Prasinophyceae (Green Algae) from the Lower Proterozoic of the Kola Peninsula

Eukaryotic organisms discovered from the earliest Lower Proterozoic phosphorites (2.04 Ga) of the Kola Peninsula are described. These are fossil forms Pechengia melezhiki gen. et sp. nov., which are tentatively assigned to green algae of the class Prasinophyceae.     

Petsamomyces, a new genus of organic-walled microfossils from the coal-bearing deposits of the Early Proterozoic, Kola Peninsula

A new genus of organic-walled microfossils of supposed fungal origin, Petsamomyces Belova gen. nov., is described from the black shales of the Pechenga complex of the Early Proterozoic (Kola Peninsula). The find testifies to the development of eukaryotic heterotrophic microorganisms as early as 2 Ga ago.     

Proterozoic microfossils from the Mara Dolomite Member, Emmerugga Dolomite, McArthur Group, from the Northern Territory, Australia

An assemblage of microfossils from the mid-Proterozoic Mara Dolomite Member of the Emmerugga Dolomite, McArthur Group, Northern Territory, Australia, has been studied. The assemblage contains 10 species, of which one is new. The classification of Proterozoic microfossils is reviewed and a morphographic scheme adopted. The new assemblage is compared with other McArthur Group assemblages, and the differences between the assemblages are explained in terms of environmental differences. Comparison with other microfossil assemblages world-wide, suggests that these assemblages have stratigraphic potential.     

Nanotechnology and Potential of Microorganisms

ABSTRACT

There is a growing need to develop clean, nontoxic and environmentally friendly (“green chemistry”) procedures for synthesis and assembly of nanoparticles. The use of biological organisms in this area is rapidly gaining importance due to its growing success and ease of formation of nanoparticles. Presently, the potential of bio-organisms ranges from simple prokaryotic bacterial cells to eukaryotic fungus and even live plants. In this article we have reviewed some of these biological systems, which have revolutionized the art of nano-material synthesis.     

The oldest records of photosynthesis

There is diverse, yet controversial fossil evidence for the existence of photosynthesis 3500 million years ago. Among the most persuasive evidence is the stromatolites described from low grade metasedimentary rocks in Western Australia and South Africa. Based on the understanding of the paleobiology of stromatolites and using pertinent fossil and Recent analogs, these Early Archean stromatolites suggest that phototrophs evolved by 3500 million years ago. The evidence allows further interpretation that cyanobacteria were involved. Besides stromatolites, microbial and chemical fossils are also known from the same rock units. Some microfossils morphologically resemble cyanobacteria and thus complement the adduced cyanobacterial involvement in stromatolite construction. If cyanobacteria had evolved by 3500 million years ago, this would indicate that nearly all prokaryotic phyla had already evolved and that prokaryotes diversified rapidly on the early Earth.     

The Size of Cells and Organisms in Relation to the Evolution of Embryophytes

Abstract: The earliest O₂-_-evolvers were marine cyanobacteria (3.5 billion years ago) with marine eukaryotic phototrophs from 2.0 billion years ago. These organisms were, and are, poikilo-hydric, i.e., cannot remain hydrated when exposed to a desiccating atmosphere (as can occur for intertidal benthic algae and cy anobacteria at low tide). The smallest marine primarily poikilo-hydric O₂-_-evolvers are close to the lower size limit imposed by non-scaleable components such as minimum genome size and constant membrane thickness, with cyanobacterial unicells 0.65 μn in diameter and eukaryotic unicells 0.95 μm in diameter. The largest (multicellular) marine primarily aquatic poikilohydric O₂-_-evolvers are brown algae at least 60 m long and over 100 kg fresh mass; there are no obvious constraints on the max imum size of such organisms. In freshwaters the size range for primarily poikilohydric O₂-_-evolving organisms is smaller, due to the absence of very large organisms. An even smaller size range characterizes terrestrial algae and cyanobacteria which have occurred for about 1 billion years. Desiccation-tolerant cyanobacterium and algae (intertidal, freshwater, terrestrial) are at the lower end of the size ranges. Embryophytic terrestrial O₂-_-evolvers arose some 450 million years ago and were than all poikilohydric and (probably) desiccation-tolerant. Embryophytic defining structural features re quire organisms of at least 100 μm equivalent spherical diameter for both gametophyte and sporophyte phases. Primarily poi kilohydric embryophytes are not more than 1 m tall as a result of a mechanistically mysterious size limit for desiccation-tolerant organisms. Homoiohydric embryophytes evolved some 420 mil lion years ago in the sporophyte phase (later to become the dominant terrestrial vegetation) and possibly in the gameto phyte phase (although no such homoiohydric gametophytes are known today). The homoiohydric features of gas spaces, stomata, cuticle, endohydric water conducting system and water and nutrient uptake structures require an organism at least 5 mm high; this has implications for the minimum size of mega-spores and seeds. The tallest homoiohydric plants are (or were within historic times) 130 m high, with height constrained by re source costs of the synthesis and maintenance of the mechanical and water conduction systems, andbr of xylem water trans port. Secondarily poikilohydric embryophytes in aquatic, or very damp terrestrial, habitats are derived from homoiohydric plants; they retain most homoiohydric features but are not functionally homoiohydric. The smaller secondarily poikilohydric plants are less than one tenth of the size of the smallest functionally homoiohydric plants.     

On the species-specificity of DNA: Fifty years later

Modern approaches in DNA-based species identification are considered. Long used methods of species identification in procaryotes (G+C ratio, 16S rRNA nucleotide sequence, DNA-DNA hybridization) have recently been supplemented by the method of multilocus sequence analysis based on comparison of nucleotide sequences of fragments of several genes. Species identification in eukaryotes also employs one or two standard short fragments of the genome (known as DNA-barcodes). Potential benefits of new approaches and some difficulties during their practical realization are discussed.     

Structure and molecular phylogeny of sasA genes in cyanobacteria: insights into evolution of the prokaryotic circadian system

Cyanobacteria are the simplest organisms known to have a circadian system. In addition to the three well-studied kai genes, kaiA, kaiB, and kaiC, an important element of this system is a two-component sensory transduction histidine kinase sasA. Using publicly available data of complete prokaryotic genomes, we performed structural and phylogenetic analyses of the sasA genes. Results show that this gene has a triple-domain structure, and the domains are under different selective constraints. The sasA gene originated in cyanobacteria probably through the fusion of the ancestral kaiB gene with a double-domain, two-component sensory transduction histidine kinase. The results of the phylogenetic analyses suggest that sasA emerged before the kaiA gene, about 3,000-2,500 MYA, and has evolved in parallel with the evolution of the kaiBC cluster. The observed concordant patterns of the sasA and kaiBC evolution suggest that these genes might compose an ancient KaiBC-SasA-based circadian system, without the kaiA gene, and that such a system still exists in some unicellular cyanobacteria.     

Associative Cyanobacteria Isolated from the Roots of Epiphytic Orchids

Associative cyanobacteria were isolated from the rhizoplane and velamen of the aerial roots of the epiphytic orchids Acampe papillosa, Phalaenopsis amabilis, and Dendrobium moschatum and from the substrate roots of A. papillosa and D. moschatum. Cyanobacteria were isolated on complete and nitrogen-free variants of BG-11 medium. On all media and in all samples, cyanobacteria of the genus Nostoc predominated. Nostoc, Anabaena, and Calothrixwere isolated from the surface of the A. papillosa aerial roots, whereas the isolates from the substrate roots were Nostoc, Oscillatoria,and representatives of the LPP group (Lyngbia, Phormidium, and Plectonema, incapable of nitrogen fixation). On the D. moschatum substrate roots, Nostoc and LPP group representatives were also found, as well as Fischerella. On the aerial roots of P. amabilis and D. phalaenopsis grown in a greenhouse simulating the climate of moist tropical forest, cyanobacteria were represented by Nostoc, LPP group, and Scytonema in D. phalaenopsis and by Nostoc, Scytonema, Calothrix, Spirulina, Oscillatoria, and the LPP group in P. amabilis. For D. moschatum, the spectra of cyanobacteria populating the substrate root rhizoplane and the substrate (pine bark) were compared. In the parenchyma of the aerial roots of P. amabilis, fungal hyphae and/or their half-degraded remains were detected, which testifies to the presence of mycorrhizal fungi in this plant. This phenomenon is attributed to the presence of a sheath formed by cyanobacteria and serving as a substrate for fungi.     

Localization of Associative Cyanobacteria on the Roots of Epiphytic Orchids

This work is the first study of the localization of phototrophic microorganisms in the rhizoplane and velamen of epiphytic orchids, namely, on the aerial and substrate roots of Acampe papillosa and Dendrobium moschatum and on the aerial roots of Phalaenopsis amabilis and Dendrobium phalaenopsis. The composition of the bacterial community on the plant roots depended on the conditions of plant growth. Under conditions simulating the climate of moist tropical forests, the aerial roots proved to be populated with phototrophic microorganisms, among which cyanobacteria predominated. Interlaced fungal hyphae and filamentous cyanobacteria formed a sheath on the surface of the aerial roots. The nitrogen-fixing capacity of the sheath of the aerial roots was studied on the example of P. amabilis.     

Recognizing and Interpreting the Fossils of Early Eukaryotes

Using molecular sequence data, biologists cangenerate hypotheses of protistan phylogeny and divergence times. Fossils, however, provide our only direct constraints on the timingand environmental context of early eukaryotic diversification. Forthis reason, recognition of eukaryotic fossils in Proterozoic rocksis key to the integration of geological and comparative biologicalperspectives on protistan evolution. Microfossils preserved in shales of the ca. 1500 Ma Roper Group, northern Australia, display characters that ally them to the Eucarya, but, at present, attribution to any particular protistan clade is uncertain. Continuing research on wall ultrastructure and microchemistry promises new insights into the nature and systematic relationshipsof early eukaryotic fossils.     

The ATP-dependent proteases and proteolytic complexes involved into intracellular protein degradation

The review characterizes the main enzymatic systems of selective proteolysis responsible for maintenance of intracellular proteome in prokaryotes, eukaryotes and archaea. The features of proteolytic components of the ATP-dependent proteases as well as similarity and diversity of their regulatory components belonging to AAA⁺ ATPases are discussed.     

Bioactive Compounds from Cyanobacteria and Microalgae: An Overview

ABSTRACT

Cyanobacteria (blue-green algae) are photosynthetic prokaryotes used as food by humans. They have also been recognized as an excellent source of vitamins and proteins and as such are found in health food stores throughout the world. They are also reported to be a source of fine chemicals, renewable fuel and bioactive compounds. This potential is being realized as data from research in the areas of the physiology and chemistry of these organisms are gathered and the knowledge of cyanobacterial genetics and genetic engineering increased. Their role as antiviral, anti-tumour, antibacterial, anti-HIV and a food additive have been well established. The production of cyanobacteria in artificial and natural environments has been fully exploited. In this review the use of cyanobacteria and microalgae, production processes and biosynthesis of pigments, colorants and certain bioactive compounds are discussed in detail. The genetic manipulation of cyanobacteria and microalgae to improve their quality are also described at length.     

感染丝状蓝藻的噬藻体的裂解周期和释放量的测定

近年来 ,随着浮游病毒的认识的深入 ,人们认识到浮游病毒对水体中初级生产力的影响是巨大的[1] ,其主要证据就是发现噬藻体在海洋蓝藻的种群控制上发挥着重要作用[2 ] 。噬藻体的释放量和裂解周期是衡量噬藻体感染力的重要指标 ,很多重要的生态指标如病毒在生态系统中对宿主的致死率、病毒种群得以维持的阈浓度等都需要使用病毒的释放量和裂解周期来加以推算[3,4 ] ,因此准确地测定这两个基本参数是十分重要的。在自然界 ,很多丝状蓝藻 ,如颤藻、鱼腥藻、螺旋藻、席藻等是能够形成水华的 ,其中有些还具有产毒的功能[5] 。丝状蓝藻的形态特征…     

Ordovician Calcified Algae and Cyanobacteria, Northern Tarim Basin Subsurface, China

Boreholes between Kuqa and Korla, in the northern Tarim Basin, Xinjiang, penetrated Ordovician marine limestones at depths of 5–6.2km. From three boreholes 54 out of a total of 170 limestone samples contain calcified algae, cyanobacteria and associated Microproblematica. Calcified cyanobacteria (GirvanellaBotomaella, ?Subtifloria) account for 37 per cent of occurrences; green algae (Dasyporelleae and Vermiporella) 28 per cent; Microproblematica (NuiaBevocastriaRothpletzellaHalysis) 20 per cent; and ‘solenoporaceans’ 15 per cent GirvanellaNuia are common in the Early Ordovician deposits, and ‘solenoporaceans’ are abundant in the Mid‐Ordovician. Dasyporelleae and Vermiporella are most abundant in Mid–Late Ordovician samples. Calcified cyanobacteria are common throughout the limestone succession, but particularly in the Mid Ordovician part. MoniliporellaContextaPlexaTexturata, and Villosoporella, hitherto placed in the supposed red algal family Moniliporellaceae Gnilovskaya, are here regarded as dasycladalean green algae. Despite some omissions, this Tarim flora broadly resembles others from Kazakhstan, Baltica and North America, indicating the generally cosmopolitan nature of Ordovician calcified algae and cyanobacteria.     

Cyanobacteria and Cyanobacterial Lichens from Inselbergs of the Ivory Coast,Africa

This study focuses on the saxicolous lichens and cyanobacteria of the open, exposed rock surface of inselbergs. Twenty-three species of cyanobacteria and 17 cyanobacterial lichen species (“cyanolichens”) from several inselbergs and other rocky outcrops of three major climatic regions, savanna, transition zone and rain forest, are reported from the Ivory Coast. Inselbergs are isolated and frequently mountains consisting of Precambrian granites or gneisses that abruptly rise from the surrounding plains. Cyanobacteria were found to be the dominating organisms on all rock surfaces. The lichens found mainly belong to the family Peltulaceae and a few were present from the family Lichinaceae. Nine species of the cyanolichens and most of the cyanobacteria are new for the Ivory Coast. A gradient in total species number (cyanolichens and cyanobacteria) occurs from the savanna to the rain forest, with a decrease in species number towards the rain forest. Saxicolous cyanobacterial lichens reached a higher species number in the savanna type ecosystem (11) than on inselbergs in the rain forest (7). The cyanolichens and cyanobacteria found are characteristic for larger, light-exposed rock surfaces and species like P. congregate, P. lingulata, P. tortuosa and P. umbilicata preferentially occur on the granite or sandstone of inselbergs.     

Solar Ultraviolet and the Evolutionary History of Cyanobacteria

On the basis of photobiological, evolutionary, paleontological, paleoenvironmental and physiological arguments, a time course for the role of solar ultraviolet radiation (UVR, wavelengths below 400 nm) in the ecology and evolution of cyanobacteria is proposed in which three main periods can be distinguished. An initial stage, before the advent of oxygenic photosynthesis, when high environmental fluxes of UVC (wavelengths below 280 nm) and UVB (280–320 nm) may have depressed the ability of protocyanobacteria to develop large populations or restricted them to UVR refuges. A second stage lasting between 500 and 1500 Ma (million years), started with the appearance of true oxygen-evolving cyanobacteria and the concomitant formation of oxygenated (micro)environments under an oxygen free-atmosphere. In this second stage, the age of UV, the overall importance of UVR must have increased substantially, since the incident fluxes of UVC and UVB remained virtually unchanged, but additionally the UVA portion of the spectrum (320–400 nm) suddenly became biologically injurious and extremely reactive oxygen species must have formed wherever oxygen and UVR spatially coincided. The last period began with the gradual oxygenation of the atmosphere and the formation of the stratospheric ozone shield. The physiological stress due to UVC all but disappeared and the effects of UVB were reduced to a large extent. Evidence in support of this dynamics is drawn from the phylogenetic distribution of biochemical UV-defense mechanisms among cyanobacteria and other microorganisms. The specific physical characteristics of UVR and oxygen exposure in planktonic, sedimentary and terrestrial habitats are used to explore the plausible impact of UVR in each of the periods on the ecological distribution of cyanobacteria.     

Relative Uptake of Urea and Ammonium by Dinoflagellates or Cyanobacteria in Shrimp Mesocosms

The relative role of the organic nitrogen source, urea, versus ammonium as a nitrogen source for two species of dinoflagellates was compared with one species of cyanobacteria. Experiments were conducted opportunistically in nutrient-rich marine water during blooms of 34either cyanobacteria or dinoflagellates in outdoor mesocosms. These replicate mesocosms, which were stocked with shrimp fed high-protein formulated feeds, contained high biomasses of phytoplankton (mean chlorophyll a concentrations, 439.2–811.2 μg l⁻¹). ¹⁵N-urea and ammonium uptake rates for dinoflagellate-dominated blooms (Gymnodinium pulchellum-complex (Larsen), Karlodinium micrum (Larsen) (Dinophyceae)) were compared with blooms of the cyanobacterium, Romeria sp. (Cyanophyceae) in mesocosms with mean urea and ammonium concentrations ranging from 2.32 to 3.24 μM, and 7.39 to 64.85 μM, respectively. Urea uptake rates were significantly (p < 0.005) lower than ammonium uptake rates irrespective of which algal species dominated the bloom. Additionally urea uptake rates were not significantly higher in G. pulchellum-complex or K. micrum-dominated blooms than in Romeria sp. blooms. These results suggest that G pulchellum complex and K. micrum may not be gaining a competitive advantage in waters high in dissolved organic matter simply by preferentially utilizing urea. The periodic dominance of these species in highly organic environments, such as shrimp ponds, is likely to have a more complex explanation.