Description of Cellulophaga algicola sp. nov., isolated from the surfaces of Antarctic algae, and reclassification of Cytophaga uliginosa (ZoBell and Upham 1944) Reichenbach 1989 as Cellulophaga uliginosa comb. nov

A group of strains with potent extracellular enzymic activity were isolated from the surfaces of the chain-forming sea-ice diatom Melosira and from an unidentified macrophyte collected from the Eastern Antarctic coastal zone. 16S rDNA sequence analysis indicated that the strains belonged to the genus Cellulophaga and showed greatest similarity to the species Cellulophaga baltica (sequence similarity 97%). Phenotypic characteristics, DNA base composition and DNA-DNA hybridization values clearly separate the Antarctic strains from Cellulophaga baltica and other Cellulophaga species. Thus, the strains form a distinct and novel species and have the proposed name Cellulophaga algicola sp. nov. (type strain IC166T = ACAM 630T). In addition, it was recognized that the species Cytophaga uliginosa (ZoBell and Upham 1944) Reichenbach 1989, a species phylogenetically remote from the type species of the genus Cytophaga, possessed 16S rDNA sequences and phenotypic and chemotaxonomic traits similar to those of other Cellulophaga species. Thus, it was proposed that the species Cytophaga uliginosa be renamed as Cellulophaga uliginosa comb. nov.

Bacterioplankton compositions of lakes and oceans: a first comparison based on fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes was used to investigate the phylogenetic composition of bacterioplankton communities in several freshwater and marine samples. An average of about 50% of the cells were detected by probes for the domains Bacteria and Archaea, and of these, about half could be identified at the subdomain level with a set of group-specific probes. Beta subclass proteobacteria constituted a dominant fraction in freshwater systems, accounting for 16% (range, 3 to 32%) of the cells, although they were essentially absent in the marine samples examined. Members of the Cytophaga-Flavobacterium cluster were the most abundant group detected in the marine systems, accounting for 18% (range, 2 to 72%) of the 4',6-diamidino-2-phenylindole (DAPI) counts, and they were also important in freshwater systems (7%, range 0 to 18%). Furthermore, members of the alpha and gamma subclasses of Proteobacteria as well as members of the Planctomycetales were detected in both freshwater and marine water in abundances <7%.

Phylogenetic analysis of the human gut microbiota using 16S rDNA clone libraries and strictly anaerobic culture-based methods

The human gut microbiota from three healthy subjects were compared by the use of a sequence analysis of 16S rDNA libraries and a culture-based method. Direct counts ranged from 1.9 X 10" to 4.0 X 10" cells/g (wet weight), and plate counts totaled 6.6 X 10(10) to 1.2 X 10(11) CFU/g (wet weight). Sixty to seventy percent of the bacteria in the human intestinal tract cannot be cultured with currently available methods. The 16S rDNA libraries from three subjects were generated from total community DNA in the intestinal tract with universal primer sets. Randomly selected clones were partially sequenced. All purified colonies detected from the surface of the agar plate were used for a partial sequencing of 16S rDNA. On the basis of sequence similarities, the clones and colonies were classified into several clusters corresponding to the major phylum of the domain Bacteria. Among a total of 744 clones obtained, approximately 25% of them belonged to 31 known species. About 75% of the remaining clones were novel "phylotypes" (at least 98% similarity of clone sequence). The predominant intestinal microbial community consisted of 130 species or phylotypes according to the sequence data in this study. The 16S rDNA libraries and colonies included the Bacteroides group, Streptococcus group, Bifidobacterium group, and Clostridium rRNA clusters IV, IX, XIVa, and XVIII. Moreover, several previously uncharacterized and uncultured microorganisms were recognized in clone libraries and colonies. Our results also showed marked individual differences in the composition of intestinal microbiota.

Phylogenetic analysis and taxonomic study of marine Cytophaga-like bacteria: proposal for Tenacibaculum gen. nov. with Tenacibaculum maritimum comb. nov. and Tenacibaculum ovolyticum comb. nov., and description of Tenacibaculum mesophilum sp. nov. and Tenacibaculum amylolyticum sp. nov

Bacterial strains were isolated from sponge and green algae which were collected on the coast of Japan and Palau. The phylogenetic relationships of these isolates among marine species of the Cytophaga-Flavobacterium-Bacteroides complex were analysed by using their gyrB nucleotide sequences and translated peptide sequences (GyrB) in addition to 16S rDNA sequences. These isolates were closely related to the previously characterized marine Flexibacter species, [Flexibacter] maritimus and [Flexibacter] ovolyticus. These Flexibacter species are distantly related to Flexibacter flexilis, the type species of the genus Flexibacter, and phylogenetically belong to the family Flavobacteriaceae (according to analysis using both 16S rDNA and GyrB sequences). Their phylogenetic, chemotaxonomic and phenotypic characteristics prompted the proposal that these two species should be transferred to the new genus Tenacibaculum, as Tenacibaculum maritimum and Tenacibaculum ovolyticum, respectively. Two additional new species of the genus Tenacibaculum, Tenacibaculum mesophilum gen. nov., sp. nov. (= MBIC 1140T = IFO 16307T) and Tenacibaculum amylolyticum gen. nov., sp. nov. (= MBIC 4355T = IFO 16310T), which were isolated from sponges and macroalgae, are also reported. For taxonomic considerations at the species level, the resolution of gyrB sequences was superior to that of 16S rDNA sequences, and the grouping based on the gyrB phylogram was consistent with DNA-DNA hybridization results.

Polaribacter gen. nov., with three new species, P. irgensii sp. nov., P. franzmannii sp. nov. and P. filamentus sp. nov., gas vacuolate polar marine bacteria of the Cytophaga-Flavobacterium-Bacteroides group and reclassification of 'Flectobacillus glomeratus' as Polaribacter glomeratus comb. nov

Several psychrophilic, gas vacuolate strains of the Cytophage-Flavobacterium-Bacteroides (CFB) phylogenetic group were isolated from sea ice and water from the Arctic and the Antarctic. The closest taxonomically defined species by 16S rRNA sequence analysis is 'Flectobacillus glomeratus'. However, 'Flc. glomeratus' is phylogenetically distant from the Flectobacillus type species, Flc. major. On the basis of phenotypic, genotypic and 16S rRNA sequence analyses we propose a new genus, Polaribacter, with three new species, Polaribacter irgensii strain 23-P (ATCC 700398), Polaribacter franzmannii strain 301 (ATCC 700399) and Polaribacter filamentus strain 215 (ATCC 700397). P. filamentus is the type species of the genus. None of these species exhibits a cosmopolitan or bipolar distribution. This is the first taxonomic description of gas vacuolate bacteria in the CFB group. Additionally, we propose that 'Flc. glomeratus' be reclassified to the genus Polaribacter as P. glomeratus, comb. nov.

Intraspecific variation in small-subunit rRNA sequences in GenBank: why single sequences may not adequately represent prokaryotic taxa

Small-subunit rRNA (SSU rRNA) sequencing is a powerful tool to detect, identify, and classify prokaryotic organisms, and there is currently an explosion of SSU rRNA sequencing in the microbiology community. We report unexpectedly high levels of intraspecific variation (within and between strains) of prokaryote SSU rRNA sequences deposited in GenBank. A total of 82% of the prokaryote species with two published SSU rRNA sequences had more variable positions than a 0.1% random sequencing error would predict, and 48% of these sequence pairs had more variable positions than predicted by a 1.0% random sequencing error. Other sources of sequence variability must account for some of this intraspecific variation. Given these results, phylogenetic studies and biodiversity estimates obtained by using prokaryotic SSU rRNA sequences cannot proceed under the assumption that rRNA sequences of single operons from single isolates adequately represent their taxa. Sequencing SSU rRNA molecules from multiple operons and multiple isolates is highly recommended to obtain meaningful phylogenetic hypotheses, as is careful attention to accurate strain identification.

Chryseobacterium defluvii sp. nov., isolated from wastewater

A Gram-negative, rod-shaped, non-spore-forming, yellow-pigmented bacterium (strain B2T) isolated from wastewater of a sequence batch reactor showing enhanced phosphorus removal was investigated to determine its taxonomic status. Complete 16S rRNA gene sequence analysis indicated that the organism should be placed in the genus Chryseobacterium. The strain contained a polyamine pattern with sym-homospermidine as the major compound, menaquinone MK-6 as the predominant menaquinone and ai-C15:0, i-C15:0 and C16:1 as the major fatty acids. Phosphatidylethanolamine and several unidentified lipids were detected in the polar lipid profile. Phylogenetically, strain B2T was most closely related to Chryseobacterium indoltheticum and Chryseobacterium gleum (96.2 and 95-9% 16S rRNA gene sequence similarity, respectively). The phylogenetic distance from any validly described species within the genus Chryseobacterium, as indicated from 16S rRNA gene sequence similarities, and its phenotypic properties demonstrate that strain B2T represents a novel species, for which the name Chryseobacterium defluvii sp. nov. is proposed; the type strain is B2T (=DSM 14219T =CIP 107207T).

Riemerella anatipestifer gen. nov., comb. nov., the causative agent of septicemia anserum exsudativa, and its phylogenetic affiliation within the Flavobacterium-Cytophaga rRNA homology group

The phylogenetic position of the causative agent of septicemia anserum exsudativa, now most often referred to as [Moraxella] anatipestifer (brackets indicate a generically misnamed taxon) or "[Pasteurella] anatipestifer," was established by performing rRNA cistron similarity studies. [Moraxella] anatipestifer belongs to rRNA superfamily V, together with the genera Flavobacterium, Cytophaga, Flexibacter, Weeksella, Capnocytophaga, and Sphingobacterium. The detailed structure of rRNA superfamily V, which now contains five major rRNA homology groups, is described. An analysis of various phenotypic parameters, including new data (cellular proteins and fatty acids) and previously published data (respiratory quinones, enzyme activities, and classical phenotypic features), revealed that [Moraxella] anatipestifer differs in many aspects from its closest relatives, Flavobacterium indologenes, Flavobacterium gleum, Flavobacterium indoltheticum, Flavobacterium balustinum, Flavobacterium meningosepticum, and Weeksella zoohelcum. The combined genotypic and phenotypic data indicate that this organism should be placed in a separate genus; the name Riemerella anatipestifer gen. nov., comb. nov. is proposed for this bacterium. The specific epithet anatipestifer is kept in order to avoid nomenclatural confusion. However, it should be emphasized that the illness caused by this organism is a septicemic disease which is not restricted to ducks.

Hymenobacter roseosalivarius gen. nov., sp. nov. from continental Antartica soils and sandstone: bacteria of the Cytophaga/Flavobacterium/Bacteroides line of phylogenetic descent

Aseptically collected sandstone and soil samples from the antarctic Dry Valleys were inoculated into oligotrophic media and incubated under low light intensities. A total of 41 Gram-negative isolates were obtained with reddish colonies spreading on agar. A sandstone isolate and four soil strains were characterized further. They were nearly identical in morphological, physiological, biochemical and chemotaxonomic properties. They produced large amounts of extracellular polymer and utilized for growth: glucose, saccharose, mannitol, sorbitol, L-aspartate, malate and acetate, but not D-ribose, adonitol, DL-alanine, glutamate, glycolate, lactate or succinate. All strains hydrolyzed gelatin, starch, casein, xylan, Tweens 80 or 60 and dead or living yeast cells, but not cellulose or pectin. Nitrate was not reduced, ethanol was not oxidized and acid was not produced from maltose, mannitol or dulcitol. Ammonia was not produced from peptone. They were strictly aerobic. Major fatty acids were n 16:1 d 9, n 16:1 d 11, n 17:1 d 11, and i 15:0. The strains contained the quinone MK-7 and phosphatidylethanolamine as the main phospholipid. The base ratio ranged from 55 to 61 mol% G+C. A 16S rRNA sequence analysis of strains AA-688 and AA-718 showed these to be identical and to represent a special phylogenetic group within the Cytophaga/Flavobacterium/Bacteroides major line of descent. Three soil strains labeled "Taxeobacter" Txc1, Txg1, and Txo1 (Reichenbach, 1992) belonged to the same group but had lower sequence similarities (<95%). Some of their characteristics were different from those of the antarctic strains: the utilization of C-compounds, hydrolysis of polymers, temperature tolerances, major fatty acids and base ratios. Txc1 and Txg1 may later have to be considered as members of this group, possibly on the species level, while Txo1 could represent a different related genus. It is concluded that the five antarctic strains represent a new genus and species for which the name of Hymenobacter roseosalivarius is proposed. The type strain is AA-718T (DSM 11622T).

Zobellia galactanovorans gen. nov., sp. nov., a marine species of Flavobacteriaceae isolated from a red alga, and classification of [Cytophaga] uliginosa (ZoBell and Upham 1944) Reichenbach 1989 as Zobellia uliginosa gen. nov., comb. nov

A mesophilic, aerobic, non-flagellated, gliding bacterium, forming yellow colonies and designated DsijT, was isolated from a red alga on the sea-shore of Roscoff, Brittany, France. DsijT was selected for its ability to actively degrade both agars and carrageenans. The Gram-negative cells occurred singly or in pairs as long rods. The temperature range for growth was 13-45 degrees C, with an optimum at 35 degrees C. The pH range for growth at 35 degrees C was from 6.0 to 8.5, with an optimum around pH 7.0. The NaCl concentrations required for growth at 35 degrees C and pH 7.0 ranged from 5 to 60 g l(-1), with an optimum around 25 g l(-1). The G+C content of the genomic DNA was 42-43 mol%. Phylogenetic analysis of 16S rRNA gene sequences indicated that strain DsijT is closely related to [Cytophaga] uliginosa DSM 2061T. Phenotypic features, however, allowed DsijT and [Cytophaga] uliginosa strains to be distinguished on the basis of ten traits (spreading behaviour, assimilation of eight compounds and amylase production). Their total protein profiles were also different and DNA-DNA hybridization experiments confirmed that DsijT constitutes a new species, distinct from [Cytophaga] uliginosa. Based on the phenotypic features and the phylogenetic relationships of the Flavobacteriaceae, a new genus designated Zobellia gen. nov. is proposed to include Zobellia galactanovorans gen. nov., sp. nov., while [Cytophaga] uliginosa becomes Zobellia uliginosa comb. nov. The type strain of Zobellia galactanovorans is DsijT (= DSM 12802T = CIP 106680T).

Phylogenetic diversity of the genus Cytophaga revealed by 16S rRNA sequencing and menaquinone analysis

To clarify the intra- and intergeneric relationships of the genus Cytophaga, 16S rRNA sequences and respiratory isoprenoid quinones were determined for the type strains of the 21 validly published species and one isolate in the genus Cytophaga. The sequence analysis revealed extreme heterogeneity of this genus, which diverged into nine distinct lines of descent. Each lineage of Cytophaga was characterized by possessing either menaquinone-6 (MK-6) or MK-7. The MK-6-possessing species were located in the two lineages that were remote from MK-7 species. One of the MK-6 lineages was composed only of terrestrial species and the other only of marine species. Flavobacterium aquatile, the type species of the genus Flavobacterium, was located in the MK-6 terrestrial lineage. The terrestrial Cytophaga species with MK-6 should be transferred to the genus Flavobacterium. The marine facultative anaerobes with MK-7 were located in the bacteroides branch, and possessed signature sequences with features intermediate between the bacteroides and the flavobacteria subdivisions. Cytophaga hutchinsonii, the type species of the genus Cytophaga, had a close relationship only with Cytophaga aurantiaca. The genus Cytophaga should be restricted to these two cellulose-degrading species. The genus Cytophaga is so heterogeneous that it should be divided into several genera and higher taxa in accordance with the phylogenetic relationships.

Characterization and identification of numerically abundant culturable bacteria from the anoxic bulk soil of rice paddy microcosms

Most-probable-number (liquid serial dilution culture) counts were obtained for polysaccharolytic and saccharolytic fermenting bacteria in the anoxic bulk soil of flooded microcosms containing rice plants. The highest viable counts (up to 2.5 x 10(8) cells per g [dry weight] of soil) were obtained by using xylan, pectin, or a mixture of seven mono- and disaccharides as the growth substrate. The total cell count for the soil, as determined by using 4', 6-diamidino-2-phenylindole staining, was 4.8 x 10(8) cells per g (dry weight) of soil. The nine strains isolated from the terminal positive tubes in counting experiments which yielded culturable populations that were equivalent to about 5% or more of the total microscopic count population belonged to the division Verrucomicrobia, the Cytophaga-Flavobacterium-Bacteroides division, clostridial cluster XIVa, clostridial cluster IX, Bacillus spp., and the class Actinobacteria. Isolates originating from the terminal positive tubes of liquid dilution series can be expected to be representatives of species whose populations in the soil are large. None of the isolates had 16S rRNA gene sequences identical to 16S rRNA gene sequences of previously described species for which data are available. Eight of the nine strains isolated fermented sugars to acetate and propionate (and some also fermented sugars to succinate). The closest relatives of these strains (except for the two strains of actinobacteria) were as-yet-uncultivated bacteria detected in the same soil sample by cloning PCR-amplified 16S rRNA genes (U. Hengstmann, K.-J. Chin, P. H. Janssen, and W. Liesack, Appl. Environ. Microbiol. 65:5050-5058, 1999). Twelve other isolates, which originated from most-probable-number counting series indicating that the culturable populations were smaller, were less closely related to cloned 16S rRNA genes.

Biofilm community structure in polluted rivers: abundance of dominant phylogenetic groups over a complete annual cycle

The seasonal dynamics of river biofilm communities in two German rivers, the Elbe and one of its tributaries, the Spittelwasser, were investigated for the first time by using fluorescence in situ hybridization and a standardized biofilm sampling procedure. We show the importance of members of the beta subclass of the class Proteobacteria, which formed the largest single group in the massively polluted Spittelwasser at all times. Clear seasonal peaks of abundance were observed for the planctomycetes and the Cytophaga-Flavobacterium cluster.

Description of Cellulophaga baltica gen. nov., sp. nov. and Cellulophaga fucicola gen. nov., sp. nov. and reclassification of [Cytophaga] lytica to Cellulophaga lytica gen. nov., comb. nov

Phenotypic data indicate that gliding, yellow/orange-pigmented, agar-digesting bacterial strains were members of the Cytophaga-Flavobacterium-Bacteroides (CFB) group. The strains were isolated from the surface of the marine benthic macroalga Fucus serratus L. and the surrounding seawater at three localities in Danish waters. The bacteria were Gram-negative, flexirubin-negative, aerobic, catalase-positive and oxidase-negative and were psychrophilic and halophilic. All strains utilized D-fructose, L-fucose and alpha-ketobutyric acid and degraded alginic acid, carrageenan, starch and autoclaved yeast cells. Amplification with primers specific for repetitive extragenic palindromic elements by PCR divided the strains of this study into two groups. Both groups showed unique PCR amplification patterns compared to reference strains of the CFB group. Phylogenetic analysis of 16S rDNA sequences showed association of these organisms and [Cytophaga] lytica at the genus level. Hybridization of total chromosomal DNA revealed that the new strains and [Cytophaga] lytica ATCC 23178T were clearly distinct from each other and other previously described species of the CFB group. A new genus is described, Cellulophaga gen. nov. comprising two new species, Cellulophaga baltica gen. nov., sp. nov. (NN015840T = LMG 18535T) and Cellulophaga fucicola gen. nov., sp. nov. (NN015860T = LMG 18536T), as well as the emendation of [Cytophaga] lytica to Cellulophaga lytica gen. nov., comb. nov.

Phenotypic and genomic studies of "Cytophaga psychrophila" isolated from diseased rainbow trout (Oncorhynchus mykiss) in France

Five strains of gliding bacteria were isolated in France from farmed diseased rainbow trouts reared at low water temperature. The resemblance of these bacteria to the known fish pathogen "Cytophaga psychrophila" led to their comparative study with reference strain NCMB 1947 and with an American isolate. Morphological, physiological, and biochemical characteristics of the seven strains proved to be similar. Comparison of their DNA by the S1 nuclease DNA-DNA hybridization method showed that the seven strains formed a tight genomic species with DNA relatedness above 90%. This is the first identification of this fish pathogen in a European country. The main phenotypic characteristics differentiating this bacterium from other nonpathogenic gliding bacteria of fish origin include a poor gliding movement, yellow compact or weakly rhizoid colonies on solid media, and the presence of flexirubin-type pigments. The inability to metabolize any carbohydrates, the strong proteolytic activity, the absence of growth in more than 0.5% NaCl, and the tolerance to a maximum temperature of 25 degrees C are also useful characteristics of this group of bacteria.

Assimilation of polysaccharides and glucose by major bacterial groups in the Delaware Estuary

The contribution of major bacterial groups to the assimilation of extracellular polymeric substances (EPS) and glucose in the Delaware Estuary was assessed using microautoradiography and fluorescence in situ hybridization. Bacterial groups contributed to EPS and glucose assimilation in part according to their distribution in the estuary. Abundance of the phylogenetic groups explained 35% and 55% of the variation in EPS and glucose assimilation, respectively. Actinobacteria contributed 70% to glucose assimilation in freshwater, while Alphaproteobacteria assimilated 60% of this compound in saline water. In contrast, various bacterial groups dominated the assimilation of EPS. Actinobacteria and Betaproteobacteria contributed the most in the freshwater section, whereas Cytophaga-like bacteria and Alpha- and Gammaproteobacteria participated in EPS assimilation in the lower part of the estuary. In addition, we examined the fraction of bacteria in each group that assimilated glucose or EPS. Overall, the fraction of bacteria in all groups that assimilated glucose was higher than the fraction that assimilated EPS (15 to 30% versus 5 to 20%, respectively). We found no correlation between the relative abundance of a group in the estuary and the fraction of bacteria actively assimilating glucose or EPS; the more active groups were often less abundant. Our results imply that the bacterial community in the Delaware Estuary is not controlled solely by "bottom-up" factors such as dissolved organic matter.

A partial phylogenetic analysis of the "flavobacter-bacteroides" phylum: basis for taxonomic restructuring

On the basis of small subunit rRNA sequence analyses five major subgroups within the flavobacteria-bacteroides phylum have been defined. These are tentatively designated the cytophaga subgroup (comprising largely Cytophaga species), the flavobacter subgroup (comprising the true flavobacteria and the polyphyletic genus Weeksella), the bacteroides subgroup (comprising the bacteroides and certain cytophaga-like bacteria), the sphingobacter subgroup (which contains the known sphingolipid-producing members of the phylum), and the saprospira subgroup (comprising particular species of Flexibacter, Flavobacterium, Haliscomenobacter, and, of course, the genus Saprospira). These groupings are given not only by evolutionary distance analysis, but can be defined and distinguished on the basis of a simple small subunit rRNA signatures.

Transfer of [Flexibacter] sancti, [Flexibacter] filiformis, [Flexibacter] japonensis and [Cytophaga] arvensicola to the genus Chitinophaga and description of Chitinophaga skermanii sp. nov

Analysis of the 16S rRNA gene sequences of species currently assigned to the genus Flexibacter has shown extensive intrageneric phylogenetic heterogeneity. It has been shown in previous studies that the species [Flexibacter] sancti, [Flexibacter] filiformis and [Flexibacter] japonensis were most closely related to Chitinophaga pinensis. In addition, [Cytophaga] arvensicola and species of the genus Terrimonas also clustered into this phylogenetic group. Although the similarities of 16S rRNA gene sequences were low (88.5–96.4 %), there is no evidence for clear phenotypic differences between these organisms that justify assignment to different genera. A proposal is made to transfer these species to the genus Chitinophaga as Chitinophaga sancti comb. nov., Chitinophaga filiformis comb. nov., Chitinophaga japonenis comb. nov. and Chitinophaga arvensicola comb. nov. on the basis of phylogenetic and phenotypic data. Furthermore, a novel species is described within this genus, Chitinophaga skermanii sp. nov., with strain CC-SG1BT (=CCUG 52510T=CIP 109140T) as the type strain.

Comparative phylogenetic assignment of environmental sequences of genes encoding 16S rRNA and numerically abundant culturable bacteria from an anoxic rice paddy soil

We used both cultivation and direct recovery of bacterial 16S rRNA gene (rDNA) sequences to investigate the structure of the bacterial community in anoxic rice paddy soil. Isolation and phenotypic characterization of 19 saccharolytic and cellulolytic strains are described in the accompanying paper (K.-J. Chin, D. Hahn, U. Hengstmann, W. Liesack, and P. H. Janssen, Appl. Environ. Microbiol. 65:5042-5049, 1999). Here we describe the phylogenetic positions of these strains in relation to 57 environmental 16S rDNA clone sequences. Close matches between the two data sets were obtained for isolates from the culturable populations determined by the most-probable-number counting method to be large (3 x 10(7) to 2.5 x 10(8) cells per g [dry weight] of soil). This included matches with 16S rDNA similarity values greater than 98% within distinct lineages of the division Verrucomicrobia (strain PB90-1) and the Cytophaga-Flavobacterium-Bacteroides group (strains XB45 and PB90-2), as well as matches with similarity values greater than 95% within distinct lines of descent of clostridial cluster XIVa (strain XB90) and the family Bacillaceae (strain SB45). In addition, close matches with similarity values greater than 95% were obtained for cloned 16S rDNA sequences and bacteria (strains DR1/8 and RPec1) isolated from the same type of rice paddy soil during previous investigations. The correspondence between culture methods and direct recovery of environmental 16S rDNA suggests that the isolates obtained are representative geno- and phenotypes of predominant bacterial groups which account for 5 to 52% of the total cells in the anoxic rice paddy soil. Furthermore, our findings clearly indicate that a dual approach results in a more objective view of the structural and functional composition of a soil bacterial community than either cultivation or direct recovery of 16S rDNA sequences alone.

Dyadobacter fermentans gen. nov., sp. nov., a novel gram-negative bacterium isolated from surface-sterilized Zea mays stems

A Gram-negative bacterium, designated NS114T, was isolated from duplicate treatments of surface-sterilized Zea mays stems. The plants were grown in synthetic soil under greenhouse conditions and watered with fertilizer containing no nitrogen. Strain NS114T could not be isolated from plants watered with the standard level or 20% (w/v) of the standard level of nitrogen. Cells occurred as pairs in young cultures that attached to form angled arrangements in R2A broth and occasionally formed rounded, horseshoe arrangements in YM broth. Cell variation resulted in flocculent chains of coccoid cells in old cultures. Strain NS114T fermented glucose and sucrose. The G + C content was 48 mol%. Phylogenetic analysis of the 16S rRNA gene showed that the strain was a member of the domain Bacteria and branched from a point equidistant from an aquatic organism, Runella slithyformis and a marine isolate, 'Microscilla furvescens'. Phenotypic and genotypic analyses indicated that strain NS114T could not be assigned to any recognized genus; therefore a new genus and species, Dyadobacter fermentans gen. nov., sp. nov., is proposed, for which NS114T is the type strain.

New degenerate Cytophaga-Flexibacter-Bacteroides-specific 16S ribosomal DNA-targeted oligonucleotide probes reveal high bacterial diversity in River Taff epilithon

River microbial communities play an important role in global nutrient cycles, and aggregated bacteria such as those in epilithic biofilms may be major contributors. In this study the bacterial diversity of River Taff epilithon in South Wales was investigated. A 16S ribosomal DNA (rDNA) clone library was constructed and analyzed by partial sequencing of 76 of 347 clones and hybridization with taxon-specific probes. The epilithon was found to be very diverse, with an estimated 59.6% of the bacterial populations not accounted for by these clones. Members of the Cytophaga-Flexibacter-Bacteroides division (CFBs) were most abundant in the library, representing 25% of clones, followed by members of the alpha subdivision of the division Proteobacteria (alpha-Proteobacteria), gamma-Proteobacteria, gram-positive bacteria, Cyanobacteria, beta-Proteobacteria, delta-Proteobacteria, and the Prosthecobacter group. This study concentrated on the epilithic CFB populations, and a new set of degenerate 16S rDNA probes was developed to enhance their detection, namely, CFB560, CFB562, and CFB376. The commonly used probe CF319a/b may frequently lead to the underestimation of CFB populations in environmental studies, because it does not fully detect members of the division. CFB560 had exact matches to 95.6% of CFBs listed in the Ribosomal Database Project (release 8.0) small-subunit phylogenetic trees, compared to 60% for CF319a/b. The CFB probes detected 66 of 347 epilithon TAF clones, and 60 of these were partially sequenced. They affiliated with the RDP-designated groups Cytophaga, Sphingobacterium, Lewinella, and Cytophaga aurantiaca. CFB560 and CF319a/b detected 94% (62 of 66) and 48.5% (32 of 66) of clones, respectively, and therefore CFB560 is recommended for future use. Probe design in this study illustrated that multiple degenerate positions can greatly increase target range without adversely effecting specificity or experimental performance.

A molecular systematic survey of cultured microbial associates of deep-water marine invertebrates

A taxonomic survey was conducted to determine the microbial diversity held within the Harbor Branch Oceanographic Marine Microbial Culture Collection (HBMMCC). The collection consists of approximately 17,000 microbial isolates, with 11,000 from a depth of greater than 150 ft seawater. A total of 2273 heterotrophic bacterial isolates were inventoried using the DNA fingerprinting technique amplified rDNA restriction analysis on approximately 750-800 base pairs (bp) encompassing hypervariable regions in the 5' portion of the small subunit (SSU) 16S rRNA gene. Restriction fragment length polymorphism patterns obtained from restriction digests with RsaI, HaeIII, and HhaI were used to infer taxonomic similarity. SSU 16S rDNA fragments were sequenced from a total of 356 isolates for more definitive taxonomic analysis. Sequence results show that this subset of the HBMMCC contains 224 different phylotypes from six major bacterial clades (Proteobacteria (Alpha, Beta, Gamma), Cytophaga, Flavobacteria, and Bacteroides (CFB), Gram + high GC content, Gram + low GC content). The 2273 microorganisms surveyed encompass 834 alpha-Proteobacteria (representing 60 different phylotypes), 25 beta-Proteobacteria (3 phylotypes), 767 gamma-Proteobacteria (77 phylotypes), 122 CFB (17 phylotypes), 327 Gram + high GC content (43 phylotypes), and 198 Gram + low GC content isolates (24 phylotypes). Notably, 11 phylotypes were < or =93% similar to the closest sequence match in the GenBank database even after sequencing a larger portion of the 16S rRNA gene (approximately 1400 bp), indicating the likely discovery of novel microbial taxa. Furthermore, previously reported "uncultured" microbes, such as sponge-specific isolates, are part of the HBMMCC. The results of this research will be available online as a searchable taxonomic database (www.hboi.edu/dbmr/dbmr_hbmmd.html).

16S rRNA-targeted oligonucleotide probes for the in situ detection of members of the phylum Cytophaga-Flavobacterium-Bacteroides

Bacteria of the Cytophaga-Flavobacterium-Bacteroides phylum (CFB-phylum) are numerically important members of many microbial communities. A suite of five 16S rRNA-targeted oligonucleotide probes for members of this group is described which was designed to dominantly target bacteria of the CFB-phylum that are found in particular habitats. For this we initially performed a literature survey-for the sources and sites of isolation of hitherto described members of the CFB-phylum. Probe CFB286 is mostly complementary to the 16S rRNA of species originally isolated from freshwater habitats, however, detects some marine and soil isolates and is the only probe which includes some food isolates. Probe CFB563 detects marine as well as animal-associated isolates. Probe CFB719, which also detects some environmental isolates, and probe CFB972 are mostly targeting animal-associated isolates. All probes are complementary to a variety of human-associated species within the CFB-phylum which, in the data set investigated (October 1998), made up 46% of all 16S rRNA sequences from the CFB-phylum. We conclude that it is difficult to find habitat-specific probes for members of the CFB-phylum and that the design of probes for monophyletic groups should remain the standard approach. Applicability of the probes for fluorescence in situ hybridization and specificity for single cell detection were evaluated for the four mentioned probes whereas the fifth, probe CFB1082, which almost exclusively targets human-associated species, was not further characterized. The new probes are of limited determinative value and should be used together with the already established probes for the CFB-phylum. It is the hybridization pattern observed for a given cell or culture with the enlarged probe set that is suggestive for its affiliation with a defined group within the CFB-phylum.

Phylogenetic structure of the genera Flexibacter, Flexithrix, and Microscilla deduced from 16S rRNA sequence analysis

The 16S rDNA sequences of 40 strains of 17 species in the genus Flexibacter, 5 strains of 4 species in the genus Microscilla, and 1 strain of Flexithrix dorotheae, including all type strains of approved and validated species in these genera, were determined to reveal their phylogenetic relationships. The 16S rRNA sequence analysis demonstrated the extreme heterogeneity of the genera Flexibacter and Microscilla. The strains examined diverged into 24 distinct lines of descent (1 group included both flexibacteria and flexithrix, and 1 group included both flexibacteria and microscilla) that were remote from each other at the genus level or higher. Flexibacter strains were scattered across the cytophaga-flavobacteria-bacteroides phylum and divided into 20 phylogenetic groups, and the genus Microscilla was separated into 5 groups. Flexibacter flexilis, the type species of the genus Flexibacter, and Microscilla marina, the type species of the genus Microscilla, were isolated from other organisms in their respective genera. This means that each genus should be restricted to only the type species. Flexithrix dorotheae, the type species of the genus Flexithrix, clustered with Flexibacter aggregans. The heterogeneity was found not only within genera but also within species. Flexibacter aggregans, Flexibacter aurantiacus, Flexibacter flexilis, Flexibacter roseolus, Flexibacter tractuosus, and "Microscilla sericea" each contained phylogenetically distant strains. The taxonomic concept of the genera Flexibacter, Flexithrix, and Microscilla should be reorganized in accordance with the natural relationships revealed in this study.

Reichenbachia agariperforans gen. nov., sp. nov., a novel marine bacterium in the phylum Cytophaga-Flavobacterium-Bacteroides

A heterotrophic, pigmented, agarolytic, gliding bacterium was isolated from a seawater sample collected from the Gulf of Peter the Great, Sea of Japan, during June 2000. 16S rDNA sequence analysis indicated that the novel bacterium, strain KMM 3525T, was a member of the phlyum Cytophaga-Flavobacterium-Bacteroides. On the basis of phenotypic, chemotaxonomic, genotypic and phylogenetic data, it is proposed that the marine bacterium represents the sole species of a novel genus, Reichenbachia, the type species of which is Reichenbachia agariperforans (KMM 3525T =IFO 16625T =JCM 11238T).