Membrane Alterations in Pseudomonas putida F1 Exposed to Nanoscale Zerovalent Iron: Effects of Short-Term and Repetitive nZVI Exposure

Abstract

In this study, we report the effect of the commercial nanoscale zerovalent iron (nZVI) on environmental bacteria, emphasizing the importance of nZVI-bacterial membrane interaction on nZVI toxicity as well as the adaptability of bacteria to nZVI. Exposure of Pseudomonas putida F1 to 0.1, 1.0, and 5.0 g/L of nZVI caused the reduction in colony forming units (CFUs) substantially for almost 3 orders of magnitude. However, a rebound in the cell number was observed after the prolonged exposure except for 5.0 g/L nZVI at which bacterial viability was completely inhibited. Upon exposure, nZVI accumulated on and penetrated into the bacterial cell membrane. Cell membrane composition analysis revealed the conversion of the cis to trans isomer of unsaturated fatty acid upon short-term nZVI exposure, resulting in a more rigid membrane counteracting the membrane-fluidizing effect of nZVI. Several cycles of repetitive exposure of cells to 0.1 g/L nZVI induced a persistent phenotype of P. putida F1 as indicated by smaller colony morphology, a more rigid membrane, and higher tolerance to nZVI. A low interaction between nZVI particles and the surface of the nZVI-persistent phenotypic cells reduced the nZVI-induced membrane damage. This study unveils the significance of nZVI-membrane interaction on toxicity of nZVI toward bacteria.

Compositional and predicted functional dynamics of soil bacterial community in response to single pulse and repeated dosing of titanium dioxide nanoparticles

“…3 and 4). Type I represents OTUs with enhanced adaptation over TiO 2 NP dosing frequencies that showed a successive increase in relative abundance, which is similar with the reported response of Pseudomonas putida F1 to repeated exposure of nanoscale zerovalent iron (nZVI) (Kotchaplai et al, 2017). In return, the established persistent phenotypes (through acclimation, detoxification enzymes, and horizontal transfer of resistant genes) will lead to the promotion of the resistant taxa and the associated functions (Ernst et al, 2016).…”

“…For example, a tolerant bacterium (Rhodanobacter sp.) emerged in soils exposed to silver nanoparticles (Samarajeewa et al, 2019), and a persistent phenotype of Pseudomonas putida F1 with a more rigid membrane and higher tolerance was detected after several re-dosing cycle of nanoscale zerovalent iron (Kotchaplai et al, 2017). In contrast, for ammonia-oxidizing bacteria, the repetitive dosing of TiO 2 NPs was found to be more harmful than one-time exposure (Simonin et al, 2016a).…”

Chronic exposure to complex metal oxide nanoparticles elicits rapid resistance in Shewanella oneidensis MR-1

“…38 Other studies investigating nanoparticle adaptations have shown clear bacterial response but have not demonstrated a stable nanoparticle resistance phenotype. 41,48,[66][67][68][69] Due to the ability of S. oneidensis MR-1 to continue replication under increasing concentrations of NMC, the heritability and stability of the adaptation aer the pressure has been removed, and the presence of a nanoparticle-specic impact, it is rational to consider this resistance and not simply tolerance. 37,38,49,65 Microbial resistance is important to consider when addressing the regulation of soluble nanomaterials.…”

Immediate response mechanisms of Gram-negative solvent-tolerant bacteria to cope with environmental stress: cis-trans isomerization of unsaturated fatty acids and outer membrane vesicle secretion

“…Notably, the degree of cis to trans conversion correlates with the toxicity/hydrophobicity and the concentration of toxic organic hydrocarbons but does not depend on a distinctive chemical structure of the stressor (Heipieper et al 1995 ; Neumann et al 2005 ). Besides various toxic organic compounds, osmotic stress, the presence of heavy metals, and antibiotics acting on the membrane result in an increase of the trans / cis ratio (Hachicho et al 2014 ; Heipieper et al 1996 ; Isken et al 1997 ; Kotchaplai et al 2017 ; Piotrowska et al 2016 ). This reflects the importance of the system as general stress response mechanism in Gram-negative bacteria (Ramos et al 2001 ; Segura et al 1999 ; Zhang and Rock 2008 ).…”