Nitrification in terrestrial hot springs of Iceland and Kamchatka.

Archaea have been detected recently as a major and often dominant component of the microbial communities performing ammonia oxidation in terrestrial and marine environments. In a molecular survey of archaeal ammonia monooxygenase (AMO) genes in terrestrial hot springs of Iceland and Kamchatka, the amoA gene encoding the alpha-subunit of AMO was detected in a total of 14 hot springs out of the 22 investigated. Most of these amoA-positive hot springs had temperatures between 82 and 97 degrees C and pH range between 2.5 and 7. In phylogenetic analyses, these amoA genes formed three independent lineages within the known sequence clusters of marine or soil origin. Furthermore, in situ gross nitrification rates in Icelandic hot springs were estimated by the pool dilution technique directly on site. At temperatures above 80 degrees C, between 56 and 159 mumol NO(3)(-) L(-1) mud per day was produced. Furthermore, addition of ammonium to the hot spring samples before incubation yielded a more than twofold higher potential nitrification rate, indicating that the process was limited by ammonia supply. Our data provide evidence for an active role of archaea in nitrification of hot springs in a wide range of pH values and at a high temperature.

The effect of temperature change on the microbial diversity and community structure along the chronosequence of the sub-arctic glacier forefield of Styggedalsbreen (Norway).

Microbial communities in the glacier forefield of Styggedalsbreen, Norway, were investigated along a chronosequence from newly exposed soil to vegetated soils using next-generation sequencing of the 16S rRNA gene. In order to monitor the short-term effect of temperature on community successions along the soil gradient, the soil samples were incubated at three different temperatures (5°C, 10°C and 22°C). The microbial community composition along the chronosequence differed according to distance from the glacial terminus and incubation temperature. Samples close to the glacier terminus were dominated by Proteobacteria at 5°C and 10°C, while at 22°C members of Chloroflexi, Acidobacteria and Verrucomicrobia in addition to Proteobacteria accounted for most of the diversity, indicating that sites close to the glacier terminus are more closely related to former subglacial environments. Within the Archaea domain, members of the phylum Euryarchaeota dominated in samples closer to the glacier terminus with a shift to members of the phyla Thaumarchaeota-Crenarchaeota with increased soil age. Our data indicate that composition and diversity of the microbial communities along the glacier forefield depend not only on exposure time but are also to a large degree influenced by soil surface temperature and soil maturation.

Structural and functional specificities of PDGF-C and PDGF-D, the novel members of the platelet-derived growth factors family.

The platelet-derived growth factor (PDGF) family was for more than 25 years assumed to consist of only PDGF-A and -B. The discovery of the novel family members PDGF-C and PDGF-D triggered a search for novel activities and complementary fine tuning between the members of this family of growth factors. Since the expansion of the PDGF family, more than 60 publications on the novel PDGF-C and PDGF-D have been presented, highlighting similarities and differences to the classical PDGFs. In this paper we review the published data on the PDGF family covering structural (gene and protein) similarities and differences among all four family members, with special focus on PDGF-C and PDGF-D expression and functions. Little information on the protein structures of PDGF-C and -D is currently available, but the PDGF-C protein may be structurally more similar to VEGF-A than to PDGF-B. PDGF-C contributes to normal development of the heart, ear, central nervous system (CNS), and kidney, while PDGF-D is active in the development of the kidney, eye and brain. In adults, PDGF-C is active in the kidney and the central nervous system. PDGF-D also plays a role in the lung and in periodontal mineralization. PDGF-C is expressed in Ewing family sarcoma and PDGF-D is linked to lung, prostate and ovarian cancers. Both PDGF-C and -D play a role in progressive renal disease, glioblastoma/medulloblastoma and fibrosis in several organs.

Increased expression of genes encoding mitochondrial proteins in papillary thyroid carcinomas.

To investigate differences in gene expression between normal thyroid tissue and papillary thyroid carcinomas, we performed differential display (DD) polymerase chain reaction (PCR) using total RNA from fresh-frozen surgically removed thyroid specimens. Four DD fragments that were overexpressed in tumor tissue were identified as parts of genes from the mitochondrial genome: nicotinamide adenine dinucleotide (NADH) dehydrogenase 5, adenosine triphosphate (ATP) synthase 6, cytochrome b, and cytochrome c oxidase I. The expression profiles of these genes were confirmed by hybridization using a DNA dot-blot array and radioactively labeled complex cDNA probes generated from tumor (30 biopsies) and nontumor (15 biopsies) total RNA. Cytochrome c oxidase III was also found to be overexpressed in papillary carcinomas, while the nuclear-encoded mitochondrial transcription factor A showed similar mRNA expression levels in tumor and nontumor tissue. Electron microscopy showed increased number and size of mitochondria in papillary carcinomas. Immunohistochemistry using a monoclonal antibody recognizing a nuclear-encoded mitochondrial protein showed positivity in all cases of papillary carcinoma (44 samples), while normal thyroid tissue (34 samples) was negative in all cases except 3, in which there was a weak, focal cytoplasmic staining. We conclude that papillary thyroid carcinomas show increased expression of mitochondrial mRNA and proteins, encoded by nuclear as well as mitochondrial genes.

Metagenomics of Kamchatkan hot spring filaments reveal two new major (hyper)thermophilic lineages related to Thaumarchaeota.

Based on phylogenetic analyses and gene distribution patterns of a few complete genomes, a new distinct phylum within the Archaea, the Thaumarchaeota, has recently been proposed. Here we present analyses of six archaeal fosmid sequences derived from a microbial hot spring community in Kamchatka. The phylogenetic analysis of informational components (ribosomal RNAs and proteins) reveals two major (hyper-)thermophilic clades ("Hot Thaumarchaeota-related Clade" 1 and 2, HTC1 and HTC2) related to Thaumarchaeota, representing either deep branches of this phylum or a new archaeal phylum and provides information regarding the ancient evolution of Archaea and their evolutionary links with Eukaryotes.

Preparation of high-molecular weight DNA and metagenomic libraries from soils and hot springs.

Metagenomics has become an important tool for the characterization of microorganisms, as it is independent of their enrichment or cultivation in the laboratory. Its application has led to the discovery of metabolisms from widespread, yet uncharacterized organisms such as the ammonia-oxidizing archaea. Different approaches ranging from the generation of short sequence reads by direct use of high-throughput sequencing technologies to the construction and sequencing of large-insert DNA libraries are being employed. For these purposes, DNA of high quality needs to be prepared from an environmental sample, which is a particular challenge for soils and sediments. Here we describe the methods used for the isolation of high-molecular weight (hmw) DNA from soil and hot spring samples, the subsequent production of large-insert metagenomic libraries, and the analysis of the resulting genomic fragments. Detailed step-by-step procedures include (1) how to isolate good-quality hmw DNA from soils and mud; (2) how to prepare the DNA for cloning; (3) how to efficiently establish, grow, pick, replicate, and store the large-insert metagenomic fosmid library; and finally, (4) how to screen the library for genes of interest.

Nuclear localisation of endogenous SUMO-1-modified PDGF-C in human thyroid tissue and cell lines.

We investigated post-translational modification and subcellular localisation of endogenous platelet-derived growth factor-C (PDGF-C) in human thyroid papillary carcinomas (PTC), non-neoplastic thyroid tissues, and a selection of cultured cell lines. PDGF-C expressed nuclear localisation in 95% of all tested cell types in culture and in 10% of the thyrocytes from both PTC and non-neoplastic tissue. The cell lines expressed two forms of full-length PDGF-C, approximately 39 and approximately 55 kDa, in cell membrane and cytosol, while the approximately 55 kDa form dominated in the nucleus where it was partly chromatin-associated. The approximately 55 kDa form was post-translationally modified by SUMO-1. The putative PDGF-C SUMOylation site is the surface exposed (314)lysine part of a positively charged loop ((312)RPKTGVRGLHK(322)) with characteristics of a nuclear localisation signal. The tissue thyrocytes expressed a non-SUMOylated approximately 43 kDa and the 55 kDa PDGF-C. The SUMO-1 modified approximately 55 kDa PDGF-C expression was low in PTC where the approximately 43 kDa PDGF-C dominated. This is in contrast to non-neoplastic tissue and cultured cells where the SUMOylated approximately 55 kDa PDGF-C was strongly expressed. Our data provide novel evidence for nuclear localisation of PDGF-C, post-translational modification by SUMOylation and the expression of a novel form of PDGF-C in human papillary thyroid carcinomas.

Platelet-derived growth factor (PDGF)-C, a PDGF family member with a vascular endothelial growth factor-like structure.

Platelet-derived growth factor (PDGF)-C is a novel member of the PDGF family that binds to PDGF alphaalpha and alphabeta receptors. The growth factor domain of PDGF-C (GFD-PDGF-C) was expressed in high yields in Escherichia coli and was purified and refolded from inclusion bodies obtaining a biologically active growth factor with dimeric structure. The GFD-PDGF-C contains 12 cysteine residues, and Ellman assay analysis indicates that it contains three intramonomeric disulfide bonds, which is in accordance with GFD-PDGF-C being a member of the cystine knot superfamily of growth factors. The recombinant GFD-PDGF-C was characterized by CD, fluorescence, NMR, and infrared spectroscopy. Together, our data indicate that GFD-PDGF-C is a highly thermostable protein that contains mostly beta-sheet secondary structure and some (6%) alpha-helix structure. The structural model of PDGF-C, obtained by homology-based molecular modeling using the structural representatives of this family of growth factors, shows that GFD-PDGF-C has a higher structural homology to the vascular endothelial growth factor than to PDGF-B. The modeled structure can give further insights into the function and specificity of this molecule.