Isolation and identification of killer yeasts from Psidium gujava

Abstract

Killer yeasts produce mycocins, the extracellular glycoproteins that possess wide-ranging antimicrobial, therapeutic, and biocontrol qualities. They are omnipresent and compete with the sensitive strains in their ecological niches. The fact that they are not harmful to the Homo sapiens has caught the attention of academicians and industrialists in recent decades. In this study, we isolated six killer yeasts from the perennial fruit Psidium gujava. The halotolerant capability is exploited for isolating killer yeasts from the guava brought from local markets of Davangere, Karnataka, India. The isolates are urease negative and did not produce germ tubes when incubated in human serum, indicating that they are avirulent. The isolates are characterized based on their morphological, microscopic, biochemical, and molecular tests. The molecular identification using 18s rDNA sequencing revealed that the isolates consisted of two strains of Candida orthopsilosis and four strains of Pichia fermentans. This study aids to explore substitute therapies against the raising antimicrobial resistance incidences, which has become a global threat of the century.