Lipid production and cellular changes in Fremyella diplosiphon exposed to nanoscale zerovalent iron nanoparticles and ampicillin

Abstract

With the dramatic decrease in fossil fuel stocks and their detrimental effects on the environment, renewable energy sources have gained imminent importance in the mitigation of emissions. As lipid-enriched energy stocks, cyanobacteria are the leading group of microorganisms contributing to the advent of a new energy era. In the present study, the impact of Nanofer 25 s nanoscale zero-valent iron nanoparticles (nZVIs) and ampicillin on lipid production and cellular structural changes in Fremyella diplosiphon strain B481-SD were investigated. Total lipid abundance, fatty acid methyl ester (FAME) compositions, and alkene production as detected by high-resolution two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC/TOF–MS) was significantly higher (p < 0.05) in the individual application of 0.8 mg/L ampicillin, 3.2 mg/L nZVIs, and a combined regimen of 0.8 mg/L ampicillin and 3.2 mg/L nZVIs compared to the untreated control. In addition, we identified significant increases (p < 0.05) in monounsaturated fatty acids (MUFAs) in F. diplosiphon treated with the combination regimen compared to the untreated control, 0.8 mg/L of ampicillin, and 3.2 mg/L of nZVIs. Furthermore, individual treatment with 0.8 mg/L ampicillin and the combination regimen (0.8 mg/L ampicillin + 3.2 mg/L nZVIs) significantly increased (p < 0.05) Nile red fluorescence compared to the untreated control, indicating neutral membrane lipids to be the main target of ampicillin added treatments. Transmission electron microscopy studies revealed the presence of single-layered thylakoid membranes in the untreated control, while complex stacked membranes of 5–8 layers were visualized in ampicillin and nZVI-treated F. diplosiphon. Our results indicate that nZVIs in combination with ampicillin significantly enhanced total lipids, essential FAMEs, and alkenes in F. diplosiphon. These findings offer a promising approach to augment the potential of using the strain as a large-scale biofuel agent.

Impact of Zero-Valent Iron Nanoparticles and Ampicillin on Adenosine Triphosphate and Lactate Metabolism in the Cyanobacterium Fremyella diplosiphon

“…These findings are supported by a study that demonstrated visible FeO nanoparticle accumulation around the cell membrane border and increased oxidative stress in cyanobacteria [ 26 ], further substantiating the impact of iron nanoparticles on the cell membrane and the potential increase in extracellular lactate levels. In response to membrane thinning and enhanced permeability associated with ampicillin, the harmful effects of accumulated nanoparticles around the cell may be mitigated by the leakage of nZVIs into the cells [ 31 ]. Moreover, it is possible that increased intracellular iron could potentially be used as cofactors for reactions that enhance the synthesis of macromolecules such as lipids and glucose, thereby improving biofuel production efficiency and overall metabolic robustness.…”

“…Our previous results support the findings that ampicillin and the combination regimens could result in significant changes to the cell wall of the cultures. Specifically, in B481-SD treated with 0.8 mg/L ampicillin, 3.2 mg/L nZVIs, the combination regimen and the untreated control, cell wall thinning was measured at 11.3 nm, 13 nm, 8 nm, and 14 nm, respectively [ 31 ].…”

“…It can be reasoned that increased Monounsaturated Fatty Acids (MUFAs), which are known to reduce oxidative stress [35] and increase cell membrane fluidity [36], can mitigate the detrimental effects and support cell survival. Similarly, a study by Yalcin et al [31] reported that the combination regimen can produce MUFAs in 2-3-fold. Thus, we perceive that the combined stressors can instigate more complex cellular responses, resulting in different lactate levels compared to individual treatments and untreated controls.…”