Date of Completion


Document Type

Honors College Thesis


Microbiology and Molecular Genetics

Thesis Type

Honors College

First Advisor

Matthew J. Wargo


Listeria monocytogenes, Ralstonia insidiosa, food safety, dual-species biofilms


Listeria monocytogenes is a bacterial species that can contaminate a wide range of food products and cause foodborne illness. Ingestion of L. monocytogenes-contaminated food can be especially dangerous for individuals who are immunocompromised, pregnant, or over the age of 65. Previous research showed that a single strain of L. monocytogenes may form enhanced biofilms with a single strain of Ralstonia insidiosa, a bacterium commonly found in potable water systems. This study investigated how common the L. monocytogenes and R. insidiosa biofilm enhancement is across strains of each species and other species in the genus Ralstonia. Our results show that L. monocytogenes does form enhanced biofilms with eight strains of R. insidiosa, R. pickettii, and R. spp.; and, similarly, R. insidiosa forms enhanced biofilms with eight strains of L. monocytogenes. Additionally, we propose that this enhancement is not fully dependent on direct cell-to-cell contact, as enhanced biofilm formation was observed to at least some degree when one species was exposed to the cell-free supernatant of the other. These findings indicate that L. monocytogenes may have the capacity to form enhanced biofilms with R. insidiosa in food processing facilities, and thus give insight into one means by which it may endure in these environments.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.