Transcriptomic profiles of Mannheimia haemolytica planktonic and biofilm associated cells

Authors: Ma, Hao; Alt, David; FALKENBERG, SHOLLIE - Auburn University; Briggs, Robert; Tatum, Fred; Clawson, Michael - Mike; Casas, Eduardo; Dassanayake, Rohana

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2024
Publication Date: 2/8/2024
Citation: Ma, H., Alt, D.P., Falkenberg, S.M., Briggs, R.E., Tatum, F.M., Clawson, M.L., Casas, E., Dassanayake, R.P. 2024. Transcriptomic profiles of Mannheimia haemolytica planktonic and biofilm associated cells. PLOS ONE. 19(2). Article e0297692. https://doi.org/10.1371/journal.pone.0297692.
DOI: https://doi.org/10.1371/journal.pone.0297692

Interpretive Summary: Bacterial biofilms are organized communities of bacterial cells which grow by attaching to surfaces, each other, and are covered by a film-like substance called matrix. Bacteria form biofilms to protect from the host immune response and also due to the limitation of nutrients. Bacteria in the biofilms showed increased resistance to antibiotics. Mannheimia haemolytica, which is the predominant cause of bovine respiratory disease complex (BRD), is also known to form biofilms. We selected three M. haemolytica serotypes associated with BRD for biofilm transcriptomic study. To assess deferential gene regulation of M. haemolytica between biofilm and non-biofilm (planktonic) stages, transcriptomic analyses were performed. Over 400 genes differentially expressed between biofilm and planktonic cells. Some of the differentially expressed genes identified in this study could potentially be used to design new vaccines.

Technical Abstract: Mannheimia haemolytica is the predominant agent causing bovine respiratory disease (BRD) and can form biofilms with increased resistance to antibiotic treatment and host immune defenses. To investigate the molecular mechanisms underlying M. haemolytica biofilm formation and to develop strategies against BRD, transcriptomic analyses were performed with mRNA isolated and sequenced from planktonic and biofilm cultures of pathogenic serotypes 1 (strain D153) and 6 (strain D174), and serotype 2 (strain 35), which associates less with BRD than serotypes 1 and 6. The three strains were cultured in two different media, Roswell Park Memorial Institute (RPMI) 1640 and brain heart infusion (BHI) to form the biofilms. The functions of the differentially expressed genes (DEGs) in biofilm associated cells were not significantly affected by the two media. A total of 476 to 662 DEGs were identified between planktonic cells and biofilm associated cells cultured under BHI medium. Functional analysis of the DEGs indicated that the biofilm associated cells suppressed translation and many biosynthesis processes. There were 234 DEGs identified in serotypes 1 and 6, but not in serotype 2. The functions of the DEGs included structural constituents of ribosomes, transmembrane proton transportation, proton channels, and proton-transporting ATP synthase. Some of the DEGs could potentially be used to design new vaccines.