Microboring organisms in living stylasterid corals (Cnidaria,Hydrozoa)

Microboring or euendolithic microorganisms, which colonize and penetrate various carbonate substrates, are abundant in coral reef ecosystems and play a major role in reef carbonate dissolution. A few studies reported the presence of euendoliths in stylasterid coral skeletons but the biological identity, distribution and abundance of these microorganisms remain largely unknown. Observations of over 100 stylasterid colonies, collected in the Indo-Pacific area, revealed for the first time that the association between these corals and euendolith organisms appears to be quite common in shallow tropical waters. The most abundant euendolith was identified as a cryptic stage in the development of the rhodophyte Porphyra (Conchocelis stage). The euendoliths were observed in the skeletons of seven species of three genera (four Stylaster, two Distichopora and one Lepidotheca). The presence of euendoliths inside skeletons conferred a particular colour to the studied stylasterid corals. Distribution and abundance of microborings varied significantly among stylasterid species and among branches of a single colony and so did the colour of their skeletons. Colonization of skeletons and the associated colour distribution were almost uniform in some stylasterids, forming an upward gradually diminishing or sharply limited gradient. This study shows that patterns of euendolith colonization and growth in stylasterid skeletons may depend on the stage of the euendolith development as well as on their environmental requirements such as light exposure.     

Early Cretaceous record of microboring organisms in skeletons of growing corals

Ko?odziej, B., Golubic, S., Bucur, I.I., Radtke, G. & Tribollet, A. 2011: Early Cretaceous record of microboring organisms in skeletons of growing corals. Lethaia, Vol. 45, pp. 34–45. A spectacularly preserved assemblage of microbial euendoliths, penetrating into skeletons of growing scleractinian corals, has been recognized in Early Aptian (Early Cretaceous) reef limestone of the Rar?u Mountains (East Carpathians, NE Romania). Microboring euendolithic filaments were found in five coral colonies of the suborder Microsolenina. They remained in part well‐preserved, often impregnated with iron oxides, which made them visible even in strongly recrystallized parts of coral skeletons. Filaments of a wide range of sizes (2–40 μm in diameter) were concentrated within medium parts of coral septa, oriented along the septa in the direction of the coral growth. The larger filaments were tubular, occurring in bundles and branched into finer, often tapering branches. Their behaviour and organization were quite similar to the modern euendolithic siphonalean chlorophyte Ostreobium. Filament diameters exceeded those reported for the modern species, but covered a similarly wide size range. Narrower frequently branching filaments, 4–8 μm in diameter, resemble distal branching patterns of modern Ostreobium quekettii. Some very thin filaments (ca. 1–2 μm) observed within skeleton or inside the large tubular filaments, sometimes associated with globular swellings, may represent euendolithic fungi. The recrystallization of coral skeleton had limited effect on preservation of euendoliths due to their impregnation with iron oxides; microbial euendoliths were subjected to different taphonomic changes. □Chlorophytes, Early Cretaceous, fungi, microbial euendoliths, Romania, scleractinian corals.     

Microfossils from oolites and pisolites of the Upper Proterozoic Eleonore Bay Group, Central East Greenland

Silicified oolites and pisolites from Bed 18 of the Upper Proterozoic (about 700-800 Ma) Limestone-Dolomite "Series" of the Eleonore Bay Group, central East Greenland, contain a diverse suite of organically preserved microfossils that is, for the most part. [Of the] assemblages previously described from Proterozoic cherts and shales. Three principal assemblages occur in these rocks: 1) a class bound assemblage found in detrital carbonate grains (now silicified) that served as nuclei for ooid and pisoid growth, as well as in uncoated mud and mat clasts that were carried into the zone of ooid and pisoid deposition; 2) an epilithic and interstitial assemblage consisting of microorganisms that occurred on top of and between grains; and 3) a euendolithic assemblage composed of microbes that actively bored into coated grains. The Upper Proterozoic euendolithic assemblage closely resembles a community of euendolithic cyanobacteria found today in shallow marine ooid sands of the Bahama Banks. Thirteen species are described, of which eight are new, five representing new genera: Eohyella dichotoma n. sp., Eohyella endoatracta n. sp., Eohyella rectoclada n. sp., Thylacocausticus globorum n. gen. and sp., Cunicularius halleri n. gen. and sp., Graviglomus incrustus n. gen. and sp., Perulagranum obovatum n. gen. and sp., and Parenchymodiscus endolithicus n. gen. and sp.     

Prevalence of Ca²⁺-ATPase-mediated carbonate dissolution among cyanobacterial euendoliths

Recent physiological work has shown that the filamentous euendolithic cyanobacterium Mastigocoleus testarum (strain BC008) is able to bore into solid carbonates using Ca²⁺-ATPases to take up Ca²⁺ from the medium at the excavation front, promoting dissolution of CaCO₃ there. It is not known, however, if this is a widespread mechanism or, rather, a unique capability of this model strain. To test this, we undertook a survey of multispecies euendolithic microbial assemblages infesting natural carbonate substrates in marine coastal waters of the Caribbean, Mediterranean, South Pacific, and Sea of Cortez. Microscopic examination revealed the presence of complex assemblages of euendoliths, encompassing 3 out of the 5 major cyanobacterial orders. 16S rRNA gene clone libraries detected even greater diversity, particularly among the thin-filamentous forms, and allowed us to categorize the endoliths in our samples into 8 distinct phylogenetic clades. Using real-time Ca²⁺ imaging under a confocal laser scanning microscope, we could show that all communities displayed light-dependent formation of Ca²⁺-supersaturated zones in and around boreholes, a staple of actively boring phototrophs. In 3 out of 4 samples, boring activity was sensitive to at least one of two inhibitors of Ca²⁺-ATPase transporters (thapsigargin or tert-butylhydroquinone), indicating that the Ca²⁺-ATPase mechanism is widespread among cyanobacterial euendoliths but perhaps not universal. Function-community structure correlations point to one particular clade of baeocyte-forming euendoliths as the potential exception.     

四川江油渔洞子下三叠统飞仙关组巨鲕灰岩中疑似蓝细菌及早三叠世疑似蓝细菌的双幕式爆发

二叠纪末海洋生态环境的恶化导致海洋底栖生物的大灭绝及早三叠世蓝细菌的爆发,有关这一时期我国华南蓝细菌化石的报道主要来自早三叠世早期的微生物岩。四川江油渔洞子剖面下三叠统飞仙关组下部巨鲕灰岩中首次发现有丰富的疑似蓝细菌,在种类和结构上与以往所报道的蓝细菌有着明显区别。疑似蓝细菌在巨鲕内和围岩中的富集,表明巨鲕灰岩的成因与疑似蓝细菌的活动有关,与飞仙关组底部微生物岩在成因上有着密切联系,显示早三叠世早期在这一地区发生了疑似蓝细菌的双幕式爆发,同时,暗示着这一地区二叠纪-三叠纪之交至少发生了两次海洋环境恶化及动物灭绝事件。疑似蓝细菌的爆发性生长,对于海洋生态环境的修复和海洋含氧条件的改善,进而为早三叠世末、中三叠世的生物全面复苏、辐射有着重要意义。     

Cyanobacteria in mangrove ecosystems

Mangroves are subject to the effects of tides and fluctuations in environmental conditions, which may reach extreme conditions. These ecosystems are severely threatened by human activities despite their ecological importance. Although mangroves are characterized by a highly specialized but low plant diversity in comparison to most other tropical ecosystems, they support a diverse microbial community. Adapted microorganisms in soil, water, and on plant surfaces perform fundamental roles in nutrient cycling, especially nitrogen and phosphorus. Cyanobacteria contribute to carbon and nitrogen fixation and their cells act as phosphorus storages in ecosystems with extreme or oligotrophic environmental conditions such as those found in mangroves. As the high plant productivity in mangroves is only possible due to interactions with microorganisms, cyanobacteria may contribute to these ecosystems by providing fixed nitrogen, carbon, and herbivory-defense molecules, xenobiotic biosorption and bioremediation, and secreting plant growth-promoting substances. In addition to water, cyanobacterial colonies have been detected on sediments, rocks, decaying wood, underground and aerial roots, trunks, and leaves. Some mangrove cyanobacteria were also found in association to algae or seagrasses. Few studies on mangrove cyanobacteria are available, but together they have reported a substantial number of species in these ecosystems. However, the cyanobacterial diversity in this biome has been traditionally underestimated. Though mangrove communities generally host cyanobacterial taxa commonly found in marine environments, unique microhabitats found in mangroves potentially harbor several undescribed cyanobacterial taxa. The relevance of cyanobacteria for mangrove conservation is highlighted in their use for the recovery of degraded mangroves as biostimulants or in bioremediation.     

Genetic engineering in marine cyanobacteria

Many species of microalgae producing useful materials have been isolated from marine environments. For their industrial application, widely applicable and stable gene expression is required. It is necessary to establish gene transfer methods as an essential first step in genetic manipulation. Although gene transfer techniques for cyanobacteria have been developed, only naturally transformable strains have been used. Here, we describe recent progress made in developing gene transfer methods for marine cyanobacteria. The following are covered: (1) transformation, (2) electroporation, (3) conjugation, (4) particle gun. A plasmid from the marine cyanobacterium, Synechococcus sp., whose copy number is dependent on salinity, was characterized. This plasmid is being used to develop a stable and controllable gene expression system.     

Marine microorganisms as an untapped source of bioactive compounds

The search for novel biologically active molecules has extended to the screening of organisms associated with less explored environments. In this sense, Oceans, which cover nearly the 67% of the globe, are interesting ecosystems characterized by a high biodiversity that is worth being explored. As such, marine microorganisms are highly interesting as promising sources of new bioactive compounds of potential value to humans. Some of these microorganisms are able to survive in extreme marine environments and, as a result, they produce complex molecules with unique biological interesting properties for a wide variety of industrial and biotechnological applications. Thus, different marine microorganisms (fungi, myxomycetes, bacteria, and microalgae) producing compounds with antioxidant, antibacterial, apoptotic, antitumoral and antiviral activities have been already isolated. This review compiles and discusses the discovery of bioactive molecules from marine microorganisms reported from 2018 onwards. Moreover, it highlights the huge potential of marine microorganisms for obtaining highly valuable bioactive compounds.     

Identification and regulation of novel compatible solutes from hypersaline stromatolite-associated cyanobacteria

Cyanobacteria are able to survive in various extreme environments via the production of organic compounds known as compatible solutes. In particular, cyanobacteria are capable of inhabiting hypersaline environments such as those found in intertidal regions. Cyanobacteria in these environments must possess regulatory mechanisms for surviving the changing osmotic pressure as a result of desiccation, rainfall and tidal fluxes. The objective of this study was to determine the compatible solutes that are accumulated by cyanobacteria from hypersaline regions, and specifically, the stromatolite ecosystems of Shark Bay, Western Australia. Previously, the cyanobacterial populations associated with these stromatolites were characterized in two separate studies. Compatible solutes were extracted from isolated cyanobacteria here and identified by nuclear magnetic resonance. As the media of isolation contained no complex carbon source, the solutes accumulated were likely synthesized by the cyanobacteria. The data indicate that from this one habitat taxonomically distinct cyanobacteria exposed to varying salinities accumulate a range of known compatible solutes. In addition, taxonomically similar cyanobacteria do not necessarily accumulate the same compatible solutes. Glucosylglycerol, a compatible solute unique to marine cyanobacteria was not detected; however, various saccharides, glycine betaine, and trimethylamine-N-oxide were identified as the predominant solutes. We conclude that the cyanobacterial communities from these hypersaline stromatolites are likely to possess more complex mechanisms of adaptation to osmotic stress than previously thought. The characterization of osmoregulatory properties of stromatolite microorganisms provides further insight into how life can thrive in such extreme environments.     

The role of modern and fossil cyanobacterial borings in bioerosion and bathymetry

Measurements on modern coral reefs at Lee Stocking Island (Bahamas) illustrate that boring cyanobacteria species make a major contribution to microboring bioerosion rates. Borings attributed to cyanobacteria also occur in fossil environments. Bioerosional studies on Permian and Triassic reefs show similar intensities to those observed on modern equivalents. The importance of borings assigned to cyanobacterial activity is even more apparent in paleobathymetry. Comparison of the bathymétrie ranges known from modern and fossil microborings demonstrates a preference of boring cyanobacteria for shallow marine environments. Furthermore, some traces are linked to distinct portions of the shallow euphotic zone. They significantly contribute to characterize typical microboring assemblages, which are used for paleodepth reconstructions. In contrast to these stenobathic species, one cyanobacterial species turned out to be eurybathic. It has been recorded as deep as the dysphotic zone but may even extend to the aphotic zone.     

A perspective on the biotechnological potential of extremophiles.

It is well recognized that many environments considered by man to be extreme are colonized by microorganisms which are specifically adapted to these ecological niches. A diverse range of bacteria, cyanobacteria, algae and yeasts have been isolated from such habitats and it is now widely accepted that these microorganisms provide a valuable resource not only for exploitation in novel biotechnological processes but also as models for investigating how biomolecules are stabilized when subjected to extreme conditions. This short review summarizes our current state of knowledge of this unique group of microorganisms and their enzymes, and attempts to identify their future biotechnological potential.     

Freshwater cyanophages

Cyanophages are double-stranded DNA viruses that infect cyanobacteria, and they can be found in both freshwater and marine environments. They have a complex pattern of host ranges and play important roles in controlling cyanobacteria population. Unlike marine cyanophages, for which there have been a number of recent investigations, very little attention has been paid to freshwater cyanophages. This review summarizes the taxonomy and morphology, host range, distribution, seasonal dynamics, and complete genomes of freshwater cyanophages, as well as diagnostic markers that can be used to identify them.     

The role of siderophores in iron acquisition by photosynthetic marine microorganisms

The photosynthetic picocyanobacteria and eukaryotic microorganisms that inhabit the open ocean must be able to supply iron for their photosynthetic and respiratory needs from the subnanomolar concentrations available in seawater. Neither group appears to produce siderophores, although some coastal cyanobacteria do. This is interpreted as an adaptation to the dilute oceanic environment rather than a phylogenetic constraint, since there are cases in which related taxa from different environments have the capacity to produce siderophores. Most photosynthetic marine microorganisms are presumably, however, capable of accessing iron from strong chelates since the majority of dissolved iron in seawater is complexed by organic ligands, including siderophores. Rather than direct internalization of siderophores and other iron chelates, marine organisms primarily appear to use uptake pathways that involve a reduction step to free bound iron, closely coupled with transport into the cell.     

Life under Nutrient Limitation in Oligotrophic Marine Environments: An Eco/Physiological Perspective of <Emphasis Type="Italic">Sphingopyxis alaskensis</Emphasis> (formerly <Emphasis Type="Italic">Sphingomonas alaskensis</Emphasis>)

The oceans of the world are nutrient-limited environments that support a dynamic diversity of microbial life. Heterotrophic prokaryotes proliferate in oligotrophic regions and affect nutrient transformation and remineralization thereby impacting directly on the all marine biota. An important challenge in studying the microbial ecology of oligotrophic environments has been the isolation of ecologically important species. This goal has been recognized not only for its relevance in defining the dynamics of community composition, but for enabling physiological studies of competitive species and inferring their impact on the microbial food web. This review describes the successful isolation attempts of the ultramicrobacterium, Sphingopyxis alaskensis (formerly described as Sphingomonas alaskensis) using extinction dilution culturing methods. It then provides a comprehensive perspective of the unique physiological and genetic properties that have been identified that distinguish it from typical copiotrophic species. These properties are described through studies of the growth phase and growth rate control of macromolecular synthesis, stress resistance and global gene expression (proteomics). We also discuss the importance of integrating ecological and physiological approaches for studying microorganisms in marine environments.     

海洋微生物高通量培养方法和分选技术的研究进展

海洋环境中蕴含着丰富的微生物资源,其在生态系统中发挥着重要作用,与人类生活息息相关。但是迄今通过传统的培养方法可被培养分离的海洋微生物不到1%。本文论述了海洋微生物的重要性,大多数海洋微生物不可被培养的原因,以及高通量培养方法和分选技术的研究进展。随着研究的深入,将会有更加实用有效的高通量培养方法和分选技术出现。     

Carbonate ooids of the Mesoarchaean Pongola Supergroup,South Africa

Ooids from the Mesoarchaean Chobeni Formation, Pongola Supergroup, KwaZulu‐Natal, South Africa are older than any ooids reported to date. They are made of dolomite and ankerite and show concentric, radial‐concentric, micritic, and radial fabrics. Radial ooids are interpreted to have originated from high‐Mg‐calcite and probably formed by microbial activity in a low‐energy regime, while concentric ooids had an aragonite precursor and formed biotically under agitated/high‐energy environmental conditions. Micritic ooids formed via the recrystallization of concentric ooids. Ooids and other allochems, such as intraclasts and peloids, contain carbonaceous matter. The close association of carbonaceous matter within ooid cortices with metabolically important elements, such as N, S and P, as identified by nano‐scale secondary ion mass spectrometry analysis, allows us to propose a biologically induced origin for some ooids. By analogy with modern examples, a variety of microbial communities probably played a role in carbonate precipitation and ooid formation. Shale‐normalized rare earth element (REE) distribution patterns of ooids and other allochems show positive La_SN, Gd_SN and Y_SN anomalies, superchondritic Y/Ho ratios and depleted light rare earth elements (LREEs) relative to the heavy rare earth elements (HREEs), which resemble those of seawater. These anomalies are less pronounced than expected for an open marine setting, which is interpreted as evidence for deposition in restricted shallow marine environments. Non‐seawater REE patterns in recrystallized matrix and pore‐ and vein‐filling carbonate likely reflect redistribution of rare earth elements during post‐depositional alteration and/or reflect differences in the elemental and REE compositions of diagenetic fluids.     

Microbially influenced formation of Neoarchean ooids

Ooids are accretionary grains commonly reported from turbulent, shallow‐water environments. They have long been associated with microbially dominated ecosystems and often occur in close proximity to, or embedded within, stromatolites, yet have historically been thought to form solely through physicochemical processes. Numerous studies have revealed both constructive and destructive roles for microbes colonizing the surfaces of modern calcitic and aragonitic ooids, but there has been little evidence for the operation of these processes during the Archean and Proterozoic, when both ooids and microbially dominated ecosystems were more widespread. Recently described carbonate ooids from the 2.9 Ga Pongola Supergroup, South Africa, include well‐preserved examples composed of diagenetic dolomite interpreted to have formed from a high‐Mg‐calcite precursor. Spatial distributions of organic matter and elements associated with metabolic activity (N, S, and P) were interpreted as evidence for a biologically induced origin. Here, we describe exceptionally well‐preserved ooids composed of calcite, collected from Earth's oldest known carbonate lake system, the ~2.72 Ga Meentheena Member (Tumbiana Formation), Fortescue Group, Western Australia. We used optical microscopy, Raman spectroscopy, XRD, SEM‐EDS, LA‐ICP‐MS, EA‐IRMS, and a novel micro‐XRF instrument to investigate an oolite shoal deposited between stromatolites that preserve abundant evidence for microbial activity. We report an extremely fine, radial‐concentric, calcitic microfabric that is similar to the primary and early diagenetic fabrics of calcitic ooids reported from modern temperate lakes. Early diagenetic silica has trapped isotopically light and thermally mature organic matter. The close association of organic matter with mineral phases and microfabrics related to primary and early diagenetic processes suggest incorporation of organic matter occurred during accretion, likely due to the presence of microbial biofilms. We conclude that the oldest known calcitic ooids were likely formed through processes similar to those that mediate the accretion of ooids in similar environments today, including formation within a microbial biosphere.     

固氮蓝细菌束毛藻生物固氮策略研究进展

固氮蓝细菌束毛藻(Tricodesmium)是海洋中丰度最高的固氮微生物,贡献了约42%的海洋生物固氮,为海洋生态系统提供了新的氮源,驱动海洋初级生产力和食物网,在海洋生物地球化学循环中发挥重要作用。作为海洋中“新氮”主要贡献者,束毛藻是一种不产生异形胞的丝状固氮蓝细菌。因为生物固氮的关键酶固氮酶对氧气十分敏感,一般固氮蓝细菌通常产生异形胞或采用夜间固氮的方式进行生物固氮,避免氧气对固氮酶的抑制作用。近年来研究发现,束毛藻具有一套独特的生物固氮体系,能够使同一藻丝在白天同时完成光合作用和生物固氮,并具有复杂的调控机制。本文综述了近年来束毛藻生物固氮策略的最新研究进展,介绍了其生物固氮和光合作用之间的精密调控机制,对拓展固氮微生物尤其是海洋蓝细菌固氮机制的认识具有借鉴意义。     

Microbial diversity of extant stromatolites in the hypersaline marine environment of Shark Bay, Australia

Stromatolites have been present on Earth, at various levels of distribution and diversity, for more than 3 billion years. Today, the best examples of stromatolites forming in hypersaline marine environments are in Hamelin Pool at Shark Bay, Western Australia. Despite their evolutionary significance, little is known about their associated microbial communities. Using a polyphasic approach of culture-dependent and culture-independent methods, we report the discovery of a wide range of microorganisms associated with these biosedimentary structures. There are no comparable reports combining these methodologies in the survey of cyanobacteria, bacteria, and archaea in marine stromatolites. The community was characterized by organisms of the cyanobacterial genera Synechococcus, Xenococcus, Microcoleus, Leptolyngbya, Plectonema, Symploca, Cyanothece, Pleurocapsa and Nostoc. We also report the discovery of potentially free-living Prochloron. The other eubacterial isolates and clones clustered into seven phylogenetic groups: OP9, OP10, Marine A group, Proteobacteria, Low G+C Gram-positive, Planctomycetes and Acidobacteria. We also demonstrate the presence of sequences corresponding to members of halophilic archaea of the divisions Euryarchaeota and Crenarchaeota and methanogenic archaea of the order Methanosarcinales. This is the first report of such archaeal diversity from this environment. This study provides a better understanding of the microbial community associated with these living rocks.