A high-rate fluidized-bed bioreactor has been treating polychlorophenol-contaminated groundwater in southern Finland at 5 to 8°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°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.Pentachlorophenol (PCP) and various chlorophenol mixtures have been extensively used in wood treatment against blue staining and soft rot fungi all over the world. Several factors, such as temperature, pH, oxygen concentration, and the composition of the microbial community, influence the degradation of organic compounds. The bioremediation potential of polychlorophenols at low temperatures has been considered limited, since it has mainly been studied using mesophilic bacteria (for a review, see reference 34). Long-term experience with fluidized-bed processes at cold temperatures (33,35) together with the description of the boreal chlorophenol-contaminated aquifer microbiology (24), however, has conclusively shown the potential for low-temperature biodegradation and bioremediation of polychlorophenols.Chlorophenol contamination of soil and groundwater has occurred in Finland in several sawmill locations (16,18). Large-scale contamination by polychlorophenols was discovered in 1987 at Kärkölä groundwater aquifer in southern Finland (18,24). Early attempts to treat the contaminated water included a batch process with immobilized Mycobacterium chlorophenolicum PCP-1 culture (44), an activated-sludge process in a municipal treatment plant (9), and activated carbon filtration (12). A fluidized-bed polychlorophenol bioremediation process at ambient groundwater temperature was developed (13,14,22,25,26). The process was extended to full-scale treatment in 1995 and continues to operate (33, 34). Disruptions in the degradation efficiency in the Kärkölä fluidized-bed reactor (FBR) have occurred only as a consequence of failures in aeration. In 1999, the period for recovery of stable operation lasted several months, suggesting that the process depends on slow-growing bacteria. PCP degradation recovery times ranging from 10 to 40 days ...

The virulence of eight Flavobacterium columnare strains was studied to find correlations between several virulence-related factors and virulence. Virulence was tested in vivo using rainbow trout, Oncorhynchus mykiss (Walbaum). Suggested virulence-related factors such as production of the degradative enzyme chondroitin lyase, plasmid occurrence and adhesion capability were studied in vitro. Infection with the four most virulent strains resulted in 95-100% mortality within 114 h. Chondroitin lyase activity was found to be significantly related to the virulence of the strains at 25 degrees C and it was also shown to be temperature-dependent, being higher at 25 degrees C than at 20 degrees C. Virulence was not plasmid associated. The adhesion capability of the strains in vitro varied substantially when tested on crude mucus-coated slides and no statistical relationship between adhesion and virulence was found using this method.

A broad-range bacterial PCR method with universal 16S rDNA targeting primers and bacterial cultivation was used to identify the putative pathogen in flavobacterial outbreaks. Restriction fragment length polymorphism (PCR-RFLP) analysis and sequencing of the partial 16S rDNA PCR products of 10 skin samples and 10 representative isolates derived from the same fish specimens revealed differences between direct molecular and cultivation-based analysis. Flavobacterium columnare-like sequences dominated in the direct molecular analysis in most cases, whereas most of the isolates belonged to a phylogenetically heterogeneous group of flavobacteria clustering with F. hibernum. F. columnare was isolated in only 1 outbreak. The possible explanations for the different results may be attributable to difficulties in the plate cultivation procedure of external flavobacterial samples. During plate cultivation, the dominating Flavobacterium species can be masked by saprophytic species of the same genus or other genera, or the growth of flavobacteria can be completely inhibited by antagonistic bacteria such as Pseudomonas. Direct analysis of the prevailing 16S rDNA sequences avoids the problems with cultivation and may thus be preferable for the diagnosis of flavobacterial diseases. When isolating flavobacteria from external samples, serial dilution of the sample before plating can improve the results.

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Five cold-adapted bacteria belonging to the genus Mucilaginibacter were isolated from lichen and soil samples collected from Finnish Lapland and investigated in detail by phenotypic and phylogenetic analyses. Based on 16S rRNA gene phylogeny, the novel strains represent three new branches within the genus Mucilaginibacter. The strains were aerobic, chemo-organotrophic, non-motile rods and formed pigmented, smooth, mucoid colonies on solid media. The strains grew between 0 and 33 °C (optimum growth at 25 °C) and at pH 4.5–8.0 (optimum growth at pH 6.0). The main cellular fatty acids were iso-C15 : 0, summed feature 3 (C16 : 1 ω7c/iso-C15 : 0 2-OH) and iso-C17 : 0 3-OH and the major respiratory quinone was MK-7. The DNA G+C contents were 44.0–46.5 mol%. Based on phylogenetic, phenotypic and chemotaxonomic data, the strains represent three novel species of the genus Mucilaginibacter for which the names Mucilaginibacter frigoritolerans sp. nov. (type strain FT22T =ATCC BAA-1854T =LMG 25359T), Mucilaginibacter lappiensis sp. nov. (type strain ANJLI2T =ATCC BAA-1855T =LMG 25358T) and Mucilaginibacter mallensis sp. nov. (type strain MP1X4T =ATCC BAA-1856T =LMG 25360T) are proposed.