Chitinase Activity Research Articles

Selenium Improves the Control Efficacy of Phytophthora nicotianae by Damaging the Cell Membrane System and Promoting Plant Energy Metabolism.

Tobacco black shank (TBS), caused by Phytophthora nicotianae, poses a significant threat to tobacco plants. Selenium (Se), recognized as a beneficial trace element for plant growth, exhibited inhibitory effects on P. nicotianae proliferation, disrupting the cell membrane integrity. This action reduced the energy supply and hindered hyphal transport through membrane proteins, ultimately inducing hyphal apoptosis. Application of 8 mg/L Se through leaf spraying resulted in a notable decrease in TBS incidence. Moreover, Se treatment preserved chloroplast structure, elevated chitinase activities, β-1,3-GA, polyphenol oxidase, phenylalanine ammonia-lyase, and increased hormonal content. Furthermore, Se enhanced flavonoid and sugar alcohol metabolite levels while diminishing amino acid and organic acid content. This shift promoted amino acid degradation and flavonoid synthesis. These findings underscore the potential efficacy of Se in safeguarding tobacco and potentially other plants against P. nicotianae.

Decoding seasonal changes: soil parameters and microbial communities in tropical dry deciduous forests.

In dry deciduous tropical forests, both seasons (winter and summer) offer habitats that are essential ecologically. How these seasonal changes affect soil properties and microbial communities is not yet fully understood. This study aimed to investigate the influence of seasonal fluctuations on soil characteristics and microbial populations. The soil moisture content dramatically increases in the summer. However, the soil pH only gradually shifts from acidic to slightly neutral. During the summer, electrical conductivity (EC) values range from 0.62 to 1.03 ds m-1, in contrast to their decline in the winter. The levels of soil macronutrients and micronutrients increase during the summer, as does the quantity of soil organic carbon (SOC). A two-way ANOVA analysis reveals limited impacts of seasonal fluctuations and specific geographic locations on the amounts of accessible nitrogen (N) and phosphorus (P). Moreover, dehydrogenase, nitrate reductase, and urease activities rise in the summer, while chitinase, protease, and acid phosphatase activities are more pronounced in the winter. The soil microbes were identified in both seasons through 16S rRNA and ITS (Internal Transcribed Spacer) gene sequencing. Results revealed Proteobacteria and Ascomycota as predominant bacterial and fungal phyla. However, Bacillus, Pseudomonas, and Burkholderia are dominant bacterial genera, and Aspergillus, Alternaria, and Trichoderma are dominant fungal genera in the forest soil samples. Dominant bacterial and fungal genera may play a role in essential ecosystem services such as soil health management and nutrient cycling. In both seasons, clear relationships exist between soil properties, including pH, moisture, iron (Fe), zinc (Zn), and microbial diversity. Enzymatic activities and microbial shift relate positively with soil parameters. This study highlights robust soil-microbial interactions that persist mainly in the top layers of tropical dry deciduous forests in the summer and winter seasons. It provides insights into the responses of soil-microbial communities to seasonal changes, advancing our understanding of ecosystem dynamics and biodiversity preservation.

Unveiling the positive impact of biofloc culture on Vibrio parahaemolyticus infection of Pacific white shrimp by reducing quorum sensing and virulence gene expression and enhancing immunity.

This study aimed to evaluate and unveil the positive impact of biofloc culture on Vibrio parahaemolyticus infection of Pacific white shrimp by reducing quorum sensing (QS) and virulence gene expression and enhancing shrimp's immunity. The shrimp with an average body weight of 0.50 ± 0.09 g were reared in containers with a volume of 2.5 L, 21 units, and a density of 20 shrimp L-1. The shrimp were cultured for 5 days, with each treatment including biofloc system maintenance with a C/N ratio of 10 and a control treatment without biofloc, followed by a challenge test through immersion using V. parahaemolyticus at densities of 103, 105, and 107 CFU mL-1 initially. The results of the invitro experiment showed that biofloc suspension can inhibit and disperse biofilm formation, as well as reduce the exo-enzyme activity (amylase, protease, and chitinase) of V. parahaemolyticus. Furthermore, the biofloc treatment significantly reduced the expression of the QS regulatory gene OpaR, the PirB toxin gene, and the virulence factor genes T6SS1 and T6SS2 in both invitro and invivo. The biofloc system also increased the expression of shrimp immunity-related genes (LGBP, proPO, SP, and PE) and the survival rate of white shrimp challenged with V. parahaemolyticus.

Efficacy and Antifungal Mechanism of Rosemary Essential Oil against Colletotrichum gloeosporioides

The antifungal activity and mechanism of rosemary essential oil against Colletotrichum gloeosporioides, the walnut anthracnose pathogen, were investigated using scanning electron microscopy (SEM), index determination and transcriptome technique. The results showed that rosemary essential oil could inhibit the growth of C. gloeosporioides with minimum inhibitory (MIC) and fungicidal (MFC) concentrations of 15.625 μL/mL and 31.25 μL/mL, respectively. Scanning electron microscopy revealed that the mycelium morphology became shriveled, twisted, and severely deformed after being treated with rosemary essential oil. The activity of chitinase, which decomposes fungal cell wall components in C. gloeosporioides, increased. The ergosterol content in the plasma membrane decreased, while the cell contents including nucleic acids, soluble protein and soluble reducing sugar were released resulting in the extracellular electrical conductivity being changed. For metabolic activity, the enzymes succinate dehydrogenase (SDH), malate dehydrogenase (MDH), ATPase and ATP decreased, whereas phosphofructokinase (PFK) increased. Transcriptome sequencing results showed that the antifungal mechanism of rosemary essential oil involves the destruction of the cell wall and membrane, inhibition of genetic material synthesis, and cell division and differentiation. The results are helpful to understand the efficacy and antifungal mechanism of rosemary essential oil against C. gloeosporioides and provide a theoretical basis for the development of rosemary essential oil as a biological control agent.

Activity of a Recombinant Chitinase of the Atta sexdens Ant on Different Forms of Chitin and Its Fungicidal Effect against Lasiodiplodia theobromae.

This study evaluates the activity of a recombinant chitinase from the leaf-cutting ant Atta sexdens (AsChtII-C4B1) against colloidal and solid α- and β-chitin substrates. 1H NMR analyses of the reaction media showed the formation of N-acetylglucosamine (GlcNAc) as the hydrolysis product. Viscometry analyses revealed a reduction in the viscosity of chitin solutions, indicating that the enzyme decreases their molecular masses. Both solid state 13C NMR and XRD analyses showed minor differences in chitin crystallinity pre- and post-reaction, indicative of partial hydrolysis under the studied conditions, resulting in the formation of GlcNAc and a reduction in molecular mass. However, the enzyme was unable to completely degrade the chitin samples, as they retained most of their solid-state structure. It was also observed that the enzyme acts progressively and with a greater activity on α-chitin than on β-chitin. AsChtII-C4B1 significantly changed the hyphae of the phytopathogenic fungus Lasiodiplodia theobromae, hindering its growth in both solid and liquid media and reducing its dry biomass by approximately 61%. The results demonstrate that AsChtII-C4B1 could be applied as an agent for the bioproduction of chitin derivatives and as a potential antifungal agent.

Chitinase induction in Trichoderma harzianum: a solid-state fermentation approach using shrimp waste and wheat bran/commercial chitin for chitooligosaccharides synthesis

This study innovatively employed solid-state fermentation (SSF) to evaluate chitinase induction in Trichoderma harzianum. Solid-state fermentation minimizes water usage, a crucial global resource, and was applied using shrimp waste chitin and a mixture of commercial chitin with wheat bran as substrates. Shrimp waste and wheat bran were pretreated and characterized for SSF, and the fungus’s utilization of the substrates was assessed using spectrophotometric and microscopic methods. The resulting enzymes’ ability to produce chitooligosaccharides (COS) mixtures was studied. Wheat bran/commercial chitin demonstrated superior performance, with a 1.8-fold increase in chitinase activity (76.3 U/mg protein) compared to shrimp waste chitin (41.8 U/mg protein). Additionally, the COS mixture obtained from wheat bran/commercial chitin showed a higher concentration of reducing sugars, reaching 87.85 mM, compared to shrimp waste chitin (14.87 mM). The COS profile from wheat bran/commercial chitin included monomers to heptamers, while the profile from shrimp waste chitin was predominantly composed of monomers. These results highlight the advantages of SSF for chitinase induction and COS production in T. harzianum, offering potential applications as dietary fiber, antioxidants, and antimicrobial agents. The findings contribute to by-product valorization, waste reduction, and the sustainable generation of valuable products through SSF-based enzyme production.

Identification and RNAi-based function analysis of trehalase family genes in Frankliniella occidentalis (Pergande).

Insects utilize trehalases (TREs) to regulate energy metabolism and chitin biosynthesis, which are essential for their growth, development, and reproduction. TREs can therefore be used as potential targets for future insecticide development. However, the roles of TREs in Frankliniella occidentalis (Pergande), a serious widespread agricultural pest, remain unclear. Three TRE genes were identified in F. occidentalis and cloned, and their functions were then investigated via feeding RNA interference (RNAi) and virus-induced gene silencing (VIGS) assays. The results showed that silencing FoTRE1-1 or FoTRE1-2 significantly decreased expression levels of FoGFAT, FoPGM, FoUAP, and FoCHS, which are members of the chitin biosynthesis pathway. Silencing FoTRE1-1 or FoTRE2 significantly down-regulated FoPFK and FoPK, which are members of the energy metabolism pathway. These changes resulted in 2-fold decreases in glucose and glycogen content, 2-fold increases in trehalose content, and 1.5- to 2.0-fold decreases in chitinase activity. Furthermore, knocking down FoTRE1-1 or FoTRE1-2 resulted in deformed nymphs and pupae as a result of hindered molting. The VIGS assay for the three FoTREs revealed that FoTRE1-1 or FoTRE2 caused shortened ovarioles, and reduced egg-laying and hatching rates. The results suggest that FoTRE1-1 and FoTRE1-2 play important roles in the growth and development of F. occidentalis, while FoTRE1-1 and FoTRE2 are essential for its reproduction. These three genes could be candidate targets for RNAi-based management and control of this destructive agricultural pest. © 2024 Society of Chemical Industry.

The American cockroach (Periplaneta americana) residue could partially replace the dietary fish meal in the juvenile Nile tilapia (Oreochromis niloticus)

The American cockroach (Periplaneta americana) residue is a by-product of P. americana meal after extracting active ingredients with ethanol, and it still contains high protein, lipid, and a certain amount of active ingredients, may be a potential fish meal alternative. Five isonitrogenous and isolipidic experimental diets were formulated to replace 0%, 25%, 50%, 75%, and 100% of dietary fish meal with P. americana residue, and defined as Diet 1, Diet 2, Diet 3, Diet 4, and Diet 5, respectively. The juvenile Nile tilapia (Oreochromis niloticus) with an initial body weight of 2.98 ± 0.01 g was fed with respective diets for 10 weeks, which was conducted to investigate the effects of dietary fish meal replacement by P. americana residue on the growth performance, proximate composition, amino acid profile, metabolism, antioxidant capacity, and immunity of juvenile O. niloticus. There were no significant differences in the final body weight, weight gain rate, and specific growth rate among five diet groups, while the highest feed conversion ratio and the lowest protein efficiency ratio were recorded in Diet 4. There were no significant differences in the contents of crude protein, total lipid, ash, and total amino acid in the whole fish body among all groups. The Diet 1 and Diet 2 had higher activities of trypsin, α-amylase, and chitinase in the intestine and α-amylase in the liver. The highest serum urea content was detected in Diet 4, while the lowest liver urea content and the highest serum total protein content were detected in Diet 3. A higher liver catalase, glutathione peroxidase, and serum lysozyme activities were detected in Diet 2, and the lowest serum malondialdehyde content was detected in Diet 2. In conclusion, dietary fish meal replacement by the P. americana residue had no negative effects on the growth performance and body composition of juvenile O. niloticus, and significantly improved the antioxidant capacity and immunity, while feed utilization rate was reduced when dietary fish meal replacement levels exceeded 75%.

Characterization of Extracellular Chitinase from Bacillus cereus SAHA 12.13 and Its Potency as a Biocontrol of Curvularia affinis

Bacillus cereus SAHA 12.13 can produce chitinase, an enzyme that digests chitin in the main compounds of cell walls, mycelia, and spores in pathogenic fungi that cause leaf spots on oil palm plants such as Curvularia affinis. This study aims to determine the properties of the chitinase enzyme B. cereus SAHA 12.13 that can inhibit the growth of C. affinis. Chitinase enzyme production and characterization were measured using the Spindler method. Antagonism test against pathogenic fungi using dual culture method by testing cell culture and enzyme crude extract. This result showed that the isolate produced a high level of specific chitinase activity at 37 °C for 45 h of incubation with 8.45 U mg-1 proteins with a growth rate (k) of 0.25 generation/h, and the generation time was 3.96 h/generation. The optimum chitinase activity was achieved at pH 7.0 and 45 °C and was stable for 3 h with a half-life (t1/2) of 770 min. The crude enzyme and cell culture of strain can inhibit the growth of C. affinis by 36.27±0.043% and 34.25±0.041%, respectively. These characteristics indicate that B. cereus strain SAHA12.13 can be used to inhibit C. affinis, which causes leaf blight of oil palm, under varying pH and temperature conditions.

Chitinous material bioconversion by three new chitinases from the yeast Mestchnikowia pulcherrima

BackgroundChitinases are widely distributed enzymes that perform the biotransformation of chitin, one of the most abundant polysaccharides on the biosphere, into useful value-added chitooligosaccharides (COS) with a wide variety of biotechnological applications in food, health, and agricultural fields. One of the most important group of enzymes involved in the degradation of chitin comprises the glycoside hydrolase family 18 (GH18), which harbours endo- and exo-enzymes that act synergistically to depolymerize chitin. The secretion of a chitinase activity from the ubiquitous yeast Mestchnikowia pulcherrima and their involvement in the post-harvest biological control of fungal pathogens was previously reported.ResultsThree new chitinases from M. pulcherrima, MpChit35, MpChit38 and MpChit41, were molecularly characterized and extracellularly expressed in Pichia pastoris to about 91, 90 and 71 mU ml− 1, respectively. The three enzymes hydrolysed colloidal chitin with optimal activity at 45 ºC and pH 4.0-4.5, increased 2-times their activities using 1 mM of Mn2+ and hydrolysed different types of commercial chitosan. The partial separation and characterization of the complex COS mixtures produced from the hydrolysis of chitin and chitosan were achieved by a new anionic chromatography HPAEC-PAD method and mass spectrometry assays. An overview of the predicted structures of these proteins and their catalytic modes of action were also presented. Depicted their high sequence and structural homology, MpChit35 acted as an exo-chitinase producing di-acetyl-chitobiose from chitin while MpChit38 and MpChit41 both acted as endo-chitinases producing tri-acetyl-chitotriose as main final product.ConclusionsThree new chitinases from the yeast M. pulcherrima were molecularly characterized and their enzymatic and structural characteristics analysed. These enzymes transformed chitinous materials to fully and partially acetylated COS through different modes of splitting, which make them interesting biocatalysts for deeper structural-function studies on the challenging enzymatic conversion of chitin.

Enhancement of disease resistance against Alternaria alternata in winter jujube fruit by phenyllactic acid through regulating Ca2+ signaling transduction and mitogen-activated protein kinase cascades

Alternaria rot caused by Alternaria alternata is one of destructive fungal diseases of postharvest winter jujubes. This study performed to evaluate the potential mechanisms participated in the enhancement disease resistance of winter jujubes by phenyllactic acid (PLA). Results demonstrated that PLA reduced the lesion diameter of A. alternata-inoculated winter jujubes. Additionally, PLA treatment led to an up-regulation in the transcription levels of ZjCML23/28, ZjCIPK11/12/20, ZjCDPK1/3/5, ZjMAPKKK18, ZjMAPKK6, and ZjMAPK7/19 as well as ZjNPR1 and ZjWRKY14/22/44/55/64 in fruit. Conversely, the transcription levels of ZjMAPK15 and ZjMAPKKK17 were down-regulated. Simultaneously, PLA enhanced the gene transcription levels and enzymatic activities of peroxidase, β-1,3-glucanase, and chitinase in winter jujubes, while facilitating the deposition of lignin, flavonoids, and total phenolics. Overall, these findings suggest that PLA enhances the resistance of winter jujube fruit via positively modulating the transcription of key Ca2+ receptor protein, activating the mitogen-activated protein kinase cascades, and potentially involving NPR1 and WRKY transcription factors.

Impact of chitin-derived β-N-acetyl-d-glucosaminyl-(1,4)-d-glucosamine on chitinase upregulation in Shewanella baltica.

The first steps in chitin degradation in marine bacteria involve chitinase, which produces N,N'-diacetylchitobiose (GlcNAc)2 from chitin. Moreover, in Vibrio bacteria, chitinase activity is enhanced by heterodisaccharide β-N-acetyl-d-glucosaminyl-(1,4)-d-glucosamine (GlcNAc-GlcN) produced from (GlcNAc)2 by chitin oligosaccharide deacetylase (COD). However, the role of COD in other marine bacteria, such as Shewanella, remains unexplored. This study investigates GlcNAc-GlcN's impact on chitinase gene expression and enzyme production in S. baltica ATCC BAA-1091, drawing parallels with Vibrio parahaemolyticus RIMD2210633. Using real-time quantitative PCR, the study assesses the upregulation of chitinase gene expression in S. baltica in response to GlcNAc-GlcN, informed by COD's known ability to produce GlcNAc-GlcN from (GlcNAc)2. In Vibrio, GlcNAc-GlcN considerably upregulates chitinase gene expression. This study posits a similar regulatory mechanism in S. baltica, with preliminary investigations indicating COD's capacity to produce GlcNAc-GlcN. This study highlights the importance of exploring GlcNAc-GlcN's regulatory role in chitin metabolism across diverse marine bacteria. The potential induction of chitinase production in S. baltica suggests broader ecological implications. Further research is crucial for a comprehensive understanding of chitin utilization and regulatory pathways in marine bacterial genera.

The phytocytokine systemin enhances postharvest tomato fruit resistance to Botrytis cinerea

The 18-amino acid peptide systemin is the first identified phytocytokine and plays important roles in tomato resistance to pathogens and insects. However, the function of systemin in postharvest fruit is unknown. Here, we found pretreatment of systemin increased the resistance of postharvest tomato fruit to Botrytis cinerea and the resistance ability was dependent on the concentration of systemin. As a phytocytokine, systemin induced the early immune responses in postharvest fruit, including the expression of immune-related genes, activation of mitogen-activated protein kinases (MAPKs), and production of reactive oxygen species. Transcriptome results indicated that systemin enhanced the expression of genes in the MAPK signaling pathway, phenypropanoid biosynthesis pathway and fatty acid desaturase (FAD) genes. Moreover, systemin regulated the activity of chitinase, phenylalanine ammonia lyase and peroxidase, and the concentration of FAD2 during storage. Therefore, our findings suggested that systemin could be a promising molecule to increase tomato fruit resistance against pathogens during storage.

Transcriptome differential expression analysis of defoliation in different lemon varieties under drought treatment.

'Allen Eureka' is a bud variety of Eureka lemon with excellent fruiting traits, but severe winter defoliation affects the following year's yield, and the response mechanism of lemon defoliation is currently unknown. Two lemon cultivars ('Allen Eureka' and 'Yunning No. 1') with different defoliation traits were used as materials to investigate the molecular regulatory mechanisms of different leaf abscission periods in lemons. The petiole abscission zone was collected at three different defoliation stages, namely, the predefoliation stage (k15), the middefoliation stage (k30), and the postdefoliation stage (k45). Transcriptome sequencing was performed to analyze the gene expression differences between these two cultivars. A total of 1141, 2695, and 1433 differentially expressed genes (DEGs) were obtained in k15, k30, and k45, respectively, and the number of DEGs in k30 was the largest. GO analysis revealed that the DEGs between the two cultivars were mainly enriched in processes related to hydrolase activity, chitinase activity, oxidoreductase activity, and transcription regulator activity in the defoliation stages. KEGG analysis showed that the DEGs were concentrated in k30, which involved plant hormone signal transduction, phenylpropanoid biosynthesis, and biosynthesis of amino acids. The expression trends of some DEGs suggested their roles in regulating defoliation in Lemon. Seven genes were obtained by WGCNA, including sorbitol dehydrogenase (CL9G068822012_alt, CL9G068820012_alt, CL9G068818012_alt), abscisic acid 8'-hydroxylase (CL8G064053012_alt, CL8G064054012_alt), and asparagine synthetase (CL8G065162012_alt, CL8G065151012_alt), suggesting that these genes may be involved in the regulation of lemon leaf abscission.

Biocontrol mechanisms of the Antarctic yeast Debaryomyces hansenii UFT8244 against post-harvest phytopathogenic fungi of strawberries.

The use of yeasts has been explored as an efficient alternative to fungicide application in the treatment and prevention of post-harvest fruit deterioration. Here, we evaluated the biocontrol abilities of the Antarctic yeast strain Debaryomyces hansenii UFT8244 against the post-harvest phytopathogenic fungi Botrytis cinerea and Rhizopus stolonifer for the protection and preservation of strawberry fruit. The strongest inhibition of germination of B. cinerea (57%) was observed at 0 °C, followed by 40% at 25 °C. In addition, germ tubes and hyphae of B. cinerea were strongly surrounded and colonized by D. hansenii. Production of the enzymes β-1,3-glucanase, chitinase and protease by D. hansenii was detected in the presence of phytopathogenic fungus cell walls. The activity of β-1,3-glucanase was highest on day 12 of incubation and remained high until day 15. Chitinase and protease activities reached their highest levels on the day 15 of incubation. D. hansenii additionally demonstrated the ability to resist oxidative stress. Our data demonstrated that the main biocontrol mechanisms displayed by D. hansenii were the control of phytopathogenic fungal spore germination, production of antifungal enzymes and resistance to oxidative stress. We conclude that isolate D. hansenii UFT8422 should be further investigated for use at commercial scales at low temperatures.

Transcriptional survey of abiotic stress response in maize (Zea mays) in the level of gene co-expression network and differential gene correlation analysis.

Abstract. Maize may be exposed to several abiotic stresses in the field. Therefore, identifying the tolerance mechanisms of natural field stress is mandatory. Gene expression data of maize upon abiotic stress were collected, and 560 differentially expressed genes (DEGs) were identified through meta-analysis. The most significant gene ontology terms in up-regulated genes were 'response to abiotic stress' and 'chitinase activity'. 'Phosphorelay signal transduction system' was the most significant enriched biological process in down-regulated DEGs. The co-expression analysis unveiled seven modules of DEGs, with a notable positive correlation between the modules and abiotic stress. Furthermore, the statistical significance was strikingly high for the turquoise, green and yellow modules. The turquoise group played a central role in orchestrating crucial adaptations in metabolic and stress response pathways in maize when exposed to abiotic stress. Within three up-regulated modules, Zm.7361.1.A1_at, Zm.10386.1.A1_a_at and Zm.10151.1.A1_at emerged as hub genes. These genes might introduce novel candidates implicated in stress tolerance mechanisms, warranting further comprehensive investigation and research. In parallel, the R package glmnet was applied to fit a logistic LASSO regression model on the DEGs profile to select candidate genes associated with abiotic responses in maize. The identified hub genes and LASSO regression genes were validated on an independent microarray dataset. Additionally, Differential Gene Correlation Analysis (DGCA) was performed on LASSO and hub genes to investigate the gene-gene regulatory relationship. The P value of DGCA of 16 pairwise gene comparisons was lower than 0.01, indicating a gene-gene significant change in correlation between control and abiotic stress. Integrated weighted gene correlation network analysis and logistic LASSO analysis revealed Zm.11185.1.S1_at, Zm.2331.1.S1_x_at and Zm.17003.1.S1_at. Notably, these 3 genes were identified in the 16 gene-pair comparisons. This finding highlights the notable significance of these genes in the abiotic stress response. Additional research into maize stress tolerance may focus on these three genes.

Engineering the Relatively Conserved Residues in Active Site Architecture of Thermophilic Chitinase SsChi18A Enhanced Catalytic Activity.

Chitinase plays a vital role in the efficient biotransformation of the chitin substrate. This study aimed to modify and elucidate the contribution of the relatively conserved residues in the active site architecture of a thermophilic chitinase SsChi18A from Streptomyces sp. F-3 in processive catalysis. The enzymatic activity on colloidal chitin increased to 151%, 135%, and 129% in variants Y286W, E287A, and K186A compared with the wild type (WT). Also, the apparent processive parameter G2/G1 was lower in the variants compared to the WT, indicating the essential role of Tyr-286, Glu-287, and Lys-186 in processive catalysis. Additionally, the enzymatic activity on the crystalline chitin of F48W and double mutants F48W/Y209F and F48W/Y286W increased by 35%, 16%, and 36% compared with that for WT. Molecular dynamics simulations revealed that the driving force of processive catalysis might be related to the changes in interaction energy. This study provided a rational design strategy targeting relatively conserved residues to enhance the catalytic activity of GH18 processive chitinases.

Digestive glycosidases from cannonball jellyfish (Stomolophus sp. 2): identification and temporal-spatial variability.

Jellyfish are economically important organisms in diverse countries, carnivorous organisms that consume various prey (crustaceans, mollusks, bivalves, etc.) and dissolved carbohydrates in marine waters. This study was focused on detecting and quantifying the activity of digestive glycosidases from the cannonball jellyfish (Stomolophus sp. 2) to understand carbohydrate digestion and its temporal-spatial variation. Twenty-three jellyfish gastric pouches were collected in 2015 and 2016 in the Gulf of California in three localities (Las Guásimas, Hermosillo, and Caborca). Nine samples were in intra-localities from Las Guásimas. Chitinase (Ch), β-glucosidase (β-glu), and β-N-acetylhexosaminidase (β-NAHA) were detected in the gastric pouches. However, cellulase, exoglucanase, α-amylase, polygalacturonase, xylanase, and κ-carrageenase were undetected. Detected enzymes showed halotolerant glycolytic activity (i = 0-4 M NaCl), optimal pH, and temperature at 5.0 and 30-50 °C, respectively. At least five β-glucosidase and two β-N-acetylhexosaminidase were detected using zymograms; however, the number of proteins with chitinase activity is not precise. The annual variation of cannonball jellyfish digestive glycosidases from Las Guásimas between 2015-2016 does not show significant differences despite the difference in phytoplankton measured as chlorophyll α (1.9 and 3.4 mg/m3, respectively). In the inter-localities, the glycosidase activity was statistically different in all localities, except for β-N-acetylhexosaminidase activity between Caborca and Hermosillo (3,009.08 ± 87.95 and 3,101.81 ± 281.11 mU/g of the gastric pouch, respectively), with chlorophyll α concentrations of 2.6, 3.4 mg/m3, respectively. For intra-localities, the glycosidase activity did not show significant differences, with a mean chlorophyll α of 1.3 ± 0.1 mg/m3. These results suggest that digestive glycosidases from Stomolophus sp. 2 can hydrolyze several carbohydrates that may belong to their prey or carbohydrates dissolved in marine waters, with salinity over ≥ 0.6 M NaCl and diverse temperature (4-80 °C) conditions. Also, chlorophyll α is related to glycosidase activity in both seasons and inter-localities, except for chitinase activity in an intra-locality (Las Guásimas).

Divergent response of maize and soybean rhizosphere to arbuscular mycorrhiza

Maize and soybean are capable of forming symbiotic relationship with arbuscular mycorrhizal fungi (AMF), which enables the plants to overcome P limitations and resist drought effects. The results indicate that the activities of β-glucosidase, chitinase and acid phosphatase in the rhizosphere were double those in the bulk soil, regardless of plant species. Both soybean and maize demonstrated a decrease in β-glucosidase activity. However, chitinase activity displayed a divergent pattern between the two plant species under AMF influence, with a notable 18.5% increase in maize compared to a substantial 44.8% decrease in soybean. The presence of AMF resulted in a 50% reduction in rhizosphere microbial biomass phosphorus (MBP) in soybean, whereas this effect was not observed in maize. The distinct nutrient demands of each plant species appear to regulate the impact of AMF on the characteristics of microbial activities in the rhizosphere.

Microbial carbon use efficiency and soil organic carbon stocks across an elevational gradient in the Peruvian Andes

Soils of mountain ecosystems are one of the most vulnerable ecosystems to climate change, while the ecosystem services they produce are significant and currently at risk. High altitude soils contain high C stocks, but due to difficult access to sites these areas are understudied. Moreover, how the C and N cycling is changing in response to climate change in these ecosystems, is still unclear. Microbial carbon use efficiency (CUE) and its dependency on the environmental constraints along the altitudinal gradients is one important unknown factor. Here we present results from an altitudinal gradient study (3500 to 4500 m a.s.l.) from a Polylepis forest in the Peruvian Andes. We measured the soil organic carbon (SOC) stocks and microbial metabolic CUE by 13C glucose tracing and microbial resource use efficiency (CUEC:N) based on enzyme activity measurements. We expected to find an increase in SOC stock, microbial nutrient limitations, and lower CUE with elevation. SOC stocks depended on soil development and followed a unimodal curve that peaks at 4000 m in two of the three studied valleys. Neither 13CUE nor CUEC:N changed significantly with altitude. Soil C:N ratio, β-glucosidase, chitinase, and phosphatase enzyme activities increased with elevation, but peroxidase activity decreased with elevation. We suggest that more labile organic matter left at high elevation could compensate for the increasing nutrient limitation at high elevation, resulting in no noticeable change in CUE with elevation.