Negative regulation of biofilm formation by nitric oxide sensing proteins

Abstract

Biofilm-based infections pose a serious threat to public health. Biofilms are surface-attached communities of microorganisms, most commonly bacteria and yeast, residing in an extracellular polymeric substance (EPS). The EPS is composed of several secreted biomolecules that shield the microorganisms from harsh environmental stressors and promote antibiotic resistance. Due to the increasing prominence of multidrug-resistant microorganisms and a decreased development of bactericidal agents in clinical production, there is an increasing need to discover alternative targets and treatment regimens for biofilm-based infections. One promising strategy to combat antibiotic resistance in biofilm-forming bacteria is to trigger biofilm dispersal, which is a natural part of the bacterial biofilm life cycle. One signal for biofilm dispersal is the diatomic gas nitric oxide (NO). Low intracellular levels of NO have been well documented to rapidly disperse biofilm macrostructures and are sensed by a widely conserved NO-sensory protein, NosP, in many pathogenic bacteria. When bound to heme and ligated to NO, NosP inhibits the autophosphorylation of NosP's associated histidine kinase, NahK, reducing overall biofilm formation. This reduction in biofilm formation is regulated by the decrease in secondary metabolite bis-(3′–5′)-cyclic dimeric guanosine monophosphate (c-di-GMP). The NosP/NahK signaling pathway is also associated with other major regulatory systems in the maturation of bacterial biofilms, including virulence and quorum sensing. In this review, we will focus on recent discoveries investigating NosP, NahK and NO-mediated biofilm dispersal in pathogenic bacteria.

Polydopamine Nanocarriers with Cascade-Activated Nitric Oxide Release Combined Photothermal Activity for the Therapy of Drug-Resistant Bacterial Infections

“…12−14 Additionally, the effect of NO on bacteria depends on its concentration, and NO concentrations of >10 M lead to DNA damage, lipid peroxidation, and membrane disruption because of the toxicity of NO and oxidative stress. 12,14 At lower NO concentrations (10 −12 −10 −9 M), the downregulation of biofilm-associated second messengers causes a reduction in exopolysaccharide levels and biofilm dispersion. 15,16 NO exposure disrupts crucial cellular functions or structures in bacteria, thereby impairing physiological activities and increasing vulnerability to antibacterial agents.…”

“…The potent antibacterial activity of NO is observed even at lower concentrations (<10 –9 M), which makes it a promising and feasible substitute for traditional antibiotics . Because of its antibacterial properties, NO offers benefits such as (i) demonstrating efficacy against diverse bacterial strains; (ii) efficiently penetrating biofilms; and (iii) helping to mitigate the development of drug resistance through its diverse targets. − Additionally, the effect of NO on bacteria depends on its concentration, and NO concentrations of >10 –6 M lead to DNA damage, lipid peroxidation, and membrane disruption because of the toxicity of NO and oxidative stress. , At lower NO concentrations (10 –12 –10 –9 M), the downregulation of biofilm-associated second messengers causes a reduction in exopolysaccharide levels and biofilm dispersion. , NO exposure disrupts crucial cellular functions or structures in bacteria, thereby impairing physiological activities and increasing vulnerability to antibacterial agents. − However, the wound microenvironment typically lacks endogenous NO, and therefore, meeting therapeutic requirements in that environment is a challenge. Hence, supplementing exogenous NO becomes necessary. , …”