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Staphylococcus aureus is one of the agents of bovine mastitis of hardest control due to a complex pathogenesis comprising a variety of virulence factors, which ensures its persistence in the mammary gland, causing significant health and economic losses. Therefore, understanding the pathogenesis of this agent is imperative. Galleria mellonella has stood out as an invertebrate animal model for the study of infectious diseases that affect several hosts. This work aimed to evaluate G. mellonella larvae as an experimental model for the study of virulence phenotypes in an S. aureus population isolated from bovine mastitis. Thirty genetically divergent S. aureus strains were chosen based on PFGE analysis. After experimental infection, larvae survival rates, bacterial growth in hemolymph, melanization intensity of the dorsal vessel, and histological characteristics of the infected tissues were evaluated. The G. mellonella model showed a clear diversity in the S. aureus pathogenicity pattern, allowing the differentiation of strains with virulence phenotypes ranging from high to low degrees. Histological analysis confirmed that the strains tested were capable of inducing the formation of nodules and melanization spots in the dorsal vessels of the larvae in different magnitudes. The strains 16S-717, 19C-828, and 31S-1443 presented the highest virulence intensity among the bacteria tested and will be used further for the generation of S. aureus mutant populations to prospect genetic targets aimed to develop control strategies of bovine mastitis. Altogether, our results suggest that G. mellonella is an attractive and low-cost animal model for characterizing virulence phenotypes of large S. aureus populations., (© 2023. The Author(s) under exclusive licence to Sociedade Brasileira de Microbiologia.)

The monoterpenoid 1,8-cineole is obtained from the leaves of Eucalyptus globulus and it has important biological activities. It is a cheap natural substrate because it is a by-product of the Eucalyptus cultivation for wood and pulp production. In this study, it was evaluated the potential of three filamentous fungi in the biotransformation of 1,8-cineole. The study was divided in two steps: first, reactions were carried out with 1,8-cineole at 1 g/L for 24 h; afterwards, reactions were carried out with substrate at 5 g/L for 5 days. The substrate was hydroxylated into 2-exo-hydroxy-1,8-cineole and 3-exo-hydroxy-1,8-cineole by fungi Mucor ramannianus and Aspergillus niger with high stereoselectivity. Trichoderma harzianum was also tested but no transformation was detected. M. ramannianus led to higher than 99% of conversion within 24 h with a starting high substrate concentration (1 g/L). When substrate was added at 5 g/L, only M. ramannianus was able to catalyze the reaction, but the conversion level was 21.7% after 5 days. Both products have defined stereochemistry and could be used as chiral synthons. Furthermore, biological activity has been described for 3-exo-hydroxy-1,8-cineol. To the best of our knowledge, this is the first report on the use of M. ramannianus in this reaction.

The β-ketoester benzyl acetoacetate was enantioselectively reduced to benzyl (S)-3-hydroxybutanoate by seven microorganism species. The best result using free cells was obtained with the yeast Hansenula sp., which furnished 97% ee and 85% of conversion within 24 h. After immobilization in calcium alginate spheres, K.marxianus showed to be more stable after 2 cycles of reaction.