The Bacterial Microbiome of the Coral Skeleton Algal Symbiont Ostreobium Shows Preferential Associations and Signatures of Phylosymbiosis.

Ostreobium, the major algal symbiont of the coral skeleton, remains understudied despite extensive research on the coral holobiont. The enclosed nature of the coral skeleton might reduce the dispersal and exposure of residing bacteria to the outside environment, allowing stronger associations with the algae. Here, we describe the bacterial communities associated with cultured strains of 5 Ostreobium clades using 16S rRNA sequencing.

Unravelling microalgal-bacterial interactions in aquatic ecosystems through 16S rRNA gene-based co-occurrence networks.

Interactions between microalgae and bacteria can directly influence the global biogeochemical cycles but the majority of such interactions remain unknown. 16S rRNA gene-based co-occurrence networks have potential to help identify microalgal-bacterial interactions. Here, we used data from 10 Earth microbiome projects to identify potential microalgal-bacterial associations in aquatic ecosystems.

Chrysosporum ovalisporum is synonymous with the true-branching cyanobacterium Umezakia natans (Nostocales/Aphanizomenonaceae).

True branching is a facultative characteristic only known from two cyanobacteria in the Aphanizomenonaceae, Umezakia natans and Dolichospermum brachiatum. In both cases, its expression has been associated with environmental stress, and its practical use as a diacritical feature has been previously evaluated. In this study, we undertook further evaluation of the phylogeny of Umezakia natans and its relationship to Chrysosporum ovalisporum as a previous study suggested the two were potentially congeneric.

Precision early detection of invasive and toxic cyanobacteria: A case study of Raphidiopsis raciborskii.

Blooms of the toxic cyanobacterium, Raphidiopsis raciborskii (basionym Cylindrospermopsis raciborskii), are becoming a major environmental issue in freshwater ecosystems globally. Our precision prevention and early detection of R. raciborskii blooms rely upon the accuracy and speed of the monitoring method.

Are laboratory growth rate experiments relevant to explaining bloom-forming cyanobacteria distributions at global scale?

Predicting algal population dynamics using models informed by experimental data has been used as a strategy to inform the management and control of harmful cyanobacterial blooms. We selected toxic bloom-forming species Microcystis spp. and Raphidiopsis raciborskii (basionym Cylindrospermopsis raciborskii) for further examination as they dominate in 78 % and 17 %, respectively, of freshwater cyanobacterial blooms (cyanoHABs) reported globally over the past 30 years.

Subtropical freshwater phytoplankton show a greater response to increased temperature than to increased pCO.

Global increases in atmospheric CO and temperatures will impact aquatic systems, with freshwater habitats being affected. Some studies suggest that these conditions will promote cyanobacterial dominance. There is a need for a clearer picture of how algal species and strains within species will respond to higher temperatures and CO, especially in combination.

Differential expression of phosphorus acquisition genes in response to phosphorus stress in two Raphidiopsis raciborskii strains.

The cyanobacterium Raphidiopsis raciborskii is a nuisance in freshwater ecosystems. Strains vary in their physiological responses to environmental drivers, thus a greater understanding of the magnitude of strain variation is required to characterize the species. In this study, two strains of R.

Cylindrospermopsis raciborskii Virus and host: genomic characterization and ecological relevance.

Cylindrospermopsis (Raphidiopsis) raciborskii is an invasive, filamentous, nitrogen-fixing cyanobacterium that forms frequent blooms in freshwater habitats. While viruses play key roles in regulating the abundance, production and diversity of their hosts in aquatic ecosystems, the role(s) of viruses in the ecology of C. raciborskii is almost unexplored.

Genome variation in nine co-occurring toxic Cylindrospermopsis raciborskii strains.

Cyanobacteria form harmful algal blooms and are highly adapted to a range of habitats, in part due to their phenotype plasticity. This plasticity is partially the result of co-existence of multiple strains within a single population. The toxic cyanobacterium Cylindrospermopsis raciborskii has remarkable phenotypic plasticity, strain variation and environmental adaptation resulting in an expansion of its global range.

Variation within and between cyanobacterial species and strains affects competition: Implications for phytoplankton modelling.

Cyanobacteria Microcystis aeruginosa and Cylindrospermopsis raciborskii are two harmful species which co-occur and successively dominate in freshwaters globally. Within-species strain variability affects cyanobacterial population responses to environmental conditions, and it is unclear which species/strain would dominate under different environmental conditions. This study applied a Monte Carlo approach to a phytoplankton dynamic growth model to identify how growth variability of multiple strains of these two species affects their competition.

Review: a meta-analysis comparing cell-division and cell-adhesion in Microcystis colony formation.

The freshwater cyanobacterium Microcystis is a nuisance species. It forms large blooms on the water surface and overwhelmingly dominates the ecosystem through the formation of colonies from single cells surrounded by mucilage; however, the mechanism of colony formation is poorly understood. Two mechanisms of Microcystis colony formation have been proposed: cell-division, where cells remain attached after binary fission; and cell-adhesion, where single cells stick together.

Differences in cyanobacterial strain responses to light and temperature reflect species plasticity.

Microcystis aeruginosa and Cylindrospermopsis raciborskii are two cyanobacterial species that dominate freshwaters globally. Multiple strains of each species with different physiology occur, however, many studies have focused only on one or two strains, limiting our understanding of both strain variation and characterisation of the species. Therefore, in this study we examined the variation in growth and morphology of multiple isolates of both species, isolated from two adjacent Australian reservoirs.

Understanding the winning strategies used by the bloom-forming cyanobacterium Cylindrospermopsis raciborskii.

The cyanobacterium Cylindrospermopsis raciborskii is a widespread species increasingly being recorded in freshwater systems around the world. It is of particular concern because strains in some geographic areas are capable of producing toxins with implications for human and animal health. Studies of this species have increased rapidly in the last two decades, especially in the southern hemisphere where toxic strains are prevalent.

Nitrogen fixation by the diazotroph Cylindrospermopsis raciborskii (Cyanophyceae).

Nitrogen fixation has been proposed as a mechanism that allows the diazotrophic cyanobacterium, Cylindrospermopsis raciborskii, to bloom in nitrogen-limited freshwater systems. However, it is unclear whether dinitrogen fixation (N fixation) can supplement available dissolved inorganic nitrogen (DIN) for growth, or only provides minimum nitrogen (N) for cell maintenance under DIN deplete conditions. Additionally, the rate at which cells can switch between DIN use and N fixation is unknown.

Intraspecific variation in growth, morphology and toxin quotas for the cyanobacterium, Cylindrospermopsis raciborskii.

Cylindrospermopsis raciborskii is a bloom forming cyanobacterium with complex population dynamics and toxicity. In January of 2013 a single sample was collected from surface waters in Lake Wivenhoe, Australia, and twenty-four individual trichomes were isolated. Each isolate exhibited differences in growth rate, toxin cell quota and morphology, in the absence of phylogenetic heterogeneity.

Draft Genome Assembly of Filamentous Brackish Cyanobacterium Limnoraphis robusta Strain CS-951.

Limnoraphis robusta CS-951 is a sheathed, filamentous benthic, nonheterocystous cyanobacterium. It was isolated from brackish water and identified morphologically as Lyngbya majuscula. We report the draft genome of L.

Constitutive cylindrospermopsin pool size in Cylindrospermopsis raciborskii under different light and CO2 partial pressure conditions.

Cylindrospermopsin (CYN) and 7-deoxy-cylindrospermopsin (dCYN) are potent hepatotoxic alkaloids produced by numerous species of cyanobacteria, including the freshwater Cylindrospermopsis raciborskii. C. raciborskii is an invasive cyanobacterium, and the study of how environmental parameters drive CYN production has received significant interest from water managers and health authorities.

Adhesion molecules from the diatom Phaeodactylum tricornutum (Bacillariophyceae): genomic identification by amino-acid profiling and in vivo analysis.

Cell adhesion molecules (CAMs) are important in prokaryotes and eukaryotes for cell-cell and cell-substratum interactions. The characteristics of adhesive proteins in the model diatom Phaeodactylum tricornutum were investigated by bioinformatic analysis and in vivo characterization. Bioinformatic analysis of the protein coding potential of the P.

Nutrient-related changes in the toxicity of field blooms of the cyanobacterium, Cylindrospermopsis raciborskii.

Nutrients have the capacity to change cyanobacterial toxin loads via growth-related toxin production, or shifts in the dominance of toxic and nontoxic strains. This study examined the effect of nitrogen (N) and phosphorus on cell division and strain-related changes in production of the toxins, cylindrospermopsins (CYNs) by the cyanobacterium, Cylindrospermopsis raciborskii. Two short-term experiments were conducted with mixed phytoplankton populations dominated by C.

Characterization of the extracellular matrix of Phaeodactylum tricornutum (Bacillariophyceae): structure, composition, and adhesive characteristics.

The extracellular matrix of the ovoid and fusiform morphotypes of Phaeodactylum tricornutum (Bohlin) was characterized in detail. The structural and nanophysical properties were analyzed by microscopy. Of the two morphotypes, only the ovoid form secretes adhesive mucilage; light microscopy and scanning electron microscopy images showed that the mucilage was secreted from the girdle band region of the cell as cell-substratum tethers, accumulating on the surface forming a biofilm.

Physiological and molecular evidence that environmental changes elicit morphological interconversion in the model diatom Phaeodactylum tricornutum.

Over the last decades Phaeodactylum tricornutum has become a model to study diatom biology at the molecular level. Cells have the peculiarity to be pleiomorphic and it is thought that this character is triggered by culture conditions, although few quantitative studies have been performed and nothing is known at the molecular level. Our aim was to quantify the effect of growth conditions on cell morphology of different P.

The Phaeodactylum genome reveals the evolutionary history of diatom genomes.

Diatoms are photosynthetic secondary endosymbionts found throughout marine and freshwater environments, and are believed to be responsible for around one-fifth of the primary productivity on Earth. The genome sequence of the marine centric diatom Thalassiosira pseudonana was recently reported, revealing a wealth of information about diatom biology. Here we report the complete genome sequence of the pennate diatom Phaeodactylum tricornutum and compare it with that of T.

Adhesive modular proteins occur in the extracellular mucilage of the motile, pennate diatom Phaeodactylum tricornutum.

This Letter reports on adhesive modular proteins recorded by atomic force microscopy on live cells from the extracellular mucilage secreted from, and deposited around, the motile form of the pennate diatom Phaeodactylum tricornutum. This is the first report of modular proteins and their supramolecular assemblies, called adhesive nanofibers (ANFs), to be found on diatoms that use adhesives not only for substratum adhesion, but as a conduit for cell motility. The permanent adhesive pads secreted by Toxarium undulatum, a sessile centric diatom, were previously shown to possess ANFs with a modular protein backbone.