Identification and Characterization of Dmct: A Cation Transporter in Yarrowia lipolytica Involved in Metal Tolerance.

Yarrowia lipolytica is a dimorphic fungus used as a model organism to investigate diverse biotechnological and biological processes, such as cell differentiation, heterologous protein production, and bioremediation strategies. However, little is known about the biological processes responsible for cation concentration homeostasis. Metals play pivotal roles in critical biochemical processes, and some are toxic at unbalanced intracellular concentrations. Membrane transport proteins control intracellular cation concentrations. Analysis of the Y. lipolytica genome revealed a characteristic functional domain of the cation efflux protein family, i.e., YALI0F19734g, which encodes YALI0F19734p (a putative Yl-Dmct protein), which is related to divalent metal cation tolerance. We report the in silico analysis of the putative Yl-Dmct protein's characteristics and the phenotypic response to divalent cations (Ca2+, Cu2+, Fe2+, and Zn2+) in the presence of mutant strains, Δdmct and Rdmct, constructed by deletion and reinsertion of the DMCT gene, respectively. The absence of the Yl-Dmct protein induces cellular and growth rate changes, as well as dimorphism differences, when calcium, copper, iron, and zinc are added to the cultured medium. Interestingly, the parental and mutant strains were able to internalize the ions. Our results suggest that the protein encoded by the DMCT gene is involved in cell development and cation homeostasis in Y. lipolytica.

Cryptococcus spp. isolation from excreta of pigeons (Columba livia) in and around Monterrey, Mexico.

The presence of Cryptococcus spp. has been reported in Mexico's capital city; however, to our knowledge there are no reports of its presence in the state of Nuevo León located in northeast Mexico. This is presumed to be because the hot and dry climate in this region does not favor cryptococcal proliferation. This study confirmed the presence of C. neoformans and C. albidus in 20% (10/50) of randomly selected fecal samples of pigeons (Columba livia) in the Monterrey metropolitan area. The presence of this yeast in the state of Nuevo León is proof of its adaptation to the typically hot climate of the area and is consistent with recent reviews of cryptococcosis cases in several local hospitals. The two species were identified and characterized through microbiological tests and molecular identification by DNA extraction and PCR amplification of highly conserved 18S ribosomal DNA using ITS1 and ITS2 as target regions. The PCR products were sequenced and compared with those reported in GenBank.