Catfish mucus alters the Flavobacterium columnare transcriptome

Authors: Lange, Miles; Abernathy, Jason; Farmer, Bradley

Submitted to: FEMS Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2018
Publication Date: 11/21/2018
Citation: Lange, M.D., Abernathy, J.W., Farmer, B.D. 2018. Catfish mucus alters the Flavobacterium columnare transcriptome. FEMS Microbiology Letters. 365(22)1-13. https://doi.org/10.1093/femsle/fny244.
DOI: https://doi.org/10.1093/femsle/fny244

Interpretive Summary: Columnaris disease which is caused by Flavobacterium columnare severely impacts the production of freshwater finfish species. Due to the impact on the aquaculture industry, research efforts to better understand the biological processes of F. columnare including the formation of biofilms and their contribution to disease are ongoing. To understand how biofilms develop under different growth conditions, we stimulated planktonic cells with or without fish mucus. Fish mucus has been shown to stimulate the formation of in vitro biofilms. RNA sequence analyses of planktonic cell and biofilm groups identified different genes that are required for biofilm formation. This included genes involved in the uptake of iron which is required for many biological functions. Among mucus-stimulated biofilms, we also identified unique genes that were expressed and have augmented the growth of the biofilms. These results will help us to 1) better understand the role biofilms play in the progression of columnaris disease and 2) identify additional potential protein targets for the use in developing new vaccine therapies.

Technical Abstract: Columnaris disease which is caused by Flavobacterium columnare severely impacts the production of freshwater finfish species. Due to the impact on the aquaculture industry, research efforts to better understand the biological processes of F. columnare including the formation of biofilms and their contribution to disease are ongoing. Our data shows that fish mucus enhances in vitro biofilm formation. Global analysis of F. columnare transcriptomes stimulated with or without fish mucus revealed significant variability among the differentially expressed genes (DEGs) of the planktonic and biofilm states. DEGs that were common among all biofilms were enriched for bacterial gene ontology groups such as signal transduction, ligand binding and cellular homeostasis and are likely necessary for biofilm formation. In addition different iron acquisition machinery including TonB dependent receptor and ferroxidase genes were expressed among all biofilms. The increased expression of TonB dependent receptor genes and the identification of siderophore synthesis genes among only mucus-stimulated biofilms help to validate a role for the TonB system as a virulence factor. Other DEGs specific to mucus-stimulated biofilms revealed gene ontology groups associated with ribosome biogenesis and protein translation. The current analysis of F. columnare transcriptomes adds valuable information about the basic biological processes that occur during the planktonic to biofilm transition. We were also able to show that stimulation of F. columnare with fish mucus leads to increased biofilm formation and that there is significant differential gene regulation correlated to this event. This work will no doubt serve as a basis for future studies on understanding how biofilms are established and how they contribute to disease progression.