Date Approved

2017

Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department or School

Biology

Committee Member

Michael Angell, Ph.D. Chair

Committee Member

Daniel Clemans, Ph.D.

Committee Member

Steven Francoeur, Ph.D.

Committee Member

David Kass, Ph.D.

Abstract

Throughout different times in freshwater cyanobacterial harmful algal blooms (cHAB), the availability of specific nutrients from the environment varies, causing fluctuations in the severity and species composition of a bloom. In addition to nutrient regulation of blooms, the cyanobacteria are subject to regulation by biotic factors, including phage infection. To address the potential role of cyanophages on the dominant species in most cHABs during nutrient-limited periods, we studied a specific host-phage system: Ma- LMM01 (phage) and Microcystis aeruginosa strain NIES298 (host), both of which originate from a eutrophic lake in Japan. The effect of phosphate and nitrogen limitation on phage and host replication was evaluated through modification of M. aeruginosa culture media. Growth of the host cells was monitored by culture light absorbance at 600 nm, while phage (genome) replication was quantified using real-time quantitative PCR (qPCR). Under phosphorus-limited conditions, Ma-LMM01 infected cells demonstrated a decrease in growth rate and carrying capacity compared to uninfected and infected nonlimited cultures. This relationship suggests that phage infection decreases M. aeruginosa growth to a greater degree under phosphorous stress than when the nutrient is readily available. In this model, these results indicate cyanophage replication may accelerate cHAB collapse under phosphorus-limiting conditions, and that increased concentrations of phosphorus may decrease the impact of cyanophage infections in the wild.

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