Latitudinal biodiversity patterns of meiofauna from sandy littoral beaches

Meiofaunal samples from arctic (Bear Island, Franz Josef Land, Hopen, Kolguev), temperate (Baltic Sea, North Sea), subtropical (Tunisia, Greece), tropical (Emirates, Ghana) and antarctic sandy beaches were collected at the medium water mark. The highest average meiofaunal density was found in the temperate zone (1300 individuals 10 cm^–2) and the lowest in both polar regions: in arctic (79 individuals 10 cm^–2) and in antarctic (35 individuals 10 cm^–2) samples. Nematodes dominated the meiofauna community in warm regions, while turbellarians were more common in cold water regions. Sixteen higher taxa were recorded in tropical sites, while only eight taxa were observed in the sampled cold regions. This difference was mainly due to the presence of small specimens of macrofauna in the tropics. When only true meiofauna higher taxa were compared, no latitudinal trends were found.     

Resonance Raman and crystallographic studies on the complex [Fe2(bbpnol)2]·2DMF (bbpnol=N,N′-bis(2-hydroxybenzyl)-2-ol-1,3-propanediamine)

The ligand N,N′-bis(2-hydroxybenzyl)-2-ol-1,3-propanediamine (H₃bbpnol) reacts with iron(III) perchlorate forming two dinuclear bis-μ-alkoxo complexes, a ‘cis-trans’ isomer (complex 1) previously reported and a ‘cis-cis’ isomer (complex 2) characterized in this work. The main differences found in complex 2 structure are, (a) the four phenolic oxygens are trans to the alkoxo bridges; (b) each ligand is shared by the two Fe(III) ions occupying two coordination positions at each center. The Fe(III) centers in the resulting centrosymmetric structure in complex 2 have a distorted-octahedral geometry with the equatorial plane occupied by the phenolic and alcoholic oxygen atoms and the apical positions are filled by the aminic nitrogen atoms. The resonance Raman (RR) spectra of these two isomeric complexes are somewhat different with the intensity of some low-frequency modes increasing in the less symmetric core. The electronic spectra of both complexes are similar, but the molar absorptivities are substantially increased in complex 2, indicating the presence of an electronic coupling between the phenolate moieties trans in relation to the alkoxo bridge, and that phenolates coordinated cis to the alkoxo bridge do not seem to contribute to LMCT oscillator strength. This is directly reflected in the Raman excitation profiles (REP) of the chromophore modes, with the vibrational modes of the ‘cis-cis’ isomer showing a greater intensification compared with the ‘cis-trans’ isomer.     

Human tartrate-resistant acid phosphatase becomes an effective ATPase upon proteolytic activation

Proteolytic cleavage in an exposed loop of human tartrate-resistant acid phosphatase (TRAcP) with trypsin leads to a significant increase in activity. At each pH value between 3.25 and 8.0 the cleaved enzyme is more active. Substrate specificity is also influenced by proteolysis. Only the cleaved form is able to hydrolyze unactivated substrates efficiently, and at pH >6 cleaved TRAcP acquires a marked preference for ATP. The cleaved enzyme also has altered sensitivity to inhibitors. Interestingly, the magnitude and mode of inhibition by fluoride depends not only on the proteolytic state but also pH. The combined kinetic data imply a role of the loop residue D158 in catalysis in the cleaved enzyme. Notably, at low pH this residue may act as a proton donor for the leaving group. In this respect the mechanism of cleaved TRAcP resembles that of sweet potato purple acid phosphatase.     

A gas vesiculate planktonic strain of the purple non-sulfur bacterium Rhodoferax antarcticus isolated from Lake Fryxell, Dry Valleys, Antarctica

A moderately psychrophilic purple non-sulfur bacterium, Rhodoferax antarcticus strain Fryx1, is described. Strain Fryx1 was isolated from the water column under the ice of the permanently frozen Lake Fryxell, Antarctica. Cells of Fryx1 are long thin rods and contain gas vesicles, the first report of such structures in purple non-sulfur bacteria. Gas vesicles are clustered at 2–4 sites per cell. Surprisingly, the 16S rRNA gene sequence of strain Fryx1 is nearly identical to that of Rfx. antarcticus strain AB, a short, vibrio-shaped phototroph isolated from an Antarctic microbial mat. Although showing physiological parallels, strains AB and Fryx1 differ distinctly in their morphology and absorption spectra. DNA–DNA hybridization shows that the genomes of strains AB and Fryx1 are highly related, yet distinct. We conclude that although strains AB and Fryx1 may indeed be the same species, their ecologies are quite different. Unlike strain AB, strain Fryx1 has adapted to a planktonic existence in the nearly freezing water column of Lake Fryxell.Dedicated to Prof. Dr. Hans Günter Schlegel on the occasion of his 80th birthday.     

Horizontal Transfer of the Photosynthesis Gene Cluster and Operon Rearrangement in Purple Bacteria

A 37-kb photosynthesis gene cluster was sequenced in a photosynthetic bacterium belonging to the beta subclass of purple bacteria (Proteobacteria), Rubrivivax gelatinosus. The cluster contained 12 bacteriochlorophyll biosynthesis genes (bch), 7 carotenoid biosynthesis genes (crt), structural genes for photosynthetic apparatuses (puf and puh), and some other related genes. The gene arrangement was markedly different from those of other purple photosynthetic bacteria, while two superoperonal structures, crtEF-bchCXYZ-puf and bchFNBHLM-lhaA-puhA, were conserved. Molecular phylogenetic analyses of these photosynthesis genes showed that the photosynthesis gene cluster of Rvi. gelatinosus was originated from those of the species belonging to the alpha subclass of purple bacteria. It was concluded that a horizontal transfer of the photosynthesis gene cluster from an ancestral species belonging to the alpha subclass to that of the beta subclass of purple bacteria had occurred and was followed by rearrangements of the operons in this cluster.     

The phylogeny of proteobacteria: relationships to other eubacterial phyla and eukaryotes

The evolutionary relationships of proteobacteria, which comprise the largest and phenotypically most diverse division among prokaryotes, are examined based on the analyses of available molecular sequence data. Sequence alignments of different proteins have led to the identification of numerous conserved inserts and deletions (referred to as signature sequences), which either are unique characteristics of various proteobacterial species or are shared by only members from certain subdivisions of proteobacteria. These signature sequences provide molecular means to define the proteobacterial phyla and their various subdivisions and to understand their evolutionary relationships to the other groups of eubacteria as well as the eukaryotes. Based on signature sequences that are present in different proteins it is now possible to infer that the various eubacterial phyla evolved from a common ancestor in the following order: low-G+C Gram-positive-->high-G+C Gram-positive-->Deinococcus-Thermus (green nonsulfur bacteria)-->cyanobacteria-->Spirochetes-->Chlamydia-Cytophaga-Aquifex -green sulfur bacteria-->Proteobacteria-1 (epsilon and delta)-->Proteobacteria-2 (alpha)-->Proteobacteria-3 (beta)-->Proteobacteria-4 (gamma). An unexpected but important aspect of the relationship deduced here is that the main eubacterial phyla are related to each other linearly rather than in a tree-like manner, suggesting that the major evolutionary changes within Bacteria have taken place in a directional manner. The identified signatures permit placement of prokaryotes into different groups/divisions and could be used for determinative purposes. These signatures generally support the origin of mitochondria from an alpha-proteobacterium and provide evidence that the nuclear cytosolic homologs of many genes are also derived from proteobacteria.     

Candidatus "Thiodictyon syntrophicum", sp. nov., a new purple sulfur bacterium isolated from the chemocline of Lake Cadagno forming aggregates and specific associations with Desulfocapsa sp

Strain Cad16(T) is a small-celled purple sulfur bacterium (PSB) isolated from the chemocline of crenogenic meromictic Lake Cadagno, Switzerland. Long term in situ observations showed that Cad16(T) regularly grows in very compact clumps of cells in association with bacteria belonging to the genus Desulfocapsa in a cell-to-cell three dimensional structure. Previously assigned to the genus Lamprocystis, Cad16(T), was here reclassified and assigned to the genus Thiodictyon. Based on comparative 16S rRNA gene sequences analysis, isolate Cad16(T) was closely related to Thiodictyon bacillosum DSM234(T) and Thiodictyon elegans DSM232(T) with sequence similarities of 99.2% and 98.9%, respectively. Moreover, matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis separated Cad16(T) from other PSB genera, Lamprocystis and Thiocystis. Major differences in cell morphology (oval-sphere compared to rod-shaped) and arrangement (no netlike cell aggregates), carotenoid group (presence of okenone instead of rhodopinal), chemolithotrophic growth as well as the ability to form syntrophic associations with a sulfate-reducing bacteria of the genus Desulfocapsa suggested a different species within the genus Thiodictyon. This isolate is therefore proposed and described as Candidatus "Thiodictyon syntrophicum" sp. nov., a provisionally novel species within the genus Thiodictyon.     

Symptomology and etiology of a new disease,yellow stunt,and root rot of standing milkvetch caused by <Emphasis Type="Italic">Embellisia</Emphasis> sp. in Northern China

An Embellisia sp. has been established as the cause of a new disease of the herbaceous perennial forage legume, ‹standing milkvetch’ (Astragalus adsurgens Pall.) in Northern China, which severely reduces plant density and degrades A. adsurgens stands. The disease was common at an experimental location in Gansu Province where it was recognized by the occurrence of stunted plants with reddish-brown stems and yellow and necrotic leaf blades. An Embellisia sp. was isolated from symptomatic stem, leaf blade, petiole, and root tissues at varying frequencies of up to 90%. Single-spore isolates grew very slowly on PCA, PDA, V-8 and, wheat hay decoction agar. Pathogenicity was confirmed by inoculation of seeds, dipping 2-day-old pre-germinated seedlings in inoculum and spraying inoculum on 6-month-old plants. Symptoms on test plants included yellow leaf lesions, brown lesions on stems and petioles, stunted side-shoots with yellow, small, distorted and necrotic leaves, shoot blight, bud death, crown rot, root rot, and plant death. The disease is named as ‹yellow stunt and root rot’ of A. adsurgens to distinguish it from diseases caused by other known pathogens. Embellisia sp. is also pathogenic to A. sinicus but not to 11 other tested plant species.     

<Emphasis Type="Italic">Thiocapsa imhoffii</Emphasis>, sp. nov., an alkaliphilic purple sulfur bacterium of the family <Emphasis Type="Italic">Chromatiaceae</Emphasis> from Soap Lake,Washington (USA)

An alkaliphilic purple sulfur bacterium, strain SC5, was isolated from Soap Lake, a soda lake located in east central Washington state (USA). Cells of strain SC5 were gram-negative, non-motile, and non-gas vesiculate cocci, often observed in pairs or tetrads. In the presence of sulfide, elemental sulfur was deposited internally. Liquid cultures were pink to rose red in color. Cells contained bacteriochlorophyll a and spirilloxanthin as major photosynthetic pigments. Internal photosynthetic membranes were of the vesicular type. Optimal growth of strain SC5 occurred in the absence of NaCl (range 0–4%), pH 8.5 (range pH 7.5–9.5), and 32°C. Photoheterotrophic growth occurred in the presence of sulfide or thiosulfate with only a limited number of organic carbon sources. Growth factors were not required, and cells could fix N₂. Dark, microaerobic growth occurred in the presence of both an organic carbon source and thiosulfate. Sulfide and thiosulfate served as electron donors for photoautotrophy, which required elevated levels of CO₂. Phylogenetic analysis placed strain SC5 basal to the clade of the genus Thiocapsa in the family Chromatiaceae with a 96.7% sequence similarity to its closest relative, Thiocapsa roseopersicina strain 1711^T (DSM217^T). The unique assemblage of physiological and phylogenetic properties of strain SC5 defines it as a new species of the genus Thiocapsa, and we describe strain SC5 herein as Tca. imhoffii, sp. nov.