Nitric Oxide Regulation of Bacterial Biofilms

Abstract

Biofilms are surface-associated, multicellular communities of bacteria. Once established, they are extremely difficult to eradicate by antimicrobial treatment. It has been demonstrated in many species that biofilm formation may be regulated by the diatomic signaling molecule nitric oxide (NO). Although this is still a relatively new area of research, we review here the literature reporting an effect of NO on bacterial biofilm formation, emphasizing dose-dependent responses to NO concentrations when possible. Where it has been investigated, the underlying NO sensors or signaling pathways are also discussed. Most of the examples of NO-mediated biofilm regulation have been documented with exogenously applied NO, but we also survey possible natural sources of NO in biofilm regulation, including endogenously generated NO. Finally, because of the apparent broad-spectrum, antibiofilm effects of NO, NO-releasing materials and prodrugs have also been explored in this minireview.

New insights into Legionella pneumophila biofilm regulation by c-di-GMP signaling

“…In this condition, the concentration of NO could be estimated as around 250 nM, since e ective concentrations of NO are estimated to be 1,000 times lower than the concentration of SNP (Barraud, Schleheck, et al 2009). is level of NO concentration is also considered as a non-toxic environmental signal for other species (Arora et al 2015).…”

“…On average, the bacterial population in WT bio lm decreased by a factor of 0.71 and 1.21 log (by vPCR and qPCR respectively) when it was exposed to NO ( Figure 4A). Nonetheless, the relative stability of the bacterial population was somewhat unexpected since, in most cases such as in Pseudomonas aeruginosa or Shewanella woodyii, exposure to non-toxic concentrations of NO (< 1 μM) triggers the transition from the sessile to the planktonic state and thus the release of bio lm bacteria (Barraud et al 2006;Barraud, Schleheck, et al 2009, Barraud, Storey, et al 2009Liu et al 2012;Arora et al 2015).…”

“…Among these signals, nitric oxide has been increasingly studied, especially because NO was shown to induce the dispersion of many pathogenic biolms (eg E. coli, Fusobacterium nucleatum, Staphylococcus aureus, and Vibrio cholerae) (Jardeleza et al 2014;Arora et al 2015;Barraud et al 2015), and to increase the sensitivity of bio lm bacteria to antibiotics (Barraud et al 2006;Barraud, Storey, et al 2009). However, bio lm formation by Azospirillum brazilense, Vibrio harveyi and Shewanella oneidensis appears to be induced by the addition of NO in the medium (Arruebarrena Di Palma et al 2013;Plate & Marletta 2012;Henares et al 2013).…”

Enhanced Iron and Selenium Uptake in Plants by Volatile Emissions of Bacillus amyloliquefaciens (BF06)

“…NO functions as a reciprocal signaling molecule in plant-microbe interactions, involving modulation of various physiological processes such as bacterial biofilm, plant growth, and development [55][56][57]. NO has been demonstrated to play an essential role in controlling Fe absorption in plants under Fe-limited conditions [58][59][60].…”

“…NO not only activates FER or FIT1-dependent signaling pathways [55], but also functions as an Fe chelator to increase the mobilization of cell wall Fe [60]. Intriguingly, the emission of VOCs by some bacterial strains, such as 2R or 3R-butanediol, induces NO synthesis in plants [65].…”