Cell Wall Thickness Research Articles

Different Inactivation Mechanisms of Staphylococcus aureus and Escherichia coli in Water by Reactive Oxygen and Nitrogen Species Generated from an Argon Plasma Jet.

The atmospheric pressure plasma jet (APPJ) is a promising technology for inactivating waterborne pathogens by generating diverse reactive species under ambient conditions. However, uncertainties regarding the bacterial inactivation mechanisms persist due to varying findings in prior research. This study aimed to clarify the inactivation mechanisms of two representative bacteria, Staphylococcus aureus (S. aureus, Gram-positive) and Escherichia coli (E. coli, Gram-negative), using an argon-based APPJ (Ar-APPJ) system in a controlled medium, primarily deionized water. We identified several reactive oxygen and nitrogen species (RONS), including hydrogen peroxide, peroxynitrous acid/peroxynitrite (ONOOH/ONOO-), hydroxyl radical (•OH), and hydroperoxyl radical/superoxide radical, and evaluated their roles in bacterial inactivation. Inactivation experiments and quantification of suspected RONS revealed that ONOOH was the primary lethal agent for S. aureus, while •OH predominantly inactivated E. coli. Assessment of cell membrane integrity and intracellular RONS levels showed that E. coli, with its thinner cell wall, was more vulnerable to surface damage caused by •OH. In contrast, for S. aureus, with its thicker cell wall, intracellular attack by penetrated ONOOH, being significantly more diffusive than •OH, was more effective, as •OH alone could not induce sufficient surface damage. These findings advance our understanding of bacterial inactivation by the Ar-APPJ and provide valuable insights for designing effective water disinfection strategies utilizing this technology.

OsHARBI1-1 enhances cadmium tolerance in yeast through YAP1 mediated modulation of cell wall integrity genes and catalase genes.

Harbinger transposase-derived 1 proteins (HARBI1s) play important roles in plant growth, development, and response to abiotic stress. OsHARBI1-1 has been identified as a gene encoding HARBI1-1 protein in rice and has been shown to be responsive to Cadmium (Cd) stress. However, the function of OsHARBI1-1 protein under heavy metal stress remains unclear. In this study, the function of a novel rice Cd-responsive gene, OsHARBI1-1, under Cd stress was characterized by heterologous expression in yeast. The heterologous expression OsHARBI1-1 conferred yeast with increased tolerance to Cd. In addition, the yeast cells expressing OsHARBI1-1 exhibited enhanced tolerance to Congo red and exhibited an increase in cell wall thickness under Cd stress, suggesting a potential correlation between increased Cd tolerance and cell wall thickness in the transgenic yeast. When OsHARBI1-1 was expressed in ∆yap1 or ∆yap1∆ycf1 yeast mutants, there was no significant difference in the tolerance of transgenic yeast to Cd and Congo red, as well as in cell wall thickness compared to the control. Meanwhile, the expression of cell wall integrity (CWI) genes and catalase genes in transgenic yeast was up-regulated in a YAP1-dependent manner under Cd or Congo red stress. The above facts supported the inference that OsHARBI1-1 may counteract Cd toxicity by enhancing the expression of YAP1, thereby increasing the thickness of the cell wall and activating the expression of catalase genes.

Alleviation of cadmium toxicity and minimizing its accumulation in rice plants by methyl jasmonate: Performance and mechanisms.

Heavy metal pollution is a worldwide problem that threaten agricultural production and human health. Methyl jasmonate (MeJA) is a phytohormone that could enhance plant resistance against various stresses. However, the mechanism of MeJA in cadmium (Cd) uptake, distribution, and translocation in rice plants remains elusive. In this study, we found that the Cd induced-growth inhibition was ameliorated by MeJA. Upon MeJA application, Cd content in root and shoot was decreased by 10.15 % and 36.39 %, which paralleled with less Cd2 + influx of rice roots and depressed expression of the cation transporters (OsNramp1 and OsNramp5). The subcellular distribution revealed that MeJA enriched Cd distribution in cell wall, which was accompanied by increased cell wall thickness and altered cell wall polysaccharide (pectin, cellulose, hemicellulose) content, meanwhile, the Cd content in pectin, cellulose, hemicellulose was increased, the FTIR analysis implied that functional groups (especially -OH and COO-) on cell wall were involved in Cd fixation. The root to shoot translocation of Cd was hindered by exogenous MeJA, this was validated by the decreased expression of OsHMA2 in root and declined Cd level in xylem sap. Overall, our results revealed that MeJA could act as a foliar resistance control substance to reduce Cd accumulation in rice plants. The detailed molecular mechanisms of MeJA in Cd detoxification in plants still need further investigation.

Closed-cell Polyurethane In-situ Foaming Hofneycomb for Enhanced Energy Absorption and Water Intrusion Resistance

To achieve novel core with high energy absorption and strong water intrusion resistance, a composite structure was created by employing in-situ foaming of closed-cell polyurethane (PU) in a honeycomb structure. Experimental, theoretical, and finite element analyses revealed that the in-situ foaming technique increased the honeycomb's energy absorption by 312.84% and improved impact efficiency by 61.45% while maintaining specific energy absorption (SEA). Remarkably, this composite structure surpassed the energy absorption capacity of individual honeycomb and foam. The coupling gain ratio introduced by the foam increases within a certain range as the honeycomb cell size decreases and wall thickness increases, with little influence from the foam's mechanical properties. Water intrusion, leading to ice formation at low temperatures, drastically reduced honeycomb SEA by 94.61% and impaired mechanical properties significantly. Closed-cell PU in-situ foaming provided exceptional water intrusion resistance, preserving the honeycomb's mechanical performance, including energy absorption and SEA.

Role of putative APSES family transcription factor Swi6 in cell wall synthesis regulation in the agaricomycete Pleurotus ostreatus.

Clade A APSES family transcription factor Swi6 functions alongside Mbp1 to form the MBF (MluI cell cycle box-binding factor) complex in ascomycetes. In the agaricomycete Pleurotus ostreatus, Mbp1 plays a crucial role in regulating β-glucan and chitin synthesis; however, the role of Swi6 has not been explored in this fungus. In this study, its involvement in cell wall synthesis regulation was analysed using swi6 disruption strains in P. ostreatus. The Δswi6 strains exhibited reduced growth rates and shorter aerial hyphae formation in both agar and liquid media, suggesting an essential role of Swi6 in normal vegetative growth. Furthermore, swi6 disruption affected cell wall thickness distribution, the expression of specific chitin synthase genes, the relative percentage of chitin, and sensitivity to calcofluor white, suggesting that Swi6 is required for normal chitin synthesis regulation in P. ostreatus. In contrast, no significant differences were observed between the wild-type and Δswi6 strains in the relative percentage of α- and β-glucan and the expression of α- and β-glucan synthase genes, suggesting its unimportant role in α- and β-glucan synthesis regulation. In conclusion, Swi6 is necessary for normal mycelial growth and chitin synthesis regulation in P. ostreatus. To the best of our knowledge, this study is the first report on the functional differences and overlaps between Mbp1 and Swi6 in the regulation of cell wall synthesis in agaricomycetes.

Anatomical characterization of Semi-arid Bignoniaceae using light and scanning electron microscopy

BackgroundThe present research work was done to evaluate the anatomical differences among selected species of the family Bignoniaceae, as limited anatomical data is available for this family in Pakistan. Bignoniaceae is a remarkable family for its various medicinal properties and anatomical characterization is an important feature for the identification and classification of plants.Methodology: In this study, several anatomical structures were examined, including stomata type and shape, leaf epidermis shape, epidermal cell size, and the presence or absence of trichomes and crystals (e.g., prisms, raphides, and druses). Three statistical tools—heat map analysis, correlation analysis, and principal component analysis (PCA)—were used to highlight distinctions and similarities among the species.ResultsOn both the upper and lower leaf surfaces, polygonal, irregular, and hexagonal epidermal cells with thick cell walls were observed. Three patterns of anticlinal cell walls were detected: curved, straight, and sinuous. Distinct stomatal types were also identified across the different species. For instance, sunken stomata were observed in Kigelia africana and Jacaranda mimosaefolia, while anomocytic stomata were found in Oroxylum indicum, Pyrostegia venusta, Tecoma stans, Tecomella undulata, Mansoa alliacea, Heterophragma adenophylla, Handroanthus impetiginosus, Campsis radicans, and Anemopaegma chamberlaynii. Paracytic stomata were examined in B. callistegioides and Dolichandra unguis-cati. Tabebuia aurea was the only species with Tetracytic stomata. A contiguous type of stomata was only observed in Millingtonia hortensis. This family contained three types of trichomes. Glandular peltate trichomes contained a basal epidermal cell, a very small monocellular stalk and a circular or round multicellular head containing 12 cells arranged in a single circle. Non-glandular trichomes had a thin apex without a head and a pointed end. Branched trichomes contained several arms arising from a common base.ConclusionThis anatomical examination, using advanced microscopic techniques, is the first to classify several species that are not listed in the e-flora of Pakistan. Leaf anatomical research has proven valuable in resolving challenging taxonomic issues.

Influence of surfactant type on the microstructure, mechanical and thermal properties of phenolic foams

Surfactant chemistry can affect the phenolic foam (PF) properties by controlling the collision and combination of the created bubbles during foam production. The study was accomplished using two surfactant families, nonionic: polysorbate (Tween80) and anionic: sodium and ammonium lauryl sulfates (SLS30 and ALS70) and sodium laureth sulfate (SLES270) to manufacture PF foams. Tween80 and SLS30 resulted in foams with the lowest and highest densities, 20.2 ± 0.2 and 42.72 ± 0.4 kg/m3, respectively. All the surfactants created an open-cell morphology, except Tween80 with a semi-open-cell structure consisting of large cells and thicker cell wall thickness. The anionic surfactant had better performance, the foams made by SLS30 had cells with diameters of 338.5 ± 18.5 and cell density of 2.5 cell/mm3 × 105. While the SLES270 made foam with the highest cell density and the smallest cell size that caused higher compressive strength. The SLES270 led to keeping the foam flexibility even under the fire exposition, and it increased the thermal insulation by 50% while the other samples were turned into fragile foam. A higher level of polarity in SLES270 caused better micelle production and then better bubble formation, followed by the bubble coalition.

Blue rings in trees and shrubs as indicators of early and late summer cooling events at the northern treeline.

The high temperature sensitivity of pine trees in northern Fennoscandia has led to some of the most reliable tree-ring climate reconstructions in the world for the past millennia. However, wood anatomical anomalies that likely reflect temperature-induced reductions in cell wall lignification, the so-called Blue Rings (BRs), have not yet been systematically investigated in trees and shrubs in northern Europe. Here, we present frontier research on the occurrence of BRs in Pinus sylvestris trees and Juniperus communis (L) s.l. shrubs from the upper treeline in northern Norway (69°N) in relation to instrumental temperature data covering the last ca. 150 years. The highest number of BRs was found in 1902, with 96% of Pinus trees and 68% of Juniperus shrubs showing BRs. These corresponded on average to a 42% vs. 27% proportion of the growth ring in 1902 which was less-lignified in Pinus trees and Juniperus shrubs, respectively. Another peak in BRs recorded for 1877 was more pronounced in Pinus trees (88%) than in Juniperus shrubs (36%), with a lower proportion of less lignified rings. We found the lowest monthly sums of growing degree days in June 1902 and August 1877, resulting in more uniform non-lignified BRs in 1902 than in 1877. Prolonged early growing season cooling shortened the growing season in 1902 and resulted in much thinner cell walls in trees and shrubs than in 1877, which was characterized by extended cooling at the end of the growing season. Also, after 1902 BR, Pinus trees exclusively showed no recovery in the mean cell wall thickness in the following year. Our study provides the first evidence for different impacts of early versus late growing season cooling on cell wall lignification in trees and shrubs at the northern treeline. Using the anatomy of BRs, we demonstrated the potential to refine summer cooling event reconstructions at an intra-annual resolution in northern Fennoscandia and beyond.

Morphology, histochemistry and ultrastructure of the floral glandular trichomes in three Doronicum species (Asteraceae).

Previously, it was found that four types of glandular trichomes (GTs) are developed on the surface of all aerial organs in Doronicum species. A detailed study of leaves had shown that only two types of GTs form in them. Nothing was known about any differences of GTs on vegetative and reproductive organs. Current work studies morphological, histochemical and ultrastructural features of two types of GTs arising on floral elements in three Doronicum species. The straight GTs there are on all elements of the inflorescence (peduncle, phyllaries, ray and disk florets); they have a short stalk and do not have a clearly visible head. The capitate GTs are located only on the inflorescence peduncle and phyllaries; the trichomes form a long stalk and a distinct head. The chemical composition of the secretion is confirmed by histochemical reactions. Both types of GTs have the specific ultrastructural features and secretory mechanisms. In capitate GTs, a smooth endoplasmic reticulum is the main organelle of cytoplasm and takes part in a synthesis of the phenolic substances. Phenols accumulate in the numerous small vacuoles and thick cell wall. In straight trichomes, leucoplasts of various shapes with plastoglobuli and peripheral reticulum predominate. Terpenes synthesized in leucoplasts are stored in the subcuticular cavity and are released when the cavity ruptures. The acidic polysaccharides are the additional components of a straight trichome secretion. The studied species of Doronicum differ from each other in localization, size and structure of the GTs.

Mesophyll conductance reductions due to drought stress are influenced by increases in cell wall chelator-soluble pectin content and denser microfibril alignment in cotton.

Plants commonly undergo leaf morphoanatomy and composition modifications to cope with drought stress, and these tend to reduce mesophyll conductance to CO2 diffusion (gm), a key limitation to photosynthesis. The cell wall appears to play a crucial role in this reduction, yet the specific effect of cell wall compositions on gm and the underlying regulatory mechanisms of cell wall thickness (Tcw) variation are not well understood. In this study, we subjected cotton plants to varying levels of water deficit to investigate the impact of leaf cell wall composition and the arrangement patterns of microfibrils within cell walls on Tcw and leaf gas exchange. Drought stress resulted in a significant thickening of cell walls and a decrease in gm. Concurrently, drought stress increased the content of chelator-soluble pectin and cellulose while reducing hemicellulose content. The alignment of cellulose microfibrils became more parallel and their diameter increased with under drought conditions, suggesting a decrease in cell wall effective porosity which coincides with the observed reduction in gm. This research demonstrates that reduced gm typically observed under drought stress conditions is related not only to thickened cell walls, but also to ultra-anatomical and compositional variations. Specifically, increases in cellulose content, diameter, and highly aligned arrangement collectively contributed to an increase in Tcw, which together with increases in chelator-soluble pectin content, resulted in an increased cell wall resistance to CO2 diffusion.

Halogenated meroterpenoids with antifungal activities from the Deep-Sea-Derived fungus Acremonium sclerotigenum guided by the genomic and OSMAC strategy.

Thirteen new meroterpenoids, acremorins A-M (1, 2, 4, 6, 7 and 9-16), together with three known analogues (3, 5 and 8) were isolated from the deep-sea-derived fungus Acremonium sclerotigenum LW14 guided by the genomic and OSMAC strategy. Their structures and absolute configurations were established by extensive spectroscopic analysis, electronic circular dichroism (ECD) calculations, Rh2(OCOCF3)4-induced ECD experiments, and a single-crystal X-ray diffraction experiment. Compounds 2, 4, 6 and 9 represent the rare brominated ascochlorins. Compounds 1/3 and 2/4 are two pairs of epimers isomerized at C-19. Compounds 1 and 2 are the first examples of ascochlorins which have the 19S configuration in the cyclohexanone moiety. Compounds 3/7, 8/10 and 11/12 are three pairs of epimers isomerized at C-12, C-18 and C-15, respectively. Compounds 7-10 showed moderate antifungal activity against Cryptococcus gattii 3271G1 with the same MIC values of 8μg/mL. The treatment with compound 7 led to a significant reduction in the cell wall thickness, rarefaction of cytoplasm, and damage to the structural integrity of organelles in C. gattiii 3271G1. Further RNA sequencing (RNA seq) analysis indicated that compound 7 exerted its anti-C. gattiii effect by up-regulating the biosynthesis and RNA binding of ribosomes, while concurrently inhibiting RNA and nucleic acid metabolism and ATPase activity.

A novel dual fixation method for improving the reliable assessment of pulmonary vascular morphology in pulmonary hypertension rats

This study introduced a novel dual fixation method for the pulmonary vasculature and lung tissue in pulmonary hypertension (PH) rats, addressing the limitations of traditional fixation methods that failed to accurately preserve the in vivo status of pulmonary vascular morphology. The modified method involved a dual fixation process, combining individualized ventilation support and vascular perfusion to simulate the respiratory motion, pulmonary artery pressure and right ventricular output of the rat under in vivo conditions. Utilizing a monocrotaline-induced PH rat model, this study compared the dual fixation with the traditional immersion fixation, focusing on the quantitative assessment of alveolar expansion degree, capillary patency, endothelial cell quantity and wall thickness of pulmonary vein and artery. The results demonstrated that the dual fixation is superior in maintaining the authenticity and integrity of lung tissue and more sensitive in the evaluation of pulmonary artery hypertrophy, providing a more reliable representation of pulmonary vascular remodeling associated with PH.

A Fresh Look at Celery Collenchyma and Parenchyma Cell Walls Through a Combination of Biochemical, Histochemical, and Transcriptomic Analyses.

Celery (Apium graveolens) can be considered as a model plant for studying pectin-enriched primary cell walls. In addition to parenchyma cells with xyloglucan-deficient walls, celery petioles contain collenchyma, a mechanical tissue with thickened cell walls of similar composition. This study presents a comprehensive analysis of these tissues at both early and late developmental stages, integrating data on polysaccharide yield, composition, localization, and transcriptome analysis. Our results reveal that young collenchyma walls possess distinct polysaccharide compositions, including higher levels of rhamnogalacturonan I (RG-I), branched galactans, esterified homogalacturonan, and xyloglucan, compared to parenchyma cells. A significant number of genes encoding proteins involved in pectin methylesterification and acetylation were upregulated in young collenchyma. Different gene isoforms encoding glycosyltransferases involved in RG-I biosynthesis were activated in both collenchyma and parenchyma, suggesting potential variations in RG-I structure and function across different primary cell walls. We identified a set of potential glycosyltransferases involved in RG-I biosynthesis in collenchyma and proposed synthase complexes for heteromannan and heteroxylan. The transcriptome data not only confirmed known biochemical traits of celery cell walls but also provided deeper insights into the peculiarities of cell wall polysaccharide metabolism, thereby helping to narrow down candidate genes for further molecular genetic studies.

Assessment of Fibre Characteristics and Suitability of Sida acuta Burm F. for Pulp and Paper Production

The ever-increasing demand for paper and paper products and alarming rate of global population growth necessitates research into non-wood fibre to augment the popular wood fibres in short supply. Sida acuta obtained at two locations, samples collected from 3 areas per location. Samples of dimension 10 x 10 x 20 mm macerated in equal volumes of glacial acetic acid and 30% hydrogen peroxide at 80oC in an oven. Twenty-five whole fibres in swollen condition were measured. Derivatives of fibre dimensions viz: Runkel ratio, flexibility and slenderness were also evaluated. Pooled mean fibre length was 1.04mm, pooled fibre diameter was 25.02μm, pooled fibre lumen width was 14.69μm and fibre cell wall thickness was 5.17μm. Runkel ratio was 0.73, coefficient of suppleness (flexibility) was 60.05 while felting power (slenderness) was 42. Values obtained connote that S. acuta’s fibre morphology is good for pulping much more that its Runkel ratio (0.73) is less than 1, coefficient of suppleness (60.05) is greater than 50 and its felting power (42) is greater than 33. Specific Gravity ranged from 0.416–0.468. With reference to the above, S. acuta is fairly suitable for pulp and paper making.

Effect of Chemical Foaming Process Parameters on the Performance of Epoxy Foam and Parameter Optimization Strategies

To prepare polymer foams with low‐density and high‐energy absorption efficiency, this study designs epoxy foaming experiments employing the Box–Behnken method and investigates the impact of process parameters on the microscopic geometric parameters and uniaxial compression response of foam. Finite element analysis models are created to investigate the microscale deformation mechanism. The main results are as follows: 1) The average equivalent cell diameter is significantly affected by foaming temperature and foaming agent content, while cell wall thickness is more influenced by the foaming agent content and the precuring time. 2) The compression response is most significantly affected by foaming temperature, followed by foaming agent content, with precuring time showing less significant influence. The differences in the stress–strain curves during various stages of deformation are due to the buckling of cell walls and the subsequent collapse of cells. 3) Density exhibits a highly positive correlation with strength and modulus while showing a relatively high negative correlation with energy absorption efficiency. Based on these findings, process parameters are optimized using the Hooke–Jeeves algorithm and experimentally validated, demonstrating the reliability of the optimization strategy. The experimental design and process parameter optimization strategy can be applied to other polymer foaming research.

Effect of curvature angle and structural configurations on dynamic performance of honeycomb sandwich structures

The aim of this study is to investigate the effects of curve angle and structural parameters on ballistic performance of honeycomb sandwich structures. In the study, high-velocity impact simulations were performed in LS DYNA finite element program to investigate the effects of honeycomb structural parameters, curve angle, residual velocity, specific energy absorption (SEA) and damage mechanism. Progressive damage analysis based on the combination of cohesive zone model (CZM) and bilinear traction-separation law was performed. The ballistic limit value increased by 41.9% when the facesheet thickness increased by two times. When the cell wall thickness increased by five times, the ballistic limit value increased by 13.3%. When the core height was two times increased, the ballistic limit velocity value increased by 2.076 times. Although the ballistic limit velocity value of the CFRP Facesheet and Aluminum (Al) core sandwich structure is 7.14% lower than the all Al specimen, the SEA value is 9.47% higher. When the curve angle increases from 0˚ to 180˚, the ballistic limit value decreases by 22.8%. In general, this study provides useful information about the design of ballistic structures, parameters affecting their performance and their effects.

Enhancing Thermal Insulation Property and Flexibility of Starch/Poly(butylene adipate terephthalate) (PBAT) Blend Foam by Improving Rheological Properties.

Starch foam has attracted significant attention as an alternative to expanded styrene (EPS) foam owing to its abundance and biodegradability. Despite these merits, its limited thermal insulation and flexibility compared to EPS have hindered its utilization in packaging. Herein, we report the effect of blending with starch/PBAT on foaming behavior and physical properties during foaming processing. We fabricated a starch/PBAT blend with systematically controlled blending ratios (0, 10, 15, 20, and 25 wt%) to analyze their effect on the interaction and characteristics of blended foam. The blending of starch and PBAT significantly reduced complex viscosity, enhancing resin flow during the foaming process. This improvement in resin flow led to increases in expansion ratio while reducing density and cell wall thickness. The thermo-insulation performance improved to 0.043 W/mK with 20 wt% of PBAT due to the enhanced expansion ratio and cell morphology. Additionally, the flexural strain at break improved significantly from 2.8 ± 0.6% to 9.6 ± 1.0% with increasing PBAT content. Enhanced water resistance was also observed, demonstrated by a reduction in water absorption and an extension of dissolution time. Overall, these findings underscore the potential of starch/PBAT foam to improve the thermal-insulating property, flexibility, and water resistance while maintaining their biodegradability and sustainability.

Origami-inspired auxetic structures: Design and performance in quasi-static and dynamic loading

Auxetic metamaterials have gained attention due to their unique mechanical properties. Integrating origami structures with cellular structures can significantly enhance their energy absorption capacity under mechanical loads. This study develops a novel auxetic structure by combining a curved origami design with the cross-petal auxetic structure. The structure’s behavior under in-plane compressive loading is analyzed using finite element simulations and validated through experimental testing of 3D-printed specimens. The effects of loading rates (quasi-static, low-, medium-, and high-velocity) and geometrical parameters on energy absorption are examined through parametric studies. Structure grading, based on unit cell wall thickness, is also investigated to enhance performance. Finally, the proposed structure’s energy absorption is compared with two common auxetic metamaterials (reentrant and chiral) under various loading conditions. Results indicate deformation becomes more localized with increased loading velocity, with the proposed design achieving a 70% improvement in energy absorption over non-origami designs and a 16% enhancement through grading. The main contribution of this study is the creation of a hybrid structure combining curved origami and cross-petal auxetic designs, achieving a 70% improvement in energy absorption. The dual plateau stress region and graded design further enhance performance, positioning it as an innovative solution for impact protection and soft robotics. The proposed structure exhibits up to 7.56 times higher specific energy absorption under quasi-static loading compared to reentrant and chiral designs, maintaining superior performance at higher loading velocities.

Dominant spoilage bacteria in crayfish alleviate ultrasonic stress through mechanosensitive channels but could not prevent the process of membrane destruction

Although there have been many studies on the efficacy of ultrasonic inactivation, the stress resistance mechanism of bacteria is still a challenge for complete ultrasonic inactivation. In this study, the dominant spoilage bacteria in crayfish, Shewanella baltica (S. baltica) and Aeromonas veronii (A. veronii), were subjected to high-intensity ultrasonic treatment. The results showed compromised cell membrane, decreased membrane fluidity, hyperpolarized membrane potential, and disrupted succinate-coenzyme Q reductase. Transmission electron microscopy revealed significant fragmentation of S. baltica, whereas A. veronii, with its thick cell wall and outer capsule membrane, demonstrated enhanced resistance to ultrasound. Real-time quantitative PCR indicated that in response to ultrasonic stress, bacteria initiated a stress response mechanism by increasing the expression of mechanosensitive channels; meanwhile, the outer capsule of A. veronii delayed the transformation of ultrasonic external forces into cell membrane stress. The study found that in response to ultrasonic stress, bacteria initiated a stress response mechanism by increasing the expression of mechanosensitive channels as “emergency valve” in short time but could not prevent the process of membrane destruction with prolonged exposure. This finding provided a basis for addressing bacterial stress tolerance in ultrasonic inactivation.

Single-Cell protein for feed and food

Abstract As global demand for protein sources continues to rise due to increasing populations and changing dietary preferences, the shortage of conventional protein for feed and food poses significant challenges for food security. Single-cell protein (SCP), derived from microorganisms such as yeasts and bacteria, represents a promising alternative to traditional protein sources. Among these, methanotropic bacteria such as Methylococcus sp. and Methyocystis sp. can provide protein from methane as their sole carbon and energy source. Oleaginous yeasts like Yarrowia lipolytica are gaining attention in animal nutrition, particularly chicken and aquaculture, since they not only contain protein but also lipids. Yarrowia lipolytica, which comprises approximately 20% lipids by cell weight, can effectively supplement protein in animal diets, improving feed efficiency and average daily gain (ADG). Incorporating 3% of this yeast instead of soybean meal can enhance growth performance, while higher inclusion rates may lead to adverse effects such as diarrhea in animals like piglets due to increased lipid content and reduced nutrient digestibility. The thick cell wall of Yarrowia lipolytica can limit nutrient absorption, indicating that lysis of the yeast cell walls may be necessary to optimize nutrient release. Additionally, the use of another oleaginous yeast, Lipomyces starkeyi, has demonstrated potential as a viable substitute for vegetable oils in fish diets, maintaining growth and meat quality without negative impacts. Research indicates that SCP can constitute significant portions of nitrogen intake in livestock, supporting performance without inducing adverse heat production. These findings underscore the potential of SCP and oleaginous yeasts in addressing protein shortages while promoting sustainable practices in animal nutrition. However, further studies are essential to optimize their utilization in various dietary formulations.