Wide distribution of Phycisphaera-like planctomycetes from WD2101 soil group in peatlands and genome analysis of the first cultivated representative

Phycisphaera-like WD2101 ‘soil group’ is one of the as-yet-uncultivated phylogenetic clades within the phylum Planctomycetes. Members of this clade are commonly detected in various terrestrial habitats. This study shows that WD2101 represented one of the major planctomycete groups in 10 boreal peatlands, comprising up to 76% and 36% of all Planctomycetes-affiliated 16S rRNA gene reads in raised bogs and eutrophic fens respectively. These types of peatlands displayed clearly distinct intra-group diversity of WD2101-affiliated planctomycetes. The first isolate of this enigmatic planctomycete group, strain M1803, was obtained from a humic lake surrounded by Sphagnum peat bogs. Strain M1803 displayed 89.2% 16S rRNA gene similarity to Tepidisphaera mucosa and was represented by motile cocci that divided by binary fission and grew under micro-oxic conditions. The complete 7.19 Mb genome of strain M1803 contained an array of genes encoding Planctomycetal type bacterial microcompartment organelle likely involved in l -rhamnose metabolism, suggesting participation of M1803-like planctomycetes in polysaccharide degradation in peatlands. The corresponding cellular microcompartments were revealed in ultrathin cell sections. Strain M1803 was classified as a novel genus and species, Humisphaera borealis gen. nov., sp. nov., affiliated with the formerly recognized WD2101 ‘soil group’.     

Cytological aspects of resistance to potassium tellurite conferred on Pseudomonas cells by plasmids

The ultrastructure of strains Pseudomonas putida BS228 and Pseudomonas aeruginosa ML4262 harboring plasmids pBS10, pBS31, and pBS221, which determine resistance to potassium tellurite, was studied. Bacteria were grown in media containing increasing concentrations of potassium tellurite. Crystalline structures containing tellurium appeared in their periplasmic space. The dynamics of crystal growth was studied. Crystals were released into the medium by pinching off of the outer membrane vesicles containing growing crystals. A possible mechanism of this process was described; cytobiochemical peculiarities were discussed.     

Accumulation of polyunsaturated fatty acids by cladocerans: effects of taxonomy,temperature and food

1. Zooplankton are important in transferring dietary nutrients, including polyunsaturated fatty acids (PUFA), up through aquatic food webs. 2. We tested the hypothesis that the taxonomic composition of zooplankton affects the retention and subsequent transfer of PUFA from upwards through the food web. Using laboratory experiments, we investigated dietary PUFA accumulation and bioconversion capacities of six cladoceran species (Ceriodaphnia sp., Daphnia longispina, Daphnia magna, Daphnia pulex, Scapholeberis mucronata and Simocephalus vetulus) fed on two diets (Scenedesmus obliquus and Cryptomonas sp.) that differed in their PUFA profiles. We performed experiments at two different temperatures (14 and 20 °C) to assess the role of temperature in the trophic transfer of PUFA. 3. There was little variation in the concentrations of PUFA in these cladocerans which were controlled by dietary PUFA supply. Moreover, as expected, the concentrations of PUFA in all cladoceran species were higher at low temperature. 4. However, even if the composition of PUFA in the cladoceran species generally corresponded to that in their diet, preferential accumulation of some PUFA was recorded in all these taxa. When fed on a highly unsaturated fatty acid‐deficient diet, all the cladocerans showed some ability to convert C18‐PUFA into arachidonic acid and eicosapentaenoic acid. Interspecific variation in the ability to accumulate and bioconvert PUFA in cladocerans was more pronounced at low temperature (14 °C) for both diets. 5. Our results strongly suggest that in heterogeneous habitats with food partitioning between co‐existing cladocerans, foraging behaviour may affect the transfer of PUFA more strongly than interspecific variation in accumulating and/or bioconverting dietary PUFA.     

Short‐term effects of CO2 and O2 on citrate metabolism in illuminated leaves

Although there is now a considerable literature on the inhibition of leaf respiration (CO₂ evolution) by light, little is known about the effect of other environmental conditions on day respiratory metabolism. In particular, CO₂ and O₂ mole fractions are assumed to cause changes in the tricarboxylic acid pathway (TCAP) but the amplitude and even the direction of such changes are still a matter of debate. Here, we took advantage of isotopic techniques, new simple equations and instant freeze sampling to follow respiratory metabolism in illuminated cocklebur leaves (Xanthium strumarium L.) under different CO₂/O₂ conditions. Gas exchange coupled to online isotopic analysis showed that CO₂ evolved by leaves in the light came from ‘old’ carbon skeletons and there was a slight decrease in ¹³C natural abundance when [CO₂] increased. This suggested the involvement of enzymatic steps fractionating more strongly against ¹³C and thus increasingly limiting for the metabolic respiratory flux as [CO₂] increased. Isotopic labelling with ¹³C₂‐2,4‐citrate lead to ¹³C‐enriched Glu and 2‐oxoglutarate (2OG), clearly demonstrating poor metabolism of citrate by the TCAP. There was a clear relationship between the ribulose‐1,5‐bisphosphate oxygenation‐to‐carboxylation ratio (v_o/v_c) and the ¹³C commitment to 2OG, demonstrating that 2OG and Glu synthesis via the TCAP is positively influenced by photorespiration.     

Formation of insoluble magnesium phosphates during growth of the archaea Halorubrum distributum and Halobacterium salinarium and the bacterium Brevibacterium antiquum

Stationary phase cells of the halophilic archaea Halobacterium salinarium and Halorubrum distributum, growing at 3-4 M NaCl, and of the halotolerant bacterium Brevibacterium antiquum, growing with and without 2.6 NaCl, took up approximately 90% of the phosphate from the culture media containing 2.3 and 11.5 mM phosphate. The uptake was blocked by the uncoupler FCCP. In B. antiquum, EDTA inhibited the phosphate uptake. The content of polyphosphates in the cells was significantly lower than the content of orthophosphate. At a high phosphate concentration, up to 80% of the phosphate taken up from the culture medium was accumulated as Mg(2)PO(4)OH x 4H(2)O in H. salinarium and H. distributum and as NH(4)MgPO(4) x 6H(2)O in B. antiquum. Consolidation of the cytoplasm and enlargement of the nucleoid zone were observed in the cells during phosphate accumulation. At phosphate surplus, part of the H. salinarium and H. distributum cell population was lysed. The cells of B. antiquum were not lysed and phosphate crystals were observed in the cytoplasm.     

Fluorescence Microscopic Study of Microorganisms Treated with Chaotropic Agents

The yeasts Saccharomyces cerevisiae and Pichia pastoris and the bacteria Micrococcus luteus, Bacillus subtilis, and Anaerobacter polyendosporus have been treated with the chaotropic agents guanidine hydrochloride and guanidine thiocyanate and certain detergents and studied using fluorescence microscopy. Studies with the use of fluorochromes that can selectively stain nucleic acids (diamidino-2-phenylindole (DAPI), propidium iodide, and acridine orange) show that treatment of the bacterial and yeast cells at 37°C for 3–5 h induces a release of DNA from the cytoplasm and its accumulation in the cellular zone, known as ectoplasm, located between the cell wall and the remainder of the cytoplasm (called endoplasm) in the form of one or several large granules. After treating the cells with the chaotropic agents at 100°C for 5–6 min, the DNA is diffusively distributed over the ectoplasm. The fluorochromes used do not allow the detection of RNA. These findings are in agreement with previous data obtained from electron microscopic study of thin cell sections. After 33 PCR cycles, a considerable portion of DNA leaves the cells; as a result, they show a low level of diffusive fluorescence when stained with DAPI. When endospores of B. subtilis are treated with the chaotropic agents, they become highly permeable to the fluorochromes. Fluorescence microscopic study of such endospores shows that they contain DNA in the central part of their cores.__________Translated from Mikrobiologiya, Vol. 74, No. 4, 2005, pp. 505–510.Original Russian Text Copyright © 2005 by Duda, Danilevich, Akimov, Suzina, Dmitriev, Shorokhova.     

Methanotrophs and methylobacteria are found in woody plant tissues within the winter period

Samples of tree seeds, buds, and needles collected within the winter period at ambient temperatures from –11 to –17°C were analyzed for the presence of methylotrophic microflora. Thin sections of blue spruce needles were found to contain bacteria morphologically close to pink-pigmented methylobacteria. The methylobacteria that were isolated in pure cultures from samples of linden seeds and buds and pine and blue spruce needles, as well as of lilac, maple, and apple buds, were classified into the genera Methylobacterium and Paracoccus based on the data of morphological studies, enzyme assay, and DNA-DNA hybridization analysis. The methanotrophs that were isolated in pure cultures from samples of linden buds and blue spruce needles were referred to the genus Methylocystis based on the data of morphological studies, enzyme assay, DNA-DNA hybridization, and the phylogenetic analysis of the particulate methane monooxygenase gene pmoA sequences. The inference is made that aerobic methylotrophic bacteria are permanently associated with plants. At the beginning of the vegetative period in spring, the phyllosphere of coniferous and deciduous trees is colonized by methylotrophic bacteria that have wintered inside plant tissues.Translated from Mikrobiologiya, Vol. 73, No. 6, 2004, pp. 817–824.Original Russian Text Copyright © 2004 by Doronina, Ivanova, Suzina, Trotsenko.     

Methanotrophs and methylobacteria are found in woody plant tissues within a winter period

Samples of tree seeds, buds, and needles collected within a winter period at ambient temperatures from -11 to -17 degrees C were analyzed for the presence of methylotrophic microflora. Thin sections of blue spruce needles were found to contain bacteria morphologically close to pink-pigmented methylobacteria. The methylobacteria that were isolated in pure cultures from samples of linden seeds and buds, pine and blue spruce needles, as well as of lilac, maple, and apple buds, were classified into the genera Methylobacterium and Paracoccus based on the data of morphological studies, enzyme assay, and DNA-DNA hybridization analysis. The methanotrophs that were isolated in pure cultures from samples of linden buds and blue spruce needles were identified into the genus Methylocystis based on the data of morphological studies, enzyme assay, DNA-DNA hybridization, and the phylogenetic analysis of the particulate methane monooxygenase gene pmoA sequences. The inference is made that aerobic methylotrophic bacteria are permanently associated with plants. At the beginning of the vegetative period in spring, the phyllosphere of coniferous and deciduous trees is colonized by the methylotrophic bacteria that have wintered inside plant tissues.