Response to Static Magnetic Field-Induced Stress in Scenedesmus obliquus and Nannochloropsis gaditana

Life on Magnet: Long-Term Exposure of Moderate Static Magnetic Fields on the Lifespan and Healthspan of Mice

All living organisms on the Earth live and evolve in the presence of the weak geomagnetic field, a quasi-uniform static magnetic field (SMF). In the meantime, although the effects of moderate and high SMFs have been investigated on multiple aspects of a living organism, a long-term SMF exposure of more than 1 year has never been reported. Here, we investigated the influence of a moderate SMF (70-220 mT head-to-toe) long-term continuous exposure (1.7 years) to two different SMF directions on healthy male C57BL/6 mice. We found that not only was the lifespan of the mice prolonged, but their healthspan was also improved. The elevated plus maze test and open field test show that SMFs could significantly improve the exploratory and locomotive activities of the aged mice. The Morris water maze test shows that SMFs could improve their spatial learning ability and spatial memory. Tissue examinations reveal that SMFs have an ameliorative effect on oxidative stress in the brain of aged mice, which was reinforced by the cellular assays, showing that SMFs could protect the PC12 cells from D-gal-induced senescence by increasing superoxide dismutase, catalase, and reducing the malonaldehyde levels. Therefore, our data show that the 1.7-year SMF exposure can improve both the lifespan and healthspan of naturally aged mice due to reduced oxidative stress, which indicates that SMFs have the potential to be used as an adjuvant physical therapy to reduce the ageing-induced health risks to benefit animals, and even humans.

Study on high-CO2 tolerant Dunaliella salina and its mechanism via transcriptomic analysis

Microalgae has been regarded as a promising method for reducing CO2 emission. High CO2 concentration generally inhibits algal growth, and previous studies have mostly focused on breeding freshwater algae with high CO2 tolerance. In this study, one marine algal strain Dunaliella salina (D. salina) was grown under 0.03%-30 % CO2 and 3% NaCl conditions, and was evaluated to determine its potential for CO2 assimilation. The results showed that D. salina could tolerate 30% CO2 , and its maximum biomass concentration could reach 1.13 g·L-1 after 8 days incubation, which was 1.85 times higher than that of incubation in air (0.03%). The phenomenon of high-CO2 tolerance in D. salina culture was discussed basing on transcriptome analysis. The results showed that D. salina was subjected to oxidative stress under 30% CO2 conditions, and the majority genes involving in antioxidant system, such as SOD, CAT, and APX genes were up-regulated to scavenge ROS. In addition, most of the key enzyme genes related to photosynthesis, carbon fixation and metabolism were up-regulated, which are consistent with the higher physiological and biochemical values for D. salina incubation under 30% CO2 .

The use of the electromagnetic field in microbial process bioengineering

An electromagnetic field (EMF) has been shown to have various stimulatory or inhibitory effects on microorganisms. Over the years, growing interest in this topic led to numerous discoveries suggesting the potential applicability of EMF in biotechnological processes. Among these observations are stimulative effects of this physical influence resulting in intensified biomass production, modification of metabolic activity, or pigments secretion. In this review, we present the current state of the art and underline the main findings of the application of EMF in bioprocessing and their practical meaning in process engineering using examples selected from studies on bacteria, archaea, microscopic fungi and yeasts, viruses, and microalgae. All biological data are presented concerning the classification of EMF. Furthermore, we aimed to highlight missing parts of contemporary knowledge and indicate weak spots in the approaches found in the literature.

Update on the application of magnetic fields to microalgal cultures

Several studies have shown that any magnetic field (MF) applied to microalgae modifies its cultivation conditions and may favor biomolecule production since it interacts with the microorganisms and affect their growth. As a result, there are changes in concentrations and compositions of biomass and biomolecules. This review aims at updating MF applications to microalga cultures that were reported by studies conducted in the last 5 years. It shows the main studies that reached positive results of carbohydrate, lipid, protein and pigment production. Effects of MFs may be positive, negative or null, depending on some factors, such as intensity, exposure time, physiological state of cells and application devices. Therefore, this review details cultivation conditions used for reaching high concentration of biomolecules, explains the action of MFs on microalgae and describes their applicability to the biorefinery concept.

Impact of sodium pyrophosphate and static magnetic field on Haematococcus pluvialis: enhancement of astaxanthin accumulation, PAL, and antioxidant enzyme activities

The Haematococcus pluvialis microalga is known as a main source of astaxanthin with a strong antioxidant capacity and low growth rate. The induction of growth and astaxanthin content was established in H. pluvialis alga using a static magnetic field (SMF) and tetrasodium pyrophosphate (NaPP) as an inhibitor of isopentenyl pyrophosphate (precursor of astaxanthin biosynthesis) translocator between cytosol to plastid. NaPP (0.3 mM), SMF (4 mT), and their combinations were applied to the H. pluvialis cell culture. Results showed chlorophyll a and b were induced in H. pluvialis by SMF treatment, but didn't change significantly under NaPP. Astaxanthin content enhanced under NaPP, SMF, and their combination, and the highest astaxanthin content was obtained under NaPP after 21 days (late of stationary phase) of culture. A significant increase in total phenol and flavonoid contents, and activities of phenylalanine ammonia-lyase (PAL) and DPPH were observed under both NaPP and SMF treatments. In contrast to NaPP, SMF decreased H₂O₂ content, which was associated with more activity of SOD and CAT enzymes. These results revealed that NaPP and SMF might stimulate both phenol and astaxanthin biosynthesis pathways by impacting the activity of enzymes, and inhibition of IPP translocation by NaPP didn't affect astaxanthin biosynthesis at the late growth phase of H. pluvialis.

Static Magnetic Field Inhibits Growth of Escherichia coli Colonies via Restriction of Carbon Source Utilization

Magnetobiological effects on growth and virulence have been widely reported in Escherichia coli (E. coli). However, published results are quite varied and sometimes conflicting because the underlying mechanism remains unknown. Here, we reported that the application of 250 mT static magnetic field (SMF) significantly reduces the diameter of E. coli colony-forming units (CFUs) but has no impact on the number of CFUs. Transcriptomic analysis revealed that the inhibitory effect of SMF is attributed to differentially expressed genes (DEGs) primarily involved in carbon source utilization. Consistently, the addition of glycolate or glyoxylate to the culture media successfully restores the bacterial phenotype in SMF, and knockout mutants lacking glycolate oxidase are no longer sensitive to SMF. These results suggest that SMF treatment results in a decrease in glycolate oxidase activity. In addition, metabolomic assay showed that long-chain fatty acids (LCFA) accumulate while phosphatidylglycerol and middle-chain fatty acids decrease in the SMF-treated bacteria, suggesting that SMF inhibits LCFA degradation. Based on the published evidence together with ours derived from this study, we propose a model showing that free radicals generated by LCFA degradation are the primary target of SMF action, which triggers the bacterial oxidative stress response and ultimately leads to growth inhibition.