Table 1 Summary for intrinsic factors implicated in A. baumannii biofilm formation and regulation
From: Acinetobacter baumannii biofilm and its potential therapeutic targets
Biofilm factors | Function | References |
|---|---|---|
Outer membrane proteins (OmpA) | Well-characterized virulence factor in maintaining cell membrane integrity, mediating drug resistance, altering host immune response, starting the formation of biofilms, invading host epithelial cells, and inducing host cell apoptosis | |
Biofilm-associated protein (BAP) | Important for intercellular cell adhesion, bacterial cell aggregation, maintenance, biofilm development, and maturation on different surfaces such as polypropylene, polystyrene, and titanium | [40] |
Chaperon–usher (Csu) pilus assembly system of pili | Regarded as the most important virulence factor in facilitating the irreversible adhesion of cells to an abiotic surface and biofilm formation | [41] |
Bla PER1 | It’s presence and expression help in the adhesion to both biotic and abiotic surfaces, which promotes the formation of biofilm | [32] |
Extracellular polymeric substance (EPS) | Form the biofilm matrix after irreversible cell attachment to the surface and considered the most important component of biofilm matrix | [42] |
Quorum sensing (QS) system | It produces the signaling molecules, autoinducers to maintain bacterial cell-to-cell communication, population density, synchronized behavior, and interaction. QS is also responsible for activation and regulation of gene expression of virulence factors, motility, plasmid transfer, drug resistance, and biofilm formation | |
Efflux pumps | Essential for the growth and maturation of biofilms through a variety of mechanisms, including the indirect regulation of biofilm-forming genes, the efflux of antibiotics or metabolic intermediates, the efflux of quorum quenching (QQ) molecules, and the efflux of EPSs and quorum-suppressing molecules | |
Poly-β-(1, 6)-N-acetylglucosamine (PNAG) | Necessary for cell–cell adherence, biofilm development, and thickness of biofilm | |
Extracellular DNA (eDNA) | It plays a significant role in cell adhesion, biofilm development, and maintenance | [48] |
Alginate | Essential for the protection and stability of the biofilm structure. It also contributes to the preservation of contents of the matrix such as nutrients and water | [49] |
Amyloids | Facilitate bacterial cell–host adhesion and biofilm formation and contribute to host cell invasion and adhesion as well as to the host's inflammatory response | [50] |
Cyclic di-guanosine monophosphate (c-di-GMP) | Act as a universal positive regulator in the production of biofilms |