DNABII proteins play a central role in UPEC biofilm structure

Abstract

Summary Most chronic and recurrent bacterial infections involve a biofilm component, the foundation of which is the extracellular polymeric substance (EPS). Extracellular DNA (eDNA) is a conserved and key component of the EPS of pathogenic biofilms. The DNABII protein family includes integration host factor (IHF) and Histone-like protein (HU); both are present in the extracellular milieu. We have shown previously that the DNABII proteins are often found in association with eDNA and are critical for the structural integrity of bacterial communities that utilize eDNA as a matrix component. Here, we demonstrated that Uropathogenic E. coli (UPEC) strain UTI89 incorporates eDNA within its biofilm matrix and that the DNABII proteins are not only important for biofilm growth, but are limiting; exogenous addition of these proteins promotes biofilm formation that is dependent on eDNA. In addition, we show that both subunits of IHF, yet only one subunit of HU (HupB), are critical for UPEC biofilm development. We discuss the roles of these proteins in context of the UPEC EPS.

Enhanced Probiotic Potential of Lactobacillus reuteri When Delivered as a Biofilm on Dextranomer Microspheres That Contain Beneficial Cargo

“…Differential fluorescent visualization was performed using the following settings: Congo Red excitation 554 nm/emission 568 nm, and SYTO 9 excitation 490 nm/emission 525 nm. Samples were fixed using a custom biofilm fixative containing 1.5% paraformaldehyde, 0.025% glutaraldehyde, 4.0% acetic acid, and 0.1M phosphate buffer at pH 7.4 (Devaraj et al, 2015). All microscopy was performed on samples in Nunc Lab-Tek 8-well borosilicate chamber slides (Fisher Scientific, Hampton, NJ).…”

Targeting microbial biofilms: current and prospective therapeutic strategies

“…Antibodies against E. coli IHF are cross-reactive and bind to DNABII in multiple bacterial species, resulting in biofilm destabilisation and the release of individual bacteria. When combined with antibiotic therapy, immunotherapy targeting DNABII has shown efficacy in vivo against biofilms in numerous types of bacteria, including oral bacteria 56 , uropathogenic E. coli 57 and P. aeruginosa in a mouse lung infection model 58 . This approach has also shown efficacy against MRSA biofilms compared with antibiotic treatment alone in mouse models 59,60 .…”

NontypeableHaemophilus influenzaereleases DNA and DNABII proteins via a T4SS-like complex and ComE of the type IV pilus machinery

“…Extracellular DNA protects bacteria within the biofilm from host defenses via the chelation of antimicrobial peptides and divalent cations (14,64). In addition, we have shown that eDNA is an important structural component of the biofilm matrix and that the DNABII proteins IHF and HU are required to stabilize the eDNA scaffold that provides structural support to biofilms formed by NTHI and many additional human pathogens (7,13,25,27,28,30,(37)(38)(39).…”

“…We also show that biofilms formed within the chinchilla middle ear during experimental otitis media, as well as those within clinical specimens recovered from children with chronic posttympanostomy tube otorrhea and pediatric cystic fibrosis patients infected with Burkholderia cenocepacia, are stabilized by these proteins (13,26,38,39). Further, we show that targeting the DNABII proteins with IHF-and/or HU-specific antibodies induces catastrophic collapse of the biofilm structure and subsequent release of resident bacteria that are now significantly more susceptible to the action of traditional antibiotics (13,28,39). Moreover, in a rat model of periodontitis (oral osteolytic infection) due to the oral pathogen Significance Extracellular DNA and DNABII proteins are essential structural components of the extracellular polymeric substance, or matrix, of the nontypeable Haemophilus influenzae biofilm; however, the mechanisms by which these elements are released from the bacterial cell for incorporation into the biofilm matrix are not yet characterized.…”

“…eDNA provides structural stability to the matrix, acts as a sink for antimicrobial peptides, protects resident bacteria from the host immune response, provides a source of "common goods" for the resident bacteria, acts as a universal structural material conducive to microbial community architecture, and facilitates the uptake of genetic material between bacterial species via a process known as horizontal gene transfer (5,(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Members of the DNABII family of DNA-binding proteins, integration host factor (IHF) and histone-like protein (HU), are known for their strong structural influences on DNA intracellularly (18-24), and are also critical to the stability of the lattice-like 3D DNA structure found in biofilm matrices extracellularly (13,(25)(26)(27)(28)(29)(30)(31). To date, the presence of bacterial eDNA within biofilms has been attributed to release via various mechanisms, including cell lysis (autolysis or phagemediated) (12,32,33), or active secretion through type IV secretion systems (T4SSs) (34,35).…”