Mineralization dynamics in fallow dryland wheat plots,Colorado

Summary There was a flush of mineralization in fallow wheat plots in the wet and warm summer of 1982 at Akron, Colorado. Peak mineralization rates and concentrations of N and P coincided with a 2.5-fold increase in protozoan biomass. No-till contained considerably more activity than stubble mulch plots, especially in the surface 2.5 cm and there was more water storage in no-till on all dates. Differential management of agricultural residues and the resultant effects upon the microbial community significantly altered patterns of nutrient cycling.     

Regulation of carbon and electron flow in Propionispira arboris: physiological function of hydrogenase and its role in homopropionate formation

Abstract Hydrogenase activity was characterized in cell extracts of Propionispira arboris that consumed or produced H₂, coupled to methyl viologen reduction, and displayed highest levels (2.6 μmol/min/mg protein) in extracts prepared from fumarate-grown cells. Reversible hydrogenase activity in cell extracts correlated with the production of low levels of hydrogen during the growth phase and its subsequent consumption during the stationary phase of cells grown on glucose or lactate as the carbon and energy source. The addition of exogenous hydrogen to glucose, lactate or fumarate-grown cells dramatically increased propionate production at the expense of acetate formation. This accounted for the formation of propionate as nearly the sole end product of glucose fermentation under two atmospheres of hydrogen. The physiological function of hydrogenase in regulation of carbon and electron flow, and the significance of the results in applied and environmental microbiology are discussed.     

Bryophyte evolution and geography

The three extant Divisions comprising the bryophytes extend, as fossils, well back into Palaeozoic time. Bryophyte origin is part of the rise of terrestrial, vascularized, plants with sporopollenin-walled spores in the Silurian. Before the end of Carboniferous time, bryophyte lines were widely present. Separation of Gondwana and Laurasia by the Permian Tethys Sea and subsequent widespread desert episodes fragmented an already diversified bryoflora subjecting it to intense selective pressure. The cool, mesic climate of southern Gondwana provided a refugium for austral bryophytes. Warmer and drier climates of the Permo-Triassic Laurentian-Laurasia favoured drought-adapted or niche-specific groups creating marked systematic discontinuities. The Angaran wet, probably cool, temperate region provided refuge for basic stock for much of today's rich holarctic and wet ‘tropical’ bryofloras. Climatic changes, correlated with tectonic events and the rise of angiosperms, opened habitats favourable for a diversity explosion. Despite demonstrated potential for long-distance dispersal, modern distributions are mostly linked with total floras or establishment on islands prior to niche saturation. Remnants of Gondwanan bryoflora persist in high southern latitudes as disjunctions with the possibility that the folded ranges of the African Cape have been an insular fragment at higher latitudes becoming attached shortly after angiosperm diversification. Floras of southern India and east Africa have common features but the Himalayan flora shows evidence that the Gondwanan flora of the Indian plate was lost during the movement through desert and tropical latitudes; neotropical and palaeotropical floras are distinctive. Much of the northern Australian bryoflora is recently Malesian-derived while the southeast shows strong austral influence and commonality with New Zealand. Tropical Pacific island floras are mostly Malesian-derived but with both holarctic and austral elements present as in Hawaii and the Society Islands. Holarctic bryoflora is circum-polar with temperate areas of Euro-American and far eastern elements floristically bound by disjunct and vicariad species. Kroeber Coefficients of Correlation differ as Pacific island floras are compared and Guttman-Lingoes Smallest Space Coordinates indicates floristic subgroups within Polynesia. Although these and other mathematical treatments yield potentially promising results, the methods are yet unrefined and there is some uncertainty whether characteristics of numbers or of organisms are implicit in the summations.     

The biogeography of Lessoniaceae,with special reference to Macrocystis C. Agardh (Phaeophyta: Laminariales)

The bipolar distributions of Lessoniaceae and Macrocystis have been explained by migration out of a ‘centre of origin’ and across the tropics by means of dispersal, but controversy centres on the issue: which sector is the true centre of origin? We provide biological, palaeo-oceanographic and geological evidence that leads us to reject the centre of origin/migration theory and methodology in explaining ‘bipolarity’. As an alternative, a process of vicariant differentiation out of a Pacific Ocean/Southern Ocean ancestral complex is proposed. Moreover the biogeographic relationship between the southwest and northeast Pacific is shown to be a general phenomenon and not restricted to marine algae.     

The benthic deep-water siphonophore Rhodalia miranda and other coelenterates in the south-west Atlantic: ecological and oceanographical implications

The benthic deep-water siphonophore Rhodalia miranda was collected for the first time in 1876 by H.M.S. Challenger off the Rio de la Plata estuary beneath the Subtropical Convergence at about 1000 m depth. Rhodalia was reported again about 100 years later from certain distant localities in the subantarctic region of the south-west Atlantic. Hydrographic and topographic features that may be involved in creating this peculiar distribution pattern are discussed together with a likely mode of dispersal of benthic coelenterates. The disjunct distribution of Rhodalia and other benthos of the upper Argentine Slope suggests the subsurface oceanographic régime to be quite different from what we know of the surface layers.     

Cladocera and free-living Copepoda from the Fouta Djalon and adjacent mountain areas in West Africa

Thirty-two species of Cladocera and 27 species of free-living copepods were identified in a series of samples collected in 25 localities in and around the Fouta Djalon mountains, West Africa. Beside great richness in numbers of species, the nature of the fauna is noteworthy: at least 20% of the Cladocera and 50% of the copepods are endemic to West Africa. Possible palaeoclimatological reasons for this are discussed. The cladoceran genus Streblocerus is recorded from Africa for the first time. It is an element of northern origin in the fauna of West Africa. More examples of this kind are documented among the Copepoda Cyclopoida and Harpacticoida, but the bulk of the fauna is evidently of tropical origin. In particular, great adaptive radiation is occurring in the local representatives of the genus Tropocyclops. Three new species of Parastenocaris are described; they are the first representatives of this genus found in West Africa.     

高、低营养水平饲粮对环江香猪结肠菌群结构及代谢物的影响

【目的】研究两种饲粮对环江香猪结肠内容物菌群结构及其代谢物的影响。【方法】选用33.5±8.1 kg的环江香猪10头,随机分为两组,每组5头猪,单栏饲养,分别饲喂高营养水平饲粮(粗蛋白质含量为13.11%,消化能为14.73 MJ/kg)和低营养水平饲粮(粗蛋白质含量为9.77%,消化能为12.24 MJ/kg)。饲喂75 d后屠宰,每组选3头猪采集结肠内容物提取细菌总DNA,PCR扩增获得16S r RNA基因V4标签片段,用于Mi Seq高通量测序,基于QIIME平台比较结肠内容物菌群结构多样性;每组取5头猪的结肠内容物,利用气相色谱和液相色谱分析其中短链脂肪酸、氨氮、生物胺、吲哚和粪臭素的含量。【结果】硬壁菌门、拟杆菌门、螺旋体门和软壁菌门细菌为环江香猪结肠内容物中的优势菌门;饲粮组成不影响环江香猪结肠内容物菌群结构的多样性,高营养水平饲粮组结肠内容物中广古细菌含量显著低于、瘤胃球菌属和假丁酸弧菌属细菌含量显著高于低营养水平饲粮组;高营养水平饲粮组环江香猪结肠内容物中乙酸和丙酸含量显著低于、氨氮和尸胺含量显著高于低营养水平饲粮组。【结论】硬壁菌门、拟杆菌门、螺旋体门和软壁菌门细菌为环江香猪结肠内容物中的优势菌门,短期饲喂高营养水平饲粮可改变环江香猪结肠中的部分微生物含量及其代谢特性。     

模型动物中的肠道菌群分析及微生物组研究

正肠道菌群与多种疾病密切相关,从消化道疾病(如炎症性肠病)、心脑血管疾病(如动脉粥样硬化)到代谢类疾病(如II型糖尿病)和许多免疫性疾病(如风湿性关节炎),肠道菌群研究为诸多疾病研究和防治开辟了新的方向[1-3]。在肠道菌群研究领域,模型动物应用和实验结果的动物实验验证非常重要,本刊2016年第7期刊登的姬玉娇、孔祥峰等的论文"高、低营养水平饲粮对环江香猪结肠菌群结构及代谢物的影响"[4],通过对高、     

青藏高原微生物多样性研究

正青藏高原被誉为世界屋脊,其内部除平原外还有许多山峰、冰川、高山湖泊和高山沼泽,是生态环境最为奇特、生物资源最为丰富的自然资源宝库之一。同时,青藏高原的微生物群落结构及其多样性与其他区域存在巨大差异,因而具有极高的科学研究价值,并逐渐被人们所关注。研究发现气候变化对青藏高原高寒草地生态系统草丛-地境界面微生物会产生重要的影响[1]。冰川雪藻的研究主要在南部的Yala冰川开展,