Snapshot prediction of carbon productivity,carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy

Diatoms, an important group of phytoplankton, bloom annually in the Southern Ocean, covering thousands of square kilometers and dominating the region''s phytoplankton communities. In their role as the major food source to marine grazers, diatoms supply carbon, nutrients and energy to the Southern Ocean food web. Prevailing environmental conditions influence diatom phenotypic traits (for example, photophysiology, macromolecular composition and morphology), which in turn affect the transfer of energy, carbon and nutrients to grazers and higher trophic levels, as well as oceanic biogeochemical cycles. The paucity of phenotypic data on Southern Ocean phytoplankton limits our understanding of the ecosystem and how it may respond to future environmental change. Here we used a novel approach to create a ‘snapshot'' of cell phenotype. Using mass spectrometry, we measured nitrogen (a proxy for protein), total carbon and carbon-13 enrichment (carbon productivity), then used this data to build spectroscopy-based predictive models. The models were used to provide phenotypic data for samples from a third sample set. Importantly, this approach enabled the first ever rate determination of carbon productivity from a single time point, circumventing the need for time-series measurements. This study showed that Chaetoceros simplex was less productive and had lower protein and carbon content during short-term periods of high salinity. Applying this new phenomics approach to natural phytoplankton samples could provide valuable insight into understanding phytoplankton productivity and function in the marine system.     

Microbial tropicalization driven by a strengthening western ocean boundary current

Western boundary currents (WBCs) redistribute heat and oligotrophic seawater from the tropics to temperate latitudes, with several displaying substantial climate change‐driven intensification over the last century. Strengthening WBCs have been implicated in the poleward range expansion of marine macroflora and fauna, however, the impacts on the structure and function of temperate microbial communities are largely unknown. Here we show that the major subtropical WBC of the South Pacific Ocean, the East Australian Current (EAC), transports microbial assemblages that maintain tropical and oligotrophic (k‐strategist) signatures, to seasonally displace more copiotrophic (r‐strategist) temperate microbial populations within temperate latitudes of the Tasman Sea. We identified specific characteristics of EAC microbial assemblages compared with non‐EAC assemblages, including strain transitions within the SAR11 clade, enrichment of Prochlorococcus, predicted smaller genome sizes and shifts in the importance of several functional genes, including those associated with cyanobacterial photosynthesis, secondary metabolism and fatty acid and lipid transport. At a temperate time‐series site in the Tasman Sea, we observed significant reductions in standing stocks of total carbon and chlorophyll a, and a shift towards smaller phytoplankton and carnivorous copepods, associated with the seasonal impact of the EAC microbial assemblage. In light of the substantial shifts in microbial assemblage structure and function associated with the EAC, we conclude that climate‐driven expansions of WBCs will expand the range of tropical oligotrophic microbes, and potentially profoundly impact the trophic status of temperate waters.     

Identification of Alkaloid Compounds Arborinine and Graveoline from Ruta angustifolia (L.) Pers for their Antifungal Potential against Isocitrate lyase (ICL1) gene of Candida albicans

Mycopathologia - Candida albicans has been reported globally as the most widespread pathogenic species contributing candidiasis from superficial to systemic infections in immunocompromised...     

Phenotypic Plasticity of Southern Ocean Diatoms: Key to Success in the Sea Ice Habitat?

Diatoms are the primary source of nutrition and energy for the Southern Ocean ecosystem. Microalgae, including diatoms, synthesise biological macromolecules such as lipids, proteins and carbohydrates for growth, reproduction and acclimation to prevailing environmental conditions. Here we show that three key species of Southern Ocean diatom (Fragilariopsis cylindrus, Chaetoceros simplex and Pseudo-nitzschia subcurvata) exhibited phenotypic plasticity in response to salinity and temperature regimes experienced during the seasonal formation and decay of sea ice. The degree of phenotypic plasticity, in terms of changes in macromolecular composition, was highly species-specific and consistent with each species’ known distribution and abundance throughout sea ice, meltwater and pelagic habitats, suggesting that phenotypic plasticity may have been selected for by the extreme variability of the polar marine environment. We argue that changes in diatom macromolecular composition and shifts in species dominance in response to a changing climate have the potential to alter nutrient and energy fluxes throughout the Southern Ocean ecosystem.     

The central role of selenium in the biochemistry and ecology of the harmful pelagophyte,Aureococcus anophagefferens

The trace element selenium (Se) is required for the biosynthesis of selenocysteine (Sec), the 21st amino acid in the genetic code, but its role in the ecology of harmful algal blooms (HABs) is unknown. Here, we examined the role of Se in the biology and ecology of the harmful pelagophyte, Aureococcus anophagefferens, through cell culture, genomic analyses, and ecosystem studies. This organism has the largest and the most diverse selenoproteome identified to date that consists of at least 59 selenoproteins, including known eukaryotic selenoproteins, selenoproteins previously only detected in bacteria, and novel selenoproteins. The A. anophagefferens selenoproteome was dominated by the thioredoxin fold proteins and oxidoreductase functions were assigned to the majority of detected selenoproteins. Insertion of Sec in these proteins was supported by a unique Sec insertion sequence. Se was required for the growth of A. anophagefferens as cultures grew maximally at nanomolar Se concentrations. In a coastal ecosystem, dissolved Se concentrations were elevated before and after A. anophagefferens blooms, but were reduced by >95% during the peak of blooms to 0.05 nℳ. Consistent with this pattern, enrichment of seawater with selenite before and after a bloom did not affect the growth of A. anophagefferens, but enrichment during the peak of the bloom significantly increased population growth rates. These findings demonstrate that Se inventories, which can be anthropogenically enriched, can support proliferation of HABs, such as A. anophagefferens through its synthesis of a large arsenal of Se-dependent oxidoreductases that fine-tune cellular redox homeostasis.     

First description of the environmental niche of the epibenthic dinoflagellate species Coolia palmyrensis,C. malayensis,and C. tropicalis (Dinophyceae) from Eastern Australia

Environmental variables such as temperature, salinity, and irradiance are significant drivers of microalgal growth and distribution. Therefore, understanding how these variables influence fitness of potentially toxic microalgal species is particularly important. In this study, strains of the potentially harmful epibenthic dinoflagellate species Coolia palmyrensis, C. malayensis, and C. tropicalis were isolated from coastal shallow water habitats on the east coast of Australia and identified using the D1‐D3 region of the large subunit (LSU) ribosomal DNA (rDNA). To determine the environmental niche of each taxon, growth was measured across a gradient of temperature (15–30°C), salinity (20–38), and irradiance (10–200 μmol photons · m^?2 · s^?1). Specific growth rates of Coolia tropicalis were highest under warm temperatures (27°C), low salinities (ca. 23), and intermediate irradiance levels (150 μmol photons · m^?2 · s^?1), while C. malayensis showed the highest growth at moderate temperatures (24°C) and irradiance levels (150 μmol photons · m^?2 · s^?1) and growth rates were consistent across the range of salinity levels tested (20–38). Coolia palmyrensis had the highest growth rate of all species tested and favored moderate temperatures (24°C), oceanic salinity (35), and high irradiance (>200 μmol photons · m^?2 · s^?1). This is the first study to characterize the environmental niche of species from the benthic harmful algal bloom genus Coolia and provides important information to help define species distributions and inform risk management.     

Unique Aspects of the Structure and Dynamics of Elementary Iβ Cellulose Microfibrils Revealed by Computational Simulations

Flooding is detrimental for plants, primarily because of restricted gas exchange underwater, which leads to an energy and carbohydrate deficit. Impeded gas exchange also causes rapid accumulation of the volatile ethylene in all flooded plant cells. Although several internal changes in the plant can signal the flooded status, it is the pervasive and rapid accumulation of ethylene that makes it an early and reliable flooding signal. Not surprisingly, it is a major regulator of several flood-adaptive plant traits. Here, we discuss these major ethylene-mediated traits, their functional relevance, and the recent progress in identifying the molecular and signaling events underlying these traits downstream of ethylene. We also speculate on the role of ethylene in postsubmergence recovery and identify several questions for future investigations.Come gather round people wherever you roamAnd admit that the waters around you have grownAnd accept it that soon you’ll be drenched to the boneIf your time to you is worth savingAnd you’d better start swimming or you’ll sink like a stoneFor the times they are a-changing…THE TIMES THEY ARE A-CHANGIN''Words and Music by Bob DylanCopyright © 1963, 1964 Warner Bros. Inc.Copyright Renewed 1991, 1992 Special Rider MusicInternational Copyright Secured. All Rights Reserved.Reprinted by Permission.Fifty years later, these prophetic words from Dylan’s legendary song strangely ring true. We live in an increasingly wetter world. Flooding events have become more frequent, severe, and unpredictable, a trend that is linked to climate change (Arnell and Liu, 2001; Hirabayashi et al., 2013). Not only do they destroy human lives, but also, they affect plants, on which we depend so much. Flooding negatively affects plant biodiversity, natural species distribution, and global food production because of crop losses (Silvertown et al., 1999; Normile, 2008), because most terrestrial plants, including major crops, are extremely sensitive to wet conditions. It might seem counterintuitive that a molecule so biologically benign and indispensable for plant growth and function is harmful when present in excess. However, this is attributed to the fact that water is an extremely poor medium for gas diffusion. Hampered gas exchange with flooded organs leads to restriction of two vital plant processes: photosynthesis and respiration. The problem is compounded by stagnant and/or turbid floodwaters, because this further restricts the availability of light and oxygen. An energy crisis quickly results owing to an imbalance between energy production and consumption, ultimately causing plant mortality. Flooding survival tactics in the plant kingdom vary widely and include several morphological, anatomical, physiological, and molecular changes that can prolong survival and even facilitate permanent habitation in wet environments (Voesenek and Bailey-Serres, 2015). Initiation of these changes requires accurate and timely perception of water inundation to initiate adaptive responses. The term flooding encompasses both waterlogging and submergence. Waterlogging implies soil flooding, where only roots are exposed to wet conditions. Submergence also immerses the shoot (partially or wholly). Unless otherwise specified, this nomenclature will be used throughout this article.     

STATE TRANSITIONS AND NONPHOTOCHEMICAL QUENCHING DURING A NUTRIENT‐INDUCED FLUORESCENCE TRANSIENT IN PHOSPHORUS‐STARVED DUNALIELLA TERTIOLECTA1

Assessments of nutrient‐limitation in microalgae using chl a fluorescence have revealed that nitrogen and phosphorus depletion can be detected as a change in chl a fluorescence signal when nutrient‐starved algae are resupplied with the limiting nutrient. This photokinetic phenomenon is known as a nutrient‐induced fluorescence transient, or NIFT. Cultures of the unicellular marine chlorophyte Dunaliella tertiolecta Butcher were grown under phosphate starvation to investigate the photophysiological mechanism behind the NIFT response. A combination of low temperature (77 K) fluorescence, photosynthetic inhibitors, and nonphotochemical quenching analyses were used to determine that the NIFT response is associated with changes in energy distribution between PSI and PSII and light‐stress‐induced nonphotochemical quenching (NPQ). Previous studies point to state transitions as the likely mechanism behind the NIFT response; however, our results show that state transitions are not solely responsible for this phenomenon. This study shows that an interaction of at least two physiological processes is involved in the rapid quenching of chl a fluorescence observed in P‐starved D. tertiolecta: (1) state transitions to provide the nutrient‐deficient cell with metabolic energy for inorganic phosphate (P_i)‐uptake and (2) energy‐dependent quenching to allow the nutrient‐stressed cell to avoid photodamage from excess light energy during nutrient uptake.