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Bacillus strains are known to produce cyclic lipopeptides that are capable of providing protection against plant pathogens. Such abilities could be utilized to protect greenhouse tomatoes against diseases including bacterial canker caused by Clavibacter michiganensis subsp. michiganensis (Cmm). In the present study, Bacillus velezensis strain 1B-23 and Bacillus sp. strain 1D-12 were assessed for their potential biocontrol abilities against Cmm strain 98–1 (Cmm98–1). Both Bacillus strains interfered with growth of Cmm98–1 in vitro, as determined by agar plate assays to screen for microbial antagonism. Inoculation of Cmm98–1 infected tomato plants with B. velezenis 1B-23 or Bacillus sp. 1D-12 lead to significantly reduced disease incidence in a greenhouse setting. Liquid Chromatography coupled to Mass Spectrometry (LC-MS) of 1B-23 and 1D-12 extracts identified [Leu7]surfactin C13 (often called surfactin A), [Leu7]surfactin C14 (often called surfactin B) and [Leu7]surfactin C15 (often called surfactin C) in fractions of extracts that inhibited growth of Cmm98–1.

Agrobacterium tumefaciens-Arabidopsis thaliana provides an excellent model system to study bacterial pathogenesis and plant interactions. It is well established that, upon recognizing plant-derived signals, A. tumefaciens activates its virulence programing, culminated by the transfer and integration of T-DNA into the plant genome. However, the initial signaling and response of the plant host during A. tumefaciens -plant interactions is less understood. In this study, A. thaliana were co-cultivated (infected) with A. tumefaciens in a sterile hydroponic system for 8 h, and the transcriptome profiles of root and shoot were determined by microarray analysis. Overall, hundreds of genes involved in plant responses to stress, regulation of transcription, signal transduction or plant metabolism are differentially expressed in roots and shoots upon A. tumefaciens infection. In total, 323 genes were up-regulated and 226 were down-regulated by a log2 transformed fold change of at least 2 in roots upon A. tumefaciens infection, as compared with mock-inoculated plants. In the shoot, 249 genes were up-regulated and 152 were down-regulated in response to A. tumefaciens infection in the roots. Functional classification and comparative analysis revealed that, in response to pathogen attack, the host plant demonstrated significantly differential signaling loops between locally (roots) and distally (shoots) affected sites, despite of little overlap between transcriptome responses. Upon A. tumefaciens infection, roots displayed a strong induction of defense and hormone signaling pathways involving salicylic acid, abscisic acid, ethylene, and auxins, which play essential roles in plant acclimation responses in the root. On the contrary, jasmonic acid and gibberellic acid signaling processes were most activated in the shoots. The identification of genes and signaling pathways that are differentially regulated in roots and shoots may serve as possible targets in molecular breeding for disease tolerant plants or for improving Agrobacterium-mediated plant transformation.

Background Bacillus velezensis is an endospore-forming, free-living soil bacterium with potential as a biopesticide against a broad spectrum of microbial pathogens of plants. Its potential for commercial development is enhanced by rapid replication and resistance to adverse environmental conditions, typical of Bacillus species. However, the use of beneficial microbes against phytopathogens has not gained dominance due to limitations that may be overcome with new biopesticidal strains and/or new biological knowledge. Results Here, we isolated B. velezensis strain 9D-6 and showed that it inhibits the in vitro growth of prokaryotic and eukaryotic pathogens, including the bacteria Bacillus cereus, Clavibacter michiganensis, Pantoea agglomerans, Ralstonia solanacearum, Xanthomonas campestris, and Xanthomonas euvesicatoria; and the fungi Alternaria solani, Cochliobolus carbonum, Fusarium oxysporum, Fusarium solani, Gibberella pulicaris, Gibberella zeae, Monilinia fructicola, Pyrenochaeta terrestris and Rhizoctonia solani. Antimicrobial compounds with activity against Clavibacter michiganensis were isolated from B. velezensis 9D-6 and characterized by high resolution LC-MS/MS, yielding formulae of C52H91N7O13 and C53H93N7O13, which correspond to [Leu7] surfactins C14 and C15 (also called surfactin B and surfactin C), respectively. We further sequenced the B. velezensis 9D-6 genome which consists of a single circular chromosome and revealed 13 gene clusters expected to participate in antimicrobial metabolite production, including surfactin and two metabolites that have not typically been found in this species - ladderane and lantipeptide. Despite being unable to inhibit the growth of Pseudomonas syringae DC3000 in an in vitro plate assay, B. velezensis 9D-6 significantly reduced root colonization by DC3000, suggesting that 9D-6 uses methods other than antimicrobials to control phytopathogens in the environment. Finally, using in silico DNA-DNA hybridization (isDDH), we confirm previous findings that many strains currently classified as B. amyloliquefaciens are actually B. velezensis. Conclusions The data presented here suggest B. velezensis 9D-6 as a candidate plant growth promoting bacterium (PGPB) and biopesticide, which uses a unique complement of antimicrobials, as well as other mechanisms, to protect plants against phytopathogens. Our results may contribute to future utilization of this strain, and will contribute to a knowledge base that will help to advance the field of microbial biocontrol. Electronic supplementary material The online version of this article (10.1186/s12866-018-1380-8) contains supplementary material, which is available to authorized users.

We report here the complete assembled genome sequence of Acinetobacter calcoaceticus CA16, which is capable of utilizing diesel and lignin as a sole carbon source. CA16 contains a 4,110,074-bp chromosome and a 5,920-bp plasmid. The assembled sequences will help elucidate potential metabolic pathways and mechanisms responsible for CA16’s hydrocarbon degradation ability.

Here, we report the complete genome sequence of the phosphate-solubilizing bacterium Burkholderia cenocepacia CR318, consisting of three circular chromosomes of 3,511,146 bp, 3,097,552 bp, and 1,056,069 bp. The data presented will facilitate further insight into the mechanisms of phosphate solubilization and its application for agricultural and ecological sustainability.

Early blight is an economically important foliar disease of processing and fresh market tomatoes. The aim of this multi-year field study was to investigate the impact of weekly foliar sprays of dried and aqueous formulations of Bacillus subtilis QST 713 (Serenade and Rhapsody), alone or as tank mixes with copper hydroxide, on early blight disease development and fruit yields of tomato. Field plots were established in London, Ontario during the 2008–2010 growing seasons and disease conditions were created artificially by inoculations with spore suspension of the early blight pathogen. The tank mixes of copper hydroxide and chlorothalonil were included as a standard spray treatment. Late blight also appeared naturally in the plots late in 2009 and 2010 field seasons and affected fruit in both years, but more severely in 2009. Spray treatments had variable effects on tomato early blight and fruit yields depending on the level of disease pressure in the inoculated plots. The weekly sprays of biofungic...

Condensed distiller's solubles (CDS), a coproduct of ethanol production from corn (Zea mays), has shown disease suppressing effects when added to pathogen-infested soils and peat-based substrate prior to planting. In this study, CDS amendment (1% and 3% w / w) to a sandy-loam soil displayed a low level of toxicity to microsclerotia of Verticillium dahliae and reduced their germination by 46% to 63% in 1 week in the laboratory soil microcosm tests. The analyses of CDS for the presence of any toxic substances revealed that it contains moderate levels (~144 mmol/L) of volatile (acetic and formic) and nonvolatile (glycolic) organic acids, and some of these are known toxicants. Glycolic, acetic, and formic acids contents were 77.1%, 17.7%, and 3.9%, respectively. Minor concentrations (0.2–0.7 mmol/L) of propionic, n -butyric, isobutyric, n -caproic, and n -valeric acids were also found in CDS. In solution assays, the viability of V. dahliae microsclerotia treated for 24 h in 1%, 2%, 5%, and 10% (v / v) CDS (pH...

A novel strain of fluorescent pseudomonad (PB-St2) was isolated from surface-sterilized stems of sugarcane grown in Pakistan. The bacterium was identified as Pseudomonas aurantiaca on the basis of 16S rRNA gene sequence analysis and results from physiological and biochemical characteristics carried out with API50 CH and QTS 24 bacterial identification kits. Assays using substrate specific media for enzymes revealed lipase and protease activities but cellulase, chitinase, or pectinase were not detected. The bacterium was unable to solubilize phosphate or produce indole acetic acid. However, it did produce HCN, siderophores, and homoserine lactones. In dual culture assays on agar, the bacterium showed antifungal activity against an important pathogen of sugarcane in Pakistan, namely Colletotrichum falcatum, as well as for pathogenic isolates of Fusarium oxysporium, F. lateritium but not against F. solani. The antifungal metabolites were identified using thin-layer chromatography, UV-spectra, and MALDI-TOFF spectra and shown to be phenazine-1-carboxylic acid (PCA), 2-hydroxyphenazine (2-OH-PHZ), and N-hexanoyl homoserine lactone (HHL) (assessed using only TLC data). The capacity of this bacterium to produce HCN and 2-OH-PHZ, as well as to inhibit the growth of C. falcatum, has not been previously reported.