Distribution of Xylella fastidiosa in citrus rootstocks and transmission of citrus variegated chlorosis between sweet orange plants through natural root grafts

To study translocation of Xylella fastidiosa to citrus rootstocks, budsticks from citrus variegated chlorosis (CVC)-affected cv. Pera sweet orange (Citrus sinenesis (L.) Osb.) were top grafted on 15 citrus rootstocks. Disease symptoms were conspicuous 3 months later on all 15 rootstocks tested. The presence of X. fastidiosa was confirmed by light microscopy, double-antibody sandwich enzyme-linked immunosorbent assays, and polymerase chain reaction in rootlets and main roots of CVC-symptomatic Pera sweet orange in 11 of the 15 rootstocks tested. These results suggest that bacterial translocation from the aerial plant parts to the root system occurs but is not essential for X. fastidiosa to induce symptoms in the aerial parts. Bacterial translocation to the roots was not correlated with CVC leaf-symptom severity in the Pera scion. To determine if CVC disease could be transmitted by natural root grafts, two matched seedlings of each of four sweet orange cultivars (Pera, Natal, Valencia, and Caipira) were transplanted into single pots. One seedling rootstock of each pair was inoculated by top grafting with a CVC-contaminated budstick while the other seedling rootstock was cut but not graft inoculated. Transmission of X. fastidiosa from an inoculated plant to a noninoculated plant sharing the same pot was observed in all four sweet orange cultivars tested. Transmission was confirmed by observation of natural roots grafts between the two plants, presence of X. fastidiosa in the root grafts, and disease development in the uninoculated plants. This is the first report of transmission of CVC disease through natural root grafts.

Analysis of the Virulence of an Atypical Enteropathogenic Escherichia coli Strain In Vitro and In Vivo and the Influence of Type Three Secretion System

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Síntese e estudos de sistemas de bioencapsulação associados a peptídeos antimicrobianos miméticos da toxina natural CcdB

Pós-graduação em Biotecnologia - IQ

The bacterial chromosome segregation protein Spo0J spreads along DNA from parS nucleation sites

Regulation of chromosome inheritance is essential to ensure proper transmission of genetic information. To accomplish accurate genome segregation, cells organize their chromosomes and actively separate them prior to cytokinesis. In Bacillus subtilis the Spo0J protein is required for accurate chromosome segregation and it regulates the developmental switch from vegetative growth to sporulation. Spo0J is a DNA-binding protein that recognizes at least eight identified parS sites located near the origin of replication. As judged by fluorescence microscopy, Spo0J forms discrete foci associated with the oriC region of the chromosome throughout the cell cycle. In an attempt to determine the mechanisms utilized by Spo0J to facilitate productive chromosome segregation, we have investigated the DNA binding activity of Spo0J. In vivo we find Spo0J associates with several kilobases of DNA flanking its specific binding sites (parS) through a parS-dependent nucleation event that promotes lateral spreading of Spo0J along the chromosome. Using purified components we find that Spo0J has the ability to coat non-specific DNA substrates. These 'Spo0J domains' provide large structures near oriC that could potentially demark, organize or localize the origin region of the chromosome.

Molecular analysis of the bacterial diversity in a specialized consortium for diesel oil degradation

Diesel oil is a compound derived from petroleum, consisting primarily of hydrocarbons. Poor conditions in transportation and storage of this product can contribute significantly to accidental spills causing serious ecological problems in soil and water and affecting the diversity of the microbial environment. The cloning and sequencing of the 16S rRNA gene is one of the molecular techniques that allows estimation and comparison of the microbial diversity in different environmental samples. The aim of this work was to estimate the diversity of microorganisms from the Bacteria domain in a consortium specialized in diesel oil degradation through partial sequencing of the 16S rRNA gene. After the extraction of DNA metagenomics, the material was amplified by PCR reaction using specific oligonucleotide primers for the 16S rRNA gene. The PCR products were cloned into a pGEM-T-Easy vector (Promega), and Escherichia coli was used as the host cell for recombinant DNAs. The partial clone sequencing was obtained using universal oligonucleotide primers from the vector. The genetic library obtained generated 431 clones. All the sequenced clones presented similarity to phylum Proteobacteria, with Gammaproteobacteria the most present group (49.8 % of the clones), followed by Alphaproteobacteira (44.8 %) and Betaproteobacteria (5.4 %). The Pseudomonas genus was the most abundant in the metagenomic library, followed by the Parvibaculum and the Sphingobium genus, respectively. After partial sequencing of the 16S rRNA, the diversity of the bacterial consortium was estimated using DOTUR software. When comparing these sequences to the database from the National Center for Biotechnology Information (NCBI), a strong correlation was found between the data generated by the software used and the data deposited in NCBI.

Molecular detection of tick-borne bacterial agents in Brazilian and exotic captive carnivores

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Bacterial diversity in soil in response to different plans, phosphate fertilizers and liming

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Bacterial diversity of terra preta and pristine forest soil from the Western Amazon

The survey presented here describes the bacterial diversity and community structures of a pristine forest soil and an anthropogenic, terra preta from the Western Amazon forest using molecular methods to identify the predominant phylogenetic groups. Bacterial community similarities and species diversity in the two soils were compared using oligonucleotide fingerprint grouping of 16S rRNA gene sequences for 1500 clones (OFRG) and by DNA sequencing. The results showed that both soils had similar bacterial community compositions over a range of phylogenetic distances, among which Acidobacteria were predominant, but that terra preta supported approximately 25% greater species richness. The survey provides the first detailed analysis of the composition and structure of bacterial communities from terra preta anthrosols using noncultured-based molecular methods. (c) 2006 Elsevier Ltd. All rights reserved.

Bacterial functional redundancy along a soil reclamation gradient

A strategy to measure bacterial functional redundancy was developed and tested with soils collected along a soil reclamation gradient by determining the richness and diversity of bacterial groups capable of in situ growth on selected carbon substrates. Soil cores were collected from four sites along a transect from the Jamari tin mine site in the Jamari National Forest, Rondonia, RO, Brazil: denuded mine spoil, soil from below the canopy of invading pioneer trees, revegetated soil under new growth on the forest edge, and the forest floor of an adjacent preserved forest. Bacterial population responses were analyzed by amending these soil samples with individual carbon substrates in the presence of bromodeoxyuridine (BrdU), BrdU-labeled DNA was then subjected to a 16S-23S rRNA intergenic analysis to depict the actively growing bacteria from each site, the number and diversity of bacterial groups responding to four carbon substrates (L-serine, L-threonine, sodium citrate, and or-lactose hydrate) increased along the reclamation-vegetation gradient such that the preserved forest soil samples contained the highest functional redundancy for each substrate. These data suggest that bacterial functional redundancy increases in relation to the regrowth of plant communities and may therefore represent an important aspect of the restoration of soil biological functionality to reclaimed mine spoils. They also suggest that bacterial functional redundancy may be a useful indicator of soil quality and ecosystem functioning.

A novel system for large-scale gene expression analysis: bacterial colonies array

In the present work, we report the use of bacterial colonies to optimize macroarray technique. The devised system is significantly cheaper than other methods available to detect large-scale differential gene expression. Recombinant Escherichia coli clones containing plasmid-encoded copies of 4,608 individual expressed sequence tag (ESTs) were robotically spotted onto nylon membranes that were incubated for 6 and 12 h to allow the bacteria to grow and, consequently, amplify the cloned ESTs. The membranes were then hybridized with a beta-lactamase gene specific probe from the recombinant plasmid and, subsequently, phosphorimaged to quantify the microbial cells. Variance analysis demonstrated that the spot hybridization signal intensity was similar for 3,954 ESTs (85.8%) after 6 h of bacterial growth. Membranes spotted with bacteria colonies grown for 12 h had 4,017 ESTs (87.2%) with comparable signal intensity but the signal to noise ratio was fivefold higher. Taken together, the results of this study indicate that it is possible to investigate large-scale gene expression using macroarrays based on bacterial colonies grown for 6 h onto membranes.

Molecular characterization of bacterial populations of different soils

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Compared boron uptake and translocation in cotton cultivars

O boro (B) tem baixa mobilidade no floema das plantas e é reconhecidamente o micronutriente cuja deficiência é mais comum no algodoeiro. Neste trabalho foi estudada a absorção e mobilidade do B em cultivares de algodão. O experimento foi conduzido em casa de vegetação, e as plantas foram cultivadas em solução nutritiva. Os tratamentos foram constituídos de três cultivares de algodão (FMT 701, DP 604BG e FMX 993) e cinco doses de B (0,0; 2,5; 5,0; 10,0 e 20,0 µmol L-1). As avaliações foram feitas em quatro semanas consecutivas, a partir da primeira semana após emissão do primeiro botão floral. A época de aparecimento e a intensidade de sintomas de deficiência de boro entre cultivares de algodão são diferentes. A cultivar DP604BG é inicialmente menos exigente em B, porém há necessidade de maior disponibilidade desse micronutriente no meio nutritivo para evitar o aparecimento de deficiência. O crescimento do algodoeiro é prejudicado pela carência de B, independentemente das diferenças no aparecimento de sintomas, não havendo diferença entre as cultivares.

Grapevine bacterial canker in the State of São Paulo, Brazil: detection and eradication

Sintomas do cancro bacteriano da videira na variedade Red Globe foram observados em agosto de 2009 em pomar de Tupi Paulista, Estado de São Paulo, Brasil, e o agente causal Xanthomonas campestris pv. viticola foi identificado por meio de testes patológicos e moleculares. O procedimento de erradicação foi adotado e aproximadamente 4.700 plantas foram destruídas. Um levantamento realizado nas regiões produtoras do Estado de São Paulo não encontrou nenhum outro pomar contaminado, e essa espécie bacteriana é considerada ausente neste estado.