Phanerozoic stromatolites: noncompetitive ecologic restriction by grazing and burrowing animals

The abundance of stromatolites (algal laminated sedimentary structures) in the Precambrian followed by a decline in the Phanerozoic is explained by the evolution and diversification during the Phanerozoic of grazing animals which feed on surface algal mats and of burrowing animals which destroy sedimentary laminations.     

Microfossils in conophyton from the soviet union and their bearing on precambrian biostratigraphy

Silicified specimens of the Vendian (late Precambrian) "index fossil" Conophyton gaubitza from South Kazakstan contain a diverse assemblage of well-preserved cyanophytic and apparently eukaryotic algae, the first stromatolitic microbiota to be reported from the Soviet Union. Unlike the stromatolites in which they occur, the microorganisms that apparently built this form of Conophyton did not become extinct at the end of the Precambrian.     

Algal stromatolites: deepwater forms in the devonian of Western australia

A diverse assemblage of algal stromatolites occurs in Devonian reef complexes of the Canning Basin, Western Australia. Some forms grew on fore-reef depositional slopes down to at least 45 meters below sea level and are believed to be products of deepwater nonskeletal algae. It is concluded that algal stromatolites in the stratigraphic record are not to be regarded as diagnostic evidence for deposition in very shallow water.     

Algal stromatolites: use in stratigraphic correlation and paleocurrent determination

Algal stromatolites are used for detailed rock-stratigraphic correlation for a distance of 160 kilometers in the Pethei Formation, of Aphebian (Precambrian) age, in the Northwest Territories, Canada. Laterally linked stromatolites are initiated by the draping of successive laminations over intraclasts or other irregularities in the bedding surface. Stromatolite shapes and orientations are related to paleocurrent direction determined from associated sedimentary structures. Thus stromatolite geometry is at least in part environmentally controlled.     

Precambrian columnar stromatolites in australia: morphological and stratigraphic analysis

The stratigraphic distribution in Australian Precambrian rocks of columnar stromatolites, organosedimentary structures formed by blue-green algae, has been investigated. Their morphology is being studied according to methods developed in Russia. The discovery of successive different assemblages supports not only regional but also intercontinental stratigraphic correlations which are in agreement with available isotopic datings.     

Precambrian columnar stromatolite diversity: reflection of metazoan appearance

Columnar stromatolites (organosedimentary structures built by bluegreen algae) show a marked decrease in diversity in the Late Precambrian; this decrease in diversity occurs at approximately the same time as the appearance of metazoans, 600 to 700 million years ago.     

Photosynthesis-induced biofilm calcification and calcium concentrations in Phanerozoic oceans

Photosynthetic carbon assimilation is commonly invoked as the cause of calcium carbonate precipitation in cyanobacterial biofilms that results in the formation of calcareous stromatolites. However, biofilm calcification patterns in recent lakes and simulation of photosynthetically induced rise in calcium carbonate supersaturation demonstrate that this mechanism applies only in settings low in dissolved inorganic carbon and high in calcium. Taking into account paleo-partial pressure curves for carbon dioxide, we show that Phanerozoic oceans sustaining calcified cyanobacteria must have had considerably higher calcium concentrations than oceans of today. In turn, the enigmatic lack of calcified cyanobacteria in stromatolite-bearing Precambrian sequences can now be explained as a result of high dissolved inorganic carbon concentrations.     

Algal fossils from a late precambrian, hypersaline lagoon

Organically preserved algal microfossils from the Ringwood evaporite deposit in the Gillen Member of the Bitter Springs Formation (late Precambrian of central Australia) are of small size, low diversity, and probable prokaryotic affinities. These rather primitive characteristics appear to reflect the stressful conditions that prevailed in a periodically stagnant, hypersaline lagoon. This assemblage (especially in comparison with the much more diverse assemblages preserved in the Loves Creek Member of the same formation) illustrates the potential utility of Proterozoic microbiotas for basin analysis and local stratigraphic correlation and demonstrates the need to base evolutionary considerations and Precambrian intercontinental biostratigraphy on biotas that inhabited less restricted environments.     

Heliotropism in modern stromatolites

Modern microbial mats and stromatolites exhibiting a preferred orientation toward specular sunlight were found at two sites. In Hamelin Pool of Shark Bay, Western Australia, subtidal decimeter-sized columns and intertidal centimeter-sized tufts were found pointing north. In thermal spring effluents and pools of Yellowstone National Park, mats were found with columnar and conical centimeter-sized structures inclined to the south. These examples of heliotropism in modern stromatolites are each built by a different community of photosynthetic microbes under markedly different environmental conditions. These new observations support the proposal that stromatolites can orient themselves toward the sun.     

温湿度对云南潞江坝幼龄胡椒生长量及发病率的影响

[目的]探讨温度和湿度对胡椒生长特性及发病率的影响。[方法]于2011年3月至2012年2月在云南保山潞江坝胡椒试验示范基地研究了大气温度和湿度对胡椒生长量及主要病害发病率的影响。[结果]在5～10月温湿度绝对值相对大时,胡椒生长变化量较大,且在这高温高湿的月份胡椒细菌性叶斑病、叶斑病、藻斑病及炭疽病发生也较严重,发病率最高分别达44.0%、46.4%、17.7%和25.5%;在11月至次年2月温湿度绝对值相对小时,胡椒生长变化量较小,且在这低温低湿的月份胡椒细菌性叶斑病、叶斑病、藻斑病及炭疽病发病程度也较小,发病率分别达4.0%、9.5%、0.7%和6.3%。[结论]温度和湿度均对胡椒生长特性及发病率有一定影响。     

水库温排水增温模拟及其对富营养化影响分析

温排水导致的水库增温及衍生富营养化是水库生态学领域的研究热点。以承纳温排水的北方某浅水水库为例,利用MIKE21模型构建平面二维水温模拟模型,针对可能出现的调水量和气温极端情况,设定4个情景,分别模拟不同情景下水库水温时空分布规律,对温升带来的富营养化及水华爆发风险进行了分析。结论如下:(1)受温排水口位置、温排水流向及水深共同影响,水库水温呈西高东低,北高南低的分布规律;(2)气温对水库水温的影响较水深更为强烈,取水口1处水域年均温升最大,取水口1和取水口2处水域温升波动较大;(3)调水量和气温等条件变化会导致水华爆发风险变化:除取水口2附近水域外,相对于情景1,情景2和情景3高风险发生时间提前一个月;情景4增温幅度较大,导致东支和取水口1附近高风险延续时段比情景1短一个月。     

水稻种子内生泛菌促进小球藻生长和油脂积累

【目的】从水稻种子中分离出优势内生菌,研究其对小球藻生长、生化组分及油脂积累的影响,探索植物内生菌作为促进微藻生长和生化品质改良的新微生物资源的可行性。【方法】以收获自大田的粳稻品种日本晴种子为试验材料,采用传统表面消毒法分离获得内生菌。内生菌的鉴定采用形态观察和16S rDNA序列分析法。以蛋白核小球藻为研究对象,采用共培养法评估内生菌对小球藻生长及生化指标的影响,以纯藻为对照,将内生菌与蛋白核小球藻种子细胞按菌藻比（10﹕1）接种至BG11培养基进行共培养。采用血球板计数法测定藻细胞数目。同时以纯菌培养为对照,采用平板稀释菌落计数法测定菌藻共培养体系中菌浓的变化曲线。小球藻细胞中叶绿素a和类胡萝卜素的提取采用甲醇浸提法,定量测定采用紫外分光光度法。小球藻油脂提取采用氯仿甲醇浸提法,脂肪酸组分分析采用气相色谱-质谱联用法。【结果】分离获得一株在水稻种子中常见且数量较多的内生细菌,编号为REY-1。REY-1为革兰氏阴性短杆状,经16S rDNA鉴定属于泛菌属Pantoea sp.。REY-1与蛋白核小球藻共培养14 d后,菌藻共培养组中藻细胞浓度达到1.15×10⁸ cells/mL,是对照组的1.97倍。菌藻共培养组与纯菌培养对照组中水稻内生泛菌REY-1的浓度均呈现峰谷式变化曲线,但菌藻共培养组中REY-1的菌浓同比显著低于纯菌培养对照组。14 d培养结束时,菌藻共培养组的菌藻比反转为1﹕100,说明REY-1促进蛋白核小球藻的生长,其自身增殖又受到藻细胞的抑制,二者存在显著的互作效应。菌藻共培养组藻细胞叶绿素a和类胡萝卜素总浓度与对照差异不显著,但单细胞叶绿素a和类胡萝卜素含量分别比对照组下降42.58%和42.68%,二者差异均显著。菌藻共培养组藻细胞油脂含量达到细胞干重的29.90%,比对照组增加78.00%,差异显著,油脂产率（2.14 mg·L^-1·d^-1）比对照组增加了1.68倍。2种培养体系中藻细胞脂肪酸主要组分相似,均为棕榈酸（16﹕0）、亚油酸（18﹕2）和亚麻酸（18﹕3）。REY-1共培养处理使藻细胞的单不饱和脂肪酸相对含量比对照增加了32.37%,短链脂肪酸肉豆蔻酸（14﹕0）相对含量比对照增加了2.12倍,差异显著。此外共培养组藻细胞新合成一种长链脂肪酸-芥酸（22﹕1）,相对含量达到藻细胞总脂肪酸的1.68%。【结论】水稻种子内生泛菌REY-1能在BG11培养液中长期存活并与蛋白核小球藻产生互作,显著提高小球藻生物量和油脂含量,大幅提高小球藻油脂产率并影响脂肪酸相对组成比例的生物学效应。水稻种子内生菌可以作为开发小球藻共生菌的优良微生物新资源。     

Native cellulose: a composite of two distinct crystalline forms

Multiplicities in the resonances of chemically equivalent carbons, which appear in the solid-state carbon-13 nuclear magnetic resonance spectra of native celluloses, have been examined at high resolution. The patterns of variation are consistent with the existence of two distinct crystalline forms. One form is dominant in bacterial and algal celluloses, whereas the other is dominant in celluloses from higher plants.     

火锅蘸酱常温贮存过程中的微生物变化的研究

主要研究了火锅蘸酱在常温贮藏期间的微生物生长规律,利用DPS软件,建立Gompertz模型,评价该调味酱的保质期,然后用生产日期相近的两个组的微生物变化验证其是否符合所建立的生长模型。结果表明：该调味酱在12个月的保质期内食用安全,所建模型能有效地拟合在贮藏期间调味酱中细菌总数的动态变化。     

Blue-light-activated histidine kinases: two-component sensors in bacteria

Histidine kinases, used for environmental sensing by bacterial two-component systems, are involved in regulation of bacterial gene expression, chemotaxis, phototaxis, and virulence. Flavin-containing domains function as light-sensory modules in plant and algal phototropins and in fungal blue-light receptors. We have discovered that the prokaryotes Brucella melitensis, Brucella abortus, Erythrobacter litoralis, and Pseudomonas syringae contain light-activated histidine kinases that bind a flavin chromophore and undergo photochemistry indicative of cysteinyl-flavin adduct formation. Infection of macrophages by B. abortus was stimulated by light in the wild type but was limited in photochemically inactive and null mutants, indicating that the flavin-containing histidine kinase functions as a photoreceptor regulating B. abortus virulence.     

毕节地区辣椒有害生物种类调查及主要病虫发生规律

为了摸清毕节地区辣椒有害生物发生种类及主要病虫害发生规律,对该地区辣椒主要种植乡镇开展了有害生物种类调查和主要病虫害发生规律研究.结果表明:毕节地区辣椒有害生物发生种类共计93种.其中,病害23种,虫害16种,草害54种,主要有害生物40种;同时掌握了辣椒猝倒病、立枯病、早疫病、褐斑病、白星病、细菌性叶斑病、疮痂病、疫病、炭疽病、白粉病、病毒病、熠青虫、蚜虫、小地老虎和印度谷螟等主要病虫害的发生规律.     

新型光合菌肥的肥效及增产机理研究

通过田间微区试验,对新型固体光合菌肥在蔬菜作物上的肥效及增产机理进行了研究,结果表明:这种光合菌肥不但可以提高茄子、辣椒和番茄的产量,而且还能降低茄子、辣椒番茄的坏果率。叶面喷施2￣3次光合菌肥,对茄子和辣椒有明显的增产作用,茄子的产量比对照增加39.03%￣43.21%;辣椒的产量比对照增加17.33%￣27.86%。喷施对番茄增产作用不明显。光合菌肥灌根处理对茄子和辣椒不仅没有增产作用,反而还会引起减产。但灌根对番茄增产作用明显,番茄的产量比对照增加11.06%￣15.34%,并且产量有随施用量增加而增加的趋势。此外,茄子、辣椒、番茄用光合菌肥灌根能显著增加耕层土壤中有效氮、磷、钾和铁、锰、铜、锌的含量。     

杀菌剂和生物菌肥混合使用对玉米的影响

玉米播种前用杀菌剂"根复特"和生物菌肥"坤奇尔"混合处理种子,对苗龄满8d幼苗的各项物理和生理指标进行测定,结果表明:该杀菌剂与该生物菌肥混合使用对玉米种子的发芽率和幼苗的生长均有显著的效果.     

Drifting organisms in the precambrian sea

Drag marks in the Upper Precambrian Winnall Beds of central Australia were made by semibuoyant flexible objects at least 15 centimeters long, which presumably were algae. This find extends the range of such marks into the Precambrian era and supplements the discovery of microflora in the same Sedimentary Sequence.     

Hardened subtidal stromatolites, bahamas

Hardened, high-relief stromatolites have been discovered along the margins of some Bahamian platforms. They occur in high-energy (tidal) oolitic sand environments in waters ranging in depth from about 1 to 5 meters. Physical stress produced by actively migrating bed forms of oolitic sand appears to exclude grazing gastropods and subsequent community successions, permitting stromatolite growth.