Plant growth promoting bacteria associated with langsdorffia hypogaea-rhizosphere-host biological interface : a neglected model of bacterial prospection.

Soil is a habitat where plant roots and microorganisms interact. In the region of the Brazilian Iron Quadrangle (IQ), studies involving the interaction between microbiota and plants have been neglected. Even more neglected are the studies involving the holoparasite plant Langsdorffia hypogaea Mart. (Balanophoraceae). The geomorphological peculiarities of IQ soil, rich in iron ore, as well as the model of interaction between L. hypogaea, its hosts and the soil provide a unique niche that acts as selective pressure to the evolution of plant growth-promoting bacteria (PGPB). The aim of this study was to prospect the bacterial microbiota of holoparasitic plant L. hypogaea, its plant host and corresponding rhizosphere of IQ soil, and to analyze the potential of these isolates as PGPB. We obtained samples of 11 individuals of L. hypogaea containing fragments of host and rhizosphere remnants, resulting in 81 isolates associated with Firmicutes and Proteobacteria phyla. The ability to produce siderophores, hydrocyanic acid (HCN), indole-3-acetic acid (IAA), nitrogen (N2) fixation, hydrolytic enzymes secretion and inhibition of enteropathogens, and phytopathogens were evaluated. Of the total isolates, 62, 86, and 93% produced, respectively, siderophores, IAA, and were able to fix N2. In addition, 27 and 20% of isolates inhibited the growth of enteropathogens and phytopathogens, respectively, and 58% were able to produce at least one hydrolytic activity investigated. The high number of isolates that produce siderophores and indole-3-acetic acid suggests that this microbiota may be important for adaptation of plants to IQ. The results demonstrate for the first time the biological importance of Brazilian IQ species as reservoirs of specific microbiotas that might be used as PGPB on agricultural land or antropized soils that needs to be reforested

Plant growth promoting bacteria associated with langsdorffia hypogaea-rhizosphere-host biological interface : a neglected model of bacterial prospection.

Soil is a habitat where plant roots and microorganisms interact. In the region of the Brazilian Iron Quadrangle (IQ), studies involving the interaction between microbiota and plants have been neglected. Even more neglected are the studies involving the holoparasite plant Langsdorffia hypogaea Mart. (Balanophoraceae). The geomorphological peculiarities of IQ soil, rich in iron ore, as well as the model of interaction between L. hypogaea, its hosts and the soil provide a unique niche that acts as selective pressure to the evolution of plant growth-promoting bacteria (PGPB). The aim of this study was to prospect the bacterial microbiota of holoparasitic plant L. hypogaea, its plant host and corresponding rhizosphere of IQ soil, and to analyze the potential of these isolates as PGPB. We obtained samples of 11 individuals of L. hypogaea containing fragments of host and rhizosphere remnants, resulting in 81 isolates associated with Firmicutes and Proteobacteria phyla. The ability to produce siderophores, hydrocyanic acid (HCN), indole-3-acetic acid (IAA), nitrogen (N2) fixation, hydrolytic enzymes secretion and inhibition of enteropathogens, and phytopathogens were evaluated. Of the total isolates, 62, 86, and 93% produced, respectively, siderophores, IAA, and were able to fix N2. In addition, 27 and 20% of isolates inhibited the growth of enteropathogens and phytopathogens, respectively, and 58% were able to produce at least one hydrolytic activity investigated. The high number of isolates that produce siderophores and indole-3-acetic acid suggests that this microbiota may be important for adaptation of plants to IQ. The results demonstrate for the first time the biological importance of Brazilian IQ species as reservoirs of specific microbiotas that might be used as PGPB on agricultural land or antropized soils that needs to be reforested

Alcaligenes faecalis associated with Mimosa calodendron rizhosphere assist plant survival in arsenic rich soils.

The ferruginous rupestrian grasslands (FRG) in the Iron Quadrangle (IQ) are ecosystems characterized by rocky soils with reduced availability of water and nutrients, but high levels of metals. In order to comprehend the interference of microorganisms on the adaptive process of endemic plant Mimosa calodendrum (Fabaceae), bacteria associated with its roots and rhizosphere were isolated. Fourteen isolates were obtained and subsequently grown in the presence of different concentrations of arsenic (As) species. The isolate Mc250, an Alcaligenes faecalis strain, resisted to 10 mM of As (III) and 800 mM of As (V). In the presence of this strain, atomic spectrometer detected a reduction of 55% for As (III) and 72% for As (V) respectively in 10 mM and 500 mM solution. Scanning electron microscopy of this isolate demonstrated morphological modification and EDX spectroscopy revealed the presence of both As species adsorbed on the membrane, justifying the removal observed in the in vitro assays. To validate this potential removal of As in vivo, tomato plants were used as grown model in the presence and absence of A. faecalis in soil previously contaminated with 5 mM of As (III). After 14 days, plants from contaminated soil had their growth improved when compared to untreated control plants. All these results suggest for the first time that plant-associated bacteria from FRG-IQ present potential for soil rhizoremediation and may benefit the adaptive processes of plants in extreme environments including application in recovering degraded areas

Gene expression analysis identifies hypothetical genes that may be critical during the infection process of Xanthomonas citri subsp. citri.

Background: Gene expression analysis via microarray is widely used in phytobacteria to validate differential gene expression associated with virulence or to compare biological profiles of wild type and mutant strains. Here, we employed DNA microarrays to study the early stages of the infection process (24, 72 and 120 h post-inoculation) of Xanthomonas citri subsp. citri (Xac) infecting Citrus sinensis to interrogate the expression profiles of hypothetical genes. Results: Under infective conditions, 446 genes were up- and 306 downregulated. Outstanding among genes upregulated during infection were those involved in synthesizing the Type 3 Secretion System and effectors, xanthan gum and quorum-sensing induction, and flagellum synthesis and regulation. Additionally, 161 hypothetical genes were up- and 100 were downregulated, 49 of which are known to have a significant biological role. To understand hypothetical gene co-regulation or -expression, nine expression profiles including 158 genes were identified during the three infection phases. Of these, 47 hypothetical genes were identified as having expression profiles associated with at least one connected to a gene associated with adaptation and virulence. Conclusions: Expression patterns of six differentially expressed genes were validated by quantitative reverse transcription polymerase chain reaction, thus demonstrating the effectiveness of this tool in global gene expression analysis in Xac

Analyses of seven new genomes of Xanthomonas citri pv. aurantifolii strains, causative agents of Citrus Canker B and C, show a reduced repertoire of pathogenicity-related genes.

Xanthomonas citri pv. aurantifolii pathotype B (XauB) and pathotype C (XauC) are the causative agents respectively of citrus canker B and C, diseases of citrus plants related to the better-known citrus canker A, caused by Xanthomonas citri pv. citri. The study of the genomes of strains of these related bacterial species has the potential to bring new understanding to the molecular basis of citrus canker as well as their evolutionary history. Up to now only one genome sequence of XauB and only one genome sequence of XauC have been available, both in draft status. Here we present two new genome sequences of XauB (both complete) and five new genome sequences of XauC (two complete). A phylogenomic analysis of these seven genome sequences along with 24 other related Xanthomonas genomes showed that there are two distinct and wellsupported major clades, the XauB and XauC clade and the Xanthomonas citri pv. citri clade. An analysis of 62 Type III Secretion System effector genes showed that there are 42 effectors with variable presence/absence or pseudogene status among the 31 genomes analyzed. A comparative analysis of secretion-system and surfacestructure genes showed that the XauB and XauC genomes lack several key genes in pathogenicity-related subsystems. These subsystems, the Types I and IV Secretion Systems, and the Type IV pilus, therefore emerge as important ones in helping explain the aggressiveness of the A type of citrus canker and the apparent dominance in the field of the corresponding strain over the B and C strains

Detection and identification of Xanthomonas pathotypes associated with citrus diseases using comparative genomics and multiplex PCR.

Background. In Citrus cultures, three species of Xanthomonas are known to cause distinct diseases. X. citri subsp. citri patothype A, X. fuscans subsp. aurantifolii pathotypes B and C, and X. alfalfae subsp. citrumelonis, are the causative agents of cancrosis A, B, C, and citrus bacterial spots, respectively. Although these species exhibit different levels of virulence and aggressiveness, only limited alternatives are currently available for proper and early detection of these diseases in the fields. The present study aimed to develop a new molecular diagnostic method based on genomic sequences derived from the four species of Xanthomonas. Results. Using comparative genomics approaches, primers were synthesized for the identification of the four causative agents of citrus diseases. These primers were validated for their specificity to their target DNA by both conventional and multiplex PCR. Upon evaluation, their sensitivity was found to be 0.02 ng/?l in vitro and 1.5 ? 104 CFU ml?1 in infected leaves. Additionally, none of the primers were able to generate amplicons in 19 other genomes of Xanthomonas not associated with Citrus and one species of Xylella, the causal agent of citrus variegated chlorosis (CVC). This denotes strong specificity of the primers for the different species of Xanthomonas investigated in this study. Conclusions. We demonstrated that these markers can be used as potential candidates for performing in vivo molecular diagnosis exclusively for citrus-associated Xanthomonas. The bioinformatics pipeline developed in this study to design specific genomic regions is capable of generating specific primers. It is freely available and can be utilized for any other model organism

Potencial biotecnol?gico de bact?rias associadas a plantas do Quadril?tero Ferr?fero.

Programa de P?s-Gradua??o em Biotecnologia. N?cleo de Pesquisas em Ci?ncias Biol?gicas, Pr?-Reitoria de Pesquisa de P?s Gradua??o, Universidade Federal de Ouro Preto.A ciclagem de nutrientes, a promo??o do crescimento de plantas, a biorremedia??o de ambientes polu?dos e o controle biol?gico de pragas e doen?as vegetais s?o algumas das fun??es que residem em meio ? diversidade gen?tica e metab?lica dos microrganismos do solo e associados a plantas. O crescimento vegetal muitas vezes est? relacionado ? capacidade de alguns microrganismos solubilizarem fosfatos minerais ou outros nutrientes do solo e produzir ou aumentar a concentra??o de horm?nios vegetais como ?cido indol ac?tico, ?cido giber?lico, citocininas e etileno ou ainda fixar nitrog?nio associativamente. Alguns desses microrganismos controlam organismos fitopatog?nicos provenientes do solo ou das sementes atrav?s da produ??o de sider?foros, 1,3-glucanase, quitinases, ?cido cian?drico e antimicrobianos. Outros s?o respons?veis pela remedia??o de solos contaminados e assim permitem o crescimento de plantas em ambientes antes in?spitos. Sob tal perspectiva, o objetivo do trabalho foi isolar bact?rias associadas a plantas do Quadril?tero Ferr?fero (QF) e analisar o potencial biotecnol?gico relacionado ? biofertiliza??o, biocontrole e biorremedia??o. Dentre todas as plantas analisadas, um total de 307 bact?rias foram isoladas, sendo muitas dessas capazes de produzir compostos classificados como promotores de crescimento vegetal. Algumas bact?rias foram capazes de inibir pat?genos humanos e de plantas. Do total, oito bact?rias foram capazes de resistir e remediar ambientes contaminados com ars?nio. Alcaligenes faecalis Mc250 foi um dos isolados que apresentou destacado potencial biorremediador, resistindo a 5 e 800mM de arsenito e arsenato, respectivamente, al?m de remover mais de 50% desse metal do meio. An?lises gen?micas desse isolado comprovaram suas adapta??es ao ambiente hostil de origem. Os resultados demonstram a import?ncia biol?gica de plantas brasileiras do QF como reservat?rios de microrganismos com potencial biotecnol?gico.Nutrient cycling, plant growth promotion, bioremediation of polluted environments and the biological control of pests and plant diseases are some of the functions that reside in the genetic and metabolic diversity of soil microorganisms and associated with plants. Plant growth is often related to the ability of some microorganisms to solubilize mineral phosphates or other nutrients in the soil and to produce or increase the concentration of plant hormones such as indole acetic acid, gibberellic acid, cytokinins and ethylene, or to fix nitrogen associatively. Some of these microorganisms control phytopathogenic organisms from soil or seeds through the production of siderophores, 1,3-glucanase, chitinases, hydrocyanic acid and antimicrobials. Others are responsible for the remediation of contaminated soils and thus allow the growth of plants in previously inhospitable environments. From this perspective, the objective of this work was to isolate bacteria associated with plants from Iron Quadrangle (IQ) and analyze the biotechnological potential related to biofertilization, biocontrol and bioremediation. Of all the analyzed plants, a total of 307 bacteria were isolated, many of them capable of producing compounds classified as plant growth promoters. Some bacteria were able to inhibit human and plant pathogens. Of the total, eight bacteria were able to resist and remediate environments contaminated with arsenic. Alcaligenes faecalis Mc250 was one of the isolates that presented a remarkable bioremediation potential, resisting 5 and 800mM of arsenite and arsenate, respectively, besides removing more than 50% of this metal from the medium. Genomic analyzes of this isolate proved their adaptations to the hostile environment of origin. The results demonstrate the biological importance of Brazilian plants of IQ as reservoirs of microorganisms with biotechnological potential

Arsenic resistance in cultured cutaneous microbiota is associated with anuran lifestyles in the Iron Quadrangle, Minas Gerais State, Brazil.

The microbiota of the anuran skin contributes significantly to the maintenance and survival of these animals. In the present study, we investigated the composition of culturable microbiota on the skin of frogs from Tripui Ecological Station (TES), a locality in the Brazilian Iron Quadrangle that is naturally contaminated with arsenic. A total of 328 culturable bacterial isolates were obtained from 21 individuals belonging to seven anuran species, captured in different microenvironments within TES. The results indicate that higher numbers of culturable bacterial isolates, as well as higher resistance to arsenic and a higher capacity to produce biofilms, were associated with three frog species that had come into contact with arsenic-contaminated water during their reproductive period. These results raise the possibility that the adaptation of these anurans species to arsenicladen environments may have a direct correlation with a specialized microbiota

Reproductive phenology and floral visitors of a Langsdorffia hypogaea (Balanophoraceae) population in Brazil.

The floral biology and reproductive phenology of Langsdorffia hypogaea were investigated. Flowering is annual and high synchronicity was observed along two years, with significant correlation with rainfall. The post-reproductive death of rhizomes suggests monocarpy. Flowers have anthers with extrorse dehiscence and a stigma exposed above the perigonium, and are arranged in dense inflorescences which produce extrafloral nectar. A total of 259 floral visitors were observed, mostly Hymenoptera/Formicidae (149 individuals, 17 ant species), and eight species of Araneae. Although ants were frequent floral visitors, a Coleoptera (Nitidulidae, Stelidota; 28% of total visits) species was the most abundant pollinator. In consequence of herbivory only 12.5% of all inflorescence clusters fruited, and we could not evaluate the percentage of pollinated plants due to insect damage. By being a rich resource in a season of scarcity, activity on inflorescences of L. hypogaea of both pollinators and herbivores was high

TabPath : interactive tables for metabolic pathway analysis.

Information about metabolic pathways in a comparative context is one of the most powerful tool to help the understanding of genome-based differences in phenotypes among organisms. Although several platforms exist that provide a wealth of information on metabolic pathways of diverse organisms, the comparison among organisms using metabolic pathways is still a difficult task. We present TabPath (Tables for Metabolic Pathway), a web-based tool to facilitate comparison of metabolic pathways in genomes based on KEGG. From a selection of pathways and genomes of interest on the menu, TabPath generates user-friendly tables that facilitate analysis of variations in metabolism among the selected organisms