Bacterial response to spatial gradients of algal-derived nutrients in a porous microplate

Photosynthetic microalgae are responsible for 50% of the global atmospheric CO2 fixation into organic matter and hold potential as a renewable bioenergy source. Their metabolic interactions with the surrounding microbial community (the algal microbiome) play critical roles in carbon cycling, but due to methodological limitations, it has been challenging to examine how community development is influenced by spatial proximity to their algal host. Here we introduce a copolymer-based porous microplate to co-culture algae and bacteria, where metabolites are constantly exchanged between the microorganisms while maintaining physical separation. In the microplate, we found that the diatom Phaeodactylum tricornutum accumulated to cell abundances ~20 fold higher than under normal batch conditions due to constant replenishment of nutrients through the porous structure. We also demonstrate that algal-associated bacteria, both single isolates and complex communities, responded to inorganic nutrients away from their host as well as organic nutrients originating from the algae in a spatially predictable manner. These experimental findings coupled with a mathematical model suggest that host proximity and algal culture growth phase impact bacterial community development in a taxon-specific manner through organic and inorganic nutrient availability. Our novel system presents a useful tool to investigate universal metabolic interactions between microbes in aquatic ecosystems.

Bacterial response to spatial gradients of algal-derived nutrients in a porous microplate

Photosynthetic microalgae are responsible for 50% of the global atmospheric CO2 fixation into organic matter and hold potential as a renewable bioenergy source. Their metabolic interactions with the surrounding microbial community (the algal microbiome) play critical roles in carbon cycling, but due to methodological limitations, it has been challenging to examine how community is developed by spatial proximity to their algal host. Here we introduce a hydrogel-based porous microplate to co-culture algae and bacteria, where metabolites are constantly exchanged between the microorganisms while maintaining physical separation. In the microplate we found that the diatom Phaeodactylum tricornutum accumulated to cell abundances ~20 fold higher than under normal batch conditions due to constant replenishment of nutrients through the hydrogel. We also demonstrate that algal-associated bacteria, both single isolates and complex communities, responded to inorganic nutrients away from their host as well as organic nutrients originating from the algae in a spatially predictable manner. These experimental findings coupled with a mathematical model suggest that host proximity and algal culture growth phase impact bacterial community development in a taxon-specific manner through organic and inorganic nutrient availability. Our novel system presents a useful tool to investigate universal metabolic interactions between microbes in aquatic ecosystems.

Utilization of Semi-Continuous Algae Culture for the Treatment of Recycled Dairy Lagoon Wash Water

Background: The utilization of animal wastes in algal culture has proven to be challenging. The utilization of “free” nutrients has drawn many researchers and industries to developing business models that call for the use of these free nutrients, which comes at a cost. Some of these costs include reduced productivity, increased contamination, lower-value target markets, and lower treatment capabilities (for wastewater treatment applications). This paper evaluates the impact of dairy lagoon effluent on productivity and wastewater treatment ability. Methods: Screened dairy lagoon wash water was fed to four three square meter outdoor open paddlewheel algal cultivation reactors. The units were operated semi-continuously for one and a half years. Seasonal productivity and nutrient uptake rates for nitrogen (N) and phosphorous (N) were measured against wastewater dilution requirements. Seasonal algal species dominance was also recorded. Wastewater was added at two levels, and the lower level was supplemented with synthetic fertilizer. Results: Seasonal N uptake rates ranged from 0.5 to 1.2 grams of N uptake per square meter per day, while P uptake ranged from 0.17 to 0.3 grams of P per square meter per day depending on season and hydraulic residence time (HRT). N removal efficiency ranged at 40 to 70% for semicontinuous operation, depending on HRT, season, and dilution of influent wastewater, which was made up from 1.5% to 13% of the daily water exchange. Conclusion: Algal reactors tended to be N limited due to the inability to add enough dairy wastewater to mitigate the high turbidity and dark color. Treatments with lower levels of added dairy wastewater tended to show higher nutrient removal. Algal culture from dairy wash water could benefit from a pretreatment step to reduce turbidity and color, promoting algal growth and productivity.

The analysis of the genetic polymorphism of Chlorella vulgaris Beyer. culture growing in the presence of sodium selenite, zinc sulfate and chromium chloride

The use of microalgae for the economic needs and the commercial goals determines the areas of the scientific researches that will make it possible to increase their productivity. It is also important to direct the metabolism of the algae to the activating of certain synthetic processes in order to obtain the desired compounds. The metals and non-metals, entering into the cell, have a high biochemical activity. These elements modify the metabolic reactions in general and the metabolic reactions related to the functioning of the genome of microalgae cells. Aim. The aim was to study the genetic polymorphism of Chlorella vulgaris under the action of such trace elements as selenium, zinc and chromium in order to optimize the methods of algae cultivation and the obtaining of the beneficial compounds. Methods. The hydrobiological methods of algae cultivation, DNA isolation method by Rogers S. and Bendich A. (1985), PCR-analysis with ISSR (inter simple sequence repeats)- and IRAP-markers (inter-retransposon amplified polymorphism) have been used. Results. For all samples of C. vulgaris 109 DNA-fragments were obtained and 42 of them were polymorphic (38.5%). Jacquard distances (DJ) between the samples of C. vulgaris culture (cultures are grown on the media with different elements compositions and control (standard conditions) were 0.232 (only selenite), 0.206 (selenite and zinc) and 0.300 (selenite and chromium). Conclusions. Probably the genetic modifications of C. vulgaris cells are caused by the additional introduction of the microelements into the culture medium. The genetic polymorphism of the algae grown on media with various trace elements and their combinations was like the genetic polymorphism of the unicellular green algae grown in the natural conditions. It indicates the absence of significant genotoxic effects of the trace elements and high metabolic and genetic plasticity of algal culture.

Biochemical Composition of Chlorella vulgaris Grown on Sugarcane Molasses

The quest for green and sustainable biofuel to serve as alternative to the conventional fossil fuel have remained a grey area in biotechnology. The Chlorella vulgaris was isolated from the African Regional Aquacultural Centre Aluu, Port Harcourt, Nigeria. Sugarcane Molasses modified Bold Basal medium was used to cultivate the Microalgae mixotrophically. The algal culture was incubated at room temperature for 15 days with continuous aeration and 12:12 hour photoperiod under artificial illumination of 2000 lux. The proximate composition of the biomass showed 6.28%wt, 67.37% wt and 11.35%wt of moisture, volatile organic matter and Fixed carbon content respectively. The ultimate composition of Chlorella biomass revealed that Carbon was 42.46% while Oxygen content was 27.93%. Nitrogen content was 6.62% while Sulphur content was 0.82% while hydrogen content was 6.74%. The study further identified that algal biomass from C. vulgaris has the potential of serving as both nutraceuticals and bioenergy feedstock. There is need for further studies around the algae oil oriented optimization as a veritable tool for biotechnological advancements.

Effect of pluronic block polymers and N-acetylcysteine culture media additives on growth rate and fatty acid composition of six marine microalgae species

The efficiency of microalgal biomass production is a determining factor for the economic competitiveness of microalgae-based industries. N-acetylcysteine (NAC) and pluronic block polymers are two compounds of interest as novel culture media constituents because of their respective protective properties against oxidative stress and shear-stress-induced cell damage. Here we quantify the effect of NAC and two pluronic (F127 and F68) culture media additives upon the culture productivity of six marine microalgal species of relevance to the aquaculture industry (four diatoms-Chaetoceros calcitrans, Chaetoceros muelleri, Skeletonema costatum, and Thalassiosira pseudonana; two haptophytes-Tisochrysis lutea and Pavlova salina). Algal culture performance in response to the addition of NAC and pluronic, singly or combined, is dosage- and species-dependent. Combined NAC and pluronic F127 algal culture media additives resulted in specific growth rate increases of 38%, 16%, and 24% for C. calcitrans, C. muelleri, and P. salina, respectively. Enhanced culture productivity for strains belonging to the genus Chaetoceros was paired with an ~27% increase in stationary-phase cell density. For some of the species examined, culture media enrichments with NAC and pluronic resulted in increased omega-3-fatty acid content of the algal biomass. Larval development (i.e., growth and survival) of the Pacific oyster (Crassostrea gigas) was not changed when fed a mixture of microalgae grown in NAC- and F127-supplemented culture medium. Based upon these results, we propose that culture media enrichment with NAC and pluronic F127 is an effective and easily adopted approach to increase algal productivity and enhance the nutritional quality of marine microalgal strains commonly cultured for live-feed applications in aquaculture. Key points • Single and combined NAC and pluronic F127 culture media supplementation significantly enhanced the productivity of Chaetoceros calcitrans and Chaetoceros muelleri cultures. • Culture media enrichments with NAC and F127 can increase omega-3-fatty acid content of algal biomass. • Microalgae grown in NAC- and pluronic F127-supplemented culture media are suitable for live-feed applications.

Paraphysoderma sedebokerense Infection in Three Economically Valuable Microalgae: Host Preference Correlates with Parasite Fitness

The blastocladialean fungus Paraphysoderma sedebokerense parasitizes three microalgae species of economic interest: Haematococcus pluvialis, Chromochloris zofingiensis and Scenedesmus dimorphus. For the first time, we characterized the developmental stages of isolated fungal propagules in H. pluvialis co-culture, finding a generation time of 16 h. We established a patho-system to compare the infection in the three different host species for 48 h, with two different setups to quantify parameters of the infection and parameters of the parasite fitness. The prevalence of the parasite in H. pluvialis and C. zofingiensis cultures was 100%, but only 20% in S. dimorphus culture. The infection of S. dimorphus not only reached lower prevalence but was also qualitatively different; the infection developed preferentially on senescent cells and more resting cysts were produced, being consistent with a reservoir host. In addition, we carried out cross infection experiments and the inoculation of a mixed algal culture containing the three microalgae, to determine the susceptibility of the host species and to investigate the preference of P. sedebokerense for these microalgae. The three tested microalgae showed different susceptibility to P. sedebokerense, which correlates with blastoclad’s preference to the host in the following order: H. pluvialis > C. zofingiensis > S. dimorphus.

Monoclonal Culture and Characterization of Symbiodiniaceae C1 Strain From the Scleractinian Coral Galaxea fascicularis

The symbiosis between cnidarian hosts and photosynthetic dinoflagellates of the family Symbiodiniaceae (i.e., zooxanthellae) provides the energy foundation of coral reef ecosystems in oligotrophic waters. The structure of symbiont biota and the dominant species of algal symbiont partly shape the environmental adaptability of coral symbiotes. In this study, the algal symbiont cells were isolated from the tentacles of Galaxea fascicularis, a hermatypic coral with obvious differentiation in heat resistance, and were cultured in vitro with an improved L1 medium. An algal monoclonal cell line was established using separated algal culture drops and soft agar plating method, and named by GF19C1 as it was identified as Cladocopium sp. C1 (Symbiodiniaceae) based on its ITS1, ITS2, and the non-coding region of the plastid psbA minicircle (psbAncr) sequences. Most GF19C1 cells were at the coccoid stage of the gymnodinioid, their markedly thickened (ca. two times) cell wall suggests that they developed into vegetative cysts and have sexual and asexual reproductive potential. The average diameter of GF19C1 cells decreased significantly, probably due to the increasing mitotic rate. The chloroplasts volume density of GF19C1 was significantly lower than that of their symbiotic congeners, while the surface area density of thylakoids relative to volumes of chloroplasts was not significantly changed. The volume fraction of vacuoles increased by nearly fivefold, but there was no significant change in mitochondria and accumulation bodies. Light-temperature orthogonal experiments showed that, GF19C1 growth preferred the temperature 25 ± 1°C (at which it is maintained post-isolation) rather than 28 ± 1°C under the light intensity of 42 ± 2 or 62 ± 2 μmol photons m–2 s–1, indicating an inertia for temperature adaptation. The optimum salinity for GF19C1 growth ranged between 28–32 ppt. The monoclonal culture techniques established in this study were critical to clarify the physiological and ecological characteristics of various algal symbiont species, and will be instrumental to further reveal the roles of algal symbionts in the adaptive differentiation of coral-zooxanthellae holobionts in future studies.