The microbial community of Vetiver root and its involvement into essential oil biogenesis

Microbial regulation of plant secondary metabolites: Impact, mechanisms and prospects

Plant secondary metabolites possess a wide range of pharmacological activities and play crucial biological roles. They serve as both a defense response during pathogen attack and a valuable drug resource. The role of microorganisms in the regulation of plant secondary metabolism has been widely recognized. The addition of specific microorganisms can increase the synthesis of secondary metabolites, and their beneficial effects depend on environmental factors and plant-related microorganisms. This article summarizes the impact and regulatory mechanisms of different microorganisms on the main secondary metabolic products of plants. We emphasize the mechanisms by which microorganisms regulate hormone levels, nutrient absorption, the supply of precursor substances, and enzyme and gene expression to promote the accumulation of plant secondary metabolites. In addition, the possible negative feedback regulation of microorganisms is discussed. The identification of additional unknown microbes and other driving factors affecting plant secondary metabolism is essential. The prospects for further analysis of medicinal plant genomes and the establishment of a genetic operation system for plant secondary metabolism research are proposed. This study provides new ideas for the use of microbial resources for biological synthesis research and the improvement of crop anti-inverse traits for the use of microbial resources.

Drought-Adapted Mediterranean Diet Plants: A Source of Bioactive Molecules Able to Give Nutrigenomic Effects per sè or to Obtain Functional Foods

The Mediterranean diet features plant-based foods renowned for their health benefits derived from bioactive compounds. This review aims to provide an overview of the bioactive molecules present in some representative Mediterranean diet plants, examining their human nutrigenomic effects and health benefits as well as the environmental advantages and sustainability derived from their cultivation. Additionally, it explores the facilitation of producing fortified foods aided by soil and plant microbiota properties. Well-studied examples, such as extra virgin olive oil and citrus fruits, have demonstrated significant health advantages, including anti-cancer, anti-inflammatory, and neuroprotective effects. Other less renowned plants are presented in the scientific literature with their beneficial traits on human health highlighted. Prickly pear's indicaxanthin exhibits antioxidant properties and potential anticancer traits, while capers kaempferol and quercetin support cardiovascular health and prevent cancer. Oregano and thyme, containing terpenoids like carvacrol and γ-terpinene, exhibit antimicrobial effects. Besides their nutrigenomic effects, these plants thrive in arid environments, offering benefits associated with their cultivation. Their microbiota, particularly Plant Growth Promoting (PGP) microorganisms, enhance plant growth and stress tolerance, offering biotechnological opportunities for sustainable agriculture. In conclusion, leveraging plant microbiota could revolutionize agricultural practices and increase sustainability as climate change threatens biodiversity. These edible plant species may have crucial importance, not only as healthy products but also for increasing the sustainability of agricultural systems.

Plants and endophytes interaction: a "secret wedlock" for sustainable biosynthesis of pharmaceutically important secondary metabolites

Many plants possess immense pharmacological properties because of the presence of various therapeutic bioactive secondary metabolites that are of great importance in many pharmaceutical industries. Therefore, to strike a balance between meeting industry demands and conserving natural habitats, medicinal plants are being cultivated on a large scale. However, to enhance the yield and simultaneously manage the various pest infestations, agrochemicals are being routinely used that have a detrimental impact on the whole ecosystem, ranging from biodiversity loss to water pollution, soil degradation, nutrient imbalance and enormous health hazards to both consumers and agricultural workers. To address the challenges, biological eco-friendly alternatives are being looked upon with high hopes where endophytes pitch in as key players due to their tight association with the host plants. The intricate interplay between plants and endophytic microorganisms has emerged as a captivating subject of scientific investigation, with profound implications for the sustainable biosynthesis of pharmaceutically important secondary metabolites. This review delves into the hidden world of the "secret wedlock" between plants and endophytes, elucidating their multifaceted interactions that underpin the synthesis of bioactive compounds with medicinal significance in their plant hosts. Here, we briefly review endophytic diversity association with medicinal plants and highlight the potential role of core endomicrobiome. We also propose that successful implementation of in situ microbiome manipulation through high-end techniques can pave the way towards a more sustainable and pharmaceutically enriched future.

Genomic, Molecular, and Phenotypic Characterization of Arthrobacter sp. OVS8, an Endophytic Bacterium Isolated from and Contributing to the Bioactive Compound Content of the Essential Oil of the Medicinal Plant Origanum vulgare L

Medicinal plants play an important role in the discovery of new bioactive compounds with antimicrobial activity, thanks to their pharmacological properties. However, members of their microbiota can also synthesize bioactive molecules. Among these, strains belonging to the genera Arthrobacter are commonly found associated with the plant's microenvironments, showing plant growth-promoting (PGP) activity and bioremediation properties. However, their role as antimicrobial secondary metabolite producers has not been fully explored. The aim of this work was to characterize the Arthrobacter sp. OVS8 endophytic strain, isolated from the medicinal plant Origanum vulgare L., from molecular and phenotypic viewpoints to evaluate its adaptation and influence on the plant internal microenvironments and its potential as a producer of antibacterial volatile molecules (VOCs). Results obtained from the phenotypic and genomic characterization highlight its ability to produce volatile antimicrobials effective against multidrug-resistant (MDR) human pathogens and its putative PGP role as a producer of siderophores and degrader of organic and inorganic pollutants. The outcomes presented in this work identify Arthrobacter sp. OVS8 as an excellent starting point toward the exploitation of bacterial endophytes as antibiotics sources.

Endophytic Bacteria Associated with Origanum heracleoticum L. (Lamiaceae) Seeds

Seed-associated microbiota are believed to play a crucial role in seed germination, seedling establishment, and plant growth and fitness stimulation, due to the vertical transmission of a core microbiota from seeds to the next generations. It might be hypothesized that medicinal and aromatic plants could use the seeds as vectors to vertically transfer beneficial endophytes, providing plants with metabolic pathways that could influence phytochemicals production. Here, we investigated the localization, the structure and the composition of the bacterial endophytic population that resides in Origanum heracleoticum L. seeds. Endocellular bacteria, surrounded by a wall, were localized close to the aleurone layer when using light and transmission electron microscopy. From surface-sterilized seeds, cultivable endophytes were isolated and characterized through RAPD analysis and 16S RNA gene sequencing, which revealed the existence of a high degree of biodiversity at the strain level and the predominance of the genus Pseudomonas. Most of the isolates grew in the presence of six selected antibiotics and were able to inhibit the growth of clinical and environmental strains that belong to the Burkholderia cepacia complex. The endophytes production of antimicrobial compounds could suggest their involvement in plant secondary metabolites production and might pave the way to endophytes exploitation in the pharmaceutical field.

Perspectives and potential applications of endophytic microorganisms in cultivation of medicinal and aromatic plants

Ensuring food and nutritional security, it is crucial to use chemicals in agriculture to boost yields and protect the crops against biotic and abiotic perturbations. Conversely, excessive use of chemicals has led to many deleterious effects on the environment like pollution of soil, water, and air; loss of soil fertility; and development of pest resistance, and is now posing serious threats to biodiversity. Therefore, farming systems need to be upgraded towards the use of biological agents to retain agricultural and environmental sustainability. Plants exhibit a huge and varied niche for endophytic microorganisms inside the planta, resulting in a closer association between them. Endophytic microorganisms play pivotal roles in plant physiological and morphological characteristics, including growth promotion, survival, and fitness. Their mechanism of action includes both direct and indirect, such as mineral phosphate solubilization, fixating nitrogen, synthesis of auxins, production of siderophore, and various phytohormones. Medicinal and aromatic plants (MAPs) hold a crucial position worldwide for their valued essential oils and several phytopharmaceutically important bioactive compounds since ancient times; conversely, owing to the high demand for natural products, commercial cultivation of MAPs is on the upswing. Furthermore, the vulnerability to various pests and diseases enforces noteworthy production restraints that affect both crop yield and quality. Efforts have been made towards enhancing yields of plant crude drugs by improving crop varieties, cell cultures, transgenic plants, etc., but these are highly cost-demanding and time-consuming measures. Thus, it is essential to evolve efficient, eco-friendly, cost-effective simpler approaches for improvement in the yield and health of the plants. Harnessing endophytic microorganisms as biostimulants can be an effective and alternative step. This review summarizes the concept of endophytes, their multidimensional interaction inside the host plant, and the salient benefits associated with endophytic microorganisms in MAPs.

Comparative analysis of the structure and function of rhizosphere microbiome of the Chinese medicinal herb Alisma in different regions

Rhizoma Alismatis, a commonly used traditional Chinese medicine, is the dried tuber of Alisma orientale and Alisma A. plantago-aquatica, mainly cultivated in Fujian and Sichuan provinces (China), respectively. Studies have shown that the rhizosphere microbiome is a key factor determining quality of Chinese medicinal plants. Here we applied metagenomics to investigate the rhizosphere microbiome of Alisma in Fujian and Sichuan, focusing on its structure and function and those genes involved in protostane triterpenes biosynthesis. The dominant phyla were Proteobacteria, Actinobacteria, Chloroflexi, Acidobacteria, and Gemmatimonadetes. Compared with Fujian, the rhizosphere of Sichuan has a greater α diversity and stronger microbial interactions but significantly lower relative abundance of archaea. Microbes with disease-suppressing functions were more abundant in Sichuan than Fujian, but vice versa for those with IAA-producing functions. Gemmatimonas, Anaeromyxobacter, and Pseudolabrys were the main contributors to the potential functional difference in two regions. Genes related to protostane triterpenes biosynthesis were enriched in Fujian. Steroidobacter, Pseudolabrys, Nevskia, and Nitrospira may contribute to the accumulation of protostane triterpenes in Alisma. This work fills a knowledge gap of Alisma's rhizosphere microbiome, providing a valuable reference for studying its beneficial microorganisms.

Prospecting potential of endophytes for modulation of biosynthesis of therapeutic bioactive secondary metabolites and plant growth promotion of medicinal and aromatic plants

Medicinal and aromatic plants possess pharmacological properties (antidiabetes, anticancer, antihypertension, anticardiovascular, antileprosy, etc.) because of their potential to synthesize a wide range of therapeutic bioactive secondary metabolites. The concentration of bioactive secondry metabolites depends on plant species, local environment, soil type and internal microbiome. The internal microbiome of medicinal plants plays the crucial role in the production of bioactive secondary metabolites, namely alkaloids, steroids, terpenoids, peptides, polyketones, flavonoids, quinols and phenols. In this review, the host specific secondry metabolites produced by endophytes, their therapeutic properties and host-endophytes interaction in relation to production of bioactive secondry metaboloites and the role of endophytes in enhancing the production of bioactive secondry metabolites is discussed. How biological nitrogen fixation, phosphorus solubilization, micronutrient uptake, phytohormone production, disease suppression, etc. can play a vital role in enhacing the plant growth and development.The role of endophytes in enhancing the plant growth and content of bioactive secondary metabolites in medicinal and aromatic plants in a sustainable mode is highlighted.

Evaluation of Vetiver Volatile Compound Production under Aeroponic-Grown Conditions for the Perfume Industry

Vetiver (Chrysopogon zizanioides (L.) Roberty) is a major tropical perfume crop. Access to its essential oil (EO)-filled roots is nevertheless cumbersome and land-damaging. This study, therefore, evaluated the potential of vetiver cultivation under soilless high-pressure aeroponics (HPA) for volatile organic compound (VOC) production. The VOC accumulation in the roots was investigated by transmission electron microscopy, and the composition of these VOCs was analyzed by gas chromatography coupled with mass spectrometry (GC/MS) after sampling by headspace solid-phase microextraction (HS-SPME). The HPA-grown plants were compared to plants that had been grown in potting soil and under axenic conditions. The HPA-grown plants were stunted, demonstrating less root biomass than the plants that had been grown in potting soil. The roots were slender, thinner, more tapered, and lacked the typical vetiver fragrance. HPA cultivation massively impaired the accumulation of the less-volatile hydrocarbon and oxygenated sesquiterpenes that normally form most of the VOCs. The axenic, tissue-cultured plants followed a similar and more exacerbated trend. Ultrastructural analyses revealed that the HPA conditions altered root ontogeny, whereby the roots contained fewer EO-accumulating cells and hosted fewer and more immature intracellular EO droplets. These preliminary results allowed to conclude that HPA-cultivated vetiver suffers from altered development and root ontology disorders that prevent EO accumulation.

Chrysopogon zizanioides-a review on its pharmacognosy, chemical composition and pharmacological activities

Vetiver is a traditional plant with versatile applications in medicine, aroma, commerce, environmental-protection, and agriculture. This review was designed to compile all the latest information on phytochemistry, pharmacology, and traditional uses of C. zizanioides. All the information related to this plant was gathered from several authentic sites, using keywords like Chrysopogon zizanioides, Vetiveria zizanioides, Khus, and Khas-Khas. The included resources were journaled articles, book chapters, books, Ayurvedic Pharmacopoeias, and Ayurvedic Formulary of India, from science direct, PubMed, research gate etc. All the necessary, relevant, authentic, and updated information were tried to inculcate in the manuscript. The literature was collected via online sites like Pub med, Scopus, and Science direct as well. During compilation, it observed that many traditional utilities of vetiver got their authentication when tested using different disease-based pharmacological models taking various extracts of roots, leaves, and root oil as test samples. However, systematic studies for isolation of active constituents and establishing their mechanism of action are still required to be validated. On the other hand, the development of novel and robust techniques needed for oil extraction can further enhance the exploration of biological utilities faster. Moreover, the cultivators and harvesters must address carefully to prevent the linked drawback of soil erosion.

Review of Antimicrobial and Other Health Effects in 5 Essential Oil Producing Grass Species

The warm season essential oil producing grass species including lemongrass (Cymbopogon citratus), palmarosa grass (C. martini), geranium grass (C. schoenanthus), vetiver grass (Chrysopogon zizanioides), and scented top grass (Capillipedium parviflorum) are used worldwide for their cosmetic and health properties. A discussion providing evidence from literature reviews about the potential uses of these grass species for antimicrobial and other health uses are presented. These species could be used as new therapies for treating microbial infections. The purpose of this study is to discuss in detail, evidence from literature reviews supporting potential health uses and to provide some discussion regarding some agronomic traits for these essential oil producing species.

Back to the Roots-An Overview of the Chemical Composition and Bioactivity of Selected Root-Essential Oils

Since ancient times, plant roots have been widely used in traditional medicine for treating various ailments and diseases due to their beneficial effects. A large number of studies have demonstrated that-besides their aromatic properties-their biological activity can often be attributed to volatile constituents. This review provides a comprehensive overview of investigations into the chemical composition of essential oils and volatile components obtained from selected aromatic roots, including Angelica archangelica, Armoracia rusticana, Carlina sp., Chrysopogon zizanioides, Coleus forskohlii, Inula helenium, Sassafras albidum, Saussurea costus, and Valeriana officinalis. Additionally, their most important associated biological impacts are reported, such as anticarcinogenic, antimicrobial, antioxidant, pesticidal, and other miscellaneous properties. Various literature and electronic databases-including PubMed, ScienceDirect, Springer, Scopus, Google Scholar, and Wiley-were screened and data was obtained accordingly. The results indicate the promising properties of root-essential oils and their potential as a source for natural biologically active products for flavor, pharmaceutical, agricultural, and fragrance industries. However, more research is required to further establish the mechanism of action mediating these bioactivities as well as essential oil standardization because the chemical composition often strongly varies depending on external factors.

Composition and functional comparison of vetiver root endophytic microbiota originating from different geographic locations that show antagonistic activity towards Fusarium graminearum

Given the current trend towards reducing the use of chemical controls in agriculture, microbial resources such as plant endophytes are being intensively investigated for traits that are conducive to plant protection. Among the various important target pathogens, Fusarium graminearum is a fungal pathogen of cereal crops that is responsible for severe yield losses and mycotoxin contamination in grains. In the present study, we investigated the bacterial endophytic communities from vetiver (Chrysopogon zizanioides (L.) Roberty) roots originating from 5 different geographic locations across Europe and Africa. This study relies on a global 16S metabarcoding approach and the isolation/functional characterization of bacterial isolates. The results we obtained showed that geographical location is a factor that influences the composition and relative abundance of root endophyte communities in vetiver. Three hundred eighty-one bacterial endophytes were isolated and assessed for their in vitro antagonistic activities towards F. graminearum mycelium growth. In total, 46 % of the isolates showed at least 50 % inhibitory activity against F. graminearum. The taxonomic identification of the bioactive isolates revealed that the composition of these functional culturable endophytic communities was influenced by the geographic origins of the roots. The selected communities consisted of 15 genera. Some endophytes in Bacillus, Janthinobacterium, Kosakonia, Microbacterium, Pseudomonas, and Serratia showed strong growth inhibition activity (≥70 %) against F. graminearum and could be candidates for further development as biocontrol agents.

In Silico Identification of miRNA and Targets from Chrysopogon zizanioides (L.) Roberty with Functional Validation from Leaf and Root Tissues

microRNAs are small non-coding RNA molecule that plays an important role in metabolism. Chrysopogon zizanioides (L.) Roberty is an important aromatic plant used in perfumery industries, soil, water conservation, and agricultural practices. In this study, the transcriptomic sequence of vetiver leaf and root was subjected to miRNA identification by the computational methods. miRNA identification was carried out using a homology-based method by C-mii software with several other online tools. A total of 80 miRNA were identified from both leaf and root sequences. Target identification was done by identified miRNA sets. A total of 25 and 31 miRNA families were identified in both leaf and root, respectively, with ten common families involve in different ontological function. miR169 and miR5021 regulate most of the target in leaf and root. In vetiver, many primary and secondary metabolism elements are regulated by miRNA as photo-system, transcription factor, terpenoid metabolism, etc. Here is the first in silico study revealing the specific miRNAs and their target genes for corresponding root and leaf tissues respectively in C. zizanioides.

Plant Secondary Compounds in Soil and Their Role in Belowground Species Interactions

Knowledge of the effect of plant secondary compounds (PSCs) on belowground interactions in the more diffuse community of species living outside the rhizosphere is sparse compared with what we know about how PSCs affect aboveground interactions. We illustrate here that PSCs from foliar tissue, root exudates, and leaf litter effectively influence such belowground plant-plant, plant-microorganism, and plant-soil invertebrate interactions. Climatic factors can induce PSC production and select for different plant chemical types. Therefore, climate change can alter both quantitative and qualitative PSC production, and how these compounds move in the soil. This can change the soil chemical environment, with cascading effects on both the ecology and evolution of belowground species interactions and, ultimately, soil functioning.

The Effect of Auxin and Auxin-Producing Bacteria on the Growth, Essential Oil Yield, and Composition in Medicinal and Aromatic Plants

Aromatic plants had been used since ancient times for their preservative and medicinal properties, and to impart aroma and flavor to food. Also their secondary metabolites are economically important as drugs, flavor and fragrances, pharmaceuticals, agrochemicals, dye, and pigments, pesticides, cosmetics, food additives, other industrially biochemical, and also play a major role in the adaptation of plants to their environment. Indole acetıc acid-producing rhizobacteria inoculations increase in stomatal density and level of secondary metabolite and have a synergistic effect on monoterpene biosynthesis. Bacterial inoculation significantly affected and increased the chemical composition of essential oil, citronellol, and geraniol content in rose-scented geranium; essential oil composition and total phenolic content in marigold; density, number, and size of glandular trichomes in sweet wormwood and peppermint essential oil components such as geranyl acetate, limonene, and β-pinene in coriander; oil yield and content in calendula; yield of the herb in hyssop; oxygenated compounds, essential oil content and yield, anethol and changing the chemical composition in fennel; growth, number of glandular trichomes and essential oil yield, root branching and length, and total amount of essential oil, production of monoterpenes such as pulegone, menthol, menthone, menthofuran, and terpineol content, biosynthesis of secondary metabolites in peppermint; growth and essential oil yield in marjoram; glandular hair abundance, essential oil yield, and monoterpene biosynthesis in basil; phellandrene, limonene, borneol, and campor in rosemary; carvacrol, thymol, linalool, and borneol in oregano; and α-thujene, α-pinene, α-terpinene, p-simen, β-pinene, and γ-terpinene contents and essential oil yield in summer savory. Inoculation with IAA-producing bacteria medicinal roots increased the valerenic acid in valerian, essential oil and quality in vetiver, curcumin content in turmeric alkaloid and ginsenoside content in ginseng, and inulin content in Jerusalem artichoke.

Metabolite profiling reveals a complex response of plants to application of plant growth-promoting endophytic bacteria

Endophytic bacteria have been explored for their role in plant growth promotion, however, not much has been explored in cucumber. The metabolomic response of plants to application of such microbes also remains largely unknown. Thus, we investigated the application of endophytic bacteria to cucumber to infer their role in plant growth promotion and document metabolome response. The lowest healthy leaf-stalks were sampled from four differently sourced cucumber plants, and endophytic bacteria were isolated after surface disinfection. Initial plant growth-promoting (PGP) screening was performed to identify PGP strains out of numerous isolates, and five strains (Strains 4=Curtobacterium spp., 72=Brevibacillus spp., 167=Paenibacillus spp., 193=Bacillus spp., and 227=Microbacterium spp.) were selected based on their contribution to root growth compared with the control. The selected strains were further evaluated in pot experiments, axenic PGP trait assays, and metabolomic analysis. Results revealed that the selected isolates possessed different qualitative characteristics among indole acetic acid, siderophore production, phosphate solubilization, and 1-aminocyclopropane-1-carboxylate (ACC)-deaminase and nifH genes, and all isolates significantly enhanced plant growth in both pot experiments compared with the uninoculated control and fertilizer control. Metabolomic profiling revealed that both strains affected the plant metabolomes compared with the uninoculated control. Around 50 % of the metabolites explored had higher concentrations in either or both bacteria-applied plants compared with the uninoculated control. Differences were observed in both strains' regulation of metabolites, although both enhanced root growth near equally. Overall, endophytic bacteria significantly enhanced plant growth and tended to produce or induce release of certain metabolites within the plant endosphere.

Endophytes enhance the production of root alkaloids ajmalicine and serpentine by modulating the terpenoid indole alkaloid pathway in Catharanthus roseus roots

AIM

The aim of this study was to identify and characterize promising endophytes capable of enhancing the content of root alkaloids ajmalicine and serpentine in low alkaloid yielding genotype of Catharanthus roseus cultivar Prabal and the possible mechanisms involved.

METHOD AND RESULT

Of the four strains isolated from alkaloid-rich genotype of C. roseus cultivar Dhawal, endophytic strains CATDLF5 (Curvularia sp.) and CATDLF6 (Choanephora infundibulifera) enhanced serpentine content by 211·7-337·6%, while CATDRF2 (Aspergillus japonicus) and CATDS5 (Pseudomonas sp.) increased the content of ajmalicine by 123·4-203·8% in cultivar Prabal. Upregulated expression of key genes, geraniol 10-hydroxylase, tryptophan decarboxylase and strictosidine synthase involved in terpenoid indole alkaloid (TIA) biosynthetic pathway was observed in endophyte inoculated plants. Upregulated Octadecanoid-derivative Responsive Catharanthus AP2/ERF domain transcription activators like ORCA3 while, and downregulation of transcriptional repressor, ZCTs (Cys2/His2-type zinc finger protein family) enhanced the expression of genes for secondary metabolite production in endophyte-inoculated plants.

CONCLUSION

The present work concluded that the selected endophytes of C. roseus can enhance the ajmalicine and serpentine contents by modulating the expression of structural and regulatory genes of TIA biosynthetic pathway in root.

SIGNIFICANCE AND IMPACT OF THE STUDY

Endophytes can play an important role to enhance in planta content of pharmaceutically important alkaloids in C. roseus and can therefore be useful in reducing the cost of production of important alkaloids.

Bacterial Semiochemicals and Transkingdom Interactions with Insects and Plants

A peculiar feature of all living beings is their capability to communicate. With the discovery of the quorum sensing phenomenon in bioluminescent bacteria in the late 1960s, it became clear that intraspecies and interspecies communications and social behaviors also occur in simple microorganisms such as bacteria. However, at that time, it was difficult to imagine how such small organisms-invisible to the naked eye-could influence the behavior and wellbeing of the larger, more complex and visible organisms they colonize. Now that we know this information, the challenge is to identify the myriad of bacterial chemical signals and communication networks that regulate the life of what can be defined, in a whole, as a meta-organism. In this review, we described the transkingdom crosstalk between bacteria, insects, and plants from an ecological perspective, providing some paradigmatic examples. Second, we reviewed what is known about the genetic and biochemical bases of the bacterial chemical communication with other organisms and how explore the semiochemical potential of a bacterium can be explored. Finally, we illustrated how bacterial semiochemicals managing the transkingdom communication may be exploited from a biotechnological point of view.

Phytobiome metabolism: beneficial soil microbes steer crop plants' secondary metabolism

Crops are negatively affected by abiotic and biotic stresses, however, plant-microbe cooperation allows prompt buffering of these environmental changes. Microorganisms exhibit an extensive metabolic capability to assist plants in reducing these burdens. Interestingly, beneficial microbes may also trigger, at the host side, a sequence of events from signal perception to metabolic responses leading to stress tolerance or protection against biotic threats. Although plants are well known for their vast chemical diversity, plant-microbial interactions often stimulate the production of a rich and different repertoire of metabolites in plants. The targeted microbial-plant interactions reprogramming plant metabolism represent potential means to foster various pest managements. However, the molecular mechanisms of microbial modulation of plant metabolic plasticity are still poorly understood. Here, we review an increasing amount of reports providing evidence for alterations to plant metabolism caused by beneficial microbial colonization. In addition, we highlight the vital importance of these metabolic reprograms for plants under stress erratic conditions. © 2019 Society of Chemical Industry.

Endophytic Consortium With Diverse Gene-Regulating Capabilities of Benzylisoquinoline Alkaloids Biosynthetic Pathway Can Enhance Endogenous Morphine Biosynthesis in Papaver somniferum

Secondary metabolite biosynthesis in medicinal plants is multi-step cascade known to be modulated by associated endophytes. While a single endophyte is not able to upregulate all biosynthetic steps, limiting maximum yield achievement. Therefore to compliment the deficient characteristics in an endophyte we tried consortium of endophytes to achieve maximum yield. Here, efforts were made to maximize the in planta morphine yield, using consortium of two endophytes; SM1B (Acinetobacter sp.) upregulating most of the genes of morphine biosynthesis except T6ODM and CODM, and SM3B (Marmoricola sp.) upregulating T6ODM and CODM in alkaloid-less Papaver somniferum cv. Sujata. Consortium-inoculation significantly increased morphine and thebaine content, and also increased the photosynthetic efficiency of poppy plants resulted in increased biomass, capsule weight, and seed yields compared to single-inoculation. The increment in morphine content was due to the modulation of metabolic-flow of key intermediates including reticuline and thebaine, via upregulating pertinent biosynthetic genes and enhanced expression of COR, key gene for morphine biosynthesis. This is the first report demonstrating the endophytic-consortium complimenting the functional deficiency of one endophyte by another for upregulating multiple genes of a metabolic pathway similar to transgenics (overexpressing multiple genes) for obtaining enhanced yield of pharmaceutically important metabolites.

Biosynthesis and Emission of Stress-Induced Volatile Terpenes in Roots and Leaves of Switchgrass (Panicum virgatum L.)

Switchgrass (Panicum virgatum L.), a perennial C4 grass, represents an important species in natural and anthropogenic grasslands of North America. Its resilience to abiotic and biotic stress has made switchgrass a preferred bioenergy crop. However, little is known about the mechanisms of resistance of switchgrass against pathogens and herbivores. Volatile compounds such as terpenes have important activities in plant direct and indirect defense. Here, we show that switchgrass leaves emit blends of monoterpenes and sesquiterpenes upon feeding by the generalist insect herbivore Spodoptera frugiperda (fall armyworm) and in a systemic response to the treatment of roots with defense hormones. Belowground application of methyl jasmonate also induced the release of volatile terpenes from roots. To correlate the emission of terpenes with the expression and activity of their corresponding biosynthetic genes, we identified a gene family of 44 monoterpene and sesquiterpene synthases (mono- and sesqui-TPSs) of the type-a, type-b, type-g, and type-e subfamilies, of which 32 TPSs were found to be functionally active in vitro. The TPS genes are distributed over the K and N subgenomes with clusters occurring on several chromosomes. Synteny analysis revealed syntenic networks for approximately 30-40% of the switchgrass TPS genes in the genomes of Panicum hallii, Setaria italica, and Sorghum bicolor, suggesting shared TPS ancestry in the common progenitor of these grass lineages. Eighteen switchgrass TPS genes were substantially induced upon insect and hormone treatment and the enzymatic products of nine of these genes correlated with compounds of the induced volatile blends. In accordance with the emission of volatiles, TPS gene expression was induced systemically in response to belowground treatment, whereas this response was not observed upon aboveground feeding of S. frugiperda. Our results demonstrate complex above and belowground responses of induced volatile terpene metabolism in switchgrass and provide a framework for more detailed investigations of the function of terpenes in stress resistance in this monocot crop.

Terpene Synthase Genes in Quercus robur - Gene Characterization, Expression and Resulting Terpenes Due to Cockchafer Feeding

Root herbivory caused by larvae of the forest cockchafer (Melolontha hippocastani) enhances the impact of drought on trees, particularly in oak forest rejuvenations. In Germany, geographically distant oak stands show differences in infestation strength by the forest cockchafer. While in Southwestern Germany this insect causes severe damage, oak forests in northern Germany are rarely infested. It is known that root-released volatile organic compounds (VOCs) are perceived by soil herbivores, thus guiding the larvae toward the host roots. In this work, we exposed seedlings of two distant oak provenances to forest cockchafer larvae and studied their population genetic properties, their root-based VOC chemotypes, their attraction for larvae and terpene synthase gene expression. Based on nuclear and chloroplast marker analysis, we found both oak populations to be genetically highly variable while showing typical patterns of migration from different refugial regions. However, no clear association between genetic constitution of the different provenances and the abundance of cockchafer populations on site was observed. In contrast to observations in the field, bioassays revealed a preference of the larvae for the northeastern oak provenance. The behavior of larvae was most likely related to root-released volatile terpenes and benzenoids since their composition and quantity differed between oak populations. We assume repellent effects of these compounds because the populations attractive to insects showed low abundance of these compounds. Five different oak terpene synthase (TPS) genes were identified at the genomic level which can be responsible for biosynthesis of the released terpenes. TPS gene expression patterns in response to larval feeding revealed geographic variation rather than genotypic variation. Our results support the assumption that root-released VOC are influencing the perception of roots by herbivores.

Fungi Indirectly Affect Plant Root Architecture by Modulating Soil Volatile Organic Compounds

The plant-growth modulating effect of microbial volatile organic compounds (VOCs) has been demonstrated repeatedly. This has most often been performed by exposing plants to VOC released by microbes grown on nutrient rich media. Here, we used soil instead to grow fungi of the Fusarium genus and investigate how VOCs emitted by this system influenced the development of Arabidopsis plants. The volatile profiles of Fusarium strains grown in soil and malt extract were also compared. Our results demonstrate that distinct volatile signatures can be attributed to different Fusarium genetic clades but also highlight a major influence of the growth medium on volatile emission. Furthermore, all soil-grown Fusarium isolates increased primary root length in Arabidopsis by decreasing VOC concentrations in soil. This result represents a major paradigm shift in plant-microbe interactions since growth modulating effects have been attributed so far to the emission and not the consumption of volatile signals.

Dynamic and Assembly of Epiphyte and Endophyte Lactic Acid Bacteria During the Life Cycle of Origanum vulgare L

Origanum vulgare L. (oregano) was chosen as suitable model to investigate the ability of the endophyte-microbiome, especially that of lactic acid bacteria, to develop specific interactions with the plant, mediated by the essential oils (EOs). Combined culture-dependent and -independent approaches analyzed the bacterial dynamic and assembly of Origanum vulgare L. throughout the life cycle. Epiphyte bacteria were more abundant than the endophyte ones. The number of presumptive lactic acid bacteria increased throughout oregano life cycle, according to the plant organ. Diverse species of lactic acid bacteria populated the plant, but Lactobacillus plantarum stably dominated both epiphyte and endophyte populations. High-throughput DNA sequencing showed highest epiphyte bacterial diversity at early vegetative and full-flowering stages, with blooming signing the main microbial differentiation among plant organs. Proteobacteria, Actinobacteria and Bacteroidetes, and Firmicutes and Cyanobacteria at lower abundance were the main phyla. Various genera were detectable, but oregano harbored mainly Methylobacterium, Sphingomonas, Rhizobium and Aurantimonas throughout phenological stages. Firmicutes epiphyte and endophyte microbiotas were different, with a core microbiota consisting of Bacillus, Exiguobacterium, Streptococcus, Staphylococcus and Lactobacillus genera. Bacillus dominated throughout phenological stages. High-throughput DNA sequencing confirmed the dominance of L. plantarum within the epiphyte and endophyte populations of lactic acid bacteria. Yields of EOs varied among plant organs and throughout plant life cycle. L. plantarum strains were the most resistant to the total EOs (mainly thymol and carvacrol) as extracted from the plant. The positive correlation among endophyte lactic acid bacteria and the EOs content seems confirm the hypothesis that the colonization within plant niches may be regulated by mechanisms linked to the synthesis of the secondary metabolites.

VOCs-mediated hormonal signaling and crosstalk with plant growth promoting microbes

In the natural environment, plants communicate with various microorganisms (pathogenic or beneficial) and exhibit differential responses. In recent years, research on microbial volatile compounds (MVCs) has revealed them to be simple, effective and efficient groups of compounds that modulate plant growth and developmental processes. They also interfere with the signaling process. Different MVCs have been shown to promote plant growth via improved photosynthesis rates, increased plant resistance to pathogens, activated phytohormone signaling pathways, or, in some cases, inhibit plant growth, leading to death. Regardless of these exhibited roles, the molecules responsible, the underlying mechanisms, and induced specific metabolic/molecular changes are not fully understood. Here, we review current knowledge on the effects of MVCs on plants, with particular emphasis on their modulation of the salicylic acid, jasmonic acid/ethylene, and auxin signaling pathways. Additionally, opportunities for further research and potential practical applications presented.

Endophytes of Withania somnifera modulate in planta content and the site of withanolide biosynthesis

Tissue specific biosynthesis of secondary metabolites is a distinguished feature of medicinal plants. Withania somnifera, source of pharmaceutically important withanolides biosynthesizes withaferin-A in leaves and withanolide-A in roots. To increase the in planta withanolides production, a sustainable approach needs to be explored. Here, we isolated endophytes from different parts of W. somnifera plants and their promising role in in planta withanolide biosynthesis was established in both in-vivo grown as well in in-vitro raised composite W. somnifera plants. Overall, the fungal endophytes improved photosynthesis, plant growth and biomass, and the root-associated bacterial endophytes enhanced the withanolide content in both in-vivo and in-vitro grown plants by modulating the expression of withanolide biosynthesis genes in leaves and roots. Surprisingly, a few indole-3-acetic acid (IAA)-producing and nitrogen-fixing root-associated endophytes could induce the biosynthesis of withaferin-A in roots by inducing in planta IAA-production and upregulating the expression of withanolide biosynthesis genes especially MEP-pathway genes (DXS and DXR) in roots as well. Results indicate the role of endophytes in modulating the synthesis and site of withanolides production and the selected endophytes can be used for enhancing the in planta withanolide production and enriching roots with pharmaceutically important withaferin-A which is generally absent in roots.

Bacteria colonising Penstemon digitalis show volatile and tissue-specific responses to a natural concentration range of the floral volatile linalool

Bacteria on floral tissue can have negative effects by consuming resources and affecting nectar quality, which subsequently could reduce pollinator visitation and plant fitness. Plants however can employ chemical defences to reduce bacteria density. In North American, bee-pollinated Penstemon digitalis, the nectar volatile S-(+)-linalool can influence plant fitness, and terpenes such as linalool are known for their antimicrobial properties suggesting that it may also play a role in plant–microbe interactions. Therefore, we hypothesized linalool could affect bacterial growth on P. digitalis plants/flowers. Because P. digitalis emits linalool from nectar and nectary tissue but not petals, we hypothesised that the effects of linalool could depend on tissue of origin due to varying exposure. We isolated bacteria from nectary tissue, petals and leaves, and compared their growth relative to control using two volatile concentrations representing the natural emission range of linalool. To assess whether effects were specific to linalool, we compared results with the co-occurring nectar volatile, methyl nicotinate. We show that response to floral volatiles can be substance and tissue-origin specific. Because linalool could slow growth rate of bacteria across the P. digitalis phyllosphere, floral emission of linalool could play a role in mediating plant–bacteria interactions in this system.

Core Microbiome of Medicinal Plant Salvia miltiorrhiza Seed: A Rich Reservoir of Beneficial Microbes for Secondary Metabolism?

Seed microbiome includes special endophytic or epiphytic microbial taxa associated with seeds, which affects seed germination, plant growth, and health. Here, we analyzed the core microbiome of 21 Salvia miltiorrhiza seeds from seven different geographic origins using 16S rDNA and ITS amplicon sequencing, followed by bioinformatics analysis. The whole bacterial microbiome was classified into 17 microbial phyla and 39 classes. Gammaproteobacteria (67.6%), Alphaproteobacteria (15.6%), Betaproteobacteria (2.6%), Sphingobacteria (5.0%), Bacilli (4.6%), and Actinobacteria (2.9%) belonged to the core bacterial microbiome. Dothideomycetes comprised 94% of core fungal microbiome in S. miltiorrhiza seeds, and another two dominant classes were Leotiomycetes (3.0%) and Tremellomycetes (2.0%). We found that terpenoid backbone biosynthesis, degradation of limonene, pinene, and geraniol, and prenyltransferases, were overrepresented in the core bacterial microbiome using phylogenetic examination of communities by reconstruction of unobserved states (PICRUSt) software. We also found that the bacterial genera Pantoea, Pseudomonas, and Sphingomonas were enriched core taxa and overlapped among S. miltiorrhiza, maize, bean, and rice, while a fungal genus, Alternaria, was shared within S. miltiorrhiza, bean, and Brassicaceae families. These findings highlight that seed-associated microbiomeis an important component of plant microbiomes, which may be a gene reservoir for secondary metabolism in medicinal plants.

A review on moringa tree and vetiver grass - Potential biorefinery feedstocks

Plants and derivatives have been explored for unlimited purposes by mankind, from crop cultivation for providing food and animal feed, to the use for cosmetics, therapeutics and energy. Moringa tree and vetiver grass features, capabilities and applications were explored through a literature review. The suitability of these plants for the bioenergy industry products is evidenced, namely for bioethanol, biogas and biodiesel, given the lignocellulosic biomass content of these plants and characteristics of moringa seed oil. In addition, moringa leaves and pods are an important source for food and animal feed industries due to their high nutrient value. Thus, the co-cultivation of moringa and vetiver could provide energy and food security, and contribute to more sustainable agricultural practices and for the development of rural areas. Policymakers, institutions and scientific community must engage to promote the cultivation of multipurpose crops to cope with energy and food industries competition for biomass.

Modulation of plant chemistry by beneficial root microbiota

Beneficial root microbiota modulate plant chemistry and represent an untapped potential to discover new pathways involved in the biosynthesis of high value natural plant products.

Microbial Volatiles: Small Molecules with an Important Role in Intra- and Inter-Kingdom Interactions

During the last decades, research on the function of volatile organic compounds focused primarily on the interactions between plants and insects. However, microorganisms can also release a plethora of volatiles and it appears that microbial volatile organic compounds (mVOCs) can play an important role in intra- and inter-kingdom interactions. So far, most studies are focused on aboveground volatile-mediated interactions and much less information is available about the function of volatiles belowground. This minireview summarizes the current knowledge on the biological functions of mVOCs with the focus on mVOCs-mediated interactions belowground. We pinpointed mVOCs involved in microbe-microbe and microbe–plant interactions, and highlighted the ecological importance of microbial terpenes as a largely underexplored group of mVOCs. We indicated challenges in studying belowground mVOCs-mediated interactions and opportunities for further studies and practical applications.

Epiphytic Bacteria Alter Floral Scent Emissions

Floral scents are key mediators of biotic interactions between flowers and various organisms such as pollinators, antagonistic animals and bacteria. It has been shown that emissions of floral volatiles are influenced by interactions with other organisms at the levels of roots, leaves and flowers. However, it is largely unknown whether and how epiphytic bacteria associated with flowers affect the composition of floral scent. By comparing volatiles of sterile and inoculated plants we found that bacteria may add components, induce or reduce the emission of compounds, and potentially catabolize others. These mechanisms collectively altered the floral scent emission and led to clearly different compositions. Our results confirm that bacteria have the potential to interfere with flower-animal interactions with consequences for pollination and plant reproduction.

Small molecules below-ground: the role of specialized metabolites in the rhizosphere

Soil communities are diverse taxonomically and functionally. This ecosystem experiences highly complex networks of interactions, but may also present functionally independent entities. Plant roots, a metabolically active hotspot in the soil, take an essential part in below-ground interactions. While plants are known to release an extremely high portion of the fixated carbon to the soil, less information is known about the composition and role of C-containing compounds in the rhizosphere, in particular those involved in chemical communication. Specialized metabolites (or secondary metabolites) produced by plants and their associated microbes have a critical role in various biological activities that modulate the behavior of neighboring organisms. Thus, elucidating the chemical composition and function of specialized metabolites in the rhizosphere is a key element in understanding interactions in this below-ground environment. Here, we review key classes of specialized metabolites that occur as mostly non-volatile compounds in root exudates or are emitted as volatile organic compounds (VOCs). The role of these metabolites in below-ground interactions and response to nutrient deficiency, as well as their tissue and cell type-specific biosynthesis and release are discussed in detail.

Cultivable gut bacteria provide a pathway for adaptation of Chrysolina herbacea to Mentha aquatica volatiles

BACKGROUND

A chemical cross-talk between plants and insects is required in order to achieve a successful co-adaptation. In response to herbivory, plants produce specific compounds, and feeding insects respond adequately7 to molecules produced by plants. Here we show the role of the gut microbial community of the mint beetle Chrysolina herbacea in the chemical cross-talk with Mentha aquatica (or watermint).

RESULTS

By using two-dimensional gas chromatography-mass spectrometry we first evaluated the chemical patterns of both M. aquatica leaf and frass volatiles extracted by C. herbacea males and females feeding on plants, and observed marked differences between males and females volatiles. The sex-specific chemical pattern of the frass paralleled with sex-specific distribution of cultivable gut bacteria. Indeed, all isolated gut bacteria from females belonged to either α- or γ-Proteobacteria, whilst those from males were γ-Proteobacteria or Firmicutes. We then demonstrated that five Serratia marcescens strains from females possessed antibacterial activity against bacteria from males belonging to Firmicutes suggesting competition by production of antimicrobial compounds. By in vitro experiments, we lastly showed that the microbial communities from the two sexes were associated to specific metabolic patterns with respect to their ability to biotransform M. aquatica terpenoids, and metabolize them into an array of compounds with possible pheromone activity.

CONCLUSIONS

Our data suggest that cultivable gut bacteria of Chrysolina herbacea males and females influence the volatile blend of herbivory induced Mentha aquatica volatiles in a sex-specific way.

Bidirectional Interaction between Phyllospheric Microbiotas and Plant Volatile Emissions

Due to their antimicrobial effects and their potential role as carbon sources, plant volatile organic compound (VOC) emissions play significant roles in determining the characteristics of the microbial communities that can establish on plant surfaces. Furthermore, epiphytic microorganisms, including bacteria and fungi, can affect plant VOC emissions in different ways: by producing and emitting their own VOCs, which are added to and mixed with the plant VOC blend; by affecting plant physiology and modifying the production and emission of VOCs; and by metabolizing the VOCs emitted by the plant. The study of the interactions between plant VOC emissions and phyllospheric microbiotas is thus of great interest and deserves more attention.

Fungal Volatiles Can Act as Carbon Sources and Semiochemicals to Mediate Interspecific Interactions Among Bark Beetle-Associated Fungal Symbionts

Mountain pine beetle (Dendroctonus ponderosae) has killed millions of hectares of pine forests in western North America. Beetle success is dependent upon a community of symbiotic fungi comprised of Grosmannia clavigera, Ophiostoma montium, and Leptographium longiclavatum. Factors regulating the dynamics of this community during pine infection are largely unknown. However, fungal volatile organic compounds (FVOCs) help shape fungal interactions in model and agricultural systems and thus may be important drivers of interactions among bark beetle-associated fungi. We investigated whether FVOCs can mediate interspecific interactions among mountain pine beetle's fungal symbionts by affecting fungal growth and reproduction. Headspace volatiles were collected and identified to determine species-specific volatile profiles. Interspecific effects of volatiles on fungal growth and conidia production were assessed by pairing physically-separated fungal cultures grown either on a carbon-poor or -rich substrate, inside a shared-headspace environment. Fungal VOC profiles differed by species and influenced the growth and/or conidia production of the other species. Further, our results showed that FVOCs can be used as carbon sources for fungi developing on carbon-poor substrates. This is the first report demonstrating that FVOCs can drive interactions among bark beetle fungal symbionts, and thus are important factors in beetle attack success.

Endophytes of opium poppy differentially modulate host plant productivity and genes for the biosynthetic pathway of benzylisoquinoline alkaloids

Endophytes reside in different parts of the poppy plant and perform the tissue-specific functions. Most leaf endophytes modulate photosynthetic efficiency, plant growth, and productivity while capsule endophytes modulate alkaloid biosynthesis. Endophytes promote plant growth, provide protection from environmental stresses and are the source of important secondary metabolites. Here, we established that the endophytes of opium poppy Papaver somniferum L. may play a role in the modulation of plant productivity and benzylisoquinoline alkaloid (BIA) biosynthesis. A total of 22 endophytes isolated from leaves, roots, capsules and seeds of the poppy plants were identified. Isolated endophytes were used to inoculate the endophytes free poppy seeds and screened for their ability to improve plant productivity and BIA production. It was evident that the endophytes from leaf were involved in improving photosynthetic efficiency, and thus crop growth and yield and the endophytes from capsule were involved in enhancing BIA biosynthesis. Capsule endophytes of alkaloid-rich P. somniferum cv. Sampada enhanced BIA production even in alkaloid-less cv. Sujata. Expression study of the genes involved in BIA biosynthesis conferred the differential regulation of their expression in the presence of capsule endophytes. The capsule endophyte SM1B (Acinetobacter) upregulated the expression of the key genes for the BIA biosynthesis except thebaine 6-O-demethylase (T6ODM) and codeine O-demethylase (CODM). On the other hand, another capsule endophyte SM3B (Marmoricola sp.) could upregulate both T6ODM and CODM. Colonization of poppy plant by endophytes isolated from leaves, roots and capsules found to be higher in their respective plant parts confirmed their tissue-specific role. Overall, the results demonstrate the specific role of endophytes in the modulation of host plant productivity and BIA production.

Chemical diversity of microbial volatiles and their potential for plant growth and productivity

Microbial volatile organic compounds (MVOCs) are produced by a wide array of microorganisms ranging from bacteria to fungi. A growing body of evidence indicates that MVOCs are ecofriendly and can be exploited as a cost-effective sustainable strategy for use in agricultural practice as agents that enhance plant growth, productivity, and disease resistance. As naturally occurring chemicals, MVOCs have potential as possible alternatives to harmful pesticides, fungicides, and bactericides as well as genetic modification. Recent studies performed under open field conditions demonstrate that efficiently adopting MVOCs may contribute to sustainable crop protection and production. We review here the chemical diversity of MVOCs by describing microbial-plants and microbial-microbial interactions. Furthermore, we discuss MVOCs role in inducing phenotypic plant responses and their potential physiological effects on crops. Finally, we analyze potential and actual limitations for MVOC use and deployment in field conditions as a sustainable strategy for improving productivity and reducing pesticide use.

Biogenic volatile emissions from the soil

Volatile compounds are usually associated with an appearance/presence in the atmosphere. Recent advances, however, indicated that the soil is a huge reservoir and source of biogenic volatile organic compounds (bVOCs), which are formed from decomposing litter and dead organic material or are synthesized by underground living organism or organs and tissues of plants. This review summarizes the scarce available data on the exchange of VOCs between soil and atmosphere and the features of the soil and particle structure allowing diffusion of volatiles in the soil, which is the prerequisite for biological VOC-based interactions. In fact, soil may function either as a sink or as a source of bVOCs. Soil VOC emissions to the atmosphere are often 1-2 (0-3) orders of magnitude lower than those from aboveground vegetation. Microorganisms and the plant root system are the major sources for bVOCs. The current methodology to detect belowground volatiles is described as well as the metabolic capabilities resulting in the wealth of microbial and root VOC emissions. Furthermore, VOC profiles are discussed as non-destructive fingerprints for the detection of organisms. In the last chapter, belowground volatile-based bi- and multi-trophic interactions between microorganisms, plants and invertebrates in the soil are discussed.

Effect of Vetiveria zizanioides essential oil on melanogenesis in melanoma cells: downregulation of tyrosinase expression and suppression of oxidative stress

The major objective of this study was to estimate the hypopigmentation function of the essential oil from Vetiveria zizanioides (VZ-EO). Our results indicated that VZ-EO exhibits potent lipid peroxidation inhibitory activity to moderate the bleaching of β-carotene and to maintain the cellular glutathione (GSH) levels. VZ-EO can markedly decrease melanin production and tyrosinase activity in α-melanin-stimulating-hormone- (α-MSH-) stimulated B16 cells. The effect of VZ-EO on melanogenesis is achieved by the suppression of cellular tyrosinase expression. The results demonstrated that the activity of VZ-EO on melanogenesis might be the result of its potent antioxidative ability, which was reflected in the decreased cellular oxidant and malondialdehyde (MDA) levels and the recovered activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) in α-MSH-stimulated B16 cells. The most abundant compound in VZ-EO is cedr-8-en-13-ol (12.4%), which has a strong capability to inhibit lipid peroxidation. Therefore, VZ-EO has the potential to become an ingredient in future hypopigmentation drugs, foods, and cosmetics.

Does the essential oil of Lippia sidoides Cham. (pepper-rosmarin) affect its endophytic microbial community?

Background

Lippia sidoides Cham., also known as pepper-rosmarin, produces an essential oil in its leaves that is currently used by the pharmaceutical, perfumery and cosmetic industries for its antimicrobial and aromatic properties. Because of the antimicrobial compounds (mainly thymol and carvacrol) found in the essential oil, we believe that the endophytic microorganisms found in L. sidoides are selected to live in different parts of the plant.

Results

In this study, the endophytic microbial communities from the stems and leaves of four L. sidoides genotypes were determined using cultivation-dependent and cultivation-independent approaches. In total, 145 endophytic bacterial strains were isolated and further grouped using either ERIC-PCR or BOX-PCR, resulting in 76 groups composed of different genera predominantly belonging to the Gammaproteobacteria. The endophytic microbial diversity was also analyzed by PCR-DGGE using 16S rRNA-based universal and group-specific primers for total bacteria, Alphaproteobacteria, Betaproteobacteria and Actinobacteria and 18S rRNA-based primers for fungi. PCR-DGGE profile analysis and principal component analysis showed that the total bacteria, Alphaproteobacteria, Betaproteobacteria and fungi were influenced not only by the location within the plant (leaf vs. stem) but also by the presence of the main components of the L. sidoides essential oil (thymol and/or carvacrol) in the leaves. However, the same could not be observed within the Actinobacteria.

Conclusion

The data presented here are the first step to begin shedding light on the impact of the essential oil in the endophytic microorganisms in pepper-rosmarin.

Removal of the sesquiterpene β-caryophyllene from air via biofiltration: performance assessment and microbial community structure

Experiments were conducted in a laboratory-scale biofilter to assess the ability of a fixed-film biological process to treat an air stream containing β-caryophyllene, a sesquiterpene emitted by a variety of conifer trees as well as industrial wood processing operations. Treatment performance was evaluated under a variety of pollutant loading conditions and nutrient supply rates over an operational period lasting more than 240 days. At empty bed contact times (EBCTs) as low as 10 s and daily average pollutant loading rate as high as 24.2 g C/(m(3) h) (grams pollutant measured as carbon per cubic meter packed bed volume per hour), removal efficiencies in excess of 95 % were observed when sufficient nutrients were supplied. Results demonstrate that, as with biofilters treating other compounds, biofilters treating β-caryophyllene can experience local nutrient limitations that result in diminished performance. The biofilter successfully recovered high removal efficiency within a few days after resumption of pollutant loading following a 14-day interval of no contaminant loading. Construction of a 16S rRNA gene library via pyrosequencing revealed the presence of a high proportion of bacteria clustering within the genera Gordonia (39.7 % of the library) and Rhodanobacter (37.6 %). Other phylotypes detected at lower relative abundances included Pandoraea (6.2 %), unclassified Acetobacteraceae (5.5 %), Dyella (3.3 %), unclassified Xanthomonadaceae (2.6 %), Mycobacterium (1.8 %), and Nocardia (0.6 %). Collectively, results demonstrate that β-caryophyllene can be effectively removed from contaminated gas streams using biofilters.