Shell deformity as a marker for retrospective detection of a pathogenic unicellular alga, Coccomyxa sp., in mytilid mussels: A first case study and research agenda.

An L-shaped shell deformity (LSSD) on the posterior shell edge is known exclusively in wild mytilid mussels infected with photosynthetic Coccomyxa-like algae. LSSD forms due to the appearance of extra shell material; it only occurs if the mussel is heavily infected with the alga. Traditionally, observation of high amount of the green spots (algal colonies) on a large area of host soft tissues (most of the mantle and in adductor muscle) has been used to indicate a high infection rate. We examined 300 Mytilus spp. (100 small, 20-30 mm; 200 large, 40-60 mm) with a high degree of LSSD (parameter "d" > 5 mm) from the Lower St. Lawrence Estuary (Québec, Canada). Green spots were absent in two large mussels, and were only present along the mantle posterior edge in 14 large mussels; other individuals had high infection levels. Our observations suggest that some individuals could be in a state of remission, or, even more optimistically - mussels may be able to resist the pathogen. LSSD is the stable through-time marker for detection of mytilid mussels that are or were infected with Coccomyxa algae, and, thus, may provide information for the study of mussel immunity and control of alga distribution/migration in coastal waters worldwide.

First report of signs of infection by Coccomyxa-like algae in wild blue mussels, Mytilus spp., in the Gulf of Maine (USA, Maine).

In August 2019, visual inspection of intertidal zones of the Gulf of Maine (ME, USA) revealed young and adult wild blue mussels, Mytilus spp., in Alley Bay (Jonesport area) with the distinctive L-shaped shell deformity (LSSD) and green spots (GS) in the mantle and adductor muscle. LSSD is a characteristic sign of current or previous mussel infection by photosynthetic unicellular alga from the group Coccomyxa, while GS are algal colonies. Based on these findings, this study represents the first report of infection signs by pathogenic Coccomyxa-like algae in mussels from the coastal waters of the Northeastern United States, providing a base for future large scale monitoring of the alga in the region.

Mytilus trossulus and hybrid (M. edulis-M. trossulus) - New hosts organisms for pathogenic microalgae Coccomyxa sp. from the Estuary and northwestern Gulf of St. Lawrence, Canada.

During summer 2014-2017, wild mytilid mussels, highly infested with the pathogenic Coccomyxa-like microalgae, were collected along the Estuary and northwestern part of Gulf of St. Lawrence (Québec, Canada). Molecular identification showed that algae can be assigned to a single taxon, Coccomyxa sp. (KJ372210), whereas hosts are represented by Mytilus edulis, M. trossulus and hybrid between these two species. This is the first record of M. trossulus and hybrid among hosts of this pathogenic alga. Our results are indicative of a possible widespread distribution of Coccomyxa sp. in the Lower St. Lawrence Estuary and along coastal waters of Canadian Maritime provinces.

First record of the green microalgae Coccomyxa sp. in blue mussel Mytilus edulis (L.) from the Lower St. Lawrence Estuary (Québec, Canada).

During autumn 2012 and spring 2013, blue mussels Mytilus edulis (L.) with strongly deformed (L-shaped) posterior shell margins and green spots in soft tissue (microalgae) were collected from intertidal zone along the south shore of the Lower St. Lawrence Estuary near Rimouski (Québec, Canada). Identification of algal cells infesting mussels as Coccomyxa sp. was confirmed by rRNA sequencing and HPLC pigment analysis. Flow cytometric analysis revealed the presence of algal cells in the hemolymph and extrapallial fluid in mussels with deformed and non-deformed shells; concentrations of algal cells were ranged from about 200mL(-1) in mussels with actually non-deformed shells to concentrations reaching up to 3.8×10(7)mL(-1) in mussels with heavily deformed ones. Chemical analyses of soft tissues led us to conclude that butyltin compounds and trace metals cannot be considered among factors responsible for the shell deformity observed. Using scanning electron microscopy, the biogenic nature of the erosion on the external shell surface and aragonitic lenses of prisms in the curvature zone of deformed shells (in sections) were recorded. The sequence of the green algae from M. edulis of the Lower St. Lawrence Estuary was closely related to Coccomyxa sp. infecting M. edulis from the Flensburg Fjord (North Sea) and Modiolus modiolus (L.) from the Vityaz Bay (Sea of Japan).

Immune and allergenic effects of the microalga Coccomyxa sp. strain KJ in healthy humans: A pilot study.

BACKGROUND: The Coccomyxa sp. strain KJ (Coccomyxa KJ), a microalga found in Japan, has a potential function in controlling viral infections. Recently, its dry powder has been marketed as a health food product. OBJECTIVES: This pilot study investigated the effects of Coccomyxa KJ powder tablet intake on allergic reactions and immune functions in healthy participants. MATERIAL AND METHODS: Nine healthy volunteers (4 males and 5 females) who expressed interest in foods containing Coccomyxa KJ, and were willing to undergo blood tests, were recruited. Each individual was asked to take 2 Coccomyxa KJ powder tablets (0.3 g) before breakfast once a day for 4 weeks. The salivary immunoglobulin A (IgA) level and blood parameters (white blood cell (WBC) count, eosinophil and lymphocyte counts and percentages, natural killer (NK) cell activity, interleukin (IL)-6 level, and T helper (Th)1/Th2 cell ratio) were evaluated at baseline and weeks 2 and 4. RESULTS: The 4-week intake of Coccomyxa KJ did not affect salivary IgA levels, WBC count, eosinophil and lymphocyte counts and percentages, or the Th1/Th2 ratio. There were significant differences in the NK cell activity after 4 weeks, with an average increase of 11.78 (95% confidence interval (95% CI): 6.80-16.76). None of the patients experienced adverse reactions during or after the study. CONCLUSIONS: Long-term Coccomyxa KJ intake improved NK cell activity without causing adverse effects on the indicators of local immunity, systemic inflammation and immune response balance. This study suggests that Coccomyxa KJ powder tablets can induce beneficial immune modifications without causing any adverse effects.

An unexpected guest: a green microalga associated with the arsenic-tolerant shrub Acacia farnesiana.

The best-known plant endophytes include mainly fungi and bacteria, but there are also a few records of microalgae growing endophytically in vascular land plants, some of which belong to the genus Coccomyxa. In this study, we isolated a single-celled photosynthetic microorganism from the arsenic-tolerant shrub Acacia farnesiana, thus we hypothesized that it is an endophytic arsenic-tolerant microalga. The microorganism was identified as belonging to the genus Coccomyxa, and the observation of algal cells within the root tissues strongly suggests its endophytic nature. The alga's tolerance to arsenate (AsV) and its influence on the fitness of A. farnesiana in the presence of AsV were evaluated. Coccomyxa sp. can tolerate up to 2000 µM of AsV for periods shorter than 10 days, however, AsV-tolerance decreased significantly in longer exposure periods. The association with the microalga increased the pigment content in aboveground tissues of A. farnesiana seedlings exposed to AsV for 50 days, without changes in plant growth or arsenic accumulation. This work describes the association, probably endophytic, between an angiosperm and a microalga, confirming the ability of the genus Coccomyxa to form associations with land plants and broadening the known variety of plant endophytes.

Effects of light-emitting diodes (LEDs) on lipid production of the aerial microalga Coccomyxa sp. KGU-D001 under liquid- and aerial-phase conditions.

Algal biofuels are a promising alternative to fossil fuels, but their widespread use is hindered by problems with mass production. Light-emitting diodes (LEDs) with specific light wavelengths could be used as an energy source for algal growth and lipid synthesis. In this study, the effects of light source on the biomass and lipid production of the aerial microalga Coccomyxa sp. KGU-D001 were evaluated using LEDs. The integration of two-phase cultures, including growth and lipid production under the stress of nitrate depletion, was assessed for efficient lipid production under liquid- or aerial-phase conditions. Different wavelengths of light (blue, green, and red) were tested under liquid- and aerial-phase conditions. Under aerial-phase culture, the fatty acid contents in biofilm reached 320 mg g DWC-1 with the red LEDs. In view of these findings, we describe a one-step culture method for growth and lipid accumulation in algal biofilm under aerial-phase culture with red LED irradiation. When Coccomyxa biofilm was cultured on wet cotton wool with BBM in a petri dish under the red LED, it was able to grow and accumulate lipids under the aerial-phase condition. Based on the results of this study, a potential method for a continuous biodiesel production system is proposed.

Adaptation of Coccomyxa sp. to Extremely Low Light Conditions Causes Deep Chlorophyll and Oxygen Maxima in Acidic Pit Lakes.

Deep chlorophyll maxima (DCM) and metalimnetic oxygen maxima (MOM) are outstanding biogeochemical features of acidic pit lakes (APL). However, knowledge of the eukaryotic phototrophs responsible for their formation is limited. We aimed at linking the dynamics of phototrophic communities inhabiting meromictic APL in Spain with the formation of these characteristic layers. Firstly, the dynamics of DCM and MOM and their relation to physico-chemical parameters (photosynthetically active radiation (PAR), pH, dissolved ferric iron concentration, temperature), pigments and nutrient distribution is described; secondly, the phototrophic community composition is studied through a combination of microscopy, biomolecular and "omics" tools. Phototrophic communities of the studied APL show a low diversity dominated by green microalgae, specifically Coccomyxa sp., which have been successfully adapted to the chemically harsh conditions. DCM and MOM are usually non-coincident. DCM correspond to layers where phototrophs have higher chlorophyll content per cell to cope with extremely low PAR (<1 µmol m-2 s-1), but where photosynthetic oxygen production is limited. MOM correspond to shallower waters with more light, higher phytoplankton biomass and intense photosynthetic activity, which affects both oxygen concentration and water temperature. The main drivers of DCM formation in these APL are likely the need for nutrient uptake and photo-acclimation.