Morphological, Biochemical and Molecular Identification of the Yeast Levica 25: A Potential Ruminal Microbial Additive

摘要

Levica 25 is a biological agent isolated from bovine rumen with potential use as an activator ofruminal fermentation because it stimulates total and cellulolytic populations and it reduces methanogenesis,which mitigates methane emissions to the environment. The aim of this study was to characterize the strainLevica 25 using morphological, biochemical and molecular methods. Morphological and biochemical studiesshowed that this strain did not produce germ tubes, grew at a temperature of 45°C, absorbed cupric sulfate,reduced bismuth sulfite, was sensitive to actidione, formed blue colonies in the presence of chromogenic agentsand presented profile number 2556175 in the API20C AUX4 system. These data suggested that Levica 25 maybe a strain of Candida tropicalis. However, analysis of the D1/D2 region of rDNA26S demonstrated that Levica25 has only 96% homology with C. tropicalis and there are 11 substitutions involving 575 bases, which isequivalent to a 1.9% difference between the two sequences. Thus, Levica 25 and C. tropicalis are different,albeit very close, species located in the same clade in the phylogenetic tree. The present results suggested thatLevica 25 is a new strain belonging to the genus Candida, which is very close to C. tropicalis.