[Induced biosynthesis of fengycin and surfactin in a strain of Bacillus amyloliquefaciens with oomyceticidal activity on zoospores of Phytophthora capsici]. / Biosíntesis inducida de fengicina y surfactina en una cepa de Bacillus amyloliquefaciens con actividad oomiceticida sobre zoosporas de Phytophthora capsica.

A potential alternative to the use of chemical products with oomyceticidal action for the control of Phytophthora capsici in vegetables is the use of antimicrobial metabolites, biosynthesized in Bacillus species. The objective of this study was to induce the biosynthesis of lipopeptides in Bacillus amyloliquefaciens KX953161.1 by using glutamic acid, iron, cellulose, chitin, or inactive Colletotrichum spp. cells. The in vitro oomyceticidal effect of the bacterial lipopeptides on zoospores of Phytophthora capsici was evaluated. The lipopeptides identified and quantified in the crude extracts by high performance thin layer chromatography (HPTLC) were fengycin and surfactin. The bacterial culture with inactive fungal cells yielded the greatest biosynthesis of lipopeptides, at 1847.02± 11.8 and 2563.45± 18.4 µg/ml of fengycin and surfactin, respectively and the treatments that obtained lower production of these lipopeptides, were those to which iron and cellulose were added with 608.05 ± 22.6 and 903.74± 22.1; 563.31± 11.9 and 936.96± 41.1 µg/ml for fengicin and surfactin, respectively. The lipopeptide extracted showed 100% germination inhibition on zoospores of P. capsici, revealing encystment, malformations in the germ tube and cellular degradation. Lipopeptides have the potential to control P. capsici; however, the biosynthesis of these lipopeptides requires further study to determine their biological mode of action and optimize lipopeptide performance and profile.

Diversity of mucoralean fungi in soils of papaya (Carica papaya L.) producing regions in Mexico.

Mexico is the fifth largest producer of papaya worldwide and has recently reported problems with mucoralean fungi in this crop. These fungi are considered saprophytes in the soil and are ubiquitous in nature. In this work, they were isolated from soil in regions of intensive papaya cultivation in Mexico. Collections were made in the states of Colima, Oaxaca and Veracruz in Apr 2016. A total of 72 mucorales fungal isolates was obtained and morphologically characterized and then molecular characterization (28S ribosomal region) of 25 representative isolates was carried out. Phylogenetic analysis of the sequences confirmed the presence of the species Gilbertella persicaria, Rhizopus oryzae, Rhizopus stolonifer, Mucor circinelloides and Mucor hiemalis, which cause soft rot in papaya fruits, therefore, spores of these fungi found in the orchard soils can be considered as a constant source of contamination that affects healthy fruits. Additionally, Choanephora cucurbitarum, Mucor ellipsoideus, Rhizopus homothallicus, Rhizopus microsporus, Rhizopus schipperae, Lichteimia ramosa, Gongronella butleri, Cunninghamella bertholletiae and Cunninghamella blakesleeana were identified which are considered to have agricultural, biotechnological and medical importance.