陕北黄土高原生物结皮中7种微藻的形态与分子生物学鉴定

陕北黄土高原实施退耕还林后,生物结皮成为其典型的地表覆盖类型,含有丰富的土生藻类,对固定土壤和促进养分循环具有极其重要的作用。该研究通过平板法与水滴稀释法对陕北黄土高原生物结皮土生藻类进行分离培养,采用光学显微镜观察结皮微藻的形态特征,并对单藻种进行分子鉴定,为黄土高原生物结皮藻类的研究奠定基础。结果显示:(1)共纯化获得7种结皮藻类,经光学显微镜初步确定,其中5株为绿藻、2株为蓝藻。(2)5株绿藻SM-2-1、DB-2-1、DB-2-2、SD-1和SD-2的序列长度分别为664 bp、663 bp、662 bp、589 bp和688 bp, GC含量分别为33.43%、49.47%、50.15%、50.76%和51.01%;2株蓝藻YJ-3、YJ-2的序列长度分别为570 bp和465 bp, GC含量分别为46.31%和49.03%。(3)序列比对并构建系统树分析发现,5株结皮绿藻可分为4个分支,分别为栅藻科(Scenedesmaceae)2株(DB-2-1和SM-2-1)、衣藻目(Chlamydomonadales)、环藻科(Sphaeropleaceae)、真眼点藻科(Eust...     

Preliminary studies of cyanobacteria, picoplankton, and virioplankton in the Salton Sea with special attention to phylogenetic diversity among eight strains of filamentous cyanobacteria

Cyanobacterial diversity in the Salton Sea, a high-salinity, eutrophic lake in Southern California, was investigated using a combination of molecular and morphological approaches. Representatives of a total of 10 described genera (Oscillatoria, Spirulina, Arthrospira, Geitlerinema, Lyngbya, Leptolyngbya, Calothrix, Rivularia, Synechococcus, Synechocystis) were identified in the samples; additionally, the morphology of two cultured strains do not conform to any genus recognized at present by the bacteriological system. Genetic analysis, based on partial 16S rRNA sequences suggested considerable cryptic genetic variability among filamentous strains of similar or identical morphology and showed members of the form-genus Geitlerinema to be distributed among three major phylogenetic clades of cyanobacteria. Cyanobacterial mats, previously described from the Sea were, in fact, composed of both filamentous cyanobacteria and a roughly equivalent biomass of the sulfur-oxidizing bacterium Beggiatoa, indicating their formation in sulfide rich regions of the lake. Flow cytometric analysis of the water samples showed three striking differences between samples from the Salton Sea and representative marine waters: (1) phycoerythrin-containing unicells, while abundant, were much less abundant in the Salton Sea than they were in typical continental shelf waters, (2) Prochlorococcus appears to be completely absent, and (3) small (3–5 m) eukaryotic algae were more abundant in the Salton Sea than in typical neritic waters by one-to-two orders-of-magnitude. Based on flow cytometric analysis, heterotrophic bacteria were more than an order of magnitude more abundant in the Salton Sea than in seawater collected from continental shelf environments. Virus particles were more abundant in the Salton Sea than in typical neritic waters, but did not show increases proportionate with the increase in bacteria, picocyanobacteria, or eukaryotic algae.     

A Novel Epiphytic Chlorophyll d‐containing Cyanobacterium Isolated from a Mangrove‐associated Red Alga

A new habitat and a new chlorophyll (Chl) d‐containing cyanobacterium belonging to the genus Acaryochloris are reported in this study. Hyperspectral microscopy showed the presence of Chl d‐containing microorganisms in epiphytic biofilms on a red alga (Gelidium caulacantheum) colonizing the pneumato‐phores of a temperate mangrove (Avicennia marina). The presence of Chl d was further proven by high performance liquid chromatography (HPLC)‐based pigment analysis and by confocal imaging of cultured cells. Enrichment of mangrove biofilm samples under near‐infrared radiation (NIR) yielded the new Acaryochloris sp. MPGRS1, which was closely related in terms of 16S rRNA gene sequence to an isolate from the hypertrophic Salton Sea, USA. The new isolate used Chl d as its major photopigment; Chl d and Chl a contents were ~98% and 1%–2% of total cellular chlorophyll, respectively. These findings expand the variety of ecological niches known to harbor Chl d‐containing cyanobacteria and support our working hypothesis that such oxyphototrophs may be ubiquitous in habitats depleted of visible light, but with sufficient NIR exposure.     

History of the genus <Emphasis Type="Italic">Didacna</Emphasis> (Bivalvia: Cardiidae)

The history of the Quaternary genus Didacna, which is endemic to the Ponto-Caspian Sea, is discussed. Quaternary stratigraphy of this region and Didacna assemblages recorded in the Neopleistocene sequence are characterized. The development of this genus against the background of the Ponto-Caspian history is reconstructed; the replacement of species and associations of Didacna, the character of speciation, and examples of homeomorphism are discussed. Seventy-seven species of this genus, which appeared over slightly more than 600 thousand years, are described; this indicates an extremely intense speciation in Pleistocene brackish-water basins, which were inhabited by only five bivalve genera belonging to two families.     

<Emphasis Type="Italic">Alona alsafadii</Emphasis> n. sp. from Yemen,a primitive,groundwater-dwelling member of the <Emphasis Type="Italic">A. karua</Emphasis>-group

The effect of algae on the production of musty-smelling compounds by actinomycetes was studied. Streptomyces spp., causing intensive musty odor, were isolated from hypertrophic Lake Kasumigaura and cultured in association with algae from the same lake. Isolate E and I effectively utilized the cyanobacteria, Microcystis aeruginosa and Anabaena spiroides, and the diatom, Synedra acus, as a carbon source and produced a musty-smelling 2-methylisoborneol in the shaken sediment cultures. High populations of algae and actinomycetes, and aerobic condition in the sediment seem responsible for the occurrence of musty odor in Lake Kasumigaura.     

Morphological analysis and taxonomical status of four fish species of the genera <Emphasis Type="Italic">Opisthocentrus</Emphasis> and <Emphasis Type="Italic">Pholidapus</Emphasis> (Perciformes: Stichaeidae)

No common opinion on the systematics position of species of the fishes of the subfamily Opisthocentrinae, Stichaeidae family has been formed up to the present. Therefore, a morphological analysis of fishes belonging to taxa Opisthocentrus ocellatus, O. tenuis, O. zonope, and Pholidapus dybowskii was undertaken. The obtained data treated by various methods of statistics implied the species independence of these taxa, which sympatrically occurred in the coastal areas of the northwest of the Sea of Japan. All the four studied species were similar in some attributes and distinct by other. Minor differences in the structure of the seismosensory system of Ph. dybowskii and Opisthocentrus species gave no basis on which to distinguish the independent genus Pholidapus. It would be correct to consider this as a subgenus of the Opisthocentrus genus, which includes three other species.     

Larval settlement of the common Australian sea urchin Heliocidaris erythrogramma in response to bacteria from the surface of coralline algae

Bacterial biofilms are increasingly seen as important for the successful settlement of marine invertebrate larvae. Here we tested the effects of biofilms on settlement of the sea urchin Heliocidaris erythrogramma. Larvae settled on many surfaces including various algal species, rocks, sand and shells. Settlement was reduced by autoclaving rocks and algae, and by treatment of algae with antibiotics. These results, and molecular and culture-based analyses, suggested that the bacterial community on plants was important for settlement. To test this, approximately 250 strains of bacteria were isolated from coralline algae, and larvae were exposed to single-strain biofilms. Many induced rates of settlement comparable to coralline algae. The genus Pseudoalteromonas dominated these highly inductive strains, with representatives from Vibrio, Shewanella, Photobacterium and Pseudomonas also responsible for a high settlement response. The settlement response to different bacteria was species specific, as low inducers were also dominated by species in the genera Pseudoalteromonas and Vibrio. We also, for the first time, assessed settlement of larvae in response to characterised, monospecific biofilms in the field. Larvae metamorphosed in higher numbers on an inducing biofilm, Pseudoalteromonas luteoviolacea, than on either a low-inducing biofilm, Pseudoalteromonas rubra, or an unfilmed control. We conclude that the bacterial community on the surface of coralline algae is important as a settlement cue for H. erythrogramma larvae. This study is also an example of the emerging integration of molecular microbiology and more traditional marine eukaryote ecology.     

Phototrophic Biofilms on Ancient Mayan Buildings in Yucatan, Mexico

Buildings at the important archaeological sites of Uxmal and Kabah, Mexico, are being degraded by microbial biofilms. Phospholipid fatty acid (PLFA) and chlorophyll a analyses indicated that phototrophs were the major epilithic microorganisms and were more prevalent on interior walls than exterior walls. Culture and microscopical techniques showed that Xenococcus formed the major biomass on interior surfaces, but the stone-degrading genera Gloeocapsa and Synechocystis were also present in high numbers. Relatively few filamentous algae and cyanobacteria were detected. The fatty acid analysis also showed that complex biofilms colonize these buildings. Circular depressions observed by scanning electron microscopy (SEM) on stone and stucco surfaces beneath the biofilm corresponded in shape and size to coccoid cyanobacteria. SEM images also demonstrated the presence of calcareous deposits on some coccoid cells in the biofilm. Phototrophic biofilms may contribute to biodegradation by (1) providing nutrients that support growth of acid-producing fungi and bacteria and (2) active “boring” behavior, the solubilized calcium being reprecipitated as calcium carbonate. Received: 15 March 1999 / Accepted: 24 June 1999     

Microbial Biofilms on the Sandstone Monuments of the Angkor Wat Complex,Cambodia

Discoloring biofilms from Cambodian temples Angkor Wat, Preah Khan, and the Bayon and West Prasat in Angkor Thom contained a microbial community dominated by coccoid cyanobacteria. Molecular analysis identified Chroococcidiopsis as major colonizer, but low similarity values (<95%) suggested a similar genus or species not present in the databases. In only two of the six sites sampled were filamentous cyanobacteria, Microcoleus, Leptolyngbya, and Scytonema, found; the first two detected by sequencing of 16S rRNA gene library clones from samples of a moist green biofilm on internal walls in Preah Khan, where Lyngbya (possibly synonymous with Microcoleus) was seen by direct microscopy as major colonizer. Scytonema was detected also by microscopy on an internal wall in the Bayon. This suggests that filamentous cyanobacteria are more prevalent in internal (high moisture) areas. Heterotrophic bacteria were found in all samples. DNA sequencing of bands from DGGE gels identified Proteobacteria (Stenotrophomonas maltophilia and Methylobacterium radiotolerans) and Firmicutes (Bacillus sp., Bacillus niacini, Bacillus sporothermodurans, Lysinibacillus fusiformis, Paenibacillus sp., Paenibacillus panacisoli, and Paenibacillus zanthoxyli). Some of these bacteria produce organic acids, potentially degrading stone. Actinobacteria, mainly streptomycetes, were present in most samples; algae and fungi were rare. A dark-pigmented filamentous fungus was detected in internal and external Preah Khan samples, while the alga Trentepohlia was found only in samples taken from external, pink-stained stone at Preah Khan. Results show that these microbial biofilms are mature communities whose major constituents are resistant to dehydration and high levels of irradiation and can be involved in deterioration of sandstone. Such analyses are important prerequisites to the application of control strategies.     

Short-term response of monospecific and natural algal biofilms to copper exposure

The effect of copper additions (Cu ranging from 0 to 30?µM) on the photosynthesis of three different microalgal biofilms was studied to identify the factors that cause sensitivity differences between benthic and pelagic algae. The response of biofilms which colonized artificial substrata in the River Meuse was compared with those of two laboratory-grown monospecific biofilms, one consisting of the diatom Synedra ulna, and the other composed of a filament-forming cyanobacterium, Oscillatoria sp. The photosynthetic yield Φ_II (quantum efficiency of photosystem II) was studied with PAM (Pulse Amplitude Modulated) fluorimetry. S. ulna biofilms appeared to be the most sensitive to Cu, followed by the cyanobacteria, while natural biofilms, dominated by supposedly very sensitive diatom species such as Melosira varians and Diatoma vulgare, were the most resistant to Cu. In the highly productive biofilms, pH is suggested to play a role in lowering toxicity by helping the precipitation of cupric ions. Cu accumulation by the biofilms during the exposure period followed a linear relationship with Cu concentration, saturation not being observed; natural biofilms had an accumulation factor of 1–2.5?×?10³ relative to the concentrations in the water, while the diatoms growing unattached to the substratum had a higher concentration factor, up to 4.9?×?10³. It was concluded that the physical structure of the biofilm (package of cells and thickness), and not the species composition, was the main factor regulating the sensitivity of the biofilm to Cu toxicity during short-term exposures.     

Phylogenetic signal of photobiont switches in the lichen genus <Emphasis Type="Italic">Pseudocyphellaria</Emphasis> s. l. follows a Brownian motion model

Lichen symbioses are defined as a symbiotic relationship between a mycobiont (generally an ascomycete) and one or more photobionts (green algae or/and cyanobacteria). It was proposed that cephalodia emancipation is an evolutionary driver for photobiont switch from chlorophyte to cyanobacteria. In this study we want to test the monophyly of cyanolichens and to measure the phylogenetic signal of the symbiotic relationship between cyanobacteria and a mycobiont partner in the lichen genus Pseudocyphellaria. This genus includes some species that have a chlorophyte as primary photobiont (and Nostoc in internal cephalodia), while others have only cyanobacteria. In a phylogenetic framework we measure the phylogenetic signal (or phylogenetic dispersion) as well as mapped photobiont switches performing stochastic character mapping. Results show that having cyanobacteria as main photobiont has a strong phylogenetic signal that follows a Brownian motion model. Seven clades in the phylogeny had an ancestor with cyanobacteria. Reversal to a green algae photobiont is rare. Several switches were estimated through evolutionary time suggesting that there was some flexibility in these traits along the phylogeny; however, close relatives retained cyanobacteria as main photobiont throughout the cyanolichen’s history. Photobiont switches from green algae to cyanobacteria might enhance ecotypical differentiation. These ecotypes could lead to several speciation events in the new lineage resulting in the phylogenetic signal found in this study. We give insights into the origin of lichen diversity exploring the photobiont switch in a phylogenetic context in Pseudocyphellaria s. l. as a model genus.     

Spatial distribution and morphologic diversity of virioplankton in Lake Donghu, China

The spatial distribution and morphological diversity of virioplankton were determined in Lake Donghu which contains three trophic regions: hypertrophic, eutrophic and mesotrophic region. Virioplankton abundance measured by transmission electron microscope (TEM) ranged from 7.7 × 10⁸ to 3.0 × 10⁹ ml^–1, being among the highest observed in any natural aquatic system examined so far. The spatial distribution of virioplankton was correlated significantly with chlorophyll a concentration (r = 0.847; P < 0.01) at the sampling sites in Lake Donghu. 76 morphotypes were observed. Most morphotypes have tails, belonging to Siphoviridae, Myoviridae and Podoviridae. The majority of tailed phages in the lake were Myoviridae. Morphotypes which were rarely reported, such as prolate-headed virus-like particles, lemon-shaped virus-like particle, and viruses resembling Tectiviridae and Corticoviridae were all observed in the lake. It is concluded that the high viral abundance might be associated with high density of phytoplankton including algae and cyanobacteria. There was high viral diversity in this eutrophic shallow lake. In addition, cyanophage represented an important fraction of the virioplankton community in Lake Donghu.     

Early stages of biofilm succession in a lentic freshwater environment

Initial events of biofilms development and succession were studied in a freshwater environment at Kalpakkam, East Coast of India. Biofilms were developed by suspending Perspex (Plexiglass) panels for 15 days at bimonthly intervals from January 1996 to January 1997. Changes in biofilm thickness, biomass, algal density, chlorophyll a concentration and species composition were monitored. The biofilm thickness, biomass, algal density and chlorophyll a concentration increased with biofilms age and colonization was greater during summer (March, May and July) than other months. The initial colonization was mainly composed of Chlorella vulgaris, Chlorococcum humicolo (green algae), Achnanthes minutissima, Cocconeis scutellum, C. placentula (diatoms) and Chroococcus minutus (cyanobacteria) followed by colonial green algae such as Pediastrum tetras, P. boryanumand Coleochaete scutata, cyanobacteria (Gloeocapsa nigrescens), low profile diatoms (Amphora coffeaeformis, Nitzschia amphibia, and Gomphonema parvulum) and long stalked diatoms (Gomphoneis olivaceumand Gomphonema lanceolatum). After the 10th day, the community consisted of filamentous green algae (Klebshormidium subtile, Oedogonium sp., Stigeoclonium tenue and Ulothrix zonata) and cyanobacteria (Calothrix elenkinii, Oscillatoria tenuis and Phormidium tenue). Based on the percentage composition of different groups in the biofilm, three phases of succession could be identified: the first phase was dominated by green algae, the second by diatoms and the third phase by cyanobacteria. Seasonal variation in species composition was observed but the sequence of colonization was similar throughout the study period.     

晋阳湖丝状蓝藻的形态学分析与分子鉴定北大核心CSCD

蓝藻是地球上最古老的生物之一,其形态结构较为简单,为产氧型光合作用的原核生物。山西省晋阳湖为华北地区最大的人工湖,该研究以采自晋阳湖水体及岸边附着的蓝藻为材料,采用经典毛细管法分离纯化出5株丝状蓝藻,利用光学显微镜观察其形态结构特征(如细胞形状、藻丝体宽度、是否有鞘)和显微结构,并采用16S rRNA序列分析其系统发育关系,以明确晋阳湖的蓝藻种类,为预防湖泊蓝藻水华的发生、维护水资源环境稳定与生态平衡提供理论数据。结果显示:(1)所分离纯化的5株丝状蓝藻依形态特征归属于3个科,其中2株(JYH005和JYH012)为细鞘丝藻亚科(Leptolyngbyaceae),2株(JYH008和JYH022)为伪鱼腥藻科(Pseudanabaenaceae),1株(JYH010)为沙丝藻科(Desertifilaceae)。(2)基于16S rRNA序列构建的系统发育树显示,5株丝状蓝藻中JYH005为结丝藻属(Nodosilinea)的一种;JYH008可归为Arthronema,该株蓝藻在培养条件下观察到不同的形态特征,可能为新物种;JYH010为沙丝藻属(Desertifilum)的一种;JYH012可归为细鞘丝藻属(Leptolyngbya);JYH022与伪鱼腥藻科聚为一支,由于与该科其他藻相似度低于90%,且不能聚为一支,因此只能归为伪鱼腥藻科。研究表明,基于16S rRNA序列系统发育分析与形态学鉴定结果相一致。该研究结果丰富了山西省晋阳湖丝状蓝藻的多样性,为该湖的资源利用和环境保护提供了一定的科学依据。     

Survival Response of <Emphasis Type="Italic">Bacteriovorax</Emphasis> in Surface Biofilm Versus Suspension when Stressed by Extremes in Environmental Conditions

The Bacteriovorax, previously in the genus Bdellovibrio, are prokaryotes that prey upon many Gram-negative bacteria. They are ubiquitous in salt-water environments and have been reported to have a strong association with biofilms. The purpose of this study was to test the hypothesis that this association affords protection for the Bacteriovorax and enhances their survival in nature when exposed to extreme environmental conditions. Experiments were designed to compare their survival in biofilms versus in suspension when exposed to extremes in salinity and temperature. Natural mixed-population biofilms generated in moderate-salinity (16‰) Patuxent River water and containing Bacteriovorax were exposed to drastic changes in salinity by placing in low-salinity (1‰) river water and salt-free (no measurable salinity) distilled water for up to 14 days. In a separate trial, the biofilm was exposed to extremes in temperature, 5°C and 35°C, for up to 12 weeks in aquarium mesocosms. Simultaneously, suspensions of the Bacteriovorax were exposed to the same extremes in salinity and temperature as biofilms. The results revealed that the Bacteriovorax typically were able to survive for a week or longer while in association with biofilms than when in suspension. These results are consistent with observations from nature and establish that biofilms are important in the survival and ecology of the Bacteriovorax.     

Photosynthetic H<Subscript>2</Subscript> metabolism in <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> (unicellular green algae)

Unicellular green algae have the ability to operate in two distinctly different environments (aerobic and anaerobic), and to photosynthetically generate molecular hydrogen (H₂). A recently developed metabolic protocol in the green alga Chlamydomonas reinhardtii permitted separation of photosynthetic O₂-evolution and carbon accumulation from anaerobic consumption of cellular metabolites and concomitant photosynthetic H₂-evolution. The H₂ evolution process was induced upon sulfate nutrient deprivation of the cells, which reversibly inhibits photosystem-II and O₂-evolution in their chloroplast. In the absence of O₂, and in order to generate ATP, green algae resorted to anaerobic photosynthetic metabolism, evolved H₂ in the light and consumed endogenous substrate. This study summarizes recent advances on green algal hydrogen metabolism and discusses avenues of research for the further development of this method. Included is the mechanism of a substantial tenfold starch accumulation in the cells, observed promptly upon S-deprivation, and the regulated starch and protein catabolism during the subsequent H₂-evolution. Also discussed is the function of a chloroplast envelope-localized sulfate permease, and the photosynthesis–respiration relationship in green algae as potential tools by which to stabilize and enhance H₂ metabolism. In addition to potential practical applications of H₂, approaches discussed in this work are beginning to address the biochemistry of anaerobic H₂ photoproduction, its genes, proteins, regulation, and communication with other metabolic pathways in microalgae. Photosynthetic H₂ production by green algae may hold the promise of generating a renewable fuel from nature’s most plentiful resources, sunlight and water. The process potentially concerns global warming and the question of energy supply and demand.     

Cyanobactericidal effect of <Emphasis Type="Italic">Rhodococcus</Emphasis> sp. isolated from eutrophic lake on <Emphasis Type="Italic">Microcystis</Emphasis> sp

A bacterium, which was observed in all cultivations of Microcystis sp., was isolated and designated as Rhodococcus sp. KWR2. The growth of bloom-forming cyanobacteria, including four strains of Microcystis aeruginosa and Anabaena variabilis, was suppressed by up to 75–88% by 2% (v/v) culture broth of KWR2 after 5 days. But KWR2 did not inhibit eukaryotic algae, Chlorella vulgaris and Scenedesmus sp. An extracellular algicidal substance produced by KWR2 showed a cyanobactericidal activity of 94% and was water-soluble with a molecular weight of lower than 8 kDa.     

Photosynthetic production of fuels and chemicals in immobilized systems

Whole cells of algae, cyanobacteria and photosynthetic bacteria entrapped in alginate gels or polyurethane foams can retain their photo-synthetic activities for months and in some cases for years. Such immobilized cells can be used in bioreactors for the production of H₂, NH₃, NADPH₂, carbohydrates, hydrocarbons, etc., with sunlight as the energy source.     

A light and electron microscopic study of the blue-green algae living either in the coralloid roots of « Macrozamia communis » or isolated in culture

Abstract

The present work is a study of the blue-green algae living in the coralloid roots of Macrozamia communis and isolated from Macrozamia communis in culture.

The light and electron microscopic study pointed out the distribution of these microorganisms in the cortical area of coralloids and did not reveal any cells invaded by bacteria. On the basis of their aspect the blue-green algae living either in the coralloid roots or in culture were classified as belonging to the genus Nosloc, with some features of Nosloc commune.

Inside the coralloids the cells of the blue-green algae were surrounded by abundant mucilage and contain granulations. In culture the blue-green algae were on the contrary very poor in mucilage and rich in polyphosphate granules. Numerous phycobilosomes were ranged along the outside of the thylakoid membranes in alternate arrangement to the granules of the neighbouring lamellae.