College of Science and Health Theses and Dissertations

Date of Award

Summer 8-21-2022

Degree Type


Degree Name

Master of Science (MS)


Biological Science

First Advisor

Joanna Brooke, PhD

Second Advisor

Megan Schrementi, PhD

Third Advisor

Timothy Sparkes, PhD


Stenotrophomonas maltophilia is a ubiquitous Gram-negative, multidrug resistant, opportunistic bacterial pathogen that causes various infections in humans. Recently, the use of bacteriophages as therapeutic agents, has gained interest as an alternative to traditional antibiotics. This thesis describes the isolation, purification, and characterization of S. maltophilia bacteriophage Bfi2 and discusses its activity against related, and often co-isolated, bacterial pathogens. Amplification of the phage resulted in clear, well-defined plaques and a titer of 1.73 ± 0.38 x 1011 PFU/ml. Bfi2 demonstrated the ability to lyse 55% of the S. maltophilia strains tested, suggesting that it has a moderate host range. However, the phage did not show cross taxonomic order infectivity, as the other bacterial species tested were not susceptible to infection. Efficiency of plating (EOP) assays shown Bfi2 to be nearly half as effective against another susceptible strain of S. maltophilia, F7221, compared to the host strain. Digestion of Bfi2 nucleic acid by type II restriction endonucleases, and visualization of products by agarose gel electrophoresis, indicated that the phage contained a dsDNA genome with an estimated size of 66.5 kb. Electron microscopy determined that Bfi2 has an icosahedral capsid 75.3 ± 3.3 nm by 69.6 ± 3.9 nm and a flexible, non-contractile tail 154.2 ± 4.6 nm by 9.3 ± 0.5 nm. Together, electron microscopy and genomic analysis suggests that Bfi2 likely belongs to the family Siphoviridae, with a B1 morphotype. Bfi2 was found to be stable at a temperature of 30°C. However, Bfi2 became increasingly unstable at 50°C over time, and quickly lost activity at 60°C. Moreover, Bfi2 was found to be stable at pH 5, 7, and 9. The kinetics of Bfi2 adsorption to host cells were determined. Bfi2 was found to have a relatively high adsorption efficiency, where ~97% of phages were adsorbed to host cells after 15 minutes of incubation. The adsorption rate constant (k) of Bfi2 was calculated to be ~2.15 ± 0.06 x 10-9 ml min-1 at a multiplicity of infection (MOI) of 0.05. Bfi2 may be suitable for future therapeutic applications based on its lytic activity and moderate host range.

SLP Collection


Included in

Biology Commons