ZnO Nanoparticles Affect Bacillus subtilis Cell Growth and Biofilm Formation

Abstract

Zinc oxide nanoparticles (ZnO NPs) are an important antimicrobial additive in many industrial applications. However, mass-produced ZnO NPs are ultimately disposed of in the environment, which can threaten soil-dwelling microorganisms that play important roles in biodegradation, nutrient recycling, plant protection, and ecological balance. This study sought to understand how ZnO NPs affect Bacillus subtilis, a plant-beneficial bacterium ubiquitously found in soil. The impact of ZnO NPs on B. subtilis growth, FtsZ ring formation, cytosolic protein activity, and biofilm formation were assessed, and our results show that B. subtilis growth is inhibited by high concentrations of ZnO NPs (≥ 50 ppm), with cells exhibiting a prolonged lag phase and delayed medial FtsZ ring formation. RedoxSensor and Phag-GFP fluorescence data further show that at ZnO-NP concentrations above 50 ppm, B. subtilis reductase activity, membrane stability, and protein expression all decrease. SDS-PAGE Stains-All staining results and FT-IR data further demonstrate that ZnO NPs negatively affect exopolysaccharide production. Moreover, it was found that B. subtilis biofilm surface structures became smooth under ZnO-NP concentrations of only 5–10 ppm, with concentrations ≤ 25 ppm significantly reducing biofilm formation activity. XANES and EXAFS spectra analysis further confirmed the presence of ZnO in co-cultured B. subtilis cells, which suggests penetration of cell membranes by either ZnO NPs or toxic Zn+ ions from ionized ZnO NPs, the latter of which may be deionized to ZnO within bacterial cells. Together, these results demonstrate that ZnO NPs can affect B. subtilis viability through the inhibition of cell growth, cytosolic protein expression, and biofilm formation, and suggest that future ZnO-NP waste management strategies would do well to mitigate the potential environmental impact engendered by the disposal of these nanoparticles.

Zinc oxide induces the stringent response and major reorientations in the central metabolism of Bacillus subtilis

“…Here, we have demonstrated that the presence of ZnO nanoparticles induces a stress that bacteria fight via large modifications of the metabolism. Similar observations have already been described by Hsueh and collaborators [81], who have demonstrated that ZnO nanoparticles affect the viability of Bacillus subtilis through the inhibition of cell growth, cytosolic protein expression and biofilm formation. Our study is a first step to understand, at a physiological level, the long-term adaptation of a gram-positive bacteria in response to nanoparticles.…”

Green Synthesis, Characterization and Antibacterial Activity of ZnO Nanoparticles

“…Our study suggests that both ZnO NP-I and ZnO NP-II showed significant an- et al, [29] and Mastanaiah et al [30] demonstrated the anti-Bacillus subtilis activity of ZnO nanoparticle and Lawsonia inermis respectively suggesting the antibacterial potential of ZnO nanoparticle and Lawsonia inermis.…”

Biofabrication of Zinc Oxide Nanoparticle fromOchradenus baccatusLeaves: Broad-Spectrum Antibiofilm Activity, Protein Binding Studies, andIn VivoToxicity and Stress Studies

“…At lower concentrations also, significant reduction in EPS production was recorded for all pathogens ( Figure 5(a)). Hsueh et al [54] have observed 92% reduced production of EPS by P. aeruginosa upon treatment with 100 ng/ml concentration of copper oxide nanoparticles. LewisOscar et al [55] also reported significant reduction of EPS produced by zinc oxide nanoparticle treated Bacillus subtilis strains.…”