Graduation Year


Document Type




Degree Granting Department

Marine Science

Major Professor

Dr. John H. Paul.


Lysogeny, Synechococcus, Prophage induction, Cyanophage, Marine prophage induction assay, Mpia, Viruses, Picoplankton, Phytoplankton, Environmental mutagenesis


Part 1:Prophage induction has been demonstrated to be a sensitive indicator for a wide variety of toxic and mutagenic compounds and, as a consequence, has been utilized for biologically based carcinogen screenings. Fourteen marine bacterial isolates were screened for development into the Marine Prophage Induction Assay (MPIA), for marine samples. The selected isolate (P99-4S3) was identified by 16S rDNA sequencing as Pseudomonas aeruginosa. This isolate demonstrated a log-linear response to increasing dose of mutagens, and sensitivity to known environmental contaminants. Field-testing of the assay over two years demonstrated the MPIA would be a useful screening tool for environmental contamination.Part 2:The observed resistance of natural populations of Synechococcus to viral infection may be due to lysogeny with associated homoimmunity.

A thirteen-month study of lysogeny in natural populations of Synechococcus demonstrated that lysogeny does occur and exhibits a seasonal pattern.Experiments were performed along a transect of the Mississippi River plume, which provided a variety of ambient nutrient regimes for comparison of lysogeny in Synechococcus. Nutrient amendments did not enable induction and often led to a decrease in viral production. Lysogeny in Synechococcus was primarily correlated with ambient host and cyanophage abundance.Cross-infectivity studies demonstrated cyanophage isolates possess variable virulence. The 35 isolates were examined by transmission electron microscopy (TEM), with 33 identified as myoviruses and two as podoviruses. This dominance of myovirus lytic cyanophage is consistent with prior observations.Twenty-five Synechococcus isolates were screened for prophage induction utilizing the inducing agent Mitomycin C.