Project description:A novel strain LTYR-11ZT that exhibited multiple plant growth promoting (PGP) traits was isolated from the surface-sterilized leaves of Alhagi sparsifolia Shap. (Leguminosae), which reprsents one of the top drought tolerant plants in north-west China. Phylogenetic analysis of 16S rRNA gene sequences and multilocus sequence analysis based on partial sequences of atpD, gyrB, infB and rpoB genes revealed that strain LTYR-11ZT was a member of the genus Pantoea, with Pantoea theicola NBRC 110557T and Pantoea intestinalis DSM 28113T as the closest phylogenetic relatives. The results of DNA-DNA hybridization, phenotypic tests and fatty acid analysis confirmed that strain LTYR-11ZT represents a novel species of the genus Pantoea, for which we propose the name Pantoea alhagi sp. nov. Confocal microscopy observation revealed that strain LTYR-11ZT effectively colonizes the rhizoplane of both Arabidopsis and wheat. Strain LTYR-11ZT was able to promote the growth of wheat enhancing its resistance to drought stress. Strain LTYR-11ZT led to increased accumulation of soluble sugars, decreased accumulation of proline and malondialdehyde (MDA), and decreased degradation of chlorophyll in leaves of drought-stressed wheat. Our findings will contribute to the development of a novel biotechnological agent to improve the adaptation of crop plants to drought in arid ecosystems.
Project description:Efficient root colonization is a prerequisite for application of plant growth-promoting (PGP) bacteria in improving health and yield of agricultural crops. We have recently identified an endophytic bacterium, Pantoea alhagi LTYR-11Z, with multiple PGP properties that effectively colonizes the root system of wheat and improves its growth and drought tolerance. To identify novel regulatory genes required for wheat colonization, we screened an LTYR-11Z transposon (Tn) insertion library and found cra to be a colonization-related gene. By using transcriptome (RNA-seq) analysis, we found that transcriptional levels of an eps operon, the ydiV gene encoding an anti-FlhD4C2 factor, and the yedQ gene encoding an enzyme for synthesis of cyclic dimeric GMP (c-di-GMP) were significantly downregulated in the Δcra mutant. Further studies demonstrated that Cra directly binds to the promoters of the eps operon, ydiV, and yedQ and activates their expression, thus inhibiting motility and promoting exopolysaccharide (EPS) production and biofilm formation. Consistent with previous findings that Cra plays a role in transcriptional regulation in response to carbon source availability, the activating effects of Cra were much more pronounced when LTYR-11Z was grown within a gluconeogenic environment than when it was grown within a glycolytic environment. We further demonstrate that the ability of LTYR-11Z to colonize wheat roots is modulated by the availability of carbon sources. Altogether, these results uncover a novel strategy utilized by LTYR-11Z to achieve host colonization in response to carbon nutrition in the environment, in which Cra bridges a connection between carbon metabolism and colonization capacity of LTYR-11Z.IMPORTANCE Rapid and appropriate response to environmental signals is crucial for bacteria to adapt to competitive environments and to establish interactions with their hosts. Efficient colonization and persistence within the host are controlled by various regulatory factors that respond to specific environmental cues. The most common is nutrient availability. In this work, we unraveled the pivotal role of Cra in regulation of colonization ability of Pantoea alhagi LTYR-11Z in response to carbon source availability. Moreover, we identified three novel members of the Cra regulon involved in EPS synthesis, regulation of flagellar biosynthesis, and synthesis of c-di-GMP and propose a working model to explain the Cra-mediated regulatory mechanism that links carbon metabolism to host colonization. This study elucidates the regulatory role of Cra in bacterial attachment and colonization of plants, which raises the possibility of extending our studies to other bacteria associated with plant and human health.
Project description:Drought is one of the most important phenomena which limit crops' production and yield. Crops demonstrate various morphological, physiological, biochemical, and molecular responses to tackle drought stress. Plants' vegetative and reproductive stages are intensively influenced by drought stress. Drought tolerance is a complicated trait which is controlled by polygenes and their expressions are influenced by various environmental elements. This means that breeding for this trait is so difficult and new molecular methods such as molecular markers, quantitative trait loci (QTL) mapping strategies, and expression patterns of genes should be applied to produce drought tolerant genotypes. In wheat, there are several genes which are responsible for drought stress tolerance and produce different types of enzymes and proteins for instance, late embryogenesis abundant (lea), responsive to abscisic acid (Rab), rubisco, helicase, proline, glutathione-S-transferase (GST), and carbohydrates during drought stress. This review paper has concentrated on the study of water limitation and its effects on morphological, physiological, biochemical, and molecular responses of wheat with the possible losses caused by drought stress.
Project description:Paenibacillus polymyxa is a common soil bacterium with broad range of practical applications. An important group of secondary metabolites in P. polymyxa are non-ribosomal peptide and polyketide derived metabolites (NRPs/PKs). Modular non-ribosomal peptide synthetases catalyze main steps in the biosynthesis of the complex secondary metabolites. Here we report on the inactivation of an A26 Sfp-type 4'-phosphopantetheinyl transferase (Sfp-type PPTase). The inactivation of the gene resulted in loss of NRPs/PKs production. In contrast to the former Bacillus spp. model the mutant strain compared to wild type showed greatly enhanced biofilm formation ability. A26?sfp biofilm promotion is directly mediated by NRPs/PKs, as exogenous addition of the wild type metabolite extracts restores its biofilm formation level. Wheat inoculation with bacteria that had lost their Sfp-type PPTase gene resulted in two times higher plant survival and about three times increased biomass under severe drought stress compared to wild type. Challenges with P. polymyxa genetic manipulation are discussed.
Project description:Global warming has become a critical challenge to food safety, causing severe yield losses of major crops worldwide. Here, we report that the endophytic bacterium Enterobacter sp. SA187 induces thermotolerance of crops in a sustainable manner. Microbiome diversity of wheat plants is positively influenced by SA187 in open field agriculture, indicating that beneficial microbes can be a powerful tool to enhance agriculture in open field agriculture.
Project description:Stain NN08200 was isolated from the surface-sterilized stem of sugarcane grown in Guangxi province of China. The stain was Gram-negative, facultative anaerobic, non-spore-forming bacteria. The complete genome SNP-based phylogenetic analysis indicate that NN08200 is a member of the genus Pantoea ananatis. Here, we summarize the features of strain NN08200 and describe its complete genome. The genome contains a chromosome and two plasmids, in total 5,176,640 nucleotides with 54.76% GC content. The chromosome genome contains 4598 protein-coding genes, and 135 ncRNA genes, including 22 rRNA genes, 78 tRNA genes and 35 sRNA genes, the plasmid 1 contains 149 protein-coding genes and the plasmid 2 contains 308 protein-coding genes. We identified 130 tandem repeats, 101 transposon genes, and 16 predicted genomic islands on the chromosome. We found an indole pyruvate decarboxylase encoding gene which involved in the biosynthesis of the plant hormone indole-3-acetic acid, it may explain the reason why NN08200 stain have growth-promoting effects on sugarcane. Considering the pathogenic potential and its versatility of the species of the genus Pantoea, the genome information of the strain NN08200 give us a chance to determine the genetic background of interactions between endophytic enterobacteria and plants.
Project description:Adaptation to osmotic stress is crucial for bacterial growth and survival in changing environments. Although a large number of osmotic stress response genes have been identified in various bacterial species, how osmotic changes affect bacterial motility, biofilm formation, and colonization of host niches remains largely unknown. In this study, we report that the LrhA regulator is an osmoregulated transcription factor that directly binds to the promoters of the flhDC, eps, and opgGH operons and differentially regulates their expression, thus inhibiting motility and promoting exopolysaccharide (EPS) production, synthesis of osmoregulated periplasmic glucans (OPGs), biofilm formation, and root colonization of the plant growth-promoting bacterium Pantoea alhagi LTYR-11Z. Further, we observed that the LrhA-regulated OPGs control RcsCD-RcsB activation in a concentration-dependent manner, and a high concentration of OPGs induced by increased medium osmolarity is maintained to achieve the high level of activation of the Rcs phosphorelay, which results in enhanced EPS synthesis and decreased motility in P. alhagi Moreover, we showed that the osmosensing regulator OmpR directly binds to the promoter of lrhA and promotes its expression, while lrhA expression is feedback inhibited by the activated Rcs phosphorelay system. Overall, our data support a model whereby P. alhagi senses environmental osmolarity changes through the EnvZ-OmpR two-component system and LrhA to regulate the synthesis of OPGs, EPS production, and flagellum-dependent motility, thereby employing a hierarchical signaling cascade to control the transition between a motile lifestyle and a biofilm lifestyle.IMPORTANCE Many motile bacterial populations form surface-attached biofilms in response to specific environmental cues, including osmotic stress in a range of natural and host-related systems. However, cross talk between bacterial osmosensing, swimming, and biofilm formation regulatory networks is not fully understood. Here, we report that the pleiotropic regulator LrhA in Pantoea alhagi is involved in the regulation of flagellar motility, biofilm formation, and host colonization and responds to osmotic upshift. We further show that this sensing relies on the EnvZ-OmpR two-component system that was known to detect changes in external osmotic stress. The EnvZ-OmpR-LrhA osmosensing signal transduction cascade is proposed to increase bacterial fitness under hyperosmotic conditions inside the host. Our work proposes a novel regulatory mechanism that links osmosensing and motile-sessile lifestyle transitions, which may provide new approaches to prevent or promote the formation of biofilms and host colonization in P. alhagi and other bacteria possessing a similar osmoregulatory mechanism.
Project description:Brevibacillus laterosporus (Bl), is an insecticidal bacterium recorded as toxic to a range of invertebrates after ingestion. Isolates of Bl, which were initially recovered from surface-sterilised cabbage (Brassica oleracea var. capitata) seeds, were able to colonise brassica plants in the laboratory and field. The bacterium was recovered from surface-sterilised leaf, stem and root sections of seedlings after inoculation with Bl vegetative cells under laboratory conditions, and from mature cabbage plants sprayed with Bl in a field trial. The identity of the recovered bacterial isolates was confirmed by PCR through amplification of 16S rDNA and two strain-specific regions. The effect on diamondback moth (DBM) insect herbivory was tested with cabbage seedlings treated with one isolate (Bl 1951) as the strains are toxic to DBM after direct ingestion. While no effect on DBM larval herbivory was observed, there was a significant reduction of DBM pupation on the Bl 1951 colonised plants. The presence of Bl 1951 wild type cells within cabbage root tissue was confirmed by confocal microscopy, establishing the endophytic nature of the bacterium. The bacterium was also endophytic in three other brassica species tested, Chinese kale (Brassica oleracea var. alboglabra), oilseed rape (Brassica napus var. oleifera) and radish (Raphanus sativus).
Project description:BACKGROUND:Exploring microorganisms especially bacteria associated with the degradation of lignocellulosic biomass shows great potentials in biofuels production. The rice endophytic bacterium Pantoea ananatis Sd-1 with strong lignocellulose degradation capacity has been reported in our previous study. However, a comprehensive analysis of its corresponding degradative system has not yet been conducted. The aim of this work is to identify and characterize the lignocellulolytic enzymes of the bacterium to understand its mechanism of lignocellulose degradation and facilitate its application in sustainable energy production. RESULTS:The genomic analysis revealed that there are 154 genes encoding putative carbohydrate-active enzymes (CAZy) in P. ananatis Sd-1. This number is higher than that of compared cellulolytic and ligninolytic bacteria as well as other eight P. ananatis strains. The CAZy in P. ananatis Sd-1 contains a complete repertoire of enzymes required for cellulose and hemicellulose degradation. In addition, P. ananatis Sd-1 also possesses plenty of genes encoding potential ligninolytic relevant enzymes, such as multicopper oxidase, catalase/hydroperoxidase, glutathione S-transferase, and quinone oxidoreductase. Quantitative real-time PCR analysis of parts of genes encoding lignocellulolytic enzymes revealed that they were significantly up-regulated (at least P < 0.05) in presence of rice straw. Further identification of secretome of P. ananatis Sd-1 by nano liquid chromatography-tandem mass spectrometry confirmed that considerable amounts of proteins involved in lignocellulose degradation were only detected in rice straw cultures. Rice straw saccharification levels by the secretome of P. ananatis Sd-1 reached 129.11 ± 2.7 mg/gds. Correspondingly, the assay of several lignocellulolytic enzymes including endoglucanase, exoglucanase, ?-glucosidase, xylanase-like, lignin peroxidase-like, and laccase-like activities showed that these enzymes were more active in rice straw relative to glucose substrates. The high enzymes activities were not attributed to bacterial cell densities but to the difference of secreted protein contents. CONCLUSION:Our results indicate that P. ananatis Sd-1 can produce considerable lignocellulolytic enzymes including cellulases, hemicellulases, and ligninolytic relevant enzymes. The high activities of those enzymes could be efficiently induced by lignocellulosic biomass. This identified degradative system is valuable for the lignocellulosic bioenergy industry.