Host genotype, soil composition, and geo-climatic factors shape the fonio seed microbiome

BACKGROUND

Fonio (Digitaria exilis), an orphan millet crop, is the oldest indigenous crop in West Africa. Although the yield is low due to pre-domestication characteristics, the quick maturation time, drought tolerance, and the ability to thrive on poor soils make fonio a climate-smart crop. Being holobionts, plants evolve in close interaction with microbial partners, which is crucial for plant phenology and fitness. As seeds are the bottleneck of vertically transmitting plant microbiota, we proposed to unravel the seed microbiome of the under-domesticated and resilient crop fonio. Our study investigated the bacterial seed endophyte diversity across 126 sequenced fonio accessions from distinct locations in West Africa. We conducted a correlation study of the structures and functions of the seed-associated microbiomes with the native geo-climate and soil structure data. We also performed Genome-wide association studies (GWAS) to identify genetic loci associated with seed endophyte diversity.

RESULT

We report that fonio millet has diverse heritable seed endophytic taxa. We analyzed the seed microbiomes of 126 fonio accessions and showed that despite the diversity of microbiomes from distinct geographical locations, all fonio genetic groups share a core microbiome. In addition, we observed that native soil composition, geo-climatic factors, and host genotype correlate with the seed microbiomes. GWAS analysis of genetic loci associated with endophyte seed bacterial diversity identified fonio SNPs associated with genes functioning in embryo development and stress/defense response.

CONCLUSION

Analysis of the seed endophyte of the climate-smart crop fonio indicated that despite possessing a heritable core microbiome, native conditions may shape the overall fonio seed microbiomes in different populations. These distinct microbiomes could play important roles in the adaptation of fonio to different environmental conditions. Our study identified the seed microbiome as a potential target for enhancing crop resilience to climate stress in a sustainable way. Video Abstract.

Engineering carbon sequestration on arid lands

To limit the effects of global warming, arid lands, which constitute approximately one-third of terrestrial surfaces and are not utilized for agriculture, could serve as an effective method for long-term carbon (C) storage. We propose that soil-plant-microbiome engineering with oxalogenic plants and oxalotrophic microbes could facilitate C sequestration on a global scale.

Complete genome sequence analysis of plant growth-promoting bacterium, Isoptericola sp. AK164 isolated from the rhizosphere of Avicennia marina growing at the Red Sea coast

Isoptericola sp. AK164 is a Gram-positive, aerobic bacterial genus from the family Promicromonosporaceae, isolated from the root rhizosphere of Avicennia marina. AK164 significantly enhanced the growth of the Arabidopsis thaliana plant under normal and saline conditions. These bacteria can produce ACC deaminase and several enzymes playing a role in carbohydrate hydrolyses, such as cellulose, hemicellulose, and chitin degradation, which may contribute to plant growth, salt tolerance, and stress elevation. The genome sequence AK164 has a single circular chromosome of approximately 3.57 Mbp with a GC content of 73.53%. A whole genome sequence comparison of AK164 with type strains from the same genus, using digital DNA-DNA hybridization and average nucleotide identity calculations, revealed that AK164 might potentially belong to a new species of Isoptericola. Genome data and biochemical analyses indicate that AK164 could be a potential biostimulant for improving agriculture in submerged saline land.

Use of Trichoderma culture filtrates as a sustainable approach to mitigate early blight disease of tomato and their influence on plant biomarkers and antioxidants production

Introduction

Alternaria solani is a challenging pathogen in the tomato crop globally. Chemical control is a rapid approach, but emerging fungicide resistance has become a severe threat. The present study investigates the use of culture filtrates (CFs) of three species of Trichoderma spp. to control this disease.

Methods

Highly virulent A. solani strain and three Trichoderma fungal strains viz., T. harzianum (Accession No: MW590687), T. atroviride (Accession No: MW590689) and T. longibrachiatum (Accession No: MW590688) previously isolated by authors were used in this study. The efficacy of culture filtrates (CFs) to mitigate early blight disease were tested under greenhouse and field conditions, experiments were conducted in different seasons of 2020 using a tomato variety "doucen".

Results and discussion

The CFs of T. harzianum, T. longibrachiatum, and T. atroviride significantly inhibited the in vitro mycelial growth of A. solani (62.5%, 48.73%, and 57.82%, respectively, followed by control 100%). In the GC-MS analysis of Trichoderma CF volatile compounds viz., harzianic acid (61.86%) in T. harzianum, linoleic acid (70.02%) in T. atroviride, and hydroxymethylfurfural (68.08%) in the CFs of T. longibrachiatum, were abundantly present. Foliar application of CFs in the greenhouse considerably reduced the disease severity (%) in all treatments, viz., T. harzianum (18.03%), T. longibrachiatum (31.91%), and T. atroviride (23.33%), followed by infected control (86.91%), and positively affected the plant biomarkers. In the greenhouse, the plants treated with CFs demonstrated higher flavonoids after 6 days of inoculation, whereas phenolic compounds increased after 2 days. The CF-treated plants demonstrated higher antioxidant enzymes, i.e., phenylalanine ammonia-lyase (PAL) and peroxidase (POD), after 4 days, whereas polyphenol oxidase (PPO) was higher after 6 days of inoculation, followed by healthy and infected controls. In open field conditions, disease severity in CF-treated plants was reduced in both seasons as compared to naturally infected plants, whereas CF-treated plants exhibited a higher fruit yield than controls. The present results conclude that CFs can be a potential biocontrol candidate and a promising alternative to the early blight pathogen for sustainable production.

Microbe-induced drought tolerance by ABA-mediated root architecture and epigenetic reprogramming

The use of beneficial microbes to mitigate drought stress tolerance of plants is of great potential albeit little understood. We show here that a root endophytic desert bacterium, Pseudomonas argentinensis strain SA190, enhances drought stress tolerance in Arabidopsis. Transcriptome and genetic analysis demonstrate that SA190-induced root morphogenesis and gene expression is mediated via the plant abscisic acid (ABA) pathway. Moreover, we demonstrate that SA190 primes the promoters of target genes in an epigenetic ABA-dependent manner. Application of SA190 priming on crops is demonstrated for alfalfa, showing enhanced performance under drought conditions. In summary, a single beneficial root bacterial strain can help plants to resist drought conditions.

PlantACT! - how to tackle the climate crisis

Greenhouse gas (GHG) emissions have created a global climate crisis which requires immediate interventions to mitigate the negative effects on all aspects of life on this planet. As current agriculture and land use contributes up to 25% of total GHG emissions, plant scientists take center stage in finding possible solutions for a transition to sustainable agriculture and land use. In this article, the PlantACT! (Plants for climate ACTion!) initiative of plant scientists lays out a road map of how and in which areas plant scientists can contribute to finding immediate, mid-term, and long-term solutions, and what changes are necessary to implement these solutions at the personal, institutional, and funding levels.

Multiple strategies of plant colonization by beneficial endophytic Enterobacter sp. SA187

Although many endophytic plant growth-promoting rhizobacteria have been identified, relatively little is still known about the mechanisms by which they enter plants and promote plant growth. The beneficial endophyte Enterobacter sp. SA187 was shown to maintain the productivity of crops in extreme agricultural conditions. Here we present that roots of its natural host (Indigofera argentea), alfalfa, tomato, wheat, barley and Arabidopsis are all efficiently colonized by SA187. Detailed analysis of the colonization process in Arabidopsis showed that colonization already starts during seed germination, where seed-coat mucilage supports SA187 proliferation. The meristematic zone of growing roots attracts SA187, allowing epiphytic colonization in the elongation zone. Unlike primary roots, lateral roots are significantly less epiphytically colonized by SA187. Root endophytic colonization was found to occur by passive entry of SA187 at lateral-root bases. However, SA187 also actively penetrates the root epidermis by enzymatic disruption of plant cell wall material. In contrast to roots, endophytic colonization of shoots occurs via stomata, whereby SA187 can actively re-open stomata similarly to pathogenic bacteria. In summary, several entry strategies were identified that allow SA187 to establish itself as a beneficial endophyte in several plant species, supporting its use as a plant growth-promoting bacterium in agriculture systems.

Root endophyte induced plant thermotolerance by constitutive chromatin modification at heat stress memory gene loci

Global warming has become a critical challenge to food security, causing severe yield losses of major crops worldwide. Conventional and transgenic breeding strategies to enhance plant thermotolerance are laborious and expensive. Therefore, the use of beneficial microbes could be an alternative approach. Here, we report that the root endophyte Enterobacter sp. SA187 induces thermotolerance in wheat in the laboratory as well as in open-field agriculture. To unravel the molecular mechanisms, we used Arabidopsis thaliana as model plant. SA187 reprogramed the Arabidopsis transcriptome via HSFA2-dependent enhancement of H3K4me3 levels at heat stress memory gene loci. Unlike thermopriming, SA187-induced thermotolerance is mediated by ethylene signaling via the transcription factor EIN3. In contrast to the transient chromatin modification by thermopriming, SA187 induces constitutive H3K4me3 modification of heat stress memory genes, generating robust thermotolerance in plants. Importantly, microbial community composition of wheat plants in open-field agriculture is not influenced by SA187, indicating that beneficial microbes can be a powerful tool to enhance thermotolerance of crops in a sustainable manner.

Desert Microbes for Boosting Sustainable Agriculture in Extreme Environments

A large portion of the earth's surface consists of arid, semi-arid and hyper-arid lands. Life in these regions is profoundly challenged by harsh environmental conditions of water limitation, high levels of solar radiation and temperature fluctuations, along with soil salinity and nutrient deficiency, which have serious consequences on plant growth and survival. In recent years, plants that grow in such extreme environments and their naturally associated beneficial microbes have attracted increased interest. The rhizosphere, rhizosheath, endosphere, and phyllosphere of desert plants display a perfect niche for isolating novel microbes. They are well adapted to extreme environments and offer an unexploited reservoir for bio-fertilizers and bio-control agents against a wide range of abiotic and biotic stresses that endanger diverse agricultural ecosystems. Their properties can be used to improve soil fertility, increase plant tolerance to various environmental stresses and crop productivity as well as benefit human health and provide enough food for a growing human population in an environment-friendly manner. Several initiatives were launched to discover the possibility of using beneficial microbes. In this review, we will be describing the efforts to explore the bacterial diversity associated with desert plants in the arid, semi-arid, and hyper-arid regions, highlighting the latest discoveries and applications of plant growth promoting bacteria from the most studied deserts around the world.

Tailoring plant-associated microbial inoculants in agriculture: a roadmap for successful application

Plants are now recognized as metaorganisms which are composed of a host plant associated with a multitude of microbes that provide the host plant with a variety of essential functions to adapt to the local environment. Recent research showed the remarkable importance and range of microbial partners for enhancing the growth and health of plants. However, plant-microbe holobionts are influenced by many different factors, generating complex interactive systems. In this review, we summarize insights from this emerging field, highlighting the factors that contribute to the recruitment, selection, enrichment, and dynamic interactions of plant-associated microbiota. We then propose a roadmap for synthetic community application with the aim of establishing sustainable agricultural systems that use microbial communities to enhance the productivity and health of plants independently of chemical fertilizers and pesticides. Considering global warming and climate change, we suggest that desert plants can serve as a suitable pool of potentially beneficial microbes to maintain plant growth under abiotic stress conditions. Finally, we propose a framework for advancing the application of microbial inoculants in agriculture.

Complete genome sequence of the endophytic bacterium Cellulosimicrobium sp. JZ28 isolated from the root endosphere of the perennial desert tussock grass Panicum turgidum

Cellulosimicrobium sp. JZ28, a root endophytic bacterium from the desert plant Panicum turgidum, was previously identified as a plant growth-promoting bacterium. The genome of JZ28 consists of a 4378,193 bp circular chromosome and contains 3930 CDSs with an average GC content of 74.5%. Whole-genome sequencing analysis revealed that JZ28 was closely related to C. aquatile 3 bp. The genome harbors genes responsible for protection against oxidative, osmotic and salinity stresses, such as the production of osmoprotectants. It also contains genes with a role in the production of volatiles, such as hydrogen sulfide, which promote biotic and abiotic stress tolerance in plants. The presence of three copies of chitinase genes indicates a possible role of JZ28 as biocontrol agent against fungal pathogens, while a number of genes for the degradation of plant biopolymers indicates potential application in industrial processes. Genome sequencing and mining of culture-dependent collections of bacterial endophytes from desert plants provide new opportunities for biotechnological applications.

Genome Insights of the Plant-Growth Promoting Bacterium Cronobacter muytjensii JZ38 With Volatile-Mediated Antagonistic Activity Against Phytophthora infestans

Salinity stress is a major challenge to agricultural productivity and global food security in light of a dramatic increase of human population and climate change. Plant growth promoting bacteria can be used as an additional solution to traditional crop breeding and genetic engineering. In the present work, the induction of plant salt tolerance by the desert plant endophyte Cronobacter sp. JZ38 was examined on the model plant Arabidopsis thaliana using different inoculation methods. JZ38 promoted plant growth under salinity stress via contact and emission of volatile compounds. Based on the 16S rRNA and whole genome phylogenetic analysis, fatty acid analysis and phenotypic identification, JZ38 was identified as Cronobacter muytjensii and clearly separated and differentiated from the pathogenic C. sakazakii. Full genome sequencing showed that JZ38 is composed of one chromosome and two plasmids. Bioinformatic analysis and bioassays revealed that JZ38 can grow under a range of abiotic stresses. JZ38 interaction with plants is correlated with an extensive set of genes involved in chemotaxis and motility. The presence of genes for plant nutrient acquisition and phytohormone production could explain the ability of JZ38 to colonize plants and sustain plant growth under stress conditions. Gas chromatography-mass spectrometry analysis of volatiles produced by JZ38 revealed the emission of indole and different sulfur volatile compounds that may play a role in contactless plant growth promotion and antagonistic activity against pathogenic microbes. Indeed, JZ38 was able to inhibit the growth of two strains of the phytopathogenic oomycete Phytophthora infestans via volatile emission. Genetic, transcriptomic and metabolomics analyses, combined with more in vitro assays will provide a better understanding the highlighted genes' involvement in JZ38's functional potential and its interaction with plants. Nevertheless, these results provide insight into the bioactivity of C. muytjensii JZ38 as a multi-stress tolerance promoting bacterium with a potential use in agriculture.

Bioprospecting desert plant Bacillus endophytic strains for their potential to enhance plant stress tolerance

Plant growth-promoting bacteria (PGPB) are known to increase plant tolerance to several abiotic stresses, specifically those from dry and salty environments. In this study, we examined the endophyte bacterial community of five plant species growing in the Thar desert of Pakistan. Among a total of 368 culturable isolates, 58 Bacillus strains were identified from which the 16 most divergent strains were characterized for salt and heat stress resilience as well as antimicrobial and plant growth-promoting (PGP) activities. When the 16 Bacillus strains were tested on the non-host plant Arabidopsis thaliana, B. cereus PK6-15, B. subtilis PK5-26 and B. circulans PK3-109 significantly enhanced plant growth under salt stress conditions, doubling fresh weight levels when compared to uninoculated plants. B. circulans PK3-15 and PK3-109 did not promote plant growth under normal conditions, but increased plant fresh weight by more than 50% when compared to uninoculated plants under salt stress conditions, suggesting that these salt tolerant Bacillus strains exhibit PGP traits only in the presence of salt. Our data indicate that the collection of 58 plant endophytic Bacillus strains represents an important genomic resource to decipher plant growth promotion at the molecular level.

Phylogenetically diverse endophytic bacteria from desert plants induce transcriptional changes of tissue-specific ion transporters and salinity stress in Arabidopsis thaliana

Salinity severely hampers crop productivity worldwide and plant growth promoting bacteria could serve as a sustainable solution to improve plant growth under salt stress. However, the molecular mechanisms underlying salt stress tolerance promotion by beneficial bacteria remain unclear. In this work, six bacterial isolates from four different desert plant species were screened for their biochemical plant growth promoting traits and salinity stress tolerance promotion of the unknown host plant Arabidopsis thaliana. Five of the isolates induced variable root phenotypes but could all increase plant shoot and root weight under salinity stress. Inoculation of Arabidopsis with five isolates under salinity stress resulted in tissue-specific transcriptional changes of ion transporters and reduced Na⁺/K⁺ shoot ratios. The work provides first insights into the possible mechanisms and the commonality by which phylogenetically diverse bacteria from different desert plants induce salinity stress tolerance in Arabidopsis. The bacterial isolates provide new tools for studying abiotic stress tolerance mechanisms in plants and a promising agricultural solution for increasing crop yields in semi-arid regions.

Loss of NifQ Leads to Accumulation of Porphyrins and Altered Metal-Homeostasis in Nitrogen-Fixing Symbioses

Symbiotic nitrogen fixation between legumes and rhizobia involves a coordinated expression of many plant and bacterial genes as well as finely tuned metabolic activities of micro- and macrosymbionts. In spite of such complex interactions, symbiotic proficiency remains a resilient process, with host plants apparently capable of compensating for some deficiencies in rhizobia. What controls nodule homeostasis is still poorly understood and probably varies between plant species. In this respect, the promiscuous Sinorhizobium (Ensifer) fredii strain NGR234 has become a model to assess the relative contribution of single gene products to many symbioses. Here, we describe how a deletion in nifQ of NGR234 (strain NGRΔnifQ) makes nodules of Vigna unguiculata, V. radiata, and Macroptilium atropurpureum but not of the mimisoid tree Leucaena leucocephala, purple-red. This peculiar dark-nodule phenotype did not necessarily correlate with a decreased proficiency of NGRΔnifQ but coincided with a 20-fold or more accumulation of coproporphyrin III and uroporphyrin III in V. unguiculata nodules. Porphyrin accumulation was not restricted to plant cells infected with bacteroids but also extended to the nodule cortex. Nodule metal-homeostasis was altered but not sufficiently to prevent assembly and functioning of nitrogenase. Although the role of NifQ in donating molybdenum during assembly of nitrogenase cofactor FeMo-co makes it essential in free-living diazotrophs, our results highlight the dispensability of NifQ in many legume species.

Desert plant bacteria reveal host influence and beneficial plant growth properties

Deserts, such as those found in Saudi Arabia, are one of the most hostile places for plant growth. However, desert plants are able to impact their surrounding microbial community and select beneficial microbes that promote their growth under these extreme conditions. In this study, we examined the soil, rhizosphere and endosphere bacterial communities of four native desert plants Tribulus terrestris, Zygophyllum simplex, Panicum turgidum and Euphorbia granulata from the Southwest (Jizan region), two of which were also found in the Midwest (Al Wahbah area) of Saudi Arabia. While the rhizosphere bacterial community mostly resembled that of the highly different surrounding soils, the endosphere composition was strongly correlated with its host plant phylogeny. In order to assess whether any of the native bacterial endophytes might have a role in plant growth under extreme conditions, we analyzed the properties of 116 cultured bacterial isolates that represent members of the phyla Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. Our analysis shows that different strains have highly different biochemical properties with respect to nutrient acquisition, hormone production and growth under stress conditions. More importantly, eleven of the isolated strains could confer salinity stress tolerance to the experimental model plant Arabidopsis thaliana suggesting some of these plant-associated bacteria might be useful for improving crop desert agriculture.

Boosting Alfalfa (Medicago sativa L.) Production With Rhizobacteria From Various Plants in Saudi Arabia

This study focused on rhizobacteria to promote sustainable crop production in arid regions of Saudi Arabia. The study isolated 17 tightly root-adhering rhizobacteria from various plants at Hada Al Sham in Saudi Arabia. All 17 rhizobacterial isolates were confirmed as plant growth promoting rhizobacteria by classical biochemical tests. Using 16S rDNA gene sequence analyses, the strains were identified as Bacillus, Acinetobacter and Enterobacter. Subsequently, the strains were assessed for their ability to improve the physiology, nutrient uptake, growth, and yield of alfalfa plants grown under desert agriculture conditions. The field trials were conducted in a randomized complete block design. Inoculation of alfalfa with any of these 17 strains improved the relative water content; chlorophyll a; chlorophyll b; carotenoid contents; nitrogen (N), phosphorus, and potassium contents; plant height; leaf-to-stem ratio; and fresh and dry weight. Acinetobacter pittii JD-14 was most effective to increase fresh and dry weight of alfalfa by 41 and 34%, respectively, when compared to non-inoculated control plants. Nevertheless, all strains enhanced crop traits when compared to controls plants, indicating that these desert rhizobacterial strains could be used to develop an eco-friendly biofertilizer for alfalfa and possibly other crop plants to enhance sustainable production in arid regions.

Ethylene induced plant stress tolerance by Enterobacter sp. SA187 is mediated by 2-keto-4-methylthiobutyric acid production

Several plant species require microbial associations for survival under different biotic and abiotic stresses. In this study, we show that Enterobacter sp. SA187, a desert plant endophytic bacterium, enhances yield of the crop plant alfalfa under field conditions as well as growth of the model plant Arabidopsis thaliana in vitro, revealing a high potential of SA187 as a biological solution for improving crop production. Studying the SA187 interaction with Arabidopsis, we uncovered a number of mechanisms related to the beneficial association of SA187 with plants. SA187 colonizes both the surface and inner tissues of Arabidopsis roots and shoots. SA187 induces salt stress tolerance by production of bacterial 2-keto-4-methylthiobutyric acid (KMBA), known to be converted into ethylene. By transcriptomic, genetic and pharmacological analyses, we show that the ethylene signaling pathway, but not plant ethylene production, is required for KMBA-induced plant salt stress tolerance. These results reveal a novel molecular communication process during the beneficial microbe-induced plant stress tolerance.

Complete Genome Sequence Analysis of Enterobacter sp. SA187, a Plant Multi-Stress Tolerance Promoting Endophytic Bacterium

Enterobacter sp. SA187 is an endophytic bacterium that has been isolated from root nodules of the indigenous desert plant Indigofera argentea. SA187 could survive in the rhizosphere as well as in association with different plant species, and was able to provide abiotic stress tolerance to Arabidopsis thaliana. The genome sequence of SA187 was obtained by using Pacific BioScience (PacBio) single-molecule sequencing technology, with average coverage of 275X. The genome of SA187 consists of one single 4,429,597 bp chromosome, with an average 56% GC content and 4,347 predicted protein coding DNA sequences (CDS), 153 ncRNA, 7 rRNA, and 84 tRNA. Functional analysis of the SA187 genome revealed a large number of genes involved in uptake and exchange of nutrients, chemotaxis, mobilization and plant colonization. A high number of genes were also found to be involved in survival, defense against oxidative stress and production of antimicrobial compounds and toxins. Moreover, different metabolic pathways were identified that potentially contribute to plant growth promotion. The information encoded in the genome of SA187 reveals the characteristics of a dualistic lifestyle of a bacterium that can adapt to different environments and promote the growth of plants. This information provides a better understanding of the mechanisms involved in plant-microbe interaction and could be further exploited to develop SA187 as a biological agent to improve agricultural practices in marginal and arid lands.

Bioglass in Alveolar Bone Regeneration in Orthodontic Patients: Randomized Controlled Clinical Trial

This study was designed as a split-mouth randomized controlled clinical trial to evaluate the effects of a novel bioactive glass scaffold-tailored amorphous multiporous (TAMP)-for the preservation of alveolar bone following tooth extraction in class II orthodontic patients. TAMP scaffolds were prepared and sterilized. Patients were screened for eligibility, and 6 patients accounting for 14 extraction sockets were included in this stage. Sockets were randomly allocated to either control (left empty) or test (grafted with TAMP scaffold particles). Follow-up was done after 1, 2, 4, 8, and 12 to 17 wk with digital periapical radiographs to evaluate changes in crestal bone height and bone mineral density (BMD), 3-dimensional volumetric analysis of impression casts, and histologic analysis of core biopsies. Furthermore, alveolar bone marrow mesenchymal stem cells were cultured from control and test sockets following biopsy retrieval to evaluate the ability of TAMP bioactive glass scaffolds to recruit host progenitor cells. Results showed that sockets grafted with TAMP bioactive glass scaffolds better preserved height after 3 mo where mesially 57.1% of test cases showed preservation of socket height, compared with 28.6% of control cases. Distally, this was 42.9% of test cases versus none of the control cases. Regarding BMD, the test sides had higher BMD in all 3 sections of the socket, with the greatest reduction in BMD found in the coronal third. Results were not statistically significant. Histologically, sockets grafted with TAMP bioactive glass scaffolds showed a distinct pattern of bone healing characterized by vertical trabeculae and large vascularized marrow spaces with sockets showing corticalization. Volumetric analysis showed a better preservation of socket contour with TAMP bioactive glass scaffolds. TAMP bioactive glass scaffolds appeared to enhance the recruitment of stem cells from the grafted sockets. In conclusion, TAMP scaffolds appear to better preserve alveolar bone following extraction and allow for a more active bone modeling and remodeling process( ClinicalTrials.gov identifier:NCT01878084). Knowledge Transfer statement: The results of this study set the stage for the recommended use of novel biomimetic scaffolds, such as the tailored amorphous multiporous bioactive glass for preservation of the socket following extraction. This can be valuable for patients and clinicians alike when deciding on long-term prosthetic alternatives that not only result in immediate bone preservation but will accommodate the dynamic nature of bone.

Nitric oxide has no obligatory role in isoflurane late preconditioning against myocardial stunning

AIMS

Isoflurane has been demonstrated to produce late preconditioning against myocardial stunning. We tested the hypothesis that this effect is dependent upon an increased production of nitric oxide.

MAIN METHODS

Studies were performed in 18 conscious dogs, chronically instrumented to measure coronary blood flow and myocardial wall thickening (WT). In Group 1 (control; n=7), a 10-min coronary occlusion was produced followed by reperfusion; WT was monitored until full recovery. In Group 2 (n=6), the same occlusion-reperfusion protocol was performed 24h after inhalation of 1 MAC isoflurane (1.4% in O(2)) for 60 min. In Group 3 (n=5), the late anti-stunning effect of isoflurane was evaluated following non-selective inhibition of NOS with N-nitro-l-arginine (l-NA, 30 mg/kg on 3 days beginning 1 day prior to isoflurane). Expression of eNOS and iNOS protein was measured by Western blotting.

KEY FINDINGS

Two to 3h of reperfusion was required for recovery of WT following isoflurane (Group 2). In contrast, without isoflurane (Group 1), WT remained markedly reduced (30% below baseline) at this time point and required more than 6h of reperfusion for recovery. Treatment with l-NA (Group 3) did not alter time-course of recovery of WT following isoflurane. Isoflurane caused an increased expression of eNOS, but not of iNOS.

SIGNIFICANCE

Isoflurane produced late preconditioning against myocardial stunning. Although this effect was associated with an up-regulation of eNOS, its persistence following l-NA suggested that an increased production of nitric oxide did not play an obligatory role.

The type 3 protein secretion system of Cupriavidus taiwanensis strain LMG19424 compromises symbiosis with Leucaena leucocephala

Cupriavidus taiwanensis forms proficient symbioses with a few Mimosa species. Inactivation of a type III protein secretion system (T3SS) had no effect on Mimosa pudica but allowed C. taiwanensis to establish chronic infections and fix nitrogen in Leucaena leucocephala. Unlike what was observed for other rhizobia, glutamate rather than plant flavonoids mediated transcriptional activation of this atypical T3SS.

Proteome analysis of Acetobacter pasteurianus during acetic acid fermentation

Acetic acid bacteria (AAB) are Gram-negative, strictly aerobic microorganisms that show a unique resistance to ethanol (EtOH) and acetic acid (AcH). Members of the Acetobacter and Gluconacetobacter genera are capable of transforming EtOH into AcH via the alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) enzymes and are used for the industrial production of vinegar. Several mechanisms have been proposed to explain how AAB resist high concentrations of AcH, such as the assimilation of acetate through the tricarboxylic acid (TCA) cycle, the export of acetate by various transporters and modifications of the outer membrane. However, except for a few acetate-specific proteins, little is known about the global proteome responses to AcH. In this study, we used 2D-DIGE to compare the proteome of Acetobacter pasteurianus LMG 1262(T) when growing in glucose or ethanol and in the presence of acetic acid. Interesting protein spots were selected using the ANOVA p-value of 0.05 as threshold and 1.5-fold as the minimal level of differential expression, and a total of 53 proteins were successfully identified. Additionally, the size of AAB was reduced by approximately 30% in length as a consequence of the acidity. A modification in the membrane polysaccharides was also revealed by PATAg specific staining.

Evaluation of 3D nano-macro porous bioactive glass scaffold for hard tissue engineering

Recently, nano-macro dual-porous, three-dimensional (3D) glass structures were developed for use as bioscaffolds for hard tissue regeneration, but there have been concerns regarding the interconnectivity and homogeneity of nanopores in the scaffolds, as well as the cytotoxicity of the environment deep inside due to limited fluid access. Therefore, mercury porosimetry, nitrogen absorption, and TEM have been used to characterize nanopore network of the scaffolds. In parallel, viability of MG 63 human osteosarcoma cells seeded on scaffold surface was investigated by fluorescence, confocal and electron microscopy methods. The results show that cells attach, migrate and penetrate inside the glass scaffold with high proliferation and viability rate. Additionally, scaffolds were implanted under the skin of a male New Zealand rabbit for in vivo animal test. Initial observations show the formation of new tissue with blood vessels and collagen fibers deep inside the implanted scaffolds with no obvious inflammatory reaction. Thus, the new nano-macro dual-porous glass structure could be a promising bioscaffold for use in regenerative medicine and tissue engineering for bone regeneration.

Persistency and pathway of isoflurane-induced inhibition of superoxide production by neutrophils

BACKGROUND

Our previous work has demonstrated that treatment with isoflurane has a preconditioning-like inhibitory effect on superoxide production (SOP) by polymorphonuclear neutrophils. The current objectives were to determine persistency of this effect and to clarify where in the signalling pathway this inhibition of SOP occurred. The latter was accomplished using two receptor-dependent neutrophil agonists, platelet activating factor (PAF) and formyl-methionyl-leucyl-phenylalanine (fMLP), and two receptor-independent neutrophil stimuli, the protein-kinase C stimulator, phorbol myristate acetate (PMA), and the calcium ionophore, A23187.

METHODS

Arterial blood samples were obtained from eight dogs under baseline condition (conscious state), during isoflurane (1 MAC) administration, and 24 and 48 hr post-isoflurane (also in conscious state). Neutrophils were isolated and stimulated with 1 muM concentrations of PAF, fMLP, PMA, and A23187. SOP was measured spectrophotometrically.

RESULTS

Isoflurane administration caused (1) an approximate 50% decrease in SOP during PAF or fMLP (P < 0.01 vs baseline), which remained evident from 24 to 48 hr following isoflurane; (2) an initial 29% decrease in SOP during PMA (P < 0.05 vs baseline), which returned to baseline by 24 hr following isoflurane; and (3) no change in SOP during A23187 (P > 0.05 vs baseline).

CONCLUSIONS

Isoflurane administration caused prolonged (from 24 to 48 hr) decreases in agonist-induced SOP by neutrophils. This effect involved inhibition at site(s) in the signalling pathway upstream from protein kinase C. The current findings suggest that the intraoperative use of isoflurane may result in an extended impairment to the antibacterial host defense mechanism and that neutrophil inhibition may play a role in the delayed tissue protection afforded by treatment with volatile anesthetics.

Rhizobia utilize pathogen-like effector proteins during symbiosis

A type III protein secretion system (T3SS) is an important host range determinant for the infection of legumes by Rhizobium sp. NGR234. Although a functional T3SS can have either beneficial or detrimental effects on nodule formation, only the rhizobial-specific positively acting effector proteins, NopL and NopP, have been characterized. NGR234 possesses three open reading frames potentially encoding homologues of effector proteins from pathogenic bacteria. NopJ, NopM and NopT are secreted by the T3SS of NGR234. All three can have negative effects on the interaction with legumes, but NopM and NopT also stimulate nodulation on certain plants. NopT belongs to a family of pathogenic effector proteases, typified by the avirulence protein, AvrPphB. The protease domain of NopT is required for its recognition and a subsequent strong inhibition in infection of Crotalaria juncea. In contrast, the negative effects of NopJ are relatively minor when compared with those induced by its Avr homologues. Thus NGR234 uses a mixture of rhizobial-specific and pathogen-derived effector proteins. Whereas some legumes recognize an effector as potentially pathogen-derived, leading to a block in the infection process, others perceive both the negative- and positive-acting effectors concomitantly. It is this equilibrium of effector action that leads to modulation of symbiotic development.

Protein-protein interactions within type III secretion system-dependent pili of Rhizobium sp. strain NGR234

Pili synthesized by the type III secretion system of Rhizobium species strain NGR234 are essential for protein secretion and thus for efficient symbiosis with many legumes. Isolation and partial purification of these pili showed that they are composed of at least three proteins, NopA, NopB, and NopX. Using biochemical assays, we show here that these proteins interact directly with one another.

NopP, a phosphorylated effector of Rhizobium sp. strain NGR234, is a major determinant of nodulation of the tropical legumes Flemingia congesta and Tephrosia vogelii

Rhizobium sp. NGR234 nodulates many plants, some of which react to proteins secreted via a type three secretion system (T3SS) in a positive- (Flemingia congesta, Tephrosia vogelii) or negative- (Crotalaria juncea, Pachyrhizus tuberosus) manner. T3SSs are devices that Gram-negative bacteria use to inject effector proteins into the cytoplasm of eukaryotic cells. The only two rhizobial T3SS effector proteins characterized to date are NopL and NopP of NGR234. NopL can be phosphorylated by plant kinases and we show this to be true for NopP as well. Mutation of nopP leads to a dramatic reduction in nodule numbers on F. congesta and T. vogelii. Concomitant mutation of nopL and nopP further diminishes nodulation capacity to levels that, on T. vogelii, are lower than those produced by the T3SS null mutant NGR(Omega)rhcN. We also show that the T3SS of NGR234 secretes at least one additional effector, which remains to be identified. In other words, NGR234 secretes a cocktail of effectors, some of which have positive effects on nodulation of certain plants while others are perceived negatively and block nodulation. NopL and NopP are two components of this mix that extend the ability of NGR234 to nodulate certain legumes.

NopA is associated with cell surface appendages produced by the type III secretion system of Rhizobium sp. strain NGR234

Rhizobium sp. strain NGR234, which is capable of interacting with a large number of legumes, utilizes a variety of signaling molecules to establish nitrogen-fixing symbioses. Among these are nodulation outer proteins (Nops) that transit through a type III secretion system (TTSS). Abolition of Nop secretion affects nodulation of certain legumes. Under free-living conditions, the secretion of Nops can be induced by the addition of flavonoids. Here, we show that an in-frame deletion of nopA abolishes secretion of all other Nops and has the same impact on nodule formation as mutations that lead to a nonfunctional TTSS. This secretion-minus phenotype of the nopA mutant, as well as bioinformatics analysis of NopA itself, suggests that NopA could be an external component of the TTSS. Electron microscopy showed that NGR234 synthesizes fibrillar structures on the cell surface in a flavonoid-inducible and NopA-dependent manner. Purification of the macromolecular surface appendages revealed that NopA is a major component of these structures.

NopB, a type III secreted protein of Rhizobium sp. strain NGR234, is associated with pilus-like surface appendages

Rhizobium sp. strain NGR234 possesses a functional type three secretion system (TTSS), through which a number of proteins, called nodulation outer proteins (Nops), are delivered to the outside of the cell. A major constraint to the identification of Nops is their low abundance in the supernatants of NGR234 strains grown in culture. To overcome this limitation, a more sensitive proteomics-based strategy was developed. Secreted proteins from wild-type NGR234 were separated by two-dimensional gel electrophoresis, and the gel was compared to similar gels containing the proteins from a TTSS mutant (NGROmegarhcN). To identify the proteins, spots unique to the NGR234 gels were analyzed by matrix-assisted laser desorption ionization-time of flight mass spectrometry and the data were compared to the sequence of the symbiotic plasmid of NGR234. A nonpolar mutant of one of these proteins was generated called NopB. NopB is required for Nop secretion but inhibits the interaction with Pachyrhizus tuberosus and augments nodulation of Tephrosia vogelii. Flavonoids and a functional TTSS are required for the formation of some surface appendages on NGR234. In situ immunogold labeling and isolation of these pili showed that they contain NopB.

NopB, a type III secreted protein of Rhizobium sp. strain NGR234, is associated with pilus-like surface appendages

Rhizobium sp. strain NGR234 possesses a functional type three secretion system (TTSS), through which a number of proteins, called nodulation outer proteins (Nops), are delivered to the outside of the cell. A major constraint to the identification of Nops is their low abundance in the supernatants of NGR234 strains grown in culture. To overcome this limitation, a more sensitive proteomics-based strategy was developed. Secreted proteins from wild-type NGR234 were separated by two-dimensional gel electrophoresis, and the gel was compared to similar gels containing the proteins from a TTSS mutant (NGROmegarhcN). To identify the proteins, spots unique to the NGR234 gels were analyzed by matrix-assisted laser desorption ionization-time of flight mass spectrometry and the data were compared to the sequence of the symbiotic plasmid of NGR234. A nonpolar mutant of one of these proteins was generated called NopB. NopB is required for Nop secretion but inhibits the interaction with Pachyrhizus tuberosus and augments nodulation of Tephrosia vogelii. Flavonoids and a functional TTSS are required for the formation of some surface appendages on NGR234. In situ immunogold labeling and isolation of these pili showed that they contain NopB.

Humoral and cellular immune responses of a murine model against Corynebacterium pseudotuberculosis antigens

Humoral and cellular immune responses were both found to be operative in five groups of Balb/c mice following two subcutaneous inoculations with different antigens of C. pseudotuberculosis. These antigens included toxoid, bacterin, bacterin-toxoid with and without oil adjuvant in addition to the live cell of C. pseudotuberculosis. The responses were assessed, twenty days after the 2nd immunization. Serum antibody levels were determined in an enzyme linked immunosorbent assay (ELISA). Cellular immune responses to C. pseudotuberculosis antigens were measured by detection of gamma interferon (IFN-gamma) in spleen cell culture media of the immunized mice, using commercial mice enzyme immuno-assay kit. All mice were challenged 2 weeks after the last dose of immunization with live C. pseudotuberclosis (2x10(5) CFU/mouse). Protection levels were observed with different degrees between the immunized mice groups.

Study of noise, hearing impairment and hypertension in Egypt

This study included 295 workers of Assiut Generation Station (Upper Egypt). Two hundred and twenty-one of the workers were exposed to different levels of noise (80 to 107 dBA) and the remaining 74 were used as a control group. There were no significant differences in risk factors viz age, duration of work, body mass index, weight, height, smoking, and previous work as determined by a questionnaire. The relationship between occupational exposure to noise, the degree of hearing loss and hypertension was determined. The results showed that there were statistically significant differences between the average hearing threshold levels of the two groups (P<0.01) which were more in those workers exposed to noise than in the control group. The mean systolic and diastolic blood pressures were also statistically significantly different in the two groups (P<0.001) and they were positively correlated (P<0.001) to the percentage of impairment of the whole body at 74 and 6 kHz, and hearing disability at 0.5, 1, 2 and 3 kHz. Stepwise multiple regression analysis revealed that age, noise level and body weight could each be used as a predictor of hypertension. A predictive formula was derived between the amount of hearing loss and blood pressure in the subjects exposed to occupational noise.

Slow negative evoked potentials in the rhesus monkey (Macaca mulatta): myogenic versus neurogenic influences

The influence of myogenic activity on the generation of slow negative evoked potentials (SN10) to octave, toneburst stimuli (0.5-2 Hz) was investigated in 5 rhesus monkeys (M. mulatta) by comparing responses obtained prior to and during total paralysis induced with curare. The SN10 could be easily elicited during paralysis, regardless of stimulus intensity, rate, or frequency. During paralysis, there were no systematic changes in either response latency or amplitude; variability in latency was less than 10% and changes in response amplitude were within 30%. These findings suggest that the myogenic contribution to the SN10 response is negligible and that this response is of neurogenic origin in the rhesus monkey.

Maturation of the auditory brain stem response in rhesus monkeys (Macaca mulatta)

To document the maturational changes in the auditory brain stem response (ABR) of the rhesus monkey, longitudinal and cross-sectional data were collected on a panel of 31 animals during the first year of life. Each ABR test consisted of averaging 2048 responses to click stimuli delivered at a rate of 21 clicks/sec and elicited at 60, 40, 20 and 10 dB HL intensities in accordance with procedures described previously. The morphology of the ABR wave form recorded at birth was similar to that at 12 months of age and the latencies of the component waves decreased exponentially over this period. The magnitude of decrease in latency was greatest for wave IV and least for wave I. The regression lines for the log of the latencies of 3 waves on age were computed for 3 animals followed longitudinally and for the cross-sectional data set. The slopes of these regression lines were different among animals, indicating differing rates of maturation. However, these slopes were identical for the component waves of any one animal, suggesting that the rate of maturation was constant over the auditory pathway. These changes were similar in pattern to those reported for human data and suggest that the rhesus monkey may serve as an appropriate model of auditory development in man.

Auditory brain stem responses in rhesus monkey with otitis media with effusion

Auditory brain stem response (ABR) tests were conducted on 17 anesthetized juvenile rhesus monkeys. Recordings were obtained for 13 control ears without otitis media with effusion (OME) and seven experimental ears with OME. The results demonstrated an increase in response latencies for the experimental ears with OME at each of four stimulus presentation levels (80, 60, 40, and 20 dB hearing level). Interwave latencies were the same for both groups of ears. The results suggest an average 25-dB peripheral loss of predominantly middle ear origin associated with OME. The ABR appeared to be a viable technique for documenting auditory impairment associated with OME in this nonhuman primate model.

Anomalous middle ear gas absorption in a non-human primate model of cleft palate

Following surgical clefting of the palates of nine Rhesus monkeys (Macaca mulatta), daily recordings of the middle ear pressure by tympanometry have shown fluctuations between high positive and negative values. High positive middle ear pressures were recorded during the recovery from otitis media, and it was suggested that these pressures were the result of a learned or reflexive autoinflation of the middle ear cavity. To test this hypothesis, animals presenting high positive middle ear pressures were anesthetized with sodium pentobarbital, and serial tympanograms were obtained at 5-minute intervals for a period of four hours. The results showed a substantial and rapid decrease in middle ear pressure following anesthesia (200 to 400 mm H2O). These findings were compared to those of similar experiments in normal animals, with near zero resting middle ear pressures or following air and oxygen politzerizations. The changes in middle ear pressure of cleft palate animals were significantly greater than those recorded for normal animals with near zero resting middle ear pressure and were essentially the same as those recorded for normal animals following air politzerization. These data suggest that abnormally high positive middle ear pressures are the result of an introduced bolus of air. This mechanism may serve as a means of ventilating the middle ear cleft in lieu of a debilitated active dilatory mechanism, and as such, may aid in the resolution of the middle ear effusion.

Morphology of the middle ear in the rhesus monkey (Macaca mulatta)

The purpose of this study was to provide a description of the morphology of the middle ear and related structures in the rhesus monkey, Macaca mulatta. From these descriptions, it can be seen that except for relative size differences, the middle ear system of the rhesus monkey bears close resemblance to that of man. The basic architecture is the same, thereby providing an anatomic foundation for the observed similarities in function [Cantekin et al,, 1981]. The few differences between the two systems can be summarized as follow: (1) The angle of inclination of the medial wall on the parasagittal plane is more acute in the rhesus monkey than in man. (2) The shape of the tympanic membrane in the monkey is almost circular compared to the irregular oval shape in man. (3) Differences in the shape of the ossicles as well as differences of relative measurements and angles between the parts of the ossicles were observed. (4) A major difference involves the pneumatic system and most prominently, the absence of a definite mastoid process in the monkey. However, the mastoid portion of the temporal bone is still very cellular in the majority of the specimens and communicates with the middle ear cavity through a well-defined mastoid antrum. The well-developed and extremely cellular petrous bulla in the monkey is absent in man.