Cláudia Majolo

O feijão-caupi (Vigna unguiculata) é uma leguminosa de grande importância socioeconômica no Brasil, especialmente nas regiões Norte e Nordeste, onde responde por cerca de 30% da produção nacional de feijão. Sua relevância está associada à segurança alimentar e à geração de renda para pequenos produtores, sobretudo em ambientes de cultivo adversos, como os da Amazônia. Entretanto, sua produtividade é limitada pelo baixo uso de tecnologias e manejo inadequado. A fixação biológica de nitrogênio (FBN), mediada por bactérias simbióticas como Bradyrhizobium e Rhizobium, constitui uma alternativa sustentável aos fertilizantes químicos. Este estudo teve como objetivo isolar e caracterizar rizóbios oriundos de solos amazônicos distintos (várzea, terra preta de índio e latossolo). As bactérias isoladas foram avaliadas em casa de vegetação quanto à promoção de crescimento do caupi e caracterizadas por sequenciamento do gene 16S rRNA. A massa seca da parte aérea (MSPA) variou de 736,67 a 2.220 mg por planta, e o acúmulo de nitrogênio (N-MSPA), de 17,09 a 66,85 mg por planta. A maioria dos isolados promoveu nodulação, com predominância do gênero Rhizobium, e vários isolados apresentaram desempenho agronômico semelhante, não diferindo estatisticamente da estirpe recomendada SEMIA 6462. Os resultados indicam o potencial desses rizóbios nativos como candidatos para o desenvolvimento de bioinoculantes adaptados às condições amazônicas.

O estudo avaliou o efeito da inoculação e da coinoculação de rizóbios nativos e do inoculante fosfatossolubilizador BiomaPhos® sobre o desenvolvimento e a produtividade do feijão-caupi (Vigna unguiculata (L.) Walp.) em sistema de plantio direto em Manaus, AM. Os experimentos foram conduzidos em dois anos consecutivos: 2024 (com irrigação suplementar) e 2025 (em condições naturais de precipitação - sem irrigação). Utilizou-se delineamento em blocos ao acaso com nove tratamentos, incluindo estirpes nativas de solos amazônicos (AM200/2022 e AM212/2022), a estirpe padrão (SEMIA 6462 - Bradyrhizobium yuanmingense), BiomaPhos® e suas combinações, além dos controles com e sem adubação. Em 2024, as estirpes AM200 e AM212 e a coinoculação AM200 + BiomaPhos® promoveram maior massa da parte aérea seca e, no isolado nativo AM212 e sua associação com BiomaPhos®, maior acúmulo de nitrogênio na planta, em comparação com o controle adubado e os demais tratamentos. Em 2025, os teores de nitrogênio nos grãos foram mantidos em AM212 e em BiomaPhos® + AM212, equivalentes aos dos controles. A ausência de diferenças na produtividade entre os dois anos sugere a eficiência da atuação dos rizóbios nativos. As estirpes AM200 e AM212 apresentam potencial inicial para uso futuro em formulações de bioinsumos regionais, devendo ser testadas em solos de menor fertilidade e em diferentes regiões do estado. Palavras-chave: Vigna unguiculata; fixação biológica de nitrogênio; bioinsumos; Bacillus; Amazônia. Inoculation and co-inoculation of native rhizobia and Biomaphos® on cowpea under no-tillage system in the Amazon This study evaluated the effect of inoculation and co-inoculation with native rhizobia and the phosphate-solubilizing inoculant BiomaPhos® on the development and yield of cowpea (Vigna unguiculata (L.) Walp.) under no-tillage system conditions in Manaus, Amazonas, Brazil. The experiments were conducted over two consecutive years: 2024 (with supplemental irrigation) and 2025 (under natural rainfall conditions without irrigation). A randomized block design with nine treatments was used, including native strains isolated from Amazonian soils (AM200/2022 and AM212/2022), the reference strain SEMIA 6462 (Bradyrhizobium yuanmingense), BiomaPhos® and their combinations, and the native strain AM212 and its association with BiomaPhos®. In 2024, the AM200 and AM212 strains and the AM200 + BiomaPhos® co-inoculation promoted greater shoot dry mass, while the native isolates and the unfertilized control showed greater nitrogen accumulation in plants compared to the fertilized control and the other treatments. In 2025, grain nitrogen contents were maintained in the AM212 and BiomaPhos® + AM212 treatments, with values equivalent to the controls. The absence of significant differences in grain yield over the two years suggests the activity of efficient native rhizobia populations in the experimental area. The AM200 and AM212 strains showed initial potential for future use in regional bioinput formulations and should be further evaluated in soils with lower fertility and in different regions of the state. Keywords: Vigna unguiculata; biological nitrogen fixation; bioinoculants; Bacillus; Amazon.

The production of seedlings with adequate shoot and root development is essential for the success of commercial cultivation systems. Bacteria of the genus Bacillus, capable of phosphate solubilization, have been widely studied for their potential to increase nutrient availability to plants. This study aimed to evaluate the effects of applying different doses of the Bacillus-based commercial biofertilizer Biomaphos® on the growth of açaí seedlings (Euterpe precatoria). The experiment was conducted in a greenhouse under a completely randomized design, with ten replicates and four treatments: a control (without inoculation) and three doses of the Biomaphos® inoculant (4, 12, and 16 × 108 CFU mL−1). 150 days after inoculation, shoot and root system variables were evaluated. The application of the biofertilizer promoted increases in shoot variables, except for plant height, and enhanced root volume, surface area, and dry mass, with a linear reduction in root diameter. The results indicate that Biomaphos® promotes the growth of açaí seedlings under controlled conditions.

Phosphorus and potassium are essential chemical elements in the life cycle of plants, considered limiting factors for the development of agriculture. Numerous commercial fertilizers are applied annually in the field, often prolonged and excessively, in order to meet the requirements and high demand of plant production, generating negative impacts on the environment. When applied to the soil, these elements are quickly fixed in clay minerals through chemical reactions, making their absorption by plant roots difficult. As an alternative to the irrational use of chemical inputs, much research is being directed towards the use of bacteria that inhabit the rhizosphere and have the ability to bioavail insoluble macronutrients. In view of this, the objective of this study is to carry out a small review of the literature on phosphate and potassium solubilizing bacteria, their mechanisms of action and the use as bioinoculants. The scientific articles were selected according to the proposal of this work and through databases from Web Science, Scielo, Google Scholar, Periódico Capes and Scopus. This review presents interesting results on the use and multifunctionality of rhizobacteria, as a low-cost strategy with different ecological applicability that promotes agricultural sustainability.

The tambaqui (Colossoma macropomum) is a species of great economic importance for fish farming in the Brazilian Amazon, and acanthocephaliasis caused by Neoechinorhynchus buttnerae (Golvan 1956) represents an obstacle to its production due to it causing severe morphological damage to the intestinal mucosa, thus impairing the absorption of nutrients and causing weight loss in the fish. Therefore, the establishment of in vitro protocols for evaluation of anthelmintic drugs is the first step to development of effective measures for in vivo control of this endoparasite. The present study evaluated the in vitro survival of N. buttnerae maintained in Eagle’s minimum essential medium under different culture conditions. Three assays were carried out to evaluate whether temperature, supplementation with the antibiotics penicillin and streptomycin, and culture medium replacement or no replacement would influence the motility and morphology of the acanthocephalans. The results of the Kaplan-Meier analysis indicated that the use of culture in minimum essential medium together with penicillin and streptomycin prolonged the parasite’s survival when kept at temperatures of 24 °C or 28 °C. We describe herein for first time an alternative protocol that is ideal for the in vitro culture of N. buttnerae. As such, this protocol ensures greater reliability in further in vitro studies with N. buttnerae.

The aim of this study was to molecularly identify different species of Aeromonas isolated from farmed tambaqui (Colossoma macropomum) from North Brazil, and evaluate their pathogenic potential by the presence of virulence genes. From the extraction of bacterial DNA, PCR (polymerase chain reaction) of the primers 16S rDNA, aerA (cytolytic enterotoxin), ast (cytotoxic enterotoxin) and act (cytotoxic enterotoxin) were performed. Of 24 isolates evaluated, eight amplified the ast gene, one amplified the act gene, but the areA gene was not amplified in any isolate. Sequencing of the 16S rRNA primer revealed a predominance of Aeromonas jandaei specie (92%). Aeromonas taiwanensis (4%), for the first time isolated from fish in Brazil, and Aeromonas hydrophila (4%) each appeared as just one isolate. Results showed that 32% of Aeromonas isolated from farmed tambaqui have considerable pathogenic potential for systemic damage, since the selected PCR primers are encoding the most common virulence genes in Aeromonas with high pathogenic intensity.

A new systematic structural study was performed using the Atomic Force Microscopy (AFM) reporting statistical parameters of polymeric particles based on gelatin and poly-ε-caprolactone (PCL) containing essential oil from Lippia origanoides. The developed biocides are efficient alternative controlling agents of Conotrachelus humeropictus and Moniliophtora perniciosa, the main pests of Theobroma grandiflorum. Our results showed that the particles morphology can be successfully controlled by advanced stereometric parameters, pointing to an appropriate concentration of encapsulated essential oil according to the particle surface characteristics. For this reason, the absolute concentration of 1000 µg·mL⁻¹ (P₁₀₀₀ system) was encapsulated, resulting in the most suitable surface microtexture, allowing a faster and more efficient essential oil release. Loaded particles presented zeta potential around (–54.3 ± 2.3) mV at pH = 8, and particle size distribution ranging from 113 to 442 nm. The hydrodynamic diameter of 90% of the particle population was found to be up to (405 ± 31) nm in the P₁₀₀₀ system. The essential oil release was evaluated up to 80 h, with maximum release concentrations of 63% and 95% for P₅₀₀ and P₁₀₀₀, respectively. The best fit for the release profiles was obtained using the Korsmeyer–Peppas mathematical model. Loaded particles resulted in 100% mortality of C. humeropictus up to 48 h. The antifungal tests against M. perniciosa resulted in a minimum inhibitory concentration of 250 µg·mL⁻¹, and the P₁₀₀₀ system produced growth inhibition up to 7 days. The developed system has potential as alternative controlling agent, due to its physical stability, particle surface microtexture, as well as pronounced bioactivity of the encapsulated essential oil.

The aim of this study was to determine the chemical composition of Lippia alba and two genotypes of L. origanoides, L. origanoides A and L. origanoides B (syn. Lippia sidoides) essential oils(EOs) and to investigate the antibacterial activity against 27 Aeromonas spp. isolated from tambaqui (Colossoma macropomum). The activity of the antibiotics Florfenicol and Oxytetracycline was also compared. The EOs were obtained by hydrodistillation and their composition determined by CG-MS. Antibacterial activity was assessed based in the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using microdilution method. The main compounds identified were carvone (55.9%) and limonene (21.9%) in L. alba EO, carvacrol (35.6%) and p‐cymene (15.7%) in L. origanoides A EO and thymol (53.5%) and p‐cymene (15.5%) in L. origanoides B EO. The Lippia species showed bacteriostatic and bactericidal action against Aeromonas isolates with MICs and MBCs ranging from 104.17 to 16,666.67 μg.mL⁻¹. Among the tested EOs, the best performance was obtained by that of the L. origanoides B genotype, followed by L. origanoides A and L. alba respectively. Among antibiotics, the best performance was of oxytetracycline (MICs and MBCs ranging from 0.195 to 0.78 μg.mL⁻¹) compared to florfenicol (MICs and MBCs ranging from 0.195 to 3.12 μg.mL⁻¹).

Bacterial diseases are important factors that limit productivity in aquaculture. To reduce negative economic impacts, fish farmers use antimicrobials, often indiscriminately, and this action has led to bacterial resistance to drugs. The objectives of this study were to isolate and identify the main putative pathogenic bacterial species in tambaqui (Colossoma macropomum), establish the profile of resistance to antimicrobials by the methods of disc diffusion, and determine the minimum inhibitory concentration (MIC) values. Two hundred and ninety asymptomatic fish were collected between March and November 2015 from ten fish farms in the Amazonas state (Brazil). Of the total strains recovered from tambaqui, seven were identified as Aeromonas spp. by sequencing the 16S rRNA gene. These seven isolates showed resistance to ampicillin, 28% to erythromycin, and 28% to sulfonamide. Additionally, the seven isolates showed a MIC higher than the range evaluated for amoxicillin, penicillin, novobiocin, tylosin tartrate, and clindamycin, and 85% showed resistance to erythromycin. The results of this study indicate the need to increase the awareness of fish farmers and, most importantly, the government, about the lack of drug regulations for use in aquaculture, and good management practices, so the indiscriminate prophylactic and systemic use of antimicrobials be inhibited.

Este estudo avaliou a atividade anti-helmíntica in vitro do eugenol, timol e ácido tânico contra o endoparasito acantocéfalo Neoechinorhynchus buttnerae. Intestinos do peixe tambaqui Colossoma macropomum foram coletados e dissecados para remoção do parasito. A atividade anti-helmíntica dos compostos estudados foi testada in vitro usando meio mínimo essencial (MEM) para manter a viabilidade do parasita. Um grupo controle e de 8 a 10 tratamentos foram realizados em triplicata. Dez espécimes de N. buttnerae foram introduzidos em cada placa MEM e, após exposição aos compostos, a motilidade dos parasitos foi observada a cada 15 minutos. O valor de CL50 do eugenol após 2, 6 e 24 h de exposição foi 1,01, 0,79 e 0,41 mg.mL^-1, respectivamente; para o timol os valores foram 1,97; 0,96 e 0,92 mg.mL-1 e para o ácido tânico foram 4,68, 1,79 e 1,30 mg.mL^-1. Dentre os compostos testados, o eugenol foi o mais eficiente contra N. buttnerae, eliminando 100% dos parasitos após 15 min de exposição às três maiores concentrações testadas (1,56; 3,125 e 6,25 mg.mL^-1). O timol eliminou mais de 90% dos parasitos após 2h de exposição aos três maiores níveis testados (0,78; 1,56 e 3,125 mg.mL^-1), e o ácido tânico apresentou a menor atividade, eliminando 100% dos parasitas após 6h de exposição a doses entre 6,25 e 50 mg.mL^-1.