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Edaphic factors can modulate the effects of microbial inoculants on crop yield promotion. Given the potential complexity of microbial inoculant responses to diverse soil management practices, we hypothesize that sustainable management of soil and water irrigation may improve soil quality and enhance the effects of plant growth-promoting bacteria (PGPB). Consequently, the primary objective was to assess the effectiveness of microbial inoculants formulated with Herbaspirillum seropedicae (Hs) and Azospirillum brasilense (Ab) on maize growth in soils impacted by different historical conservation management systems. We evaluated two soil management systems, two irrigation conditions, and four treatments: T0 - without bioinoculant and 100% doses of NPK fertilization; T1 - Hs + humic substances and 40% of NPK fertilization; T2 - Ab and 40% of NPK fertilization; T3 - co-inoculation (Hs + Ab) and 40% of NPK fertilization. Using a reduced fertilization dose (40% NPK) associated with microbial inoculants proved efficient in increasing maize shoot dry mass : on average, there was a 16% reduction compared to the treatment with 100% fertilization. In co-inoculation (Hs + Ab), the microbial inoculants showed a mutualistic effect on plant response, higher than isolate ones, especially increasing the nitrogen content in no-tillage systems irrigated by swine wastewater. Under lower nutrient availability and higher biological soil quality, the microbial bioinputs positively influenced root development, instantaneous water use efficiency, stomatal conductance, and nitrogen contents.

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As agricultural practices become more sustainable, adopting more sustainable practices will become even more relevant. Searching for alternatives to chemical compounds has been the focus of numerous studies, and bacteriocins are tools with intrinsic biotechnological potential for controlling plant diseases. We continued to explore the biotechnological activity of the bacteriocin Gluconacin from Gluconacetobacter diazotrophicus, PAL5 strain, by investigating this protein's antagonism against important tomato phytopathogens and demonstrating its effectiveness in reducing bacterial spots caused by Xanthomonas perforans. In addition to this pathogen, the bacteriocin Gluconacin demonstrated bactericidal activity in vitro against Ralstonia solanacearum and Pseudomonas syringae pv. tomato, agents that cause bacterial wilt and bacterial spots, respectively. Bacterial spot control tests showed that Gluconacin reduced disease severity by more than 66%, highlighting the biotechnological value of this peptide in ecologically correct formulations.

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Agricultural systems are highly affected by climatic factors such as temperature, rain, humidity, wind, and solar radiation, so the climate and its changes are major risk factors for agricultural activities. A small portion of the agricultural areas of Brazil is irrigated, while the vast majority directly depends on the natural variations of the rains. The increase in temperatures due to climate change will lead to increased water consumption by farmers and a reduction in water availability, putting production capacity at risk. Drought is a limiting environmental factor for plant growth and one of the natural phenomena that most affects agricultural productivity. The response of plants to water stress is complex and involves coordination between gene expression and its integration with hormones. Studies suggest that bacteria have mechanisms to mitigate the effects of water stress and promote more significant growth in these plant species. The underlined mechanism involves root-to-shoot phenotypic changes in growth rate, architecture, hydraulic conductivity, water conservation, plant cell protection, and damage restoration through integrating phytohormones modulation, stress-induced enzymatic apparatus, and metabolites. Thus, this review aims to demonstrate how plant growth-promoting bacteria could mitigate negative responses in plants exposed to water stress and provide examples of technological conversion applied to agroecosystems.

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The use of humic substances in agriculture as a biostimulant emerged as one of the promising methods to promote sustainable production. Different molecular, biochemical, and physiological processes are triggered, resulting in nutrient efficiency use and protection against abiotic stress. Understanding plant changes promoted by humic substances is essential for innovative and tailored biostimulation technologies. Cell metabolites are the final target of the response chain, and the metabolomic approach can be helpful in unveiling pathways related to plant response. This study aimed to evaluate a global metabolic alteration of rice leaves induced by humic acids (HA) applied in a hydroponics system. Using 1H NMR and GC-TOF/MS analysis, we observed a significant decrease in all main metabolites classes in leaves treated with HA, including lipids, organic acids, amino acids, and carbohydrates. Metabolites in higher concentrations in HA-treated plants are candidates as markers of HA bioactivity, including amino acids, intermediates of tricarboxylic acid cycle, and lipids, and aromatic compounds related to plant-stress response.

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Herbaspirillum seropedicae is an endophytic bacterium that can fix nitrogen and synthesize phytohormones, which can lead to a plant growth-promoting effect when used as a microbial inoculant. Studies focused on mechanisms of action are crucial for a better understanding of the bacteria-plant interaction and optimization of plant growth-promoting response. This work aims to understand the underlined mechanisms responsible for the early stimulatory growth effects of H. seropedicae inoculation in maize. To perform these studies, we combined transcriptomic and proteomic approaches with physiological analysis. The results obtained eight days after inoculation (d.a.i) showed increased root biomass (233 and 253%) and shoot biomass (249 and 264%), respectively, for the fresh and dry mass of maize-inoculated seedlings and increased green content and development. Omics data analysis, before a positive biostimulation phenotype (5 d.a.i.) revealed that inoculation increases N-uptake and N-assimilation machinery through differentially expressed nitrate transporters and amino acid pathways, as well carbon/nitrogen metabolism integration by the tricarboxylic acid cycle and the polyamine pathway. Additionally, phytohormone levels of root and shoot tissues increased in bacterium-inoculated-maize plants, leading to feedback regulation by the ubiquitin-proteasome system. The early biostimulatory effect of H. seropedicae partially results from hormonal modulation coupled with efficient nutrient uptake-assimilation and a boost in primary anabolic metabolism of carbon-nitrogen integrative pathways.

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A plethora of bacteria-fungal interactions occur on the extended fungal hyphae network in soil. The mycosphere of saprophytic fungi can serve as a bacterial niche boosting their survival, dispersion, and activity. Such ecological concepts can be converted to bioproducts for sustainable agriculture. Accordingly, we tested the hypothesis that the well-characterised beneficial bacterium Serratia marcescens UENF-22GI can enhance plant growth-promoting properties when combined with Trichoderma longibrachiatum UENF-F476. The cultural and cell interactions demonstrated S. marcescens and T. longibrachiatum mutual compatibility. Bacteria cells were able to attach, forming aggregates to biofilms and migrating through the fungal hyphae network. Long-distance bacterial migration through growing hyphae was confirmed using a two-compartment Petri dishes assay. Fungal inoculation increased the bacteria survival rates into the vermicompost substrate over the experimental time. Also, in vitro indolic compound, phosphorus, and zinc solubilisation bacteria activities increased in the presence of the fungus. In line with the ecophysiological bacteria fitness, the bacterium-fungal combination boosted tomato and papaya plantlet growth when applied into the plant substrate under nursery conditions. Mutualistic interaction between mycosphere-colonizing bacterium S. marcescens UENF-22GI and the saprotrophic fungi T. longibrachiatum UENF-F467 increased the ecological fitness of the bacteria alongside with beneficial potential for plant growth. A proper combination and delivery of mutual compatible beneficial bacteria-fungal represent an open avenue for microbial-based products for the biological enrichment of plant substrates in agricultural systems.

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We describe the synthesis and a function of melanin in Duddingtonia flagrans, a nematode-trapping fungus. We tested various culture media treated with L-DOPA, glucose and tricyclazole on fungal growth and melanin distribution using infrared spectroscopy (IS), electron paramagnetic resonance (EPR) and transmission electron microscopy (TEM). In vitro rumen digestion was used to test the environmental stress and then to evaluate the capacity of this fungus to trap nematode larvae. The growth and melanization of the fungus after 21 days of incubation at 30°C were best in Sabouraud dextrose medium. IS indicated the presence of melanin in D. flagrans, with similar bands for commercial melanin used as a control, and assigned the values obtained by EPR (g of 2.0051 ± 0.0001) to the production of melanin by the fungus. TEM indicated that melanin was produced in melanosomes but was not totally inhibited by tricyclazole. Within the limits of experimental error, the predatory activity of fungus treated with tricyclazole was drastically affected after 27 h of in vitro anaerobic stress with rumen inoculum. The deposition of melanin particles on the fungal cell wall contributed to the maintenance of D. flagrans predatory abilities after in vitro anaerobic ruminal stress.

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Humic substances have been widely used as plant growth promoters to improve the yield of agricultural crops. However, the mechanisms underlying this effect remain unclear. Root soluble protein profiles in plants 11 days after planting and cultivated with and without humic acids (HA, 50 mg CL-1), were analyzed using the label-free quantitative proteomic approach. Cultivation of maize with HA resulted in higher fresh weight of roots than in untreated plants (control). Plants treated with HA showed increased number, diameter and length of roots. In the proteomics analysis, differences were detected in the following categories: energy metabolism, cytoskeleton, cellular transport, conformation and degradation of proteins, and DNA replication. Thirty-four proteins were significantly more abundant in the seedlings treated with HA, whereas only nine proteins were abundant in the control. The effects on root architecture, such as the induction of lateral roots and biomass increase were accompanied by changes in the energy metabolism-associated proteins. The results show that the main effect of HA is protective, mainly associated with increased expression of the 2-cys peroxidase, putative VHS/GAT, and glutathione proteins. Indeed, these proteins had the highest fold-difference. Overall, these results improve our understanding of the molecular mechanisms of HA-promoted plant growth.

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ABSTRACT: This study examines the effect of inoculation with diazotrophic bacteria and nitrogen fertilization on the growth of micropropagated pineapple cv. 'Vitória' plantlets during the acclimatization period. The experiment was carried out in a greenhouse in Campos dos Goytacazes, in randomized blocks, using a 2x5x5 factorial scheme, with the factors being two types of inocula (absence or presence of a mixture of diazotrophic bacteria that contained Burkholderia sp. UENF 114111, Burkholderia silvatlantica UENF 11711, and Herbaspirillum seropedicae HRC 54), five levels of urea (0, 2, 5, 7, and 10g L-1), and five evaluation periods (30, 60, 90, 120, and 150 days following the planting of plantlets in trays), and with four replications of each treatment. An increase in the dried weight of shoots and roots of micropropagated pineapple cv. 'Vitória' plants depended on inoculation with diazotrophic bacteria, and plantlets acclimatization could be reduced by up to 57 days, depending on the concentration of urea fertilizer.

RESUMO: O objetivo deste trabalho foi estudar o efeito da inoculação de bactérias diazotróficas endofíticas e adubação nitrogenada no crescimento de mudas micropropagadas de abacaxizeiro 'Vitória' durante o período de aclimatização. O delineamento experimental foi de blocos casualizados (DBC), em esquema fatorial (2x5x5), sendo os fatores representados por dois tipos de inóculos (ausência e presença de uma mistura de bactérias diazotróficas contendo Burkholderia sp. UENF 114111, Burkholderia silvatlantica UENF 117111 e Herbaspirillum seropedicae estirpe HRC 54), cinco concentrações de ureia (0, 2, 5, 7 e 10g L-1) e em cinco épocas de avaliação do tempo de aclimatização (30, 60, 90, 120 e 150 dias após o plantio das mudas em bandejas), com quatro repetições. Verificou-se aumento na massa seca da parte aérea e massa seca da raiz de mudas micropropagadas de abacaxizeiro 'Vitória' em função da inoculação de bactérias diazotróficas. O tempo de aclimatização pode ser reduzida em até 60 dias em função da concentração de ureia.

RESUMO

This study examines the effect of inoculation with diazotrophic bacteria and nitrogen fertilization on the growth of micropropagated pineapple cv. 'Vitória' plantlets during the acclimatization period. The experiment was carried out in a greenhouse in Campos dos Goytacazes, in randomized blocks, using a 2x5x5 factorial scheme, with the factors being two types of inocula (absence or presence of a mixture of diazotrophic bacteria that contained Burkholderia sp. UENF 114111, Burkholderia silvatlantica UENF 11711, and Herbaspirillum seropedicae HRC 54), five levels of urea (0, 2, 5, 7, and 10g L-¹), and five evaluation periods (30, 60, 90, 120, and 150 days following the planting of plantlets in trays), and with four replications of each treatment. An increase in the dried weight of shoots and roots of micropropagated pineapple cv. 'Vitória' plants depended on inoculation with diazotrophic bacteria, and plantlets acclimatization could be reduced by up to 57 days, depending on the concentration of urea fertilizer.(AU)

O objetivo deste trabalho foi estudar o efeito da inoculação de bactérias diazotróficas endofíticas e adubação nitrogenada no crescimento de mudas micropropagadas de abacaxizeiro 'Vitória' durante o período de aclimatização. O delineamento experimental foi de blocos casualizados (DBC), em esquema fatorial (2x5x5), sendo os fatores representados por dois tipos de inóculos (ausência e presença de uma mistura de bactérias diazotróficas contendo Burkholderia sp. UENF 114111, Burkholderia silvatlantica UENF 117111 e Herbaspirillum seropedicae estirpe HRC 54), cinco concentrações de ureia (0, 2, 5, 7 e 10g L-¹) e em cinco épocas de avaliação do tempo de aclimatização (30, 60, 90, 120 e 150 dias após o plantio das mudas em bandejas), com quatro repetições. Verificou-se aumento na massa seca da parte aérea e massa seca da raiz de mudas micropropagadas de abacaxizeiro 'Vitória' em função da inoculação de bactérias diazotróficas. O tempo de aclimatização pode ser reduzida em até 60 dias em função da concentração de ureia.(AU)

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Vermitechnology is an effective composting method, which transforms biomass into nutrient-rich organic fertilizer. Mature vermicompost is a renewable organic product containing humic substances with high biological activity. The aim of this study was to assess the chemical characteristics and the bioactivity of humic acids isolated from different vermicomposts produced with either cattle manure, sugar cane bagasse, sunflower cake from seed oil extraction, or filter cake from a sugar cane factory. More than 200 different molecules were found, and it was possible to identify chemical markers on humic acids according to the nature of the organic source. The large hydrophobic character of humic extracts and the preservation of altered lignin derivatives confer to humic acids the ability to induce lateral root emergence in maize seedlings. Humic acid-like substances extracted from plant biomass residues represent an additional valuable product of vermicomposting that can be used as a plant growth promoter.

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Murine B16 cell lines of tumorigenic melanocytes have been widely used as cellular model for biochemicaland molecular studies in melanoma research. Despite such importance there is still a lack of information onthe microanatomy and cytopathology of these B16 models. The aim of this study was to shed light on themorpho-pathological specificities of the murine melanoma cell lines B16F10 and B16F0, and derived tumors,and correlate the findings with distinct metastatic potential. Cyto- and histopathological analysis carried outby optical and transmission electron microscopy (TEM) revealed that both tumor cell lines exhibit typicalfeatures of carcinogenic cells such as atypical mitoses, multiple nucleoli and enlarged nucleus. In agreementwith their highest metastatic potential, B16F10 cells and tumors exhibited more aberrant morphology thanthat observed in B16F0 samples. Also the histopathological analysis revealed that only the B16F10 tumor cellscould invade adjacent muscle tissues. Under TEM, B16F0 cell line presented mitochondrial hyperplasia andhypertrophia and a large number of melanosomes, while B16F10 showed a larger number of mitochondria ina wider range of shapes and sizes, numerous polyribosomes, cellular peripheral fibrillar material, and abnormalclusters of mitochondria. These morphological features related to the differential metastatic potentials ofB16F10 and B16F0, provide new insights on the cellular changes involved in melanoma metastatic progressionand also would be instrumental to expand the application of these cell lines as models in melanoma research.AU

Linhas de células B16 de melanócitos tumorais de camundongos têm sido amplamente utilizadascomo modelo celular para estudos bioquímicos e moleculares na pesquisa de melanoma. Apesardessa importância, ainda há uma falta de informação sobre a micro anatomia e citopatologia destesmodelos B16. O objetivo deste estudo foi pesquisar sobre as especificidades morfo-patológicas das linhasde células de melanoma de camundongos B16F10 e B16F0 e tumores derivados, e correlacionaros achados com potencial metastático distinto. Cito e análise histopatológica realizada por microscopiaóptica e eletrônica de transmissão (TEM) revelou que ambas as linhagens celulares tumoraisexibem características típicas de células cancerígenas, como mitoses atípicas, múltiplos nucléolos enúcleo aumentado. De acordo com seu potencial mais elevado, as células B16F10 e tumores metastáticosexibiram morfologia mais aberrante do que a observada em amostras de B16F0. A análisehistopatológica também revelou que apenas as células tumorais B16F10 poderiam invadir os tecidosmusculares adjacentes. De acordo com TEM, a linhagem de células B16F0 apresentou hiperplasiae hipertrofia mitocondrial e um grande número de melanossomas, enquanto B16F10 demonstrouum maior número de mitocôndrias em uma ampla gama de formas e tamanhos, numerosos polirribossomas,material fibrilar celular periférico e aglomerados de mitocôndrias anormais. Estascaracterísticas morfológicas relacionadas aos diferenciais pote nciais metastáticos de B16F10 e B16F0forneceram novas compreensões sobre as mudanças celulares envolvidas na progressão metastáticade melanoma e também seria fundamental para ampliar a aplicação dessas linhagens celulares comomodelo na pesquisa melanoma.(AU)

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RESUMO

Murine B16 cell lines of tumorigenic melanocytes have been widely used as cellular model for biochemicaland molecular studies in melanoma research. Despite such importance there is still a lack of information onthe microanatomy and cytopathology of these B16 models. The aim of this study was to shed light on themorpho-pathological specificities of the murine melanoma cell lines B16F10 and B16F0, and derived tumors,and correlate the findings with distinct metastatic potential. Cyto- and histopathological analysis carried outby optical and transmission electron microscopy (TEM) revealed that both tumor cell lines exhibit typicalfeatures of carcinogenic cells such as atypical mitoses, multiple nucleoli and enlarged nucleus. In agreementwith their highest metastatic potential, B16F10 cells and tumors exhibited more aberrant morphology thanthat observed in B16F0 samples. Also the histopathological analysis revealed that only the B16F10 tumor cellscould invade adjacent muscle tissues. Under TEM, B16F0 cell line presented mitochondrial hyperplasia andhypertrophia and a large number of melanosomes, while B16F10 showed a larger number of mitochondria ina wider range of shapes and sizes, numerous polyribosomes, cellular peripheral fibrillar material, and abnormalclusters of mitochondria. These morphological features related to the differential metastatic potentials ofB16F10 and B16F0, provide new insights on the cellular changes involved in melanoma metastatic progressionand also would be instrumental to expand the application of these cell lines as models in melanoma research.

Linhas de células B16 de melanócitos tumorais de camundongos têm sido amplamente utilizadascomo modelo celular para estudos bioquímicos e moleculares na pesquisa de melanoma. Apesardessa importância, ainda há uma falta de informação sobre a micro anatomia e citopatologia destesmodelos B16. O objetivo deste estudo foi pesquisar sobre as especificidades morfo-patológicas das linhasde células de melanoma de camundongos B16F10 e B16F0 e tumores derivados, e correlacionaros achados com potencial metastático distinto. Cito e análise histopatológica realizada por microscopiaóptica e eletrônica de transmissão (TEM) revelou que ambas as linhagens celulares tumoraisexibem características típicas de células cancerígenas, como mitoses atípicas, múltiplos nucléolos enúcleo aumentado. De acordo com seu potencial mais elevado, as células B16F10 e tumores metastáticosexibiram morfologia mais aberrante do que a observada em amostras de B16F0. A análisehistopatológica também revelou que apenas as células tumorais B16F10 poderiam invadir os tecidosmusculares adjacentes. De acordo com TEM, a linhagem de células B16F0 apresentou hiperplasiae hipertrofia mitocondrial e um grande número de melanossomas, enquanto B16F10 demonstrouum maior número de mitocôndrias em uma ampla gama de formas e tamanhos, numerosos polirribossomas,material fibrilar celular periférico e aglomerados de mitocôndrias anormais. Estascaracterísticas morfológicas relacionadas aos diferenciais pote nciais metastáticos de B16F10 e B16F0forneceram novas compreensões sobre as mudanças celulares envolvidas na progressão metastáticade melanoma e também seria fundamental para ampliar a aplicação dessas linhagens celulares comomodelo na pesquisa melanoma.

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The events involved in the structural interaction between the diazotrophic endophytic bacterium Herbaspirillum seropedicae, strain RAM10, labeled with green fluorescent protein, and pineapple plantlets 'Vitória' were evaluated by means of bright-field and fluorescence microscopy, combined with scanning electron microscopy for 28 days after inoculation. After 6 hours of inoculation, H. seropedicae was already adhered to the roots, colonizing mainly root hair surface and bases, followed by epidermal cell wall junctions. Bacteria adherence in the initial periods occurred mainly in the form of solitary cells and small aggregates with pleomorphic cells. Bacteria infection of root tissue occurred through the cavities caused by the disruption of epidermal cells during the emergence of lateral roots and the endophytic establishment by the colonization of intercellular spaces of the cortical parenchyma. Moreover, within 1 day after inoculation the bacteria were colonizing the shoots. In this region, the preferred sites of epiphytic colonization were epidermal cell wall junctions, peltate scutiform trichomes and non-glandular trichomes. Subsequently, the bacteria occupied the outer periclinal walls of epidermal cells and stomata. The penetration into the shoot occurred passively through stoma aperture followed by the endophytic establishment on the substomatal chambers and spread to the intercellular spaces of spongy chlorenchyma. After 21 days of inoculation, bacterial biofilm were seen at the root hair base and on epidermal cell wall surface of root and leaf, also confirming the epiphytic nature of H. seropedicae.

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Os ácidos húmicos podem atuar no aumento da população de bactérias diazotróficas introduzidas no interior da planta e, consequentemente, no incremento dos efeitos benéficos sobre a planta hospedeira. Com este trabalho, objetivou-se avaliar o efeito dos ácidos húmicos na inoculação de bactérias diazotróficas endofíticas, em sementes de milho. Foi utilizada a estirpe Herbaspirillum seropedicae Z67 BR 11175. A inoculação das sementes com as bactérias e a adição de ácidos húmicos foram realizadas pelo recobrimento das sementes de milho UENF 506-8, com a mistura de calcário, meio de cultura semisólido, água e cimentante. As sementes recobertas foram semeadas em vasos Leonard. Aos 40 dias após a semeadura, as plântulas foram coletadas, e foi realizada a contagem de bactérias nas raízes pela técnica do Número Mais Provável. Os resultados deste trabalho mostram que os ácidos húmicos não interferem negativamente no crescimento das bactérias e estimulam a colonização da microbiota nativa. No entanto, nas condições avaliadas, a aplicação conjunta de bactérias + ácidos húmicos não estimulou o crescimento da população de bactérias inoculadas nas plântulas de milho.

The objective of this research was to evaluate the effect of the humic acids in the inoculation of endophytic diazotrophic bacteria in corn seeds. It was used the bacteria Herbaspirillum seropedicae Z67 BR 11175. The inoculation of the seeds with the bacteria and the addition of humic acids were accomplished by the coating of the corn seeds UENF 506-8. The coating was accomplished with a mixture of lime, semi-solid middle culture, water and cement. The seeds covered were sown in Leonard vases. Forty days after sowing the plants were collected and the bacteria couting was accomplished in the roots by the Most probable Number technique. The results showed that the humic acids doesn't interfere negatively in the bacteria growth of and they stimulate the colonization of the native microbiota. However, in the appraised conditions, the united application of bacteria + humic acids didn't stimulate the growth of the bacteria population inoculated in the corn seedling.

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Plant surfaces are a favourable niche for bacterial establishment, and hypothetically, plant species differ in their capacity to harbour epiphytic bacterial communities. This study was conducted to evaluate and describe the structural relationship of a bacterial community at the phyllosphere level with different plant species in a tropical ecosystem. Leaf blades of 47 plant species distributed in 27 botanical families were collected on a typical small Brazilian farm and prepared for observation under light and scanning electron microscopy. Naturally occurring bacteria were the most abundant settlers of the phylloplane, followed by fungal spore or hyphae. All plant species studied were colonized by phylloepiphytic bacteria, which were observed as solitary cells, microcolonies, and biofilms. However, independent of the family, the plant species differed in the pattern of phyllosphere colonization, as reflected in bacteria frequency and presence or absence of anatomical features that would favour the association. The phylloepiphytic bacteria were preferentially established on the following sites: epidermal cell wall junctions, glandular and nonglandular trichomes, veins, stomata, and epidermal cell wall surface. Profuse bacteria and fungi colonization was observed, at a level that was at least comparable with temperate regions. Interestingly, fungi seemed to alter the bacteria colonization pattern, most probably by microenvironmental modifications. The trichome type and density as well as the presence of epicuticular wax on the leaf blade surface seemed to be the most determinant anatomical features for the pattern of phyllosphere colonization. The presence of trichomes has a favourable, and epicuticular wax an unfavourable influence on the plant-bacteria interaction.

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A interação entre plântulas de cana-de-açúcar e H. seropedicae foi investigada pelo uso da técnica de congelamento por alta pressão seguida de criosubstituição. Observações microscópicas evidenciaram diferenças marcantes entre esta técnica e preparações convencionais, especialmente relacionadas a ultraestrutura da bactéria e às estruturas envolvidas na adesão à superfície da parede celular da planta hospedeira.

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The interaction between sugar cane plantlets and H. seropedicae was investigated using High Pressure Freezing followed by Freeze Substitution. Microscopical observation showed consistent differences between this approaches when compared with the conventional preparation, specially related to appearance of the bacteria cell and the endophytic attachment to the host cell wall.

A interação entre plântulas de cana-de-açúcar e H. seropedicae foi investigada pelo uso da técnica de congelamento por alta pressão seguida de criosubstituição. Observações microscópicas evidenciaram diferenças marcantes entre esta técnica e preparações convencionais, especialmente relacionadas a ultraestrutura da bactéria e às estruturas envolvidas na adesão à superfície da parede celular da planta hospedeira.

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Earthworms (Eisenia foetida) produce humic substances that can influence plant growth by mechanisms that are not yet clear. In this work, we investigated the effects of humic acids (HAs) isolated from cattle manure earthworm compost on the earliest stages of lateral root development and on the plasma membrane H(+)-ATPase activity. These HAs enhance the root growth of maize (Zea mays) seedlings in conjunction with a marked proliferation of sites of lateral root emergence. They also stimulate the plasma membrane H(+)-ATPase activity, apparently associated with an ability to promote expression of this enzyme. In addition, structural analysis reveals the presence of exchangeable auxin groups in the macrostructure of the earthworm compost HA. These results may shed light on the hormonal activity that has been postulated for these humic substances.

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