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Molecular identification of nitrogen-fixing bacteria and the effect of inoculation on tropical forest legume species
(2025-04-11) Zúñiga Orozco, Andrés; Hernández Gómez, Lorena; Solís Ramos, Laura; Rojas Jiménez, Keilor Osvaldo
Studies on the diversity of nitrogen-fixing bacteria, particularly in tropical forest species, has been relatively less compared to other ecosystems. The aims of this study were to isolate bacteria from nodules of eight tropical forest leguminous species belonging to two subfamilies of Fabaceae (Caesalpinioideae and Papilionoideae), carry out molecular identification based on 16S rRNA gene sequencing, and evaluate their plant growth-promoting effects in the same hosts. Growth-promoting responses were determined by evaluating plant seedlings with and without inoculation of the bacteria in their respective hosts. Five-month-old seedlings were measured for the following variables: height, stem thickness, number of leaves, vigor, root length, root weight, number of nodules, leaf area, microbial respiration, and nitrogenase activity. We also quantified nutrient content in leaves and roots. The bacterial isolates were identified as Rhizobium miluonense, Rhizobium multihospitium, Bradyrhizobium japonicum, and Bradyrhizobium sp. All morphological variables were higher in inoculated seedlings compared to the uninoculated seedlings (p < 0.05), except for microbial respiration and root length. The Caesalpinioideae subfamily responded better to the inoculant than the Papilionoideae subfamily (p < 0.05). Enterolobium cyclocarpum, Cojoba arborea and Dalbergia retusa had higher nutrient levels at foliar and root levels when inoculated. This study provided insights into the potential of developing inoculants based on nitrogen-fixing bacteria, many of which are yet to be explored, for agriculture and reforestation with leguminous species.
Deepsea fungi of the eastern tropical Pacific of Costa Rica: morphological, genetic, and enzymatic characterization
(2025-04-03) Rodríguez Ramírez, Ivonne; Solano González, Stefany; Cortés Núñez, Jorge; Rojas Jiménez, Keilor Osvaldo
Introduction: Fungal communities have only been studied in a small portion of the vast variety of habitats that exist in deepsea environments, and studies aimed at understanding fungal diversity and function are minimal.
Objective: The aim of this study is to explore both the fungal diversity in deepsea sediments and the enzymatic activities present in them, which are related to the ecological roles of the strains and their biotechnological potential.
Methods: Eighteen sediment samples from three expeditions to deepsea areas of the Eastern Tropical Pacific (ETP) of Costa Rica were analyzed. Fungi were cultured on R2A medium, followed by physical characterization and molecular analysis (ITS and whole-genome sequencing) for the taxonomic identification of the strains. Once pure cultures were established, enzymatic tests for cellobiase, chitinase, lipase, cellulase, peroxidase, and laccase activities were performed, as well as surfactant activity.
Results: Fifty-five fungal strains were isolated, and genetic analysis was conducted on 27 strains, of which 7.41% belong to the Basidiomycota group and 92.59% to Ascomycota. These strains are distributed across 14 species. Among the identified strains are Periconia LEGMi281a and Hortaea LEGMi415c. Two strains exhibited cellobiase and chitinase activity, one strain exhibited cellulase activity, and one exhibited laccase production. None of the species exhibited lipase or peroxidase activity, and no clear surfactant activity was detected. Whole-genome sequencing revealed significant size differences compared to reference genomes.
Conclusion: The enzymatic activities of the strains suggest they may play a role in the degradation of organic matter and nutrient recycling, similar to terrestrial fungal counterparts. The differences in genome sizes, with the genomes of Periconia LEGMi281a and Hortaea LEGMi415c being larger than the reference genomes, pave the way for future research into deepsea adaptations, reflected in genetic changes. Additionally, the strains were identified as having high biotechnological potential.
Draft genome sequences of four potential new species of the genus Bradyrhizobium isolated from root nodules of native legumes in Costa Rican forests
(2025-05-16) Fernández Vargas, Rachelle; Jiménez Alpízar, Sara; Leandro Arce, Valeria; Mendoza Guido, Bradd; Rojas Jiménez, Keilor Osvaldo
Here, we report the draft genome sequences of four Bradyrhizobium spp. isolates obtained from root nodules of the native legumes Pentaclethra macroloba, Chamaecrista nictitans, Erythrina fusca and Zygia engelsingii in tropical forests of Costa Rica. Genomes ranged from 8.6 to 9.8 Mb with GC contents between 62.8% and 63.8%. Phylogenomic analysis, along with average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) comparisons, confirmed that these isolates represent potential new species. ANI values ranged from 88.3% to 90.3%, and dDDH values from 28.8% to 41.8%, compared with their closest Bradyrhizobium species. Functional annotation revealed some genes related to nitrogen fixation (nifA, nifB, nifH) and nodulation capacity (nodB, nodC, nodJ). These results provide insights into the diversity and symbiotic capabilities of Bradyrhizobium in tropical ecosystems.
Narrativas sobre sexualidad y daño cerebral adquirido: cambios en vínculos, doble invisibilización y resignificaciones
(2025) Víquez Sancho, Daniella; Salazar Villanea, Mónica
La vivencia de la sexualidad de personas con DCA (daño cerebral adquirido) suele quedar en un plano secundario y en ocasiones es invisibilizada en la rehabilitación y tratamiento. En esta investigación cualitativa-exploratoria con análisis temático desde entrevistas, se profundiza en la disrupción de vínculos afectivos y también se encuentra la resignificación del placer en nuevas maneras.
Research on optimization techniques applied to precision agricultural processes supported by technology in Latin America: Opportunities and a route to follow
(2021-06-28) Brenes Carranza, José Antonio; Marín Raventós, Gabriela
The agricultural sector is facing significant challenges. Producing more food while consuming fewer resources like water, fertilizers, and arable land is probably the most important. Today more than ever, farmers need specialized technological tools to achieve this goal. It is possible to improve agricultural processes by practicing technology-supported precision agriculture. However, more technology development to optimize crop yield is needed worldwide. In this research, we conducted a systematic literature review in which we studied different articles that propose optimization for agricultural processes. We identified some proposals made from multiple researchers at distinct latitudes, focused on optimizing the irrigation and management of pests and diseases. Nevertheless, there are only a few studies that focus on optimizing the crop yield. They do that by controlling the different factors that can affect it. We also found out that only a few studies have been conducted in the Latin American region. Thus, these findings show areas in which there is still a lot of opportunities to contribute to the agro sector in Latin American countries.