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Members of the flavobacterial genus Polaribacter thrive in response to North Sea spring phytoplankton blooms. We analyzed two respective Polaribacter species by whole genome sequencing, comparative genomics, substrate tests and proteomics. Both can degrade algal polysaccharides but occupy distinct niches. The liquid culture isolate Polaribacter sp. strain Hel1_33_49 has a 3.0-Mbp genome with an overall peptidase:CAZyme ratio of 1.37, four putative polysaccharide utilization loci (PULs) and features proteorhodopsin, whereas the agar plate isolate Polaribacter sp. strain Hel1_85 has a 3.9-Mbp genome with an even peptidase:CAZyme ratio, eight PULs, a mannitol dehydrogenase for decomposing algal mannitol-capped polysaccharides but no proteorhodopsin. Unlike other sequenced Polaribacter species, both isolates have larger sulfatase-rich PULs, supporting earlier assumptions that Polaribacter take part in the decomposition of sulfated polysaccharides. Both strains grow on algal laminarin and the sulfated polysaccharide chondroitin sulfate. For strain Hel1_33_49, we identified by proteomics (i) a laminarin-induced PUL, (ii) chondroitin sulfate-induced CAZymes and (iii) a chondroitin-induced operon that likely enables chondroitin sulfate recognition. These and other data suggest that strain Hel1_33_49 is a planktonic flavobacterium feeding on proteins and a small subset of algal polysaccharides, while the more versatile strain Hel1_85 can decompose a broader spectrum of polysaccharides and likely associates with algae. [ABSTRACT FROM AUTHOR]

The pathogenesis of human cancers involves complex molecular interactions regulating angiogenesis, cell-matrix interactions, cell cycle progression and apoptosis, resulting in increased survival of initiated cells, unrestrained cell growth and tumorigenesis. Importantly, genes that contribute to the genesis of human cancers can be integrated into the genome of transgenic mice or targeted genes can be rendered nonfunctional or less influential in selected tissues. Both of these approaches can be used to create de novo tumor models highly reminiscent of human cancers that can help us to better understand how tumorigenesis is influenced by nutrient-gene interactions. The intake of antioxidants in the diet is associated with protection against cardiovascular disease, atherosclerosis and a variety of other age-related degenerative diseases. Because antioxidants scavenge reactive oxygen species implicated in oxidative DNA damage and genetic alterations, dietary antioxidants have been presumed to protect against cancer. However, interventions trials using antioxidant supplements have produced mixed results, and noted review panels do not recommend increased antioxidant supplements for the prevention of cancer (World Cancer Research Fund 1997). Importantly, studies show that many types of human cancer express lower levels of antioxidant enzymes than do their normal tissue counterparts. Thus, given the important role played by reactive oxygen species in most forms of aerobic apoptosis, it is reasonable to suggest that the survival of tumor cells could be adversely affected more by a shift in tissue redox balance than normal cells could be affected. We used transgenic mouse de novo tumorigenesis models to investigate the role of cell cycle regulatory genes, cell survival genes and dietary antioxidant availability in tumorigenesis. In the transgenic TgT121 brain tumor model in which tumors are initiated by cell-specific expression of the T121 oncoprotein and inactivation of the pRb protein, we showed that feeding a diet depleted of antioxidant vitamins increased tumor oxidant stress and apoptosis, resulting in dramatically reduced tumor burden. To better understand the role of diet, apoptosis susceptibility and tumor metastasis, we performed similar studies in a strain of transgenic mice (MMTVPyVT) with mammary epithelium-targeted alterations in the expression of src and PI3 kinase. These alterations result in enhanced mitogenesis, decreased apoptosis and de novo mammary tumorigenesis and metastasis. We found that feeding an antioxidant-depleted diet enhanced tumor-targeted oxidative stress and apoptosis, resulting in decreased primary tumor burden and, significantly, decreased metastasis formation. It is becoming clear that tumor metastasis is influenced by genetic events, although it is not clear whether these genetic events are influenced by dietary alterations. We found that feeding a diet depleted of antioxidant vitamins correlated with increased tumor expression of nm23-H1, a breast cancer metastasis-suppressor factor first identified in humans. Taken together, these observations demonstrate the practical utility of transgenic mouse tumor models in understanding the possible role of nutrient-gene interactions in cancer treatment and prevention.

The globally abundant, uncultured unicellular cyanobacterium UCYN- A was recently discovered living in association with a eukaryotic cell closely related to a prymnesiophyte. Here, we established a double CAtalysed Reporter Deposition-Fluorescence In Situ Hybridization ( CARD- FISH) approach to identify both partners and provided quantitative information on their distribution and abundance across distinct water masses along a transect in the North Atlantic Ocean. The N2 fixation activity coincided with the detection of UCYN- A cells and was only observed in oligotrophic (< 0.067 [ABSTRACT FROM AUTHOR]

Highlights: [•] Single-crystal EPR spectra allow a detailed characterization of the center in quartz. [•] Three distinct A(17O) provide the first direct proof of an oxygen vacancy for E′ centers. [•] The single-oxygen-vacancy V(O)+ model cannot account for the new A(17O) data. [•] The tri-vacancy with an Al impurity model V(SiO2)Al reproduces all EPR hyperfine data. [ABSTRACT FROM AUTHOR]

The crystal structures of two elbaites from the Paraiba deposit with copper contents of 3.51 and 1.61 wt% CuO [a = 15.881(1), 15.840(3); c = 7.112(1), 7.1028(9), respectively], as well as a synthetic Cu-bearing olenite with a CuO content of 8.39 wt% [a = 15.840(4), c = 7.091(1)] have been refined to R-indices of 2.2, 3.1, and 4.1% using X-ray single-crystal diffraction. On the basis of original and published data (for six structures) the crystal-chemical relationships of copper-bearing tourmalines has been analyzed. It is shown that copper cations and cations of other 3d elements (Mn, Zn, Fe) occupy almost exclusively the Y site. Such an ordered distribution results in a change of the size of the Y-octahedra. There is an inverse correlation between the content of 3d elements (mainly Cu2+ cations) and Al3+-cations in the Y-octahedron and also between the value of and the content of Al3+ cations in the Y site. The direct correlation between values of -distance in the structures of Cu-bearing elbaites and the parameters (a, c) of the unit cell have been found. Distortions of polyhedra in the structures of Cu-bearing elbaites are similar, and significantly higher than those present in the structure of the synthetic Cu-bearing olenite. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen (N2) fixation is a globally important process often mediated by diazotrophic cyanobacteria in the open ocean. In 2010, seawater was collected near Cape Verde to identify and measure N2 and carbon (C) fixation by unicellular diazotrophic cyanobacteria. The nifH gene abundance (104–106 nifH L−1) and nifH gene transcript abundance (102–104 cDNA nifH L−1) for two unicellular groups, UCYN-A and UCYN-B, were detected. UCYN-A was also identified and quantified (104–105 cellsL−1) by new probes (UCYN-A732 and UCYN-A159) using Catalyzed Reporter Deposition-Fluorescence In Situ Hybridization (CARD-FISH) assays. The UCYN-A were observed as free cells or attached to a larger unidentified eukaryotic cell. A Halogen In Situ Hybridization-Secondary Ion Mass Spectrometry (HISH-SIMS) assay using the UCYN-A732 probe was applied on samples previously incubated with 13C-bicarbonate and 15N2. Free UCYN-A cells were enriched in both 13C and 15N and estimated C and N2 fixation rates for UCYN-A were lower compared to co-occurring unicellular cyanobacteria cells similar in size (3.1–5.6μm) and pigmentation to diazotroph Crocosphaera watsonii. Here, we identify and quantify two common co-occurring unicellular groups and measure their cellular activities by nanoSIMS. [Copyright &y& Elsevier]

Synthetic stishovite before and after electron- and γ-ray irradiation has been investigated by single-crystal electron paramagnetic resonance (EPR) spectroscopy for the first time. Room-temperature single-crystal EPR spectra of as-is stishovite reveal two high-spin (S = 3/2) Cr3+ centers: one with D2h symmetry and another of triclinic symmetry. Quantitatively determined spin Hamiltonian parameters, including matrices g, D, and A(53Cr) and high-spin Zeeman term BS³, suggest that the D2h center represents a substitutional Cr3+ ion at the Si site without an immediate charge compensator. The triclinic center, which is characterized by a well-resolved ¹H superhyperfine structure, also arises from a substitutional Cr3+ ion at the Si site but has an H+ charge compensator bonded to one of the four equatorial oxygen atoms. The magnitude and orientation of the ¹H superhyperfine structure yield the location of the H atom at (0.46, 0.12, 0). These structural models for Cr and H in stishovite also have been corroborated by periodic density functional theory (DFT) calculations using the Vienna ab initio simulation package (VASP), with 2 x 2 x 4 supercells, plane-wave basis sets and the projector augmented wave (PAW) potentials. In addition, 85 K EPR spectra of irradiated stishovite show that the two Cr3+ centers are both converted to an S = 1/2 Cr5+ center characterized by two 29Si superhyperfine structures arising from interactions with two nearest and eight second-nearest Si atoms, respectively. The spin Hamiltonian parameters of this Cr5+ center provide further support for the location of the two Cr3+ centers at the Si site. [ABSTRACT FROM AUTHOR]

A total of 151 bacterial isolates were recovered from different developmental stages (larvae, nymphs and adults) of field-collected ticks (67 strains from Ixodes ricinus, 38 from Dermacentor reticulatus, 46 from Haemaphysalis concinna). Microorganisms were identified by means of 16S rRNA gene sequencing. Almost 87 % of the strains belonged to G+ bacteria with predominantly occurring genera Bacillus and Paenibacillus. Other G+ strains included Arthrobacter, Corynebacterium, Frigoribacterium, Kocuria, Microbacterium, Micrococcus, Plantibacter, Rhodococcus, Rothia, and Staphylococcus. G− strains occurred less frequently, comprising genera Advenella, Pseudomonas, Rahnella, Stenotrophomonas, and Xanthomonas. Several strains of medical importance were found, namely Advenella incenata, Corynebacterium aurimucosum, Microbacterium oxydans, M. schleiferi, Staphylococcus spp., and Stenotrophomonas maltophilia. Data on cultivable microbial diversity in Eurasian tick species D. reticulatus and H. concinna are given, along with the extension of present knowledge concerning bacterial flora of I. ricinus. [ABSTRACT FROM AUTHOR]

Members of the Bacteroidetes, formerly known as the Cytophaga-Flavobacteria-Bacteroides (CFB) phylum, are among the major taxa of marine heterotrophic bacterioplankton frequently found on macroscopic organic matter particles (marine snow). In addition, they have been shown to also represent a significant part of free-living microbial assemblages in nutrient-rich microenvironments. Their abundance and distribution pattern in combination with enzymatic activity studies has led to the notion that organisms of this group are specialists for degradation of high molecular weight compounds in both the dissolved and particulate fraction of the marine organic matter pool, implying a major role of Bacteroidetes in the marine carbon cycle. Despite their ecological importance, comprehensive molecular data on organisms of this group have been scarce so far. Here we report on the first whole genome analysis of a marine Bacteroidetes representative, ‘ Gramella forsetii’ KT0803. Functional analysis of the predicted proteome disclosed several traits which in joint consideration suggest a clear adaptation of this marine Bacteroidetes representative to the degradation of high molecular weight organic matter, such as a substantial suite of genes encoding hydrolytic enzymes, a predicted preference for polymeric carbon sources and a distinct capability for surface adhesion. [ABSTRACT FROM AUTHOR]

Questing Ixodes ricinus L. (Acari: Ixodidae) ticks were collected on a forest trail that had been completely cleared of shrubs and ground vegetation in winter 2002 and on a nearby control uncleared forest transect in South Moravia (Czech Republic). Samples were collected each May in 2003, 2004 and 2005. Nymphal ticks were 3.4 times, 1.9 times and 1.2 times less frequent on cleared forest than on uncleared forest trails in the three respective years, whereas adult tick abundance was 27.2 times, 4.0 times and 2.2 times lower, respectively. The ticks were examined for borreliae by dark-field microscopy: prevalence of nymphal ticks infected with Borrelia burgdorferi sensu lato (12.6% to 20.0%) did not differ significantly between the cleared and uncleared trail during the 3 years. In conclusion, the habitat modification appeared to result in a decreased abundance of I. ricinus as well as a reduced frequency of infected ticks (and thus indirectly a lower potential risk of Lyme borreliosis), which lasted, however, for only 2 years. Eight cultures of borreliae isolated from the ticks were all identified as the ‘ornithophilic’ genomic species Borrelia garinii, possibly indicating a greater role of forest birds than that of forest rodents as the hosts of immature I. ricinus in the tick (and borrelial) colonization of the cleared part of the forest. [ABSTRACT FROM AUTHOR]

The primary purpose of this study was to define the clinical and morphological features of cataractogenesis in the OXYS strain of rats that generate excess reactive oxygen species. Rats were sequentially examined from birth to the development of mature cataracts with slit lamp biomicroscopy. Morphology of selected stages of cataract development was studied using light and transmission electron microscopy (TEM), immunohistochemical localization of the lipid peroxidation product 4-hydroxynonenal (HNE) and fluorescent antibody labeling for DNA oxidation products. Lenses from age-matched normal rats were used as controls.OXYS rats developed cataracts as young as two weeks of age with progression to maturity by 1 year. Clinically, cataracts appeared initially either as nuclear or sub-capsular cortical changes and progressed to pronounced nuclear cataracts within months. TEM confirmed the light microscopic impression of region-specific alterations in both fiber cell cytoplasmic protein matrix and membrane structure. The outer adult nuclear region showed extensive cellular damage similar to osmotic cataracts, which is consistent with the postulated high uptake of glucose in the OXYS strain. The adult and outer fetal nuclear cells displayed several types of focal damage. The inner fetal and embryonic nuclear cells demonstrated textured cytoplasm, suggesting protein degradation or redistribution. Staining for HNE was increased in epithelium, cortex and nucleus compared to control lenses. Fluorescent antibody probes demonstrated increased levels of DNA oxidation products in OXYS rat lenses compared to age-matched controls. Fourier analysis of nuclear cytoplasm revealed significant components with corresponding sizes greater than 100 nm and, using a new theoretical approach, the texturing of the cytoplasm was shown to be sufficient to cause opacification of the nucleus. The OXYS rat appears to be an ideal model for oxidative stress cataractogenesis. The potential oxidative damage observed is extensive and characteristic of the developmental region. The source of oxidative damage may in part be a response to elevated levels of glucose. Because oxidative stress is thought to be a major factor in cataract formation in both diabetic and non-diabetic aging humans, this animal model may be a useful tool in assessing efficacy of antioxidant treatments that may slow or prevent cataract formation. [Copyright &y& Elsevier]

The unexpected presence of archaea-like genes for tetrahydromethanopterin (H4MPT)-dependent enzymes in the completely sequenced genome of the aerobic marine planctomycetePirellulasp. strain 1 (“Rhodopirellula baltica”) and in the currently sequenced genome of the aerobic freshwater planctomyceteGemmata obscuriglobusstrain UQM2246 revives the discussion on the origin of these genes in the bacterial domain. We compared the genomic arrangement of these genes inPlanctomycetesand methylotrophic proteobacteria and performed a phylogenetic analysis of the encoded protein sequences to address the question whether the genes have been present in the common ancestor ofBacteriaandArchaeaor were transferred laterally from the archaeal to the bacterial domain and therein. Although this question could not be solved using the data presented here, some constraints on the evolution of the genes involved in archaeal and bacterial H4MPT-dependent C1-transfer may be proposed: (i) lateral gene transfer (LGT) fromArchaeato a common ancestor ofProteobacteriaandPlanctomycetesseems more likely than the presence of the genes in the common ancestor ofBacteriaandArchaea; (ii) a single event of interdomain LGT can be favored over two independent events; and (iii) the archaeal donor of the genes might have been a representative of theMethanosarcinales. In the bacterial domain, the acquired genes evolved according to distinct environmental and metabolic constraints, reflected by specific rearrangements of gene order, gene recruitment, and gene duplication, with subsequent functional specialization. During the course of evolution, genes were lost from some planctomycete genomes or replaced by orthologous genes from proteobacterial lineages. [ABSTRACT FROM AUTHOR]

We hypothesized that the phytosterols β-sitosterol (BSS), β-sitosterol glucoside (BSSG), and Moducare (MC; BSS:BSSG = 99:1) could modulate the growth of estrogen-dependent human breast cancer cells in vitro and in vivo. The present study evaluated the estrogenic and antiestrogenic effects of BSS, BSSG, and MC (0.001 to 150 μmol/L) on the proliferation of Michigan Cancer Foundation 7 (MCF-7) cells in vitro. Both BSS (>1 μmol/L) and MC (>50 μmol/L) increased MCF-7 cell proliferation. Treatment with 150 μmol/L of BSS and MC increased cell growth by 2.4 and 1.5 times, respectively, compared to the negative control (NC) group. However, BSSG had no effect at the concentrations tested. The effects of dietary BSS, BSSG, and MC on the growth of MCF-7 cells implanted in ovariectomized athymic mice were also evaluated. Estrogenic effects of the phytosterols were evaluated in the NC, BSS, BSSG, and MC treatment groups, and antiestrogenic effects were evaluated in the 17β-estradiol (E2), E2 + BSS, E2 + BSSG, and E2+ MC treatment groups. Mice were treated with dietary BSS (9.8 g/kg AIN93G diet), BSSG (0.2 g/kg diet), or MC (10.0 g/kg diet) for 11 wk. Dietary BSS, BSSG, and MC did not stimulate MCF-7 tumor growth. However, dietary BSS, BSSG, and MC reduced E2-induced MCF-7 tumor growth by 38.9% (P < 0.05), 31.6% (P = 0.08), and 42.13% (P < 0.05), respectively. The dietary phytosterols lowered serum E2 levels by 35.1, 30.2, and 36.5% in the E2 + BSS, E2 + BSSG, and E2+ MC groups, respectively (P < 0.05), compared to that of the E2 treatment group. Estrogen-responsive pS2 mRNA expression in tumors did not differ among groups, but expression of the antiapoptotic marker B-cell lymphoma/leukemia-2 (bcl-2) in tumors from the E2 + MC group was downregulated, compared to that of the E2 treatment group. In summary, BSS and MC stimulated MCF-7 cell growth in vitro. Although BSSG comprises only 1% of MC, BSSG made MC less estrogenic than BSS alone in vitro. However, dietary BSS and MC protected against E2-stimulated MCF-7 tumor growth and lowered circulating E2 levels. [ABSTRACT FROM AUTHOR]

Summary Filamentous sulphide-oxidizing Beggiatoa spp. often occur in large numbers in the coastal seabed without forming visible mats on the sediment surface. We studied the diversity, population structure and the nitrate-storing capability of such bacteria in the Danish Limfjorden and the German Wadden Sea. Their distribution was compared to the vertical gradients of O2 , NO3 – and H2 S as measured by microsensors. The main Beggiatoa spp. populations occurred in a 0.5–3 cm thick intermediate zone, below the depth of oxygen and nitrate penetration but above the zone of free sulphide. The Beggiatoa spp. filaments were found to store nitrate, presumably in liquid vacuoles up to a concentration of 370 mM NO3 – , similar to the related large marine sulphur bacteria, Thioploca and Thiomargarita . The observations indicate that marine Beggiatoa spp. can live anaerobically and conserve energy by coupling sulphide oxidation with the reduction of nitrate to dinitrogen and/or ammonia. Calculations of the diffusive nitrate flux and the potential sulphide oxidation by Beggiatoa spp. show that the bacteria may play a critical role for the sulphur cycling and the nitrogen balance in these coastal environments. 16S rDNA sequence analysis shows a large diversity of these uncultured, nitrate-storing Beggiatoa spp. Smaller (9–17 µm wide) and larger (33–40 µm wide) Beggiatoa spp. represent novel phylogenetic clusters distinct from previously sequenced, large marine Beggiatoa spp. and Thioploca spp. Fluorescence in situ hybridization (FISH) of the natural Beggiatoa spp. populations showed that filament width is a conservative character of each phylogenetic species but a given filament width may represent multiple phylogenetic species in a mixed population. [ABSTRACT FROM AUTHOR]

Apoptosis, or regulated cell suicide, eliminates unwanted and damaged cells, including precancerous and cancerous cells. Since reactive oxygen species (ROS) act as essential apoptotic mediators, we reasoned that increasing the ROS level might enhance apoptosis and thereby slow down tumor growth. Here, using a defined transgenic brain tumor model with known tumor apoptosis rates, we test the impact of antioxidant-depleted diet, capable of increasing ROS levels, or antioxidant-enriched diets on tumor growth. Dramatically increased apoptosis occurs within tumors, but not in normal tissues of antioxidant-depleted mice. The presence of detectable increased oxidant stress within tumors indicates that the likely mechanism of enhanced tumor apoptosis is via ROS and DNA oxidative impairment. Importantly, due to the ROS-enhanced apoptosis, tumor growth is inhibited in mice fed an antioxidant-depleted diet. In clear contrast, an antioxidant-rich diet had no impact on tumor growth. [ABSTRACT FROM PUBLISHER]

Seawater contains free-living and particle-attached bacteria. Only a small fraction is cultivable on plates. As free-living and particle-associated bacteria differ in their physiological traits, their cultivability on plates may coincide with particle association. Using filtration and Imhoff sedimentation cones, particles were collected during a spring phytoplankton bloom off Helgoland (North Sea) in order to obtain particle-associated bacteria as inocula. Direct dilution plating resulted in 526 strains from 3 µm filtration retentates and 597 strains from settled particles. Motile Gammaproteobacteria from the genera Pseudoalteromonas , Shewanella , Psychrobacter , Vibrio and Colwellia , as well as particle-attached Flavobacteriia affiliating with the genera Tenacibaculum and Gramella , were frequently isolated. As a result, a diverse collection comprised of 266 strains was deposited. Two strains were most likely to represent novel genera and 78 strains were probably novel species. Recently, a high-throughput cultivation study from the same site using seawater as an inoculum had retrieved 271 operational phylogenetic units (OPUs) that represented 88% of the 4136 characterized strains at the species level. A comparison of 16S rRNA gene sequences revealed that the collection obtained matched 104 of the 271 seawater OPUs at the species level and an additional 113 at the genus level. This large overlap indicated a significant contribution of particle-associated bacteria to the cultivable microbiome from seawater. The presence of 49 genera not identified in the larger seawater study suggested that sample fractionation was an efficient strategy to cultivate rare members of the planktonic microbiome. The diverse collection of heterotrophic bacteria retrieved in this study will be a rich source for future studies on the biology of particle-associated bacteria. [ABSTRACT FROM AUTHOR]

Presents a method in the identification and in situ detection of individual microbial cells without cultivation. Use of a combination of direct retrieval of ribosomal RNA (rRNA) sequences and whole-cell oligonucleotide probing in identifying and detecting uncultured bacteria; Problems associated with direct microscopic observation in detecting bacteria.

Examines the use of in situ hybridization method for the specific detection of pathogenic Candida species by designing an oligonucleotide probe which binds to the 18S rRNA of Candida albicans and Candida tropicalis. Selection of an oligonucleotide probe specific for C. albicans and C. tropicalis; Confirmation of probe specificity.

In situ hybridization with rRNA-targeted, fluorescent (Cy3-labeled) oligonucleotide probes was used to analyze bacterial community structure in ethanol- or paraformaldehyde-fixed bulk soil after homogenization of soil samples in 0.1% pyrophosphate by mild ultrasonic treatment. In ethanol-fixed samples 37 ± 7%, and in paraformaldehyde 41 ± 8% of the 4′, 6-diamidino-2-phenylindole(DAPI)-stained cells were detected with the bacterial probe Eub338. The yield could not be increased by enzymatic and/or chemical pretreatments known to enhance the permeability of bacterial cells for probes. However, during storage in ethanol for 7 months, the detectability of bacteria increased in both ethanol- and paraformaldehyde-fixed samples to up to 47 ± 8% due to an increase in the detection yield of members of the α-subdivision of Proteobacteria from 2 ± 1% to 10 ± 3%. Approximately half of the bacteria detected by probe Eub338 could be affiliated to major phylogenetic groups such as the α-, β-, γ-, and δ-subdivisions of Proteobacteria, gram-positive bacteria with a high G+C DNA content, bacteria of the Cytophaga-Flavobacterium cluster of the CFB phylum, and the planctomycetes. The analysis revealed that bacteria of the α- and δ-subdivision of Proteobacteria and the planctomycetes were predominant. Here, members of the α-subdivision of Proteobacteria accounted for approximately 10 ± 3% of DAPI-stained cells, which corresponded to 44 ± 16 × 108 cells (g soil, dry wt.)–1, while members of the δ-subdivision of Proteobacteria made up 4 ± 2% of DAPI-stained cells [17 ± 9 × 108 cells (g soil, dry wt.)–1]. A large population of bacteria in bulk soil was represented by the planctomycetes, which accounted for 7 ± 3% of DAPI-stained cells [32 ± 12 × 108 cells (g soil, dry wt.)–1]. The detection of planctomycetes in soil confirms previous reports on the occurrence of planctomycetes in soil and indicates a yet unknown ecological significance of this group, which to date has never been isolated from terrestrial environments. [ABSTRACT FROM AUTHOR]