Diverse RNA Viruses Associated with Diatom, Eustigmatophyte, Dinoflagellate, and Rhodophyte Microalgae Cultures.

Unicellular microalgae are of immense ecological importance with growing commercial potential in industries such as renewable energy, food, and pharmacology. Viral infections can have a profound impact on the growth and evolution of their hosts. However, very little is known of the diversity within, and the effect of, unicellular microalgal RNA viruses. In addition, identifying RNA viruses in these organisms that could have originated more than a billion years ago constitutes a robust data set to dissect molecular events and address fundamental questions in virus evolution. We assessed the diversity of RNA viruses in eight microalgal cultures, including representatives from the diatom, eustigmatophyte, dinoflagellate, red algae, and euglenid groups. Using metatranscriptomic sequencing combined with bioinformatic approaches optimized to detect highly divergent RNA viruses, we identified 10 RNA virus sequences, with nine constituting new viral species. Most of the newly identified RNA viruses belonged to the double-stranded Totiviridae, Endornaviridae, and Partitiviridae, greatly expanding the reported host range for these families. Two new species belonging to the single-stranded RNA viral clade Marnaviridae, commonly associated with microalgal hosts, were also identified. This study highlights that a substantial diversity of RNA viruses likely exists undetected within the unicellular microalgae. It also highlights the necessity for RNA viral characterization and for investigation of the effects of viral infections on microalgal physiology, biology, and growth, considering their environmental and industrial roles. IMPORTANCE Our knowledge of the diversity of RNA viruses infecting microbial algae-the microalgae-is minimal. However, describing the RNA viruses infecting these organisms is of primary importance at both the ecological and economic scales because of the fundamental roles these organisms play in aquatic environments and their growing value across a range of industrial fields. Using metatranscriptomic sequencing, we aimed to reveal the RNA viruses present in cultures of eight microalgae species belonging to the diatom, dinoflagellate, eustigmatophyte, rhodophyte, and euglena major clades of algae. Accordingly, we identified 10 new divergent RNA virus species belonging to RNA virus families as diverse as the double-stranded Totiviridae, Endornaviridae, and Partitiviridae and the single-stranded Marnaviridae. By expanding the known diversity of RNA viruses infecting unicellular eukaryotes, this study contributes to a better understanding of the early evolution of the virosphere and will inform the use of microalgae in industrial applications.

Modifying filamentous algae nutrient scrubbers for improved wastewater treatment and harvestability - comparison with microalgae.

Algae have been well studied for their abilities to treat wastewater, and several types of treatment systems have been demonstrated at a range of scales. High Rate Algae Ponds (HRAP) are a microalgae-based system and Filamentous Algae Nutrient Scrubbers (FANS) a filamentous algae-based system. For FANS, nutrient removal rates are typically lower and more variable than HRAPs, while HRAPs have lower productivity and poor harvestability. This study investigated if modifying a FANS to mimic HRAPs (using high rate algae mesocosms HRAM), with respect to hydraulic retention time (HRT) and smaller footprint, overcomes FANS limitations, while increasing wastewater treatment and resource recovery compared to HRAPs. Biomass productivity on the FANS (10.5 ± 2.9 g m-2 d-1) and FANS with CO2 addition (19.0 ± 4.8 g m-2 d-1) were significantly higher (p < 0.01) compared to the HRAMs (6.7 ± 1.4 g m-2 d-1) and HRAMs with CO2 addition (8.1 ± 1.2 g m-2 d-1). Under phosphorus replete conditions, biomass production was significantly higher on FANS (44.8 ± 14.4 g m-2 d-1) than HRAMs (5.0 ± 0.6 g m-2 d-1). Effluent quality (nutrient removal) was significantly higher (p < 0.05) for FANS compared to HRAMS, regardless of treatment. For harvesting, FANS (2.9-41%) yielded significantly higher (p < 0.01) percentage solids with, and, without dewatering/gravity harvesting compared to the HRAM (0.04-0.11%). Modifying the operation of the FANS to mimic longer HRT of HRAMs resulted in higher areal biomass productivity and nutrient removal in the FANS than the HRAM, regardless of treatment. The use of filamentous algae on FANS greatly improved the percentage solids yield in the harvested biomass without the need for energy intensive harvesting techniques. Further investigations need to be undertaken to determine if benefits will be realised at fullscale.

Phenotypic trait variability as an indication of adaptive capacity in a cosmopolitan marine diatom.

Determining the adaptive capacity of marine phytoplankton is important in predicting changes in phytoplankton responses to ocean warming. Phytoplankton may consist of high levels of standing phenotypic and genetic variability, the basis of rapid evolution; however, few studies have quantified trait variability within and amongst closely related diatom species. Using 35 clonal cultures of the ubiquitous marine diatom Leptocylindrus isolated from six locations, spanning 2000 km of the south-eastern Australian coastline, we found evidence of significant intraspecific morphological and metabolic trait variability, which for 8 of 9 traits (growth rate, biovolume, C:N, silica deposition, silica incorporation rate, chl-a, and photosynthetic efficiency under dark adapted, growth irradiance, and high-light adaptation) were greater within a species than between species. Moreover, only two traits revealed a latitudinal trend with strains isolated from lower latitudes showing significantly higher silicification rates and protein:lipid content compared to their higher latitude counterparts. These data mirror recent studies on diatom intraspecific genetic diversity, which has found comparable levels of genetic diversity at a single site to those thousands of kilometres apart, and provide evidence of a functional role of diatom diversity that will allow for rapid adaptation via ecological selection on standing variation in response to changing conditions.

Trade-offs between effluent quality and ammonia volatilisation with CO2 augmented microalgal treatment of anaerobically digested food-waste centrate.

Diversion of food waste from landfill disposal to waste-to-energy facilities has become both an environmentally and economically viable option to support the circular bioeconomy. However, the liquid centrate produced during anaerobic digestion is high in total ammonia, with concentrations ~2000 g m-3, and can release gaseous emissions, including ammonia, methane, CO2 and nitrous oxide, to the atmosphere. Further treatment is required before discharge to sewer, or to the environment. Microalgal wastewater treatment systems augmented with CO2 offer a promising and cost-effective treatment solution for reducing both total ammonia concentrations and ammonia volatilisation. In this study, we investigate the effects of augmenting CO2 on nutrient removal and specifically nitrogen losses, as well as biomass productivity under two difference hydraulic retention times (HRT). Both CO2 addition and HRT affect nitrogen losses, with the percentage removal of total ammonia significantly lower (p < 0.01) when CO2 was added to the treatments, while increased HRT significantly increased (p < 0.05) total ammonia percentage removal. Total nitrogen budgets showed significantly lower (p < 0.01) abiotic nitrogen losses from the system when CO2 was added to the culture but at the expense of effluent quality. Both total suspended solids and volatile suspended solids significantly increased (p < 0.01) under longer HRT (8 days), with CO2 addition, while chlorophyll-a biomass significantly increased (p < 0.01) on longer HRT, regardless of CO2 addition. These results demonstrate that, while CO2 augmentation helped to mitigate ammonia losses to atmosphere, the trade-off was poorer effluent quality. Coupling CO2 augmentation with longer HRT increased biomass production and nutrient removal efficiency. This study provides an insight into how simple operational changes can alleviate some of the trade-offs between atmospheric losses and effluent quality. However, in order to manage the trade-off between reduced atmospheric losses and poorer effluent quality, further optimisation of the operation of the microalgal system treating food-waste centrate is required.

High-throughput screening for heterotrophic growth in microalgae using the Biolog Plate assay.

Microalgae produce a broad range of organic compounds that are increasingly being recognised for their value in novel product production and biotechnological applications. Most microalgae are photoautotrophic, but some are capable of either mixotrophy or heterotrophy. Reported enhanced biomass yields or contrasting metabolite profiles compared to autotrophic growth improve the economics of large-scale production of microalgae, which currently limits industrial applications. Here, the potential of a high-throughput method for the rapid screening of microalgal metabolism was assessed against 95 different carbon sources, using the cost-effective Biolog plate. Of the 5 microalgae tested, Desmodesmus communis (30 carbon sources) and Chlorella vulgaris (19 carbon sources) had the highest number of positive responses to carbon sources, whereas Chlorella sorokiniana had the most negative (toxic) response to the various carbon sources (77 carbon sources). Comparison of Biolog plate results with traditional culture techniques showed good agreement. Species with a high number of positive responses on the Biolog plate exhibited the highest biomass yield under heterotrophic conditions, whilst those with low number of positive responses exhibited the highest biomass yield under autotrophic conditions, using traditional culturing techniques. While the use of these plates is limited to obtaining axenic lines of microalgal species, the method provided a high-throughput assessment of carbon source metabolism, without the expense of undertaking large, laborious traditional culturing assessments. Such high-throughput assessments can be regarded as useful tools for progressing species selection, metabolic capacity and optimal culture conditions for microalgal biotechnology applications.

Effects of methylphenidate on heart rate and blood pressure among inpatients with acquired brain injury.

OBJECTIVE: The purpose of this study was to evaluate the effects of methylphenidate on heart rate and blood pressure in patients with acquired brain injury. DESIGN: The records of 60 consecutive hospitalized patients with acquired brain injury were reviewed for treatment with methylphenidate. Seventeen patients met the inclusion criteria. Systolic blood pressure, diastolic blood pressure, and heart rate recordings were compared before and after the introduction of methylphenidate. RESULTS: There was no significant difference in mean systolic blood pressure, diastolic blood pressure, and heart rate when patients received (118 mm Hg, 74 mm Hg, and 88 bpm) and did not receive (118 mm Hg, 73 mm Hg, and 86 bpm) methylphenidate. It was unclear whether there was a true trend toward medication effect on heart rate and blood pressure during the peak dose period. CONCLUSIONS: This retrospective study points to safe sympathetic effects of methylphenidate, yet future prospective studies are warranted to clarify the effects of methylphenidate on heart rate and blood pressure in the acquired brain injury population.