专家论藻类学的新前沿

随着可供利用的陆生资源的日益枯竭以及系统生物学与整合生物技术的兴起,藻类学研究正面临着许多前所未有的挑战与机遇。在312次香山科学会议——《藻类学的新前沿》上,与会专家围绕“系统生物学时代的藻类学研究”、“面向资源环境新需求的藻类生物技术”、“藻类学科和藻类产业的可持续发展”、“藻类与环境”等关键问题,进行了深入的探讨。     

Taxonomic identification of algae (morphological and molecular): species concepts,methodologies, and their implications for ecological bioassessment

Algal taxonomy is a key discipline in phycology and is critical for algal genetics, physiology, ecology, applied phycology, and particularly bioassessment. Taxonomic identification is the most common analysis and hypothesis‐testing endeavor in science. Errors of identification are often related to the inherent problem of small organisms with morphologies that are difficult to distinguish without research‐grade microscopes and taxonomic expertise in phycology. Proposed molecular approaches for taxonomic identification from environmental samples promise rapid, potentially inexpensive, and more thorough culture‐independent identification of all algal species present in a sample of interest. Molecular identification has been used in biodiversity and conservation, but it also has great potential for applications in bioassessment. Comparisons of morphological and molecular identification of benthic algal communities are improved by the identification of more taxa; however, automated identification technology does not allow for the simultaneous analysis of thousands of samples. Currently, morphological identification is used to verify molecular taxonomic identities, but with the increased number of taxa verified in algal gene libraries, molecular identification will become a universal tool in biological studies. Thus, in this report, successful application of molecular techniques related to algal bioassessment is discussed.     

AIRBORNE ALGAE: THEIR PRESENT STATUS AND RELEVANCE1

Ongoing climatic changes coupled with various natural processes and the outcomes of human activities are not only loading the atmosphere with diverse kinds of biological particles but also changing their prevalence and spatial distribution. Despite having considerable ecological and economic significance, including their possible impact on human health, airborne algae are the least‐studied organisms in both aerobiological and phycological studies. The present review has been written to bring together all available information, including a brief survey of the literature, the ecology of airborne algae, mechanisms involved in their aerosolization, the role of environmental factors in shaping the structure and composition of aero‐algal flora, and other significant information associated with airborne algae. This review provides information on methodological approaches and related problems, along with suggestions for areas of future research on airborne algae.     

Molecular biotechnology of marine algae in China

Molecular biotechnology of marine algae is referred to as the biotechnology on the identification, modification, production and utilization of marine algal molecules. It involves not only the manipulation of macromolecules such as DNA, RNA and proteins, but also deals with low molecular weight compounds such as secondary metabolites. In the last decade, molecular systematic researches to investigate the relationship and to examine the evolutionary divergence among Chinese marine algae have been carried out by Chinese scientists. For example, RAPD has been widely used in several laboratories to elucidate genetic variations of the reds, such as Porphyra, Gracilaria, Grateloupia and the greens such as Ulva and Enteromorpha. Some important data have been obtained. The study on molecular genetic markers for strain improvement is now in progress. In 1990s, genetic engineering of economic seaweeds such as Laminaria, Undaria, Porphyra, Gracilaria and Grateloupia has been studied in China. For Laminaria japonica, the successfully cultivated kelp in China, a model transformation system has been set up based on the application of plant genetic techniques and knowledge of the algal life history. Progress has been made recently in incorporating a vaccine gene into kelp genome. Evidence has been provided showing the expression of gene products as detectable vaccines. In the present paper, the progress of molecular biotechnological studies of marine algae in China, especially researches on elucidating and manipulating nucleic acids of marine algae, are reviewed.     

Importance of basic research in applied phycology

Utilization of algae has extended considerably from the middle of this century, with the consequence of more and more applied research in various directions and fields, the most important of which deals with phycocolloid production and algal cultivation to provide raw material and foodstuff. It is noteworthy that this research can not avoid the use of knowledge obtained by basic research; applied phycology is especially indebted to basic research in adopting biotechnologies which are typically coming from basic research. In counterpart, such a situation is beneficial to basic research. According to the dependence of applied phycology to basic research and the fact that restricted research programs only are nowadays financially supported, the fate of all research seems to be questionable.     

ALGAL TRANSGENICS IN THE GENOMIC ERA1

The last few years have witnessed significant advances in the field of algal genomics. Complete genome sequences from the red alga Cyanidioschyzon merolae and the diatom Thalassiosira pseudonana have been published, the genomes for two more algae (Chlamydomonas reinhardtii and Ostreococcus tauri) are nearing completion, and several others are in progress or at the planning stage. In addition, large‐scale cDNA sequencing projects are being carried out for numerous algal species. This wealth of genome data is serving as a powerful catalyst for the development and application of recombinant techniques for these species. The data provide a rich resource of DNA elements such as promoters that can be used for transgene expression as well as an inventory of genes that are possible targets for genetic engineering programs aimed at manipulating algal metabolism. It is not surprising therefore that significant progress in the genetic engineering of eukaryotic algae is being made. Nuclear transformation of various microalgal species is now routine, and progress is being made on the transformation of macroalgae. Chloroplast transformation has been achieved for green, red, and euglenoid algae, and further success in organelle transformation is likely as the number of sequenced plastid, mitochondrial, and nucleomorph genomes continues to grow. Importantly, the commercial application of algal transgenics is beginning to be realized, and algal biotechnology companies are being established. Recent work has shown that recombinant proteins of therapeutic value can be produced in microalgal species, and it is now realistic to envisage the genetic engineering of commercially important species to improve production of valuable algal products. In this article we review the recent progress in algal transgenics and consider possible future developments now that phycology has entered the genomic era.     

157 Examining Phytoplankton Communities with Environmental PCR

Recent advances in biotechnology have taken much of the guesswork out of many molecular biological procedures, and promote a high rate of success even for relative beginners. In designing the laboratory component of my Phycology course, I have taken advantage of these improved methods to develop a semester-long, molecular-based class project, using "environmental PCR" to examine phytoplankton diversity. Students learn a number of common molecular techniques within the context of dynamic and unrehearsed phycological research. This provides a greater appreciation of the general utility of molecular technology, and its application to algal systems in particular. A series of easy to follow protocols are linked together, allowing students to PCR amplify sequences from mixed environmental samples, clone the resulting fragments to separate individual sequences, screen the clones by restriction enzyme digests and sequence clones with clearly different restriction patterns. The resulting sequences then are used in BLAST searches of GenBank to determine the nearest available match among sequences annotated previously. The techniques allow both qualitative and quantitative estimates of the organisms present, as well as comparative analyses of the diversity observed through direct visual observations versus those recovered by PCR. Each step of the procedure can be accomplished in the duration of a typical 3 hour lab period, and most involve intervals of incubation that permit adequate time for other lab exercises, such as a survey algal diversity, on which traditional phycological laboratories are based.     

FLOW CYTOMETRY AND THE SINGLE CELL IN PHYCOLOGY

Flow cytometers measure light scattering and fluorescence characteristics from individual particles in a fluid stream as they cross one or more light beams at rates of up to thousands of events per second. Flow cytometrically detectable optical signals may arise naturally from algae, reflecting cell size, structure, and endogenous pigmentation, or may be generated by fluorescent stains that report the presence of otherwise undetected cellular constituents. Some flow cytometers can physically sort particles with desired optical characteristics out of the flow stream and collect them for subsequent culture or other analyses. The statistically rigorous, cell‐level perspective provided by flow cytometry has been advantageous in experimental investigations of phycological problems, such as the regulation of cell cycle progression. The capacity of flow cytometry to measure large numbers of cells in large numbers of samples rapidly and quantitatively has been used extensively by biological oceanographers to define the distributions and dynamics of marine picophytoplankton. Recent work has shown that flow cytometry can be used to elucidate relationships between the optical properties of individual cells and the bulk optical properties of the water they live in, and thereby may provide an explicit link between algal physiology and global biogeochemistry. Unfortunately, commercially available flow cytometers that are optimized for biomedical applications have a limited capacity to analyze larger phytoplankton. To circumvent these limitations, many investigators are developing flow cytometers specifically designed for analyzing the broad range of sizes, shapes, and pigments found among algae. These new instruments can perform some novel measurements, including simple fluorescence excitation spectra, detailed angular scattering measurements, and in‐flow digital imaging. The growing accessibility and power of flow cytometers may allow the technology to be applied to a wider array of problems in phycology, including investigations of nonplanktonic and multicellular algae, but also presents new challenges for effectively analyzing the large quantity of multiparameter data produced. Ultimately, the detection of molecular probes by flow cytometry may allow single‐cell taxonomic and physiological information to be garnered for a variety of algae, both in culture and in nature.     

The ecology of viruses that infect eukaryotic algae

Because viruses of eukaryotic algae are incredibly diverse, sweeping generalizations about their ecology are rare. These obligate parasites infect a range of algae and their diversity can be illustrated by considering that isolates range from small particles with ssRNA genomes to much larger particles with 560?kb dsDNA genomes. Molecular research has also provided clues about the extent of their diversity especially considering that genetic signatures of algal viruses in the environment rarely match cultivated viruses. One general concept in algal virus ecology that has emerged is that algal viruses are very host specific and most infect only certain strains of their hosts; with the exception of viruses of brown algae, evidence for interspecies infectivity is lacking. Although some host-virus systems behave with boom-bust oscillations, complex patterns of intraspecies infectivity can lead to host-virus coexistence obfuscating the role of viruses in host population dynamics. Within the framework of population dynamics, host density dependence is an important phenomenon that influences virus abundances in nature. Variable burst sizes of different viruses also influence their abundances and permit speculations about different life strategies, but as exceptions are common in algal virus ecology, life strategy generalizations may not be broadly applicable. Gaps in knowledge of virus seasonality and persistence are beginning to close and investigations of environmental reservoirs and virus resilience may answer questions about virus inter-annual recurrences. Studies of algal mortality have shown that viruses are often important agents of mortality reinforcing notions about their ecological relevance, while observations of the surprising ways viruses interact with their hosts highlight the immaturity of our understanding. Considering that just two decades ago algal viruses were hardly acknowledged, recent progress affords the optimistic perspective that future studies will provide keys to unlocking our understanding of algal virus ecology specifically, and aquatic ecosystems generally.     

藻类中添加剂的应用研究进展

藻类富含多种营养元素和活性物质,具有重要的经济价值和广阔的应用前景。现阶段藻类培养多采用露天跑道池,成本低,但易受环境影响。不适宜的环境条件(温度、酸性、重金属、紫外、盐度和光强胁迫等)会造成藻类生产成本上升、产品产量及品质下降等后果,严重制约藻类养殖业及相关产业的发展。添加剂不仅能有效促进藻类生长,还能缓解环境胁迫对其带来的逆境伤害。将近年来添加剂在藻类生长及抗逆方面的应用进行系统汇总,并对已阐明的几种添加剂的作用机理进行分析整理。添加剂在藻类中的应用研究大多停留在生长及生理指标的测定,如藻细胞密度、光系统活性、渗透调节物质含量、脂质含量、过氧化氢酶和硝酸还原酶活力等,仅有少部分研究是利用分子技术测定防御基因的表达情况,尝试进一步探究藻类抗逆性分子机制。旨在为研究者进一步明确常用添加剂在藻类中的信号传导机制及改善非生物胁迫造成的产品产量及品质的问题提供理论依据,具有重要现实意义。     

空间生物技术研究与应用动态

由于空间生物技术潜在重大社会和经济效益。加强探索空间生物技术的发展。目前已经成为空间科学技术发展的重点之一。我国的空间技术在系列应用卫星成功发展的基础上,已将进入到更先进的载人飞船阶段。我国的科技人员将会有更多的机会,更好的条件在空间开展生物技术的研究。以促进其发展和应用,造福于人类,本文简要地介绍了空间发展生物技术的优越性。空间生物技术发展的热点和趋势,以及空间生物技术硬件发展的动态。     

Ecological assessments with algae: a review and synthesis

Algae have been used for a century in environmental assessments of water bodies and are now used in countries around the world. This review synthesizes recent advances in the field around a framework for environmental assessment and management that can guide design of assessments, applications of phycology in assessments, and refinements of those applications to better support management decisions. Algae are critical parts of aquatic ecosystems that power food webs and biogeochemical cycling. Algae are also major sources of problems that threaten many ecosystems goods and services when abundances of nuisance and toxic taxa are high. Thus, algae can be used to indicate ecosystem goods and services, which complements how algal indicators are also used to assess levels of contaminants and habitat alterations (stressors). Understanding environmental managers' use of algal ecology, taxonomy, and physiology can guide our research and improve its application. Environmental assessments involve characterizing ecological condition and diagnosing causes and threats to ecosystems goods and services. Recent advances in characterizing condition include site‐specific models that account for natural variability among habitats to better estimate effects of humans. Relationships between algal assemblages and stressors caused by humans help diagnose stressors and establish targets for protection and restoration. Many algal responses to stressors have thresholds that are particularly important for developing stakeholder consensus for stressor management targets. Future research on the regional‐scale resilience of algal assemblages, the ecosystem goods and services they provide, and methods for monitoring and forecasting change will improve water resource management.     

Phycoremediation coupled production of algal biomass,harvesting and anaerobic digestion: Possibilities and challenges

Biogas produced from anaerobic digestion is a versatile and environment friendly fuel which traditionally utilizes cattle dung as the substrate. In the recent years, owing to its high content of biodegradable compounds, algal biomass has emerged as a potential feedstock for biogas production. Moreover, the ability of algae to treat wastewater and fix CO₂ from waste gas streams makes it an environmental friendly and economically feasible feedstock. The present review focuses on the possibility of utilizing wastewater as the nutrient and waste gases as the CO₂ source for algal biomass production and subsequent biogas generation. Studies describing the various harvesting methods of algal biomass as well as its anaerobic digestion have been compiled and discussed. Studies targeting the most recent advancements on biogas enrichment by algae have been discussed. Apart from highlighting the various advantages of utilizing algal biomass for biogas production, limitations of the process such as cell wall resistivity towards digestion and inhibitions caused due to ammonia toxicity and the possible strategies for overcoming the same have been reviewed. The studies compiled in the present review indicate that if the challenges posed in translating the lab scale studies on phycoremediation and biogas production to pilot scale are overcome, algal biogas could become the sustainable and economically feasible source of renewable energy.     

Meeresalgen von Helgoland

This report represents a photographic documentation of the more conspicuous species of the marine algal vegetation of the island Helgoland (North Sea), based on collections and observations made since 1959. The catalogue is largely restricted to macroscopic forms, as adequate knowledge of most of the microscopic ones is not yet available. Remarks on some rare species are added in a special chapter; the list includes some 150 species. With a few exceptions, the figures have been obtained from living algae; they illustrate aspects of reproduction and development and, occasionally, demonstrate different seasonal habits. The simplified key may be useful for providing a guide both for naturalists and students of marine phycology. In addition, this algal flora enhances our knowledge of the distribution of benthic species along the European coasts, as the rocky island of Helgoland intervenes between southern Norway and the shores of the English Channel.     

Algae on the internet

Increasingly electronic communication and a variety of electronic resources are accessible to a larger group of people within the scientific community. This paper outlines the range of resources that are available, and comments on their current and future value to the phycological community. Resources discussed include mailing lists and newsgroups. These are useful tools for rapid, informal, targeted communication, although the technology employed places limitations on the type and format of information which may be distributed. The World Wide Web (WWW) has the potential to overcome these limitations, the quality, complexity and value to the phycological community of the sites on the WWW are extremely variable, with some material being of dubious quality. However, it is possible to access high quality resources including culture collection catalogues, high quality images and microbial and molecular databases. As well as some of the current resources, this paper discusses some possible directions for the future of phycology on the internet.http://wiua.nwi.ac.uk/     

Assessment of littoral algal diversity from the northern Gulf of Mexico using environmental DNA metabarcoding

Traditional methods for algal biodiversity monitoring are costly and time inefficient because they rely on high‐level taxonomic expertise to address species identity problems involving phenotypic plasticity and morphological convergence. These problems are exacerbated in regions such as the Gulf of Mexico, that has a limited history of phycological exploration, but that are economically important or threatened by numerous anthropogenic stressors. Given the high pace of disturbance to natural systems, there is a critical need for expedient and cost‐effective tools for the study of benthic algal communities. Here we document the use of environmental DNA metabarcoding, using the partial LSU rDNA and 23S rDNA plastid molecular markers, to elucidate littoral algal diversity in the Northern Gulf of Mexico. We assigned 73.7% of algal OTUs to genus and 59.6% to species ranks. Our current study detected molecular signals for 35 algal/protist species with no previous reports in the Gulf of Mexico, thus providing an important, molecular‐validated, baseline of species richness for this region. We also make several bioinformatic recommendations for the efficient use of high‐throughput sequence data to assess biological communities.     

赤潮过程中“藻-菌”关系研究进展

微生物对促进海洋物质循环,维持水生环境的生态平衡具有重要作用。在赤潮事件中,基于微生物(尤其是细菌)的多样性和重要性,它们与藻类之间的相互关系成为了研究的热点。过去20年里,人们从不同角度对"藻-菌"间的关系进行了探索,包括物理学过程、生物学过程、环境过程以及化学过程。就化学过程而言,它作为一种较早出现的技术,在以往的研究中带给人们许多认识藻菌关系的方法。随着学科的渗透,化学法有了拓展与延伸,为人们认识藻菌关系带来了新的契机。从化学生态学领域来梳理"藻-菌"关系中涉及的现象和行为,包括菌对藻的有益面、菌对藻的有害面、以及藻类应答细菌行为的化学途径;并从信号语言(群体感应、化感作用)的角度来阐释两者之间的互生或克生关系。通过文献综述的方式来解读藻菌关系的互作过程和机理,为认识赤潮的发生和防控方法提供借鉴。     

Lipids and lipid metabolism in eukaryotic algae

Eukaryotic algae are a very diverse group of organisms which inhabit a huge range of ecosystems from the Antarctic to deserts. They account for over half the primary productivity at the base of the food chain. In recent years studies on the lipid biochemistry of algae has shifted from experiments with a few model organisms to encompass a much larger number of, often unusual, algae. This has led to the discovery of new compounds, including major membrane components, as well as the elucidation of lipid signalling pathways. A major drive in recent research have been attempts to discover genes that code for expression of the various proteins involved in the production of very long-chain polyunsaturated fatty acids such as arachidonic, eicosapentaenoic and docosahexaenoic acids. Such work is described here together with information about how environmental factors, such as light, temperature or minerals, can change algal lipid metabolism and how adaptation may take place.     

Do Red and Green Make Brown?: Perspectives on Plastid Acquisitions within Chromalveolates

The chromalveolate "supergroup" is of key interest in contemporary phycology, as it contains the overwhelming majority of extant algal species, including several phyla of key importance to oceanic net primary productivity such as diatoms, kelps, and dinoflagellates. There is also intense current interest in the exploitation of these algae for industrial purposes, such as biodiesel production. However, the evolution of the constituent species, and in particular the origin and radiation of the chloroplast genomes, remains poorly understood. In this review, we discuss current theories of the origins of the extant red alga-derived chloroplast lineages in the chromalveolates and the potential ramifications of the recent discovery of large numbers of green algal genes in chromalveolate genomes. We consider that the best explanation for this is that chromalveolates historically possessed a cryptic green algal endosymbiont that was subsequently replaced by a red algal chloroplast. We consider how changing selective pressures acting on ancient chromalveolate lineages may have selectively favored the serial endosymbioses of green and red algae and whether a complex endosymbiotic history facilitated the rise of chromalveolates to their current position of ecological prominence.