[Identification and antifungal activity of halophilic bacteria isolated from saline soils in Campeche, México]. / Identificación y actividad antifúngica de bacterias halófilas aisladas de suelos salinos en Campeche, México.

Phytopathogenic fungi Alternaria alternata and Colletotrichum gloeosporioides cause diseases in plant tissues as well as significant postharvest losses. The use of chemical fungicides for their control has negative effects on health and the environment. Secondary metabolites from halophilic bacteria are a promising alternative for new antifungal compounds. In the present study, halophilic bacteria were isolated and characterized from two sites with saline soils called branquizales in Campeche, Mexico. A total of 64 bacteria were isolated. Agrobacterium, Bacillus, Inquilinus, Gracilibacillus, Metabacillus, Neobacillus, Paenibacillus, Priestia, Staphylococcus, Streptomyces and Virgibacillus were among the identified genera. The antifungal potential of the culture supernatant (CS) of 39 halophilic bacteria was investigated against C. gloeosporioides and A. alternata. The bacteria showing the greatest inhibition of mycelial growth corresponded to Bacillus subtilis CPO 4292, Metabacillus sp. CPO 4266, Bacillus sp. CPO 4295 and Bacillus sp. CPO 4279. The CS of Bacillus sp. CPO 4279 exhibited the highest activity and its ethyl acetate extract (AcOEt) inhibited the germination of C. gloeosporioides, with IC50 values of 8,630µg/ml and IC90 of 10,720µg/ml. The organic partition of the AcOEt extract led to three fractions, with acetonitrile (FAcB9) showing the highest antifungal activity, with values exceeding 66%. Halophilic bacteria from 'blanquizales' soils of the genus Bacillus sp. produce metabolites with antifungal properties that inhibit the phytopathogenic fungus C. gloeosporioides.

Nesting substrates and nest density of stingless bees in the Petenes Biosphere Reserve, Mexico / Sustratos de nidificación y densidad de nidos de abejas sin aguijón en la reserva de la biósfera de los petenes, méxico

RESUMEN Las abejas sin aguijón (ASA) son organismos relevantes en los ecosistemas por su desempeño como polinizadores. En México, la mayor diversidad de ASA se encuentra en el sureste. En este estudio se determinaron las especies de ASA y densidad de nidos en dos sitios con diferente perturbación dentro de la Reserva de la Biósfera de los Petenes (RBLP) Campeche (México). Asimismo, se identificaron los sustratos y las especies arbóreas de nidificación. En total se realizaron diez muestreos en transectos entre los meses de enero a mayo de 2018. Se registraron 56 nidos pertenecientes a ocho especies diferentes de ASA (Cephalotrigona zexmeniae, Frieseomelitta nigra, Lestrimellita niitkib, Nannotrigona perilampoides, Partamona bilineata, Plebeia frontalis, Scaptotrigona pectoralis y Trígona fulviventris). Las especies con mayor número de nidos correspondieron a F. nigra (41,07 %) y S. pectoralis (28,57 %). No se encontraron diferencias significativas en la densidad de nidos entre los sitios Hecelchakán (2,15 nidos/ha) y Calkiní (0,19 nidos/ha). El sustrato preferido para anidación son las cavidades en árboles vivos (78,57 %). En total 15 especies arbóreas fueron identificadas como sustrato de nidificación y la especie más abundante correspondió a Crescentia cujete (n = 18, 40,9 %). El grado de perturbación tuvo poco efecto en el número y densidad de nidos de ASA, sin embargo, en general, la RBLP presentó una composición de especies y densidad de nidos reducida. Por lo tanto, este estudio permitió establecer las bases para futuros estudios sobre estrategias de manejo y conservación de estas especies para evitar su desaparición en la RBLP.

ABSTRACT Stingless bees (ASA) are relevant organisms in ecosystems because of their performance as pollinators. In Mexico, the higher diversity of ASA is found in the southeast. In this study, the ASA species and nest density of nests were identified at two sites with different disturbances (Hecelchakán and Calkiní) within the Petenes Biosphere Reserve (RBLP), Campeche (Mexico). Also, the substrates and the nesting tree species were identified. In total, ten sampling transects were performed between January and May 2018. In total 56 nests belonging to eight different species of ASA (Cephalotrigonazexmeniae, Frieseomelitta nigra, Lestrimellita niitkib, Nanotrigonaperilampoides, Partamona bilineata, Plebeia frontalis, Scaptotrigona pectoralis and Trigona fulviventris) were found. The species with the highest number of nests corresponded to F. nigra (41.07 %) and S. pectoralis (28.57 %). No significant differences were found in nest density between the Hecelchakán (2.15 nests/ha) and Calkiní (0.19 nests/ha) site. The preferred substrate for nesting is cavities in living trees (78.57 %). In total 15 tree species were identified as nesting substrate and the most abundant species corresponded to Crescentia cujete (n = 8, 40.90 %). The degree of disturbance had little effect on the number and density of ASA nest, however, in general, the RBLP presented low species composition and nest density. Therefore, this study allowed to establish the bases for future studies on management and conservation strategies of these species to avoid their loss in the RBLP.