Production Of Secondary Metabolites Research Articles

Antifouling activity and ecotoxicological profile of the cyanobacterial oxadiazine nocuolin A

Pursuing effective and biocompatible natural compounds to supplant current biocidal antifouling (AF) technologies remains crucial and challenging. Among natural products hosts, cyanobacteria are recognized as producers of bioactive secondary metabolites that are underexplored in terms of anti-biofilm and AF potential. Nocuolin A, a natural oxadiazine previously isolated and known to be produced by different cyanobacterial strains, has demonstrated bioactive potential, particularly against tumor cell lines. Considering this potential and its exquisite chemical structure, here nocuolin A was investigated as a potential natural AF agent through an integrative approach including AF bioactivity testing across distinct levels of biological organization, mode of action assessment, ecotoxicity evaluation, and ecological risk predictions. Nocuolin A was found to inhibit the settlement of mussel (Mytilus galloprovincialis) plantigrades (EC50 = 3.905 μM) while showing no toxicity to this biofouling species (LC50 > 100 μM). Additionally, while exhibiting no inhibitory activity against the growth of five marine biofilm-forming bacterial strains, it significantly suppressed the growth of the marine biofilm-forming diatom Navicula sp. (EC50 = 1.561 μM), and had a lethal effect on this diatom species (>3.1 μM). The AF targets of nocuolin A on mussel plantigrades revealed no correlation with acetylcholinesterase and tyrosinase metabolic processes; however, proteins involved in oxidative stress, muscle regulation, and energy production were highlighted. The results also provide insights into the ecological risk of nocuolin A, including its ecotoxicity against Artemia salina nauplii (LC50 = 2.480 μM), Amphibalanus amphitrite nauplii (LC50 = 0.0162 μM), and Danio rerio embryos (LC50 = 0.0584 μM). When matching these results with simulated environmental values, nocuolin A was deemed a considerable threat to the ecosystems. While this research highlights the AF activity of nocuolin A, it also emphasizes the potential adverse environmental impact when applied in preventive coatings.

Application of iron oxide nanoparticles improves growth and phytochemical constituents of in vitro cultured Carum copticum L.

Iron oxide nanoparticles (FeONPs) are widely used in various applications, such as biomedicine, environmental remediation, and agriculture. Moreover, FeONPs can affect the production of secondary metabolites in plants, which are compounds that have various biological and pharmacological activities. Therefore, in this study, the ajwain (Carum copticum L.) seeds were grown in MS medium containing different levels of FeONPs (0, 100, 200, and 400 mg l−1). After four weeks, the effects of FeONPs on growth, photosynthesis pigments, total phenolic, and anthocyanin content, activities of some antioxidant enzyme and secondary metabolites of ajwain) were investigated. The results showed that low levels of FeONPs (especially 200 mg l−1) increased fresh weight (231 %), total chlorophyll (49 %), total phenolics (259 %), anthocyanin content (110 %), as well as thymol (8 %) and γ-terpinene (16 %) content. Conversely, 400 mg l−1 FeONPs reduced root length (60 %) and fresh weight (64 %) was associated with a reduction in CAT activity, phenol (55 %), thymol (22 %), and γ-terpinene (18 %) content compared to ajwain treated with 200 mg l−1 FeONPs. This reduction was probably due to the increase in ROS caused by the low catalase enzyme activity and important essential oils compounds such as thymol and γ-terpinene. Thus, our results indicate that FeONPs at certain levels can be used as a new way for in vitro production of valuable essential oils and antioxidant compounds in ajwain.

Screening of Lipid-Reducing Activity and Cytotoxicity of the Exometabolome from Cyanobacteria.

Cyanobacteria are rich producers of secondary metabolites, excreting some of these to the culture media. However, the exometabolome of cyanobacteria has been poorly studied, and few studies have dwelled on its characterization and bioactivity assessment. In this work, exometabolomes of 56 cyanobacterial strains were characterized by HR-ESI-LC-MS/MS. Cytotoxicity was assessed on two carcinoma cell lines, HepG2 and HCT116, while the reduction in lipids was tested in zebrafish larvae and in a steatosis model with fatty acid-overloaded human liver cells. The exometabolome analysis using GNPS revealed many complex clusters of unique compounds in several strains, with no identifications in public databases. Three strains reduced viability in HCT116 cells, namely Tolypotrichaceae BACA0428 (30.45%), Aphanizomenonaceae BACA0025 (40.84%), and Microchaetaceae BACA0110 (46.61%). Lipid reduction in zebrafish larvae was only observed by exposure to Dulcicalothrix sp. BACA0344 (60%). The feature-based molecular network shows that this bioactivity was highly correlated with two flavanones, a compound class described in the literature to have lipid reduction activity. The exometabolome characterization of cyanobacteria strains revealed a high chemodiversity, which supports it as a source for novel bioactive compounds, despite most of the time being overlooked.

Amycolatopsis nalaikhensis sp. nov. and Amycolatopsis carbonis sp. nov., two novel actinobacteria with antimicrobial activity isolated from a coal mining site in Mongolia.

Two-novel filamentous actinobacteria designated strains 2-2T and 2-15T were isolated from soil of a coal mining site in Mongolia, and their taxonomic positions were determined using a polyphasic approach. Phylogenetic analyses based on 16S rRNA gene sequences showed that each of the strains formed a distinct clade within the genus Amycolatopsis. The 16S rRNA gene sequence similarity analysis showed that both strains were mostly related to Amycolatopsis rhabdoformis NCIMB 14900T with 99.0 and 99.4% sequence similarity, respectively. The genome-based comparison indicated that strain 2-2T shared the highest digital DNA-DNA hybridization value of 35.6% and average nucleotide identity value of 86.9% with Amycolatopsis pretoriensis DSM 44654T, and strain 2-15T shared the corresponding values of 36.5 and 87.9% with A. rhabdoformis NCIMB 14900T, all of which being well below the thresholds for species delineation. The chemotaxonomic properties of both strains were typical of the genus Amycolatopsis. In silico prediction of chemotaxonomic markers was also carried out, and the results were consistent with the chemotaxonomic profiles of the genus. Genome mining for secondary metabolite production in strains 2-2T and 2-15T revealed the presence of 29 and 24 biosynthetic gene clusters involved in the production of polyketide synthase, non-ribosomal peptide synthetase, ribosomally synthesized and post-translationally modified peptides, lanthipeptide, terpenes, siderophore, and a number of other unknown type compounds. Both strains showed broad antifungal activity against several filamentous fungi and also antibacterial activity against methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii. The phenotypic, biochemical, and chemotaxonomic properties indicated that both strains could be clearly distinguished from other species of Amycolatopsis, and thus the names Amycolatopsis nalaikhensis sp. nov. (type strain, 2-2T=KCTC 29695T=JCM 30462T) and Amycolatopsis carbonis (type strain, 2-15T=KCTC 39525T=JCM 30563T) are proposed accordingly.

Spatiotemporal Analysis of Secondary Metabolites Produced by S.coelicolor Using Automated Sampling Mass Spectrometry

Natural products (NPs) are organic compounds that are synthesized by living organisms such as bacteria. NPs and their derivatives are very useful in the medical field to develop new drugs, particularly new antibiotics which are crucial to combat developing antibiotic resistance. The current research on the secondary metabolites (SMs) produced throughout the growth cycle of bacteria is limited, as the standard procedure is to examine the SM production at the end of the bacteria’s growth cycle. Therefore, there may be many undiscovered SMs which are produced and consumed prior to analysis. A mass spectrometer (MS) can be used to track analytes of interest, such as SMs. When the MS is paired with an ambient ionization technique like the Liquid Micro-Junction Surface Sampling Probe (LMJ-SSP) it works as a minimally invasive approach to track the SMs in real time produced throughout the bacterial growth cycle. This allows for the SMs to be tracked both temporally and spatially without killing the bacteria. The process is automated using the LMJ-SSP mounted to a 3D printer, allowing for a grid-like sampling process to map NPs production. Herein, A 3D-printed growth chamber dubbed the “Washing And Sampling Agar Bacterial Inoculation” (WASABI) Box was designed to resemble a sampling grid for simpler analysis. Another key feature of the WASABI Box are washing ports, containing 70% ethanol, to sterilize the LMJ-SSP and minimize contamination between rows. The SM production of S. coelicolor in the WASABI Box was analyzed from day 4 to 7 of the bacterial growth cycle, where the data was used to generate spatial-temporal heat maps tracking metabolites including Albaflavenone (m/z 219.2), Desferrioxamine B (m/z 561.4), Germicidin B (m/z 183.1), Kalafungin (m/z 301.1), and Streptorubin B (m/z 392.3).

Effect of Water Deficit on Secondary Metabolites and Nutrient Content on Forage Sorghum

Agronomic properties are more likely to be impacted by water deficits that affect the nutrient uptake and production of secondary metabolites based on their timing and intensity. The aim of this study was to assess the effects of the water deficit on the nutritional quality of forage sorghum (Sorghum bicolor) hybrids. For that purpose, a factorial, completely randomized experiment was conducted by considering three forage sorghum hybrids (AGRI 002-E, BREVANT SS318, and BRS 658) and two levels of evapotranspiration water replacement (50% and 100% of ETc). Parameters relating to water consumption, secondary metabolites (isoflavones daidzein, daidzin, genistein, and genistin), leaf nutrients (P, K, Ca, Mg, S, Mn, and Zn), and bromatological attributes (dry matter, crude protein, neutral detergent fiber, and mineral material) were evaluated at the end of the crop cycle. Isoflavone levels differed between the hybrids and were highest in water-deficient sorghum. There was a significant interaction between the factors only for the daidzin. The leaf content of the other compounds was influenced either by hybrids (genistein) or by the replacement of evapotranspired water levels (daidzein). The leaf content of P and S was influenced by the interaction between the factors, while the levels of K, Ca, and Mg were influenced by the effect of a single factor. The leaf contents of Mn and Zn were not influenced by the treatments. There was a difference between the hybrids for dry mass and crude protein contents, and hybrids x water deficit was only significant for dry mass. The hybrids Brevant SS318 and BRS 658 had the highest crude protein. The presented results are novel and demonstrate that water deficits can significantly affect the levels of secondary metabolites and the nutritional quality of forage sorghum, depending on the hybrid. The mentioned indices are important parameters for evaluating the nutritional quality and development of agricultural crops, particularly in response to adverse environmental conditions such as water stress.

Comparative Genomics of Fungi in Nectriaceae Reveals Their Environmental Adaptation and Conservation Strategies.

This study presents the first genome assembly of the freshwater saprobe fungus Neonectria lugdunensis and a comprehensive phylogenomics analysis of the Nectriaceae family, examining genomic traits according to fungal lifestyles. The Nectriaceae family, one of the largest in Hypocreales, includes fungi with significant ecological roles and economic importance as plant pathogens, endophytes, and saprobes. The phylogenomics analysis identified 2684 single-copy orthologs, providing a robust evolutionary framework for the Nectriaceae family. We analyzed the genomic characteristics of 17 Nectriaceae genomes, focusing on their carbohydrate-active enzymes (CAZymes), biosynthetic gene clusters (BGCs), and adaptations to environmental temperatures. Our results highlight the adaptation mechanisms of N. lugdunensis, emphasizing its capabilities for plant litter degradation and enzyme activity in varying temperatures. The comparative genomics of different Nectriaceae lifestyles revealed significant differences in genome size, gene content, repetitive elements, and secondary metabolite production. Endophytes exhibited larger genomes, more effector proteins, and BGCs, while plant pathogens had higher thermo-adapted protein counts, suggesting greater resilience to global warming. In contrast, the freshwater saprobe shows less adaptation to warmer temperatures and is important for conservation goals. This study underscores the importance of understanding fungal genomic adaptations to predict ecosystem impacts and conservation targets in the face of climate change.

Exploiting Induced Plant Resistance for Sustainable Pest Management: Mechanisms, Elicitors, and Applications: A Review

Plants and phytophagous (plant-eating) arthropods have coevolved over millions of years, leading to the development of both constitutive and inducible defense mechanisms in plants. Despite this long history of coexistence, it remains unclear how to precisely regulate each host-arthropod interaction to achieve an equilibrium that maximizes crop yield. The defensive chemicals produced by plants can significantly affect herbivores’ feeding behaviour, growth, and survival. These chemicals may be generated constitutively (continuously) or induced in response to herbivore damage. Induced resistance, a strategy where plants enhance their defences after being attacked, holds potential for reducing the number of insecticides needed in pest management. Chemical elicitors, which trigger the production of secondary metabolites that confer resistance to insects, can be used to manipulate host plant resistance, specifically by inducing resistance. By understanding the mechanisms underlying induced resistance, it is possible to predict which herbivores will be impacted by these responses. Applying induced response elicitors to crop plants can strengthen their natural defences against herbivore damage. Additionally, it is possible to genetically modify plants so that they constitutively produce defense chemicals, providing continuous protection in areas where herbivory is a constant threat. As part of integrated pest management, induced resistance can be used to develop crop cultivars that readily trigger an inducible response in the event of a mild infestation, contributing to sustainable agricultural practices and reducing reliance on chemical pesticides.

Heterologous expression of lasso peptides with apparent participation in the morphological development in Streptomyces

Lasso peptides, ribosomally synthesized and post-translationally modified peptides, are primarily produced by bacteria and some archaea. Streptomyces lasso peptides have been known for their antimicrobial, anticancer, and antiviral properties. However, understanding their role in the morphology and production of secondary metabolites remains limited. We identified a previously unknown lasso peptide gene cluster in the genome of Streptomyces sp. L06. This gene cluster (LASS) produces two distinct lasso peptides, morphosin-1 and − 2. Notably, morphosin-2 is a member of a new subfamily of lasso peptides, with BGCs exhibiting a similar structure. When LASS was expressed in different Streptomyces hosts, it led to exciting phenotypic changes, including the absence of spores and damage in aerial mycelium development. In one of the hosts, LASS even triggered antibiotic formation. These findings open up a world of possibilities, suggesting the potential role of morphosins in shaping Streptomyces’ morphological and biochemical development.

Identification of an Endogenous Strong Promoter in Burkholderia sp. JP2-270.

Burkholderia is the second largest source of natural product bacteria after Actinomyces and can produce many secondary metabolites including pyrrolnitrin (PRN). Natural products of microbial origin are usually found in trace amounts, so in metabolic engineering, promoter engineering is often used to regulate gene expression to increase yield. In this study, an endogenous strong promoter was identified based on RNA-seq to overexpress biosynthetic genes to increase the production of PRN. By analyzing the transcriptomic data of the antagonistic bacterium Burkholderia sp. JP2-270 in three different development periods, we screened 50 endogenous promoters with high transcriptional activity, nine of which were verified by an obvious fluorescent signal via fluorescence observation. Then, combined with RT-qPCR analysis, Php, the promoter of a hypothetical protein, was found to be significantly expressed in all three periods. In order to increase the suitability of endogenous promoters, the promoter Php was shortened at different lengths, and the results show that a sequence length of 173 bp was necessary for its activity. Moreover, this promoter was used to overexpress the PRN biosynthesis genes (prnA, prnB, prnC and prnD) in JP2-270, resulting in a successful increase in gene expression levels by 40-80 times. Only the overexpression of the prnB gene successfully increased PRN production to 1.46 times that of the wild type. Overall, the endogenous strong promoters screened in this study can improve gene expression and increase the production of secondary metabolites in JP2-270 and other strains.

Endophyte-based fungal elicitors for enhanced production of valepotriates and sesquiterpenoids in leaf cell suspension cultures of Valeriana jatamansi Jones.

The immense therapeutic value of Valeriana jatamansi is attributed to the presence of bioactive secondary metabolites (valepotriates and sesquiterpenoids). Its over-exploitation in wild habitats resulted in extensive depletion, necessitating alternative approaches to produce its therapeutic metabolites. This study sought to assess the ability of endophytes of V. jatamansi to boost the biosynthesis of secondary metabolites in the leaf-cell suspension (LCS) culture of V. jatamansi. A total of 11 fungal endophytes were isolated from the rhizomes of V. jatamansi. Isolated endophytes were found to belong to phylum Ascomycota, Basidiomycota, and Mucoromycota. Supplementation of extracts of endophyte Phaeosphaeriaceae sp. VRzFB, Mucor griseocyanus VRzFD, Penicillium raistrickii VRzFK, and Penicillium sajarovii VRzFL in the LCS culture of V. jatamansi increased the fresh cell biomass by 19.6%-39.1% and dry cell biomass by 23.4%-37.8%. Most of the endophytes' extract could increase the content of valepotriates (26.5%-76.5% valtrate and 40.5%-77.9% acevaltrate) and sesquiterpenoids (19.9%-61.1% hydroxyl valerenic acid) in LCS culture. However, only two endophytes, Irpex lacteus VRzFI and Fusarium oxysporum VRzFF, could increase the sesquiterpenoids acetoxy valerenic acid (36.9%-55.3%). In contrast, some endophytes' extracts caused negative or no significant effect on the cell biomass and targeted metabolites. Increased secondary metabolites were corroborated with increased expression of iridoid biosynthesis genes in LCS culture. Production of H2O2 and lipid peroxidation was also varied with different endophytes indicating the modulation of cellular oxidative stress due to endophyte elicitors. The results suggest the distinct effect of different fungal endophytes-extract on LCS culture, and endophytes can serve as biotic elicitors for increasing the secondary metabolite production in plant in vitro systems.

Secondary Metabolite Profiles: Trichoderma, Aspergillus flavus Glocladium and Penicillium as Biocontrol Agents

A fungus is utilized as a biocontrol agent to suppress plant diseases by employing an antagonistic mechanism, wherein it releases enzymes that degrade the cell walls of pathogens and inhibit their growth. The antibiosis mechanism is initiated by biocontrol fungi through the production of secondary molecules or metabolites. The objective of the research was to examine the secondary metabolite composition of the biocontrol fungi Trichoderma spp., Aspergillus flavus, and Gliocladium sp. and Penicillium species The implementation approach involved the use of qualitative phytochemical testing and HPLC analysis. The outcomes of the investigation into the metabolite profiles of Trichoderma spp., Aspergillus flavus, and Gliocladium sp. were observed. and Penicillium species The presence of alkaloids, phenolics, and flavonoids was detected in the samples. The results of the High-Performance Liquid Chromatography (HPLC) analysis indicated the presence of 10-11 compounds, as evidenced by the peaks observed in the chromatogram. These compounds are presumed to be associated with the phenolic and alkaloid groups.

Transcriptomic analysis of the metabolic characteristics of Aspergillus oryzae during the fermentation of doenjang-meju, a traditional Korean fermented soybean brick

To investigate the fermentative traits of Aspergillus oryzae in doenjang-meju, a traditional Korean fermented soybean brick, we prepared doenjang-meju bricks inoculated with both A. oryzae and Bacillus velezensis––recognized as crucial microbes in doenjang-meju fermentation, and then the transcriptomes of A. oryzae were analyzed throughout the entire fermentation period. The transcriptomic analysis of carbohydrate-active enzyme (CAZy) genes revealed that A. oryzae exhibited robust expression of CAZy genes involved in the decomposition of various carbohydrates, particularly cellulose, starch, and hemicellulose, indicating the active breakdown of soybean carbohydrates by A. oryzae during fermentation. Furthermore, KEGG analysis, metabolic pathway reconstruction, and their transcriptomic analysis provided a comprehensive overview of the decomposition patterns of various carbohydrates, lipids, and proteins and the metabolic features of various carbon compounds during fermentation. Additionally, the transcriptomic analysis of biosynthetic gene clusters indicated the potential production of various secondary metabolites by A. oryzae during fermentation. Genes related to carbohydrate and carbon compound metabolisms and secondary metabolite biosynthesis displayed unique and different transcriptional expression patterns depending on the specific gene and fermentation stage. Overall, our findings provide comprehensive insights into the metabolic characteristics of A. oryzae, thus contributing to our understanding of soybean fermentation.

L-DOPA ELICITATION THROUGH CALCIUM ION MEDIATED CHANNEL IN CALLUS CULTURES OF MUCUNA PRURIENS

Objective: The production of L-Dopa in callus cultures of Mucuna pruriens is influenced by substances that regulate calcium channels. Methods: M. pruriens seeds were gathered from the Western Ghats area in Tamil Nadu. L-Dopa was obtained by the Brain (1976) method, A. niger cultures were used for fungal elicitor preparation, and the assay of Ca2+ATPase was studied. Results: The use of fungal triggers resulted in increased L-Dopa levels on the 9th day but reduced levels on the 24th day of culture. When calcium channel modulators like verapamil and chlorpromazine were added, it decreased the growth of calli and L-Dopa production, suggesting the role played by calcium ion channels in L-Dopa synthesis. The calcium ionophore A23187 enhanced calli growth and L-Dopa production, increasing Ca2+ATPase activity. Particularly on the 12th d, Ca2+ATPase was notably active, while the presence of calcium ionophore boosted L-Dopa biosynthesis. Conclusion: The use of fungal elicitors in in vitro cultures of Mucuna pruriens is recommended as a potential method to increase the production of secondary metabolites.

Genomic analysis of secondary metabolite biosynthesis gene clusters and structural characterization of terpene synthase and cytochrome P450 enzymes in Zingiber officinale Roscoe

This study uses bioinformatics approaches to elucidate the genetic basis of secondary metabolite biosynthesis in Zingiber officinale (Z. officinale). To this end, it identifies 44 secondary metabolite biosynthetic gene clusters and maps onto individual chromosomes, with chromosomes 1A and 8A exhibiting higher concentrations. Here, protein homology modeling provided insights into the structural characteristics of terpene synthases and Cytochrome P450 enzymes, shedding light on their potential roles in stress response and secondary metabolite production. Moreover, the identification of enzymes, such as (-)-kolavenyl diphosphate synthase TPS28 and cytochrome P450 93A3-like, opens up new possibilities for investigating the intricate pathways involved in terpene diversity and stress response mechanisms within Z. officinale. This study highlights the importance of understanding the molecular mechanisms underlying plant-derived bioactive compounds for pharmaceutical applications.

In Situ Raman Hyperspectral Analysis of Microbial Colonies for Secondary Metabolites Screening.

Since the discovery of penicillin, a vast array of microbial antibiotics has been identified and applied in the medical field. Globally, the search for drug candidates via microbial screening is ongoing. Traditional screening methods, however, are time-consuming and require labor-intensive sample processing, significantly reducing throughput. This research introduces a Raman spectroscopy-based screening system tailored to the in situ analysis of microbial colonies on solid culture media. Employing multivariate curve resolution-alternating least-squares (MCR-ALS) for spectral decomposition, our approach reveals the production of secondary metabolites at the single colony level. We enhanced the microbial culture method, enabling direct, high signal-to-noise (S/N) ratio Raman spectroscopic measurements of colonies of Escherichia coli and actinomycetes species. Through semisupervised MCR analysis using the known spectra of actinorhodin and undecylprodigiosin as references, we accurately assessed the production of these compounds by Streptomyces coelicolor A3(2). Furthermore, we herein successfully detected the production of amphotericin B by Streptomyces nodosus, even in the absence of prior spectral information. This demonstrates the potential of our technique in the discovery of secondary metabolites. In addition to enabling the detection of the above-mentioned compounds, this analysis revealed the heterogeneity of the spatial distribution of their production in each colony. Our technique makes a significant contribution to the advancement of microbial screening, offering a rapid, efficient alternative to conventional methods and opening avenues for secondary metabolites discovery.

A Review of Laboratory Requirements to Culture Lichen Mycobiont Species.

Lichens are symbiotic associations between fungi (the mycobiont) and algae or cyanobacteria (the photobionts). They synthesize a large number of secondary metabolites, many of which are potential sources of novel molecules with pharmacological and industrial applications. The advancement of in vitro culture methods of lichen-forming fungi would allow the comprehensive application of these compounds at large scales, enable improvements in the synthesis, facilitate understanding of the role of the partners in the synthesis of these compounds and increase our knowledge about the genes associated with secondary metabolites production. The aim of this work is to summarize the nutritional and physicochemical requirements that have been used to date to culture different lichen-forming fungi species. In total, the requirements for the cultivation of 110 species are presented. This review can provide a starting point for future experiments and help advance the methods of culturing lichenized fungi. The type of diaspore selected to isolate the mycobiont, the composition of the isolation and culture media and the corresponding physicochemical parameters are essential in designing an efficient lichen culture system, allowing the achievement of a suitable growth of lichen-forming fungi and the subsequent production of secondary metabolites.

Whole genome–based comparative analysis of the genus Streptomyces reveals many misclassifications

Streptomyces species are experts in the production of bioactive secondary metabolites; however, their taxonomy has fallen victim of the tremendous interest shown by the scientific community, evident in the discovery of numerous synonymous in public repositories. Based on genomic data from NCBI Datasets and nomenclature from the LPSN database, we compiled a dataset of 600 Streptomyces species along with their annotations and metadata. To pinpoint the most suitable taxonomic classification method, we conducted a comprehensive assessment comparing multiple methodologies, including analysis of 16S rRNA, individual housekeeping genes, multilocus sequence analysis (MLSA), and Fast Average Nucleotide Identity (FastANI) on a subset of 409 species with complete data. Due to insufficient resolution of 16S rRNA and inconsistency observed in individual housekeeping genes, we performed a more in-depth analysis, comparing only FastANI and MLSA, which expanded our dataset to include 502 species. With FastANI validated as the preferred method, we conducted pairwise analysis on the entire dataset identifying 59 non-unique species among the 600, and subsequently refined the dataset to 541 unique species. Additionally, we collected data on 724 uncharacterized Streptomyces strains to investigate the uniqueness potential of the unannotated fraction of the Streptomyces genus. Utilizing FastANI, 289 strains could be successfully classified into one of the 541 Streptomyces species.Key points• Evaluation of taxonomic classification methods for Streptomyces species.• Whole genome analysis, specifically FastANI, has been chosen as preferred method.• Various reclassifications are proposed within the Streptomyces genus.Graphical abstract

Harnessing nature's defenders: unveiling the potential of microbial consortia for plant defense induction against Alternaria blight in cumin.

Present study was aimed to develop an efficient microbial consortium for combating Alternaria blight disease in cumin. The research involved isolating biocontrol agents against Alternaria burnsii, characterizing their biocontrol and growth promotion traits, and assessing compatibility. A pot experiment was conducted during rabi season of 2022-2023 to evaluate the bioefficacy of four biocontrol agents (1F, 16B, 31B, and 223B) individually and in consortium, focusing on disease severity, plant growth promotion, and defense responses in cumin challenged with A. burnsii. Microbial isolates 1F, 16B, 31B, and 223B significantly inhibited A. burnsii growth in dual plate assays (~ 86%), displaying promising biocontrol and plant growth promotion activities. They were identified as Trichoderma afroharzianum 1F, Aneurinibacillus aneurinilyticus 16B, Pseudomonas lalkuanensis 31B, and Bacillus licheniformis 223B, respectively. The excellent compatibility was observed among all selected biocontrol agents. Cumin plants treated with consortia of 1F + 16B + 31B + 223B showed least percent disease index (32.47%) and highest percent disease control (64.87%). Consortia of biocontrol agents significantly enhanced production of secondary metabolites (total phenol, flavonoids, antioxidant, and tannin) and activation of antioxidant-defense enzymes (POX, PPOX, CAT, SOD, PAL, and TAL) compared to individual biocontrol treatment and infected control. Moreover, consortium treatments effectively reduced electrolyte leakage over the individual biocontrol agent and infected control treatment. The four-microbe consortium significantly enhanced chlorophyll (154%), carotenoid content (88%), plant height (78.77%), dry weight (72.81%), and seed yield (104%) compared to infected control. Based on these findings, this environmentally friendly four-microbe consortium may be recommended for managing Alternaria blight in cumin.

The role of yeast propagation aeration for subsequent primary fermentation with respect to performance and aroma development

SummaryDuring the primary fermentation of beer, the yeast simultaneously carries out a series of processes such as cell growth, pH shift, and the formation and degradation of essential flavour components. Harvested yeast from a previous fermentation can be used to inoculate the fermentation or fresh cells can be produced through aerobic propagation. This study investigated the influence of different aeration conditions during Saccharomyces pastorianus ssp. carlsbergensis propagation on the cell count development and the production of secondary metabolites during the subsequent primary beer fermentation. Propagations were conducted by applying six different dissolved oxygen concentrations, and the cells were used as inoculum for the subsequent fermentation. Cell count, pH shift, and the development of key aroma compounds were monitored throughout the primary fermentation to evaluate any difference between the conducted fermentations. The outcomes revealed significant distinctions between fermentations using yeast propagated under elevated oxygen levels and those propagated under reduced oxygen levels. Cells propagated using lower oxygen concentrations showed earlier cell growth with 40% lower final cell counts, resulting in 50% reduced biomass yields. Additionally, lower oxygen concentrations during propagation led to lower pH shifts during primary fermentation with 20% more higher alcohols and elevated formation of acetaldehyde, and esters.