Microbial Research Articles

Understanding the role of the human gut microbiome in overweight and obesity.

The gut microbiome may be related to the prevalence of overweight and obesity, but high interindividual variability of the human microbiome complicates our understanding. Obesity often occurs concomitantly with micronutrient deficiencies that impair energy metabolism. Microbiota composition is affected by diet. Host-microbiota interactions are bidirectional. We propose three pathways whereby these interactions may modulate the gut microbiome and obesity: (1) ingested compounds or derivatives affecting small intestinal transit, endogenous secretions, digestion, absorption, microbiome balance, and gut barrier function directly affect host metabolism; (2) substrate availability affecting colonic microbial composition and contact with the gut barrier; and (3) microbial end products affecting host metabolism. The quantity/concentration, duration, and/or frequency (circadian rhythm) of changes in these pathways can alter the gut microbiome, disrupt the gut barrier, alter host immunity, and increase the risk of and progression to overweight and obesity. Host-specific characteristics (e.g., genetic variations) may further affect individual sensitivity and/or resilience to diet- and microbiome-associated perturbations in the colonic environment. In this narrative review, the effects of selected interventions, including fecal microbiota transplantation, dietary calorie restriction, dietary fibers and prebiotics, probiotics and synbiotics, vitamins, minerals, and fatty acids, on the gut microbiome, body weight, and/or adiposity are summarized to help identify mechanisms of action and research opportunities.

Pretreated sugarcane bagasse matches performance of synthetic media for lipid production with Yarrowia lipolytica

Engineered strains of Yarrowia lipolytica with modified lipid profiles and other desirable properties for microbial oil production are widely reported but are almost exclusively characterized in synthetic laboratory-grade media. Ensuring translatable performance between synthetic media and industrially scalable lignocellulosic feedstocks is a critical challenge. Yarrowia lipolytica growth and lipid production were characterized in media derived from two-step acid-catalyzed glycerol pretreatment of sugarcane bagasse. Fermentation performance was benchmarked against laboratory-grade synthetic growth media, including detailed characterization of media composition, nitrogen utilization, biomass and lipid production, and fatty acid product profile. A Yarrowia lipolytica strain modified to enable xylose consumption consumed all sugars, glycerol, and acetic acid, accumulating lipids to 34–44 % of cell dry weight. Growth and lipid content when grown in sugarcane bagasse-derived media were equivalent to or better than that observed with synthetic media. These sugarcane bagasse-derived media are suitable for transferable development of Yarrowia lipolytica fermentations from synthetic media.

Methane-driven microbial nitrous oxide production and reduction in denitrifying anaerobic methane oxidation cultures

Methane (CH4) and nitrous oxide (N2O) are two important greenhouse gases (GHGs), and it is very important to achieve the reduction of both gases in the case of increasingly serious climate change. The study confirms the simultaneous mitigation of potent GHGs N2O and CH4 in denitrifying anaerobic methane oxidation (DAMO) enrichment, supplementing the understanding that DAMO microorganisms do not produce and reduce N2O. We observed rapid accumulation and consumption of N2O in DAMO cultures subjected to high nitrate and nitrite loadings. Moreover, when N2O served as the sole electron acceptor, a significant correlation was found between the flux of N2O reduction and CH4 oxidation. Inhibition of the particulate methane monooxygenase (pMMO) led to a notable decrease of 95% in N2O reduction and 50% in CH4 oxidation. Metagenomic analysis revealed that Candidatus Methanoperedens and Candidatus Methylomirabilis were the dominant genera, with all functional genes related to denitrification and methane oxidation identified, including NO reductase (nor) of Ca. Methylomirabilis. Transcriptomic analysis further confirmed that the transcripts of nor were one order of magnitude higher than other functional genes. These results indicate that when the substrate NO2- surpasses the dismutation capacity of NO dismutase (nod), DAMO bacteria can alternatively induce nor to reduce NO to N2O. However, considering that N2O reductase (nosZ) is still missing in Ca. Methylomirabilis, the partner Methyloversatilis may be responsible for N2O reduction. Our results provide new insights into the link between GHG emissions in DAMO systems under anaerobic conditions.

Recent trends in metabolic engineering for microbial production of value-added natural products

Microbe-mediated chemical production is a sustainable approach for production of natural products that are important for our society. Traditional fermentation production of natural products viz. drugs, nutraceuticals, pigments, aromatic compounds, and biofuels has limitations such as low yield, high cost and time- consuming process. Significant success in the economical production of these natural products has been established by altering the metabolic pathways of microorganisms through metabolic engineering. Recent advancements in new tools and strategies have led to a significant reduction in the turnaround time in the classic approach i.e. design-build-test-learn (DBTL) cycle in metabolic engineering. Here, we summarize various tools and strategies developed in the area of metabolic engineering with a focus on value-added natural products Also, this review lists bioprospecting of microorganisms through metabolic engineering in last five years for production of natural products. At the end, outlook, challenges and opportunities for the successful establishment of robust engineered microbial cell factories have been reported.

Quorum sensing on the activated performances of gravity-driven membrane (GDM) system at low temperatures: Ammonia removal and flux stabilization

Gravity-driven membrane (GDM) filtration technology offers a low-energy, low-maintenance solution for water purification due to its powerful bio-cake, but faces predicament in contaminant removal under low temperatures. Quorum sensing (QS), a microbial communication process mediated by signaling molecules such as C6-HSL (N-Hexanoyl-L-homoserine lactone), has been shown to influence microbial behavior and enhance biofilm formation, with promising potential for consolidation of GDM operation at low temperature. This study investigates the application of C6-HSL to enhance ammonia nitrogen and organics removal in low-temperature GDM systems. C6-HSL was administered at varying dosages (0/50/250/500 nM/d) at 5 °C, with further experiments conducted at 25 °C to assess the impact of QS regulation on GDM performance under room temperature. The results demonstrated that the optimized presence of C6-HSL (500 nM/d) improved the removal efficiency of dissolved organic carbon, ammonia nitrogen, and raised the stable normalized flux (increase ratios at low vs. room temperature: ∼19 % vs. ∼7 %, ∼38 % vs. ∼9 %, and ∼22 % vs. ∼12 %, respectively). Analysis of the biofouling layer’s structural characteristics, composition, and biological activity indicated that the increased C6-HSL effectively promoted microbial growth and migration/movement, increased the production of extracellular polymeric substances (EPS) and soluble microbial products (SMP), and accelerated biofilm formation. The resulting thicker (∼172.98 vs. ∼119.21 μm), rougher (∼62.1 vs. ∼55.0 nm) cake layer, equipped with abundant channels for water penetration, contributed to increased contaminant degradation, but also stabilized the flux with slight growth (∼3.26 vs. ∼3.02 LMH) under low temperature. Notably, the enhancement effect of QS regulation was more pronounced at low temperature than at room temperature, attributing to the optimized release and diffusion of signal molecules and the more substantial stimulation of metabolic and enzymatic activity in nitrifying bacteria. This study provides valuable insights and technical support for decentralized water treatment in winter via reliable GDM process operation in challenging temperature conditions.

Biochar-driven fouling mitigation in sustainable microalgal-bacterial membrane bioreactors

Microalgal-bacterial membrane bioreactor (MB-MBR) have emerged as a crucial technology for sustainable wastewater treatment. However, membrane fouling caused by free microalgae remains a major obstacle to their cost-effective operation. This study investigated the impact of biochar addition on membrane fouling in MB-MBR. The findings indicated that biochar significantly reduced membrane fouling, primarily due to the enlargement of floc size and the reduction of soluble microbial products (SMP). Detailed analyses suggested that biochar's adsorptive properties and its effect on decreasing the abundance of algae and bacteria species, such as Proteobacteria and Leptolyngbya, which promote fouling, are key factors. This alteration enhanced specific amino acid metabolic pathways, thereby reducing SMP production and fouling potential. Consequently, adhesion interaction energy of the flocs and membrane fouling were both diminished. This study demonstrated that biochar addition is an effective strategy for mitigating membrane fouling in MB-MBR systems, providing a theoretical foundation for their stable and sustainable operation.

Microbial production of methyl-uranium via the Wood-Ljungdahl pathway

The misuse of uranium is a major threat to human health and the environment. In microbial ecosystems, microbes deploy various strategies to cope with uranium-induced stress. However, the exact ecological strategies and mechanisms underlying uranium tolerance in microbes remain unclear. Therefore, this study aimed to investigate the survival strategies and tolerance mechanisms of microbial communities in uranium-contaminated soil and groundwater. Microbial co-occurrence networks and molecular biology techniques were used to analyze the properties of microbes in groundwater and soil samples from various depths of uranium-contaminated areas in Northwest China. Uranium pollution altered microbial ecological strategies. Uranium stress facilitated the formation of microbial community structures, leading to symbiosis. Furthermore, microbes primarily resisted uranium hazards by producing polysaccharides and phosphate groups that chelate uranium, releasing phosphate substances that precipitate uranium, and reducing U(VI) through sulfate- and iron-reducing processes. The relative abundance of metal-methylation genes in soil microorganisms positively correlated with uranium concentration, indicating that soil microorganisms can produce methyl uranium via the Wood-Ljungdahl pathway. Furthermore, soil and groundwater microorganisms demonstrated different responses to uranium stress. This study provides new insights into microbial responses to uranium stress and novel approaches for the bioremediation of uranium-contaminated sites.

Not all cytochrome b5s are created equal: how a specific CytB5 boosts forskolin biosynthesis in Saccharomyces cerevisiae

Cytochrome B5s, or CytB5s, are small heme-binding proteins, ubiquitous across all kingdoms of life that serve mainly as electron donors to enzymes engaged in oxidative reactions. They often function as redox partners of the cytochrome P450s (CYPs), a superfamily of enzymes participating in multiple biochemical processes. In plants, CYPs catalyze key reactions in the biosynthesis of plant specialized metabolites with their activity dependent on electron donation often from cytochrome P450 oxidoreductases (CPRs or PORs). In eukaryotic microsomal CYPs, CytB5s frequently participate in the electron transfer process although their exact role remains understudied, especially in plant systems. In this study, we assess the role of CytB5s in the heterologous biotechnological production of plant specialized metabolites in yeast. For this, we used as a case-study the biosynthesis of forskolin - a bioactive diterpenoid produced exclusively from the plant Coleus forskohlii. The complete biosynthetic pathway for forskolin is known and includes three CYP enzymes. We reconstructed the entire forskolin pathway in the yeast Saccharomyces cerevisiae, and upon co-expression of the three CytB5s - identified in C. forskohlii transcriptomes - alleviation of a CYP-related bottleneck step was noticed only when a specific CytB5, CfCytB5A, was used. Co-expression of CfCytB5A in yeast, in combination with forskolin pathway engineering, resulted in forskolin production at titers of 1.81 g/L in a bioreactor. Our findings demonstrate that CytB5s not only play an important role in plant specialized metabolism but also, they can interact with precision with specific CYPs, indicating that the properties of CytB5s are far from understood. Moreover, our work highlights how CytB5s may act as indispensable components in the sustainable microbial production of plant metabolites, when their biosynthetic pathways involve CYP enzymes.

Genome-resolved metagenomics revealed novel microbial taxa with ancient metabolism from macroscopic microbial mat structures inhabiting anoxic deep reefs of a Maldivian Blue Hole.

Blue holes are vertical water-filled openings in carbonate rock that exhibit complex morphology, ecology, and water chemistry. In this study, macroscopic microbial mat structures found in complete anoxic conditions in the Faanu Mudugau Blue Hole (Maldives) were studied by metagenomic methods. Such communities have likely been evolutionary isolated from the surrounding marine environment for more than 10,000 years since the Blue Hole formation during the last Ice Age. A total of 48 high-quality metagenome-assembled genomes (MAGs) were recovered, predominantly composed of the phyla Chloroflexota, Proteobacteria and Desulfobacterota. None of these MAGs have been classified to species level (<95% ANI), suggesting the discovery of several new microbial taxa. In particular, MAGs belonging to novel bacterial genera within the order Dehalococcoidales accounted for 20% of the macroscopic mat community. Genome-resolved metabolic analysis of this dominant microbial fraction revealed a mixotrophic lifestyle based on energy conservation via fermentation, hydrogen metabolism and anaerobic CO2 fixation through the Wood-Ljungdahl pathway. Interestingly, these bacteria showed a high proportion of ancestral genes in their genomes providing intriguing perspectives on mechanisms driving microbial evolution in this peculiar environment. Overall, our results provide new knowledge for understanding microbial life under extreme conditions in blue hole environments.

Acidophilic sulphate-reducing bacteria: Diversity, ecophysiology, and applications.

Acidophilic sulphate-reducing bacteria (aSRB) are widespread anaerobic microorganisms that perform dissimilatory sulphate reduction and have key adaptations to tolerate acidic environments (pH <5.0), such as proton impermeability and Donnan potential. This diverse prokaryotic group is of interest from physiological, ecological, and applicational viewpoints. In this review, we summarize the interactions between aSRB and other microbial guilds, such as syntrophy, and their roles in the biogeochemical cycling of sulphur, iron, carbon, and other elements. We discuss the biotechnological applications of aSRB in treating acid mine drainage (AMD, pH <3), focusing on their ability to produce biogenic sulphide and precipitate metals, particularly in the context of utilizing microbial consortia instead of pure isolates. Metal sulphide nanoparticles recovered after AMD treatment have multiple potential technological uses, including in electronics and biomedicine, contributing to a cost-effective circular economy. The products of aSRB metabolisms, such as biominerals and isotopes, could also serve as biosignatures to understand ancient and extant microbial life in the universe. Overall, aSRB are active components of the sulphur and carbon cycles under acidic conditions, with potential natural and technological implications for the world around us.

CSEL-BGC: A Bioinformatics Framework Integrating Machine Learning for Defining the Biosynthetic Evolutionary Landscape of Uncharacterized Antibacterial Natural Products.

The sluggish pace of new antibacterial drug development reflects a vulnerability in the face of the current severe threat posed by bacterial resistance. Microbial natural products (NPs), as a reservoir of immense chemical potential, have emerged as the most promising avenue for the discovery of next generation antibacterial agent. Directly accessing the antibacterial activity of potential products derived from biosynthetic gene clusters (BGCs) would significantly expedite the process. To tackle this issue, we propose a CSEL-BGC framework that integrates machine learning (ML) techniques. This framework involves the development of a novel cascade-stacking ensemble learning (CSEL) model and the establishment of a groundbreaking model evaluation system. Based on this framework, we predict 6,666 BGCs with antibacterial activity from 3,468 complete bacterial genomes and elucidate a biosynthetic evolutionary landscape to reveal their antibacterial potential. This provides crucial insights for interpretating the synthesis and secretion mechanisms of unknown NPs.

A comprehensive study on the effects of electrocoagulation integrated in a membrane bioreactor treating sunflower oil refinery wastewater on treatment performance, biological properties, and fouling behavior.

This study evaluated the effects of electrocoagulation integrated in a laboratory-scale membrane bioreactor (MBR), namely EC-MBR, on the treatment performance, activated sludge morphological characterization, and membrane fouling of MBR treating actual sunflower oil refinery wastewater. The EC-MBR system exhibited significantly higher chemical oxygen demand (COD) and oil and grease (O&G) removal efficiency compared to the MBR system. Additionally, both systems achieved excellent turbidity removal, with a percentage above 99%. The membrane fouling rate was higher in the EC-MBR system compared to the MBR system. Despite the decrease in the soluble microbial product (SMP) and extracellular polymeric substance (EPS) concentration in the EC-MBR system, especially their protein fraction, the significant increase in MLSS and carbohydrates/protein ratio, and the decrease in the mixed liquor and the cake layer particles size were the main membrane fouling factors. The membrane fouling resistance distribution showed that the EC-MBR system had a higher percentage of pore blocking resistance compared to the MBR. FTIR analysis identified a greater proportion of carbohydrate compounds in the cake layer of the EC-MBR system. SEM images revealed dense microbial clusters, mainly rod- and oval-shaped bacteria, in the EC-MBR system. Furthermore, EDX analysis detected elements such as Ca, K, O, Al, and P in both systems, with the EC-MBR system showing a higher Al content. The EC-MBR system showed low energy consumption (0.431kWhm-3) and total operating costs ($0.90m-3), showcasing its effectiveness and affordability for sustainable wastewater management.

Testing microbial pest control products in bees, a comparative study on different bee species and their interaction with two representative microorganisms

BackgroundThe evaluation of the impact of pesticides on non-target species, like bees, is a crucial factor in registration procedures. Therefore, standardized test procedures have been developed on OECD level assessing the effects of chemicals on honey bees or bumble bees. Unfortunately, these protocols cannot directly be adapted for testing products that contain microorganisms. Interest in the use of microorganisms has increased in recent years due to their specificity to target species while not harming non-target organisms. This study aimed to evaluate optimal conditions to assess the effects of microbial plant protection products on bee species according to currently available test protocols. Some of the most commonly used microorganisms for plant protection, Bacillus thuringiensis subspecies aizawai (B. t. a. ABTS 1857) and Beauveria bassiana (B. b. ATCC 74040) were tested on Apis mellifera, Bombus terrestris, and Osmia bicornis at different temperatures (18, 26, 33 °C) under laboratory conditions.ResultsExposure to the product containing B. t. a. ABTS 1857 resulted in higher mortality compared to B. b. ATCC 74040 in all tested bee species. A temperature-dependent effect towards higher mortality at higher temperatures of 26 °C or 33 °C was observed in O. bicornis exposed to both microorganisms. A. mellifera showed variable responses, but for B. terrestris there was mostly no effect of temperature when exposed to microorganisms in high concentrations. However, temperature affected longevity of bee species in the non-exposed control group. A. mellifera mortality increased with decreasing temperatures, while B. terrestris and O. bicornis mortality increased with increasing temperatures. A test duration of 15 or 20 days was found to be suitable for testing these microorganisms.ConclusionIn conclusion, 26 °C should be considered the worst-case scenario for testing B. bassiana on all tested bee species. For testing B. thuringiensis, a temperature of 33 °C is recommended for A. mellifera, whereas B. terrestris and O. bicornis should be tested at 26 °C.

Microbial production of levulinic acid from glucose by engineered Pseudomonas putida KT2440

Levulinic acid(LA) is produced through acid-catalyzed hydrolysis and dehydration of lignocellulosic biomass. It is a key platform chemical used as an intermediate in various industries including biofuels, cosmetics, pharmaceuticals, and polymers. Traditional LA production uses chemical conversion, which requires high temperatures and pressures, strong acids, and produces undesirable side reactions, repolymerization products, and waste problems Therefore, we designed an integrated process to produce LA from glucose through metabolic engineering of Pseudomonas putida KT2440. As a metabolic engineering strategy, codon optimized phospho-2-dehydro-3-deoxyheptonate aldolase (AroG), 3-dehydroshikimate dehydratase (AsbF), and acetoacetate decarboxylase (Adc) were introduced to express genes of the shikimate and β-ketoadipic acid pathways, and the 3-oxoadipate CoA-transferase (pcaIJ) gene was deleted to prevent loss of biosynthetic intermediates. To increase the accumulation of the produced LA, the lva operon encoding levulinyl-CoA synthetase (LvaE) was deleted resulting in the high LA-producing strain P. putida HP203. Culture conditions such as medium, temperature, glucose concentration, and nitrogen source were optimized, and under optimal conditions, P. putida HP203 strain biosynthesized 36.3 mM (4.2 g/L) LA from glucose in a fed-batch fermentation system. When lignocellulosic biomass hydrolysate was used as the substrate, this strain produced 7.31 mM of LA. This is the first report of microbial production of LA from glucose by P. putida. This study suggests the possibility of manipulating biosynthetic pathway to produce biological products from glucose for various applications.

Состояние микробиоты секрета предстательной железы у больных хроническим бактериальным простатитом до и после антибактериального лечения

Introduction. The effect of antibiotics on the microbiota of different organs is the subject of close attention and an urgent problem of modern medicine. The literature mainly contains works related to the effect of antibiotics on the intestinal microflora and some other organs other than the genitourinary organs. On the other hand, the microbiota of many organs, including the prostate, largely depends on the gut microbiota. Objective: to conduct a comparative analysis of the microbiota of prostate secretion (PS) in patients with chronic bacterial prostatitis (CBP) before and after antibacterial treatment. Material and methods. A prospective study of PS was conducted in 38 patients with CBP aged 25 to 50 years. The study of the microbiota of prostate secretion was carried out using cultural methods, real-time PCR and using a gas chromatograph of the Maestro mass spectrometer (Interlab LLC, Russia), by the methods of mass-spectrometry microbes markers (MSMM). Results. According to the statistical analysis of absolute indicators obtained from the MSMM data, a sharp decrease in the number of almost all groups of microorganisms (MO) has been established. At the same time, the level of the cocco-bacillary group decreased from 1,049.50 x cells/g to 142.00 x 105 cells/g, the level of anaerobes from 1,638.00 to 221.50, the level of actinobacteria from 197.00 to 40.00, the level of enterobacteria from 452.50 to 87.00, the level of gram-negative rods from 79.00 to 25.00, the level of fungi and yeast from 56.00 to 23.00, the level of viruses from 24.50 to 3.00x105 cells/g (p &lt;0.0001; p = 0.0004; p = 0.0033; p = 0.0007; p &lt;0.0001). In addition, there was a decrease in the level of resident MO, transient opportunistic, normally non-occurring MO and MO sum, as well as a decrease in the level of plasmologens and endotoxin sum (p &lt;0.0001). When analyzing the relative value in the microbiome of individual MO, a decrease in the proportion of cocco-bacillar flora, actinobacteria, enterobacteria, viruses, transient and normally non-occurring microorganisms was noted, while the proportion of grams of negative rods increased by 48.4% (p = 0.0033), fungi and yeast by 74.4% (p&lt;0.0001), anaerobes by 6.3% (p&lt;0.0001), resident bacteria by 5.3% (p&lt;0.0001). The decrease in the level of plasmologen reached 63.9% (p&lt;0.0001), endotoxin 64.3% (p&lt;0.0001). Conclusion. The analysis showed that antibiotics lead to a decrease in the level of absolute values in almost all microorganisms, regardless of belonging to different taxonomic groups, while the relative values in some groups increase and in others decrease. Keywords: microbiota, prostate secretion, gas chromatography-mass spectrometry, microorganisms.

Leveraging tardigrade proteins Dsup and CAHS D for enhanced neural protection in neurosurgery and neuroscience.

Tardigrades are microscopic organisms known for their remarkable resilience to extreme environmental conditions, including radiation and desiccation. Two key proteins, Dsup (Damage suppressor protein) and CAHS D (Cytoplasmic Abundant Heat Soluble protein D), play crucial roles in this resilience. Dsup protects DNA from radiation-induced damage, while CAHS D stabilizes cellular structures during desiccation by interacting with, but not retaining, water. These unique mechanisms have significant potential applications in neurosurgery and neuroscience. Dsup could inspire the development of protective agents for neural tissues during radiation-based treatments, minimizing collateral damage and improving patient outcomes. Meanwhile, CAHS D's stabilization properties could lead to new neuroprotective strategies, safeguarding brain cells under stress. Together, these tardigrade proteins offer innovative solutions for enhancing neural protection, opening new avenues for treating neurological conditions and improving the safety and efficacy of neurosurgical procedures.

From gut to bone: deciphering the impact of gut microbiota on osteoporosis pathogenesis and management.

Osteoporosis (OP) is characterized by decreased bone mineral density (BMD) and increased fracture risk, poses a significant global health burden. Recent research has shed light on the bidirectional relationship between gut microbiota (GM) and bone health, presenting a novel avenue for understanding OP pathogenesis and developing targeted therapeutic interventions. This review provides a comprehensive overview of the GM-bone axis, exploring the impact of GM on OP development and management. We elucidate established risk factors and pathogenesis of OP, delve into the diversity and functional changes of GM in OP. Furthermore, we examine experimental evidence and clinical observations linking alterations in GM composition or function with variations in BMD and fracture risk. Mechanistic insights into microbial mediators of bone health, such as microbial metabolites and products, are discussed. Therapeutic implications, including GM-targeted interventions and dietary strategies, are also explored. Finally, we identify future research directions and challenges in translating these findings into clinical practice.

Production of neohesperidin from hesperetin by an engineered strain of Escherichia coli

Neohesperidin is a flavonoid glycoside widely used in the food and pharmaceutical industries. The current production of neohesperidin mainly relies on extraction from plants. Microbial fermentation demonstrates a promising prospect as an environmentally friendly, efficient, and economical method. In this study, we designed and constructed the biosynthetic pathway of neohesperidin in an Escherichia coli strain by introducing the glycosyltransferase UGT73B2 from Arabidopsis thaliana, rhamnose synthase VvRHM-NRS from Vitis vinifera, and rhamnose transferase Cm1,2RhaT from Citrus maxima. After optimization of the module and the uridine diphosphate (UDP)-glucose synthetic pathway, the engineered strain produced 4.64 g/L neohesperidin in a 5 L bioreactor, and the molar conversion rate of hesperetin was 45.8%. This has been the highest titer reported to date for the biosynthesis of neohesperidin in microorganisms. This study lays a foundation for the construction and application of strains with high yields of neohesperidin and provides a potential choice for the microbial production of other flavonoid glycosides.

Host Material Viscoelasticity Determines Wrinkling of Fungal Films.

Microbial organisms react to their environment and are able to change it through biological and physical processes. For example, fungi exhibit various growth morphologies depending on their host material. Here, we show how the rheological properties of the host material influence the fungal wrinkling morphology. Rheological data of the host material was set in relation to the growth morphology. On host material with high storage modulus, the fungal film was flat, whereas on host material with low storage modulus, the fungus showed a morphology made of folds and wrinkles. We combined our findings with mechanical instability theories and found that the formation of wrinkles and folds is dependent on the storage modulus of the host material. The connection between the wrinkling morphology and the storage modulus of the host material is shown with simple scaling theories. The amplitude, number of wrinkles, and wrinkle length follow geometrical laws, and the mechanical properties of the fungal film are expected to increase with increasing host material elasticity. The obtained results show the connection between living biological films, how they react to their surroundings, and the underlying physical mechanisms. They can provide a framework to further design fungal materials with specific surface morphologies.

Recovery of bacterial network complexity and stability after simulated extreme rainfall is mediated by K−/r-strategy dominance

The complexity and stability of belowground microbial communities are among the core mechanisms that drive ecosystem functions. Disturbances, such as climate extremes, can exert a substantial influence on these microbial attributes. However, the role of the microbial life history strategy in determining the complexity and stability of desert soil microbial communities after extreme rainfall is poorly understood. Here, we explored the response patterns of bacterial network complexity and stability and characterized the bacterial life history strategy on the basis of the oligotroph (K-strategist)-to-copiotroph (r-strategist) ratio after three extreme rainfall treatments (11, 15, and 25 mm). Experimental results demonstrated that the bacterial communities immediately shifted from the K-strategy to the r-strategy one day after extreme rainfall and gradually recovered to the K-strategy over time, as verified by the increase (31.46 %–125.51 %) then decrease (41.51 % – 95.78 %) in the weighted rrn copy number. Meanwhile, bacterial network complexity and stability showed three-phase patterns [dramatic decline (decreased by 211.67 %–388.46 %)–gradual recovery (increased by 45.60 %–103.65 %)–insignificant change] after three extreme rainfall events. The decline/recovery of these bacterial attributes was highly pronounced/slow after the large extreme rainfall treatment. Specifically, the responses of bacterial network complexity and stability to extreme rainfall showed negative correlations with the response of the weighted rrn copy number (R = -0.55 – -0.74, P < 0.01). The mechanisms underlying the response patterns of bacterial network complexity and stability were related to the prevalence of the r-strategy of the bacterial communities (Phase 1) and the shifts from the r-strategy to the K-strategy due to the gradual reduction in soil moisture (Phase 2 and 3). These results emphasize the importance of the microbial life history strategy in maintaining network complexity and stability and help in understanding how belowground communities can withstand future disturbances.