Cationic penetrating antioxidants switch off Mn cluster of photosystem II in situ.

Mitochondria-targeted antioxidants (also known as 'Skulachev Ions' electrophoretically accumulated by mitochondria) exert anti-ageing and ROS-protecting effects well documented in animal and human cells. However, their effects on chloroplast in photosynthetic cells and corresponding mechanisms are scarcely known. For the first time, we describe a dramatic quenching effect of (10-(6-plastoquinonyl)decyl triphenylphosphonium (SkQ1) on chlorophyll fluorescence, apparently mediated by redox interaction of SkQ1 with Mn cluster in Photosystem II (PSII) of chlorophyte microalga Chlorella vulgaris and disabling the oxygen-evolving complex (OEC). Microalgal cells displayed a vigorous uptake of SkQ1 which internal concentration built up to a very high level. Using optical and EPR spectroscopy, as well as electron donors and in silico molecular simulation techniques, we found that SkQ1 molecule can interact with Mn atoms of the OEC in PSII. This stops water splitting giving rise to potent quencher(s), e.g. oxidized reaction centre of PSII. Other components of the photosynthetic apparatus proved to be mostly intact. This effect of the Skulachev ions might help to develop in vivo models of photosynthetic cells with impaired OEC function but essentially intact otherwise. The observed phenomenon suggests that SkQ1 can be applied to study stress-induced damages to OEC in photosynthetic organisms.

Fimbriiglobus ruber gen. nov., sp. nov., a Gemmata-like planctomycete from Sphagnum peat bog and the proposal of Gemmataceae fam. nov.

An aerobic, budding, dark pink to red-pigmented bacterium was isolated from an acidic boreal Sphagnum peat bog and designated strain SP5T. Cells of this strain were non-motile spheres that were uniformly covered with crateriform pits and fimbria, and tended to form aggregates during growth in liquid media. Strain SP5T was capable of growth between pH 4.0 and pH 6.8 (optimum at pH 5.5-6.0) and at temperatures between 10 and 30 °C (optimum at 20-25 °C). The preferred growth substrates were sugars and some heteropolysaccharides. The major fatty acids were C20 : 1ω9c, C16 : 1ω9c and C16 : 0, and the major polar lipid was trimethylornithine. Cells contained also significant amounts of bound (ω-1)OH-C30 : 1 fatty acid. The quinone was menaquinone-6, and the G+C content of the DNA was 60.7 mol%. Strain SP5T was a member of the order Planctomycetales and belonged to the phylogenetic lineage defined by the genus Gemmata. It displayed 88 and 89 % 16S rRNA gene sequence similarity to Gemmata obscuriglobusUQM 2246T and 'Gemmata massiliana' IIL30, 89 % to Zavarzinella formosa A10T and 86 % to Telmatocola sphagniphila SP2T. However, strain SP5T differed from members of these genera by cell morphology, substrate utilization pattern and fatty acid composition. Based on these data, the novel isolate should be considered as representing a novel species of a new genus of planctomycetes, for which the name Fimbriiglobus ruber gen. nov., sp. nov, is proposed. The type strain is SP5T (=LMG 29572T=VKM B-3045T). We also suggest the establishment of a novel family, Gemmataceaefam. nov., which includes the phylogenetically related genera Gemmata, Zavarzinella, Telmatocola and Fimbriiglobus.

Similarity and diversity of the Desmodesmus spp. microalgae isolated from associations with White Sea invertebrates.

Similarity and diversity of the phenotype and nucleotide sequences of certain genome loci among the single-celled microalgae isolated from White Sea benthic invertebrates were studied to extend the knowledge of oxygenic photoautotrophs forming microbial communities associated with animals. We compared four Desmodesmus isolates (1Hp86E-2, 1Pm66B, 3Dp86E-1, 2Cl66E) from the sponge Halichondria panicea, trochophore larvae of the polychaete Phyllodoce maculata, and the hydroids Dynamena pumila and Coryne lovenii, respectively. The microalgae appeared to be very similar featuring the phenotypic and genetic traits characteristics of unicellular representatives of the genus Desmodesmus. At the same time, isolates from different animal species displayed certain differences in (i) the epistructure morphology; (ii) type and number of the inclusions such as interthylakoid starch grains and cytoplasmic oil bodies and (iii) fatty acid composition; in Desmodesmus sp. 1Hp86E-2, these differences were most pronounced. Phylogenetic analysis based on ITS1-5.8S rRNA-ITS2 and rbcL sequences showed that all isolates studied differ from known classified representatives of Desmodesmus combining a deletion in the conservative 5.8S rRNA gene and long AC-microsatellite repeats in the ITS1 whereas 1Hp86E-2 represented a distinct branch within this group.

Zavarzinella formosa gen. nov., sp. nov., a novel stalked, Gemmata-like planctomycete from a Siberian peat bog.

An aerobic, pink-pigmented, budding and rosette-forming bacterium was isolated from an acidic Sphagnum peat bog and designated strain A10(T). The 16S rRNA gene sequence analysis showed that strain A10(T) was a member of the order Planctomycetales and belonged to a phylogenetic lineage defined by the genus Gemmata, with 90 % sequence similarity to that of Gemmata obscuriglobus, the only taxonomically described organism of this group. Ellipsoid-shaped cells of strain A10(T) were uniformly covered with crateriform pits and possessed long (up to 10-15 mum) and unusually thick (0.5-0.7 mum) stalks of a unique ultrastructure. Thin sections revealed a complex intracellular membrane system compartmentalizing the cells. Strain A10(T) was a moderately acidophilic, mesophilic organism capable of growth at pH values between 3.8 and 7.2 (with an optimum at pH 5.5-6.0) and at temperatures between 10 and 30 degrees C (with an optimum at 20-25 degrees C). The major fatty acids were C(18 : 0), C(18 : 1)omega5c and C(16 : 1)omega5c and the major quinone was MK-6. Cells of strain A10(T) contained high amounts of bound saturated and monounsaturated C(26)-C(32) (omega-1) hydroxy fatty acids. The G+C content of the DNA was 62.5 mol%. The unique cell morphology, the capability of growth in acidic conditions and a number of chemotaxonomic and genotypic characteristics served to differentiate strain A10(T) from G. obscuriglobus. Based on these data, the novel isolate should be considered as representing a novel genus and species of planctomycetes, for which the name Zavarzinella formosa gen. nov., sp. nov. is proposed The type strain is A10(T) (=DSM 19928(T)=VKM B-2478(T)).

Singulisphaera acidiphila gen. nov., sp. nov., a non-filamentous, Isosphaera-like planctomycete from acidic northern wetlands.

Four novel strains of budding bacteria, designated MOB10T, PO2, MPL1015 and BG32, were isolated from acidic wetlands of northern Russia. Cells of these four strains were aerobic, non-motile spheres that occurred singly or in shapeless aggregates and attached to surfaces by means of a holdfast material. The isolates were moderately acidophilic, mesophilic organisms capable of growth between pH 4.2 and 7.5 (optimum growth at pH 5.0-6.2) and at temperatures between 4 and 33 degrees C (optimum growth at 20-26 degrees C). The strains possessed a complex intracellular membrane system that compartmentalized the cells. The major fatty acids were C16 : 0, C18 : 1omega9c and C18 : 2omega6c,12c. The major quinone was menaquinone-6 (MK-6). The G+C content of the DNA was 57.8-59.9 mol%. 16S rRNA gene sequence analysis showed that strains MOB10T, PO2, MPL1015 and BG32 were members of the order Planctomycetales and belonged to a phylogenetic lineage defined by the genus Isosphaera, exhibiting 90 % sequence similarity to the type strain of the thermophilic planctomycete Isosphaera pallida and 95-95.5 % sequence similarity to a taxonomically uncharacterized group of filamentous bacteria from activated sludge, 'Nostocoida limicola' III. However, compared with 'Nostocoida limicola' III and Isosphaera pallida, the new isolates from acidic wetlands were non-filamentous, unpigmented bacteria, which possessed highly distinctive phospholipid fatty acid profiles and were capable of growth and of degrading several biopolymers under acidic, microaerobic and cold conditions. The data suggest that the four isolates should be considered as representing a novel species of a new genus of the order Planctomycetales, for which the name Singulisphaera acidiphila gen. nov., sp. nov. is proposed. The type strain of Singulisphaera acidiphila is MOB10T (=ATCC BAA-1392T =VKM B-2454T =DSM 18658T).

Schlesneria paludicola gen. nov., sp. nov., the first acidophilic member of the order Planctomycetales, from Sphagnum-dominated boreal wetlands.

Three strains of budding, ellipsoid-shaped and rosette-forming bacteria were isolated from acidic Sphagnum-dominated boreal wetlands of northern Russia and were designated strains MPL7T, MOB77 and SB2. The presence of crateriform pits and numerous fibrillar appendages on the cell surface and an unusual spur-like projection on one pole of the cell indicated a planctomycete morphotype. These isolates are moderately acidophilic, mesophilic organisms capable of growth at pH values between 4.2 and 7.5 (with an optimum at pH 5.0-6.2) and at temperatures between 4 and 32 degrees C (optimum 15-26 degrees C). The major fatty acids are C16:0 and C16:1omega7c; the major quinone is MK-6. The G+C content of the DNA is 54.4-56.5 mol%. Strains MPL7T, MOB77 and SB2 possess nearly identical 16S rRNA gene sequences and belong to the planctomycete lineage defined by the genus Planctomyces, being most closely related to Planctomyces limnophilus DSM 3776T (86.9-87.1% sequence similarity). However, strain MPL7T showed only 28% DNA-DNA hybridization with P. limnophilus DSM 3776T. Compared with currently described members of the genus Planctomyces, the isolates from northern wetlands do not form long and distinctive stalks, have greater tolerance of acidic conditions and low temperatures, are more sensitive to NaCl, lack pigmentation and degrade a wider range of biopolymers. The data therefore suggest that strains MPL7T, MOB77 and SB2 represent a novel genus and species, for which the name Schlesneria paludicola gen. nov., sp. nov., is proposed. Strain MPL7T (=ATCC BAA-1393T=VKM B-2452T) is the type strain of Schlesneria paludicola.