Environmental algal phage isolates and their impact on production potential for food and biofuel applications.

AIMS: The United States Department of Energy is aiming to bring microalgal biofuels into commercial use by 2030 at the price of $3 per gasoline gallon equivalent. Large-scale production of biofuel faces many challenges including naturally occurring algal phages; and characterizing this threat is the aim of this study. METHODS AND RESULTS: Bench-scale experiments were performed to study the impact of viral infectivity on the production of microalgal in bioreactors. All environmental samples were tested positive for algal phages which showed various levels of infectivity against Synechocystis PCC 6803 and the environmental isolates of microalgae. The viral attachment to algal cells was observed under transmission electron microscopy (TEM) and to determine the shape and size of the viral particles. All the viruses detected were c. 50-60 nm icosahedral particles. Viral infection resulted in 48% reduction in the biomass of the infected algal culture in 22 days. CONCLUSIONS: This study has lead to the conclusion that the microalgal phages prevalent in natural environment may cause infections in broad range of microalgae used for biofuel production. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has detected and quantified the phages that can infect algal populations in natural freshwater habitats and laboratory cultures of microalgal strains. The impact of viral threat to health of commercial algal production operations has been identified in this study.

Bacteriophage-prokaryote dynamics and interaction within anaerobic digestion processes across time and space.

BACKGROUND: Bacteriophage-prokaryote dynamics and interaction are believed to be important in governing microbiome composition and ecosystem functions, yet our limited knowledge of the spatial and temporal variation in phage and prokaryotic community compositions precludes accurate assessment of their roles and impacts. Anaerobic digesters are ideal model systems to examine phage-host interaction, owing to easy access, stable operation, nutrient-rich environment, and consequently enormous numbers of phages and prokaryotic cells. RESULTS: Equipped with high-throughput, cutting-edge environmental genomics techniques, we examined phage and prokaryotic community composition of four anaerobic digesters in full-scale wastewater treatment plants across China. Despite the relatively stable process performance in biogas production, phage and prokaryotic groups fluctuated monthly over a year of study period, showing significant correlations between those two groups at the α- and ß-diversity levels. Strikingly, phages explained 40.6% of total variations of the prokaryotic community composition, much higher than the explanatory power by abiotic factors (14.5%). Consequently, phages were significantly (P < 0.010) linked to parameters related to process performance including biogas production and volatile solid concentrations. Association network analyses showed phage-prokaryote pairs were shallowly conserved since they were detected only within small viral clades. CONCLUSIONS: Those results collectively demonstrate phages as a major biotic factor in controlling prokaryotic composition and process performance. Therefore, phages may play a larger role in shaping prokaryotic community dynamics and process performance of anaerobic digesters than currently appreciated.