Klebsiella pneumoniae, a Gram-negative bacterium known for antibiotic-resistant and hypervirulent infections, builds protective biofilms that shield it from treatment. A new study published in BMC Microbiology reports that outer membrane vesicles (OMVs) released by the bacterium actively promote biofilm formation, and that these vesicles are enriched with messenger RNAs linked to biofilm regulation.
OMVs are nanoscale vesicular structures produced by Gram-negative organisms. They have previously been implicated in various aspects of K. pneumoniae physiology and pathogenesis, but the specific role of these vesicles in biofilm regulation remained poorly understood. The research team set out to explore how OMVs affect biofilm development and to clarify the potential mechanisms involved.
The study systematically compared planktonic OMVs (pOMVs) and biofilm OMVs (bOMVs) derived from classical K. pneumoniae (cKP) and hypervirulent K. pneumoniae (hvKP) strains with distinct biofilm-forming capacities. Using ultracentrifugation, dynamic light scattering, and transmission electron microscopy, the researchers confirmed that K. pneumoniae produces OMVs in both planktonic and biofilm states.
The two vesicle types differed markedly. Biofilm-derived OMVs showed significantly higher yields and larger diameters than their planktonic counterparts. Among the strains tested, the hypervirulent strain NTUH-K2044 produced the most abundant vesicles, which also displayed a more pronounced double-membrane structure under electron microscopy.
Functional testing showed that adding exogenous OMVs increased biofilm development. Crystal violet staining, scanning electron microscopy, and Live/Dead staining assays revealed that OMVs—particularly bOMVs—raised biofilm biomass, bacterial adhesion, matrix integrity, and bacterial viability, with effects that scaled in a dose-dependent manner. When the researchers applied GW4869, an inhibitor of OMV production, these biofilm-promoting effects disappeared, pointing to the vesicles themselves as the active agents.
To probe what the vesicles might be carrying, the team performed mRNA sequencing of the OMVs. The transcripts were abundant in genes encoding components of the quorum sensing (QS) system, fimbriae, lipopolysaccharides (LPS), capsular polysaccharides (CPS), efflux pumps, iron-metabolism proteins, and the two-component system. All of these are well-established regulators of biofilm development in bacteria.
A particularly striking finding concerned the Type II quorum sensing system. Genes involved in AI-2 biosynthesis within this system were markedly enriched in OMVs derived from K. pneumoniae cells in the biofilm state, compared with vesicles from planktonic growth. This pattern suggests that the RNA cargo of OMVs changes depending on the bacterial lifestyle, and that vesicles released within a biofilm may carry a molecular message tailored to biofilm maintenance.
The authors conclude that K. pneumoniae OMVs can enhance biofilm formation and matrix integrity while carrying abundant biofilm-associated mRNAs, suggesting a potential link between OMV mRNA transcripts and biofilm regulation in this pathogen. They describe this previously unrecognized role in biofilm formation as highlighting OMVs as a possible therapeutic target for managing K. pneumoniae biofilm infections. As the findings come from laboratory assays on bacterial strains, translating this concept into clinical strategies against biofilm-associated infections will require further research.
Subject of Research: Outer membrane vesicles from Klebsiella pneumoniae and their role in biofilm formation
Article Title: Outer membrane vesicles derived from Klebsiella pneumoniae enhance biofilm formation and are enriched in biofilm-associated mRNAs
Article References: Wang, J., Jian, Z., Chen, X., Li, Y., Liu, P., Yan, Q., & Liu, W. (2026). Outer membrane vesicles derived from Klebsiella pneumoniae enhance biofilm formation and are enriched in biofilm-associated mRNAs. BMC Microbiology. https://doi.org/10.1186/s12866-026-05850-7
Image Credits: AI Generated
DOI: 10.1186/s12866-026-05850-7
Keywords: Klebsiella pneumoniae, outer membrane vesicles, biofilm, mRNA transcriptome, quorum sensing, hypervirulent strains, antibiotic resistance, BMC Microbiology, GW4869, biofilm matrix, Outer, membrane
News Source: Drew Townsend. (October 27, 2026). Klebsiella pneumoniae outer membrane vesicles boost biofilm growth and carry biofilm-related mRNAs. Scienmag.
