR analysis, and restriction fragment length polymorphism analysis. The molecular study revealed that the process was dependent on a stable bacterial community with low species diversity. The dominant organism, Novosphingobium sp. strain MT1, was isolated and characterized. Novosphingobium sp. strain MT1 degraded the main contaminants of the groundwater, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, and pentachlorophenol, at 8 degrees C. The strain carried a homolog of the pcpB gene, coding for the pentachlorophenol-4-monooxygenase in Sphingobium chlorophenolicum. Spontaneous deletion of the pcpB gene homolog resulted in the loss of degradation ability. Phenotypic dimorphism (planktonic and sessile phenotypes), low growth rate (0.14 to 0.15 h(-1)), and low-copy-number 16S rDNA genes (single copy) were characteristic of strain MT1 and other MT1-like organisms isolated from the bioreactor.
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, 40351 Jyväskylä, Finland.
authors.forename: Marja A
authors.initials: MA
authors.lastname: Tiirola
authors.forename: Minna K
authors.initials: MK
authors.lastname: Männistö
authors.forename: Jaakko A
authors.initials: JA
authors.lastname: Puhakka
authors.forename: Markku S
authors.initials: MS
authors.lastname: Kulomaa
mesh_terms: D020561:Alphaproteobacteria / Q000145:classification* / Q000302:isolation & purification* / Q000378:metabolism / Q000502:physiology; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D002733:Chlorophenols / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000032:analysis; D004587:Electrophoresis, Agar Gel / Q000379:methods; D005618:Fresh Water / Q000382:microbiology; D020459:Genes, rRNA; D006899:Mixed Function Oxygenases / Q000235:genetics; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014874:Water Pollutants, Chemical / Q000378:metabolism
chemical_list: D002733:Chlorophenols; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D006899:Mixed Function Oxygenases; C069781:pentachlorophenol monooxygenase