Mapping of ure1, ure2 and ure3 markers in fission yeast

Ethyl Carbamate Formation Regulated by Lactic Acid Bacteria and Nonconventional Yeasts in Solid-State Fermentation of Chinese Moutai-Flavor Liquor

This study aimed to identify specific microorganisms related to the formation of precursors of EC (ethyl carbamate) in the solid-state fermentation of Chinese Moutai-flavor liquor. The EC content was significantly correlated with the urea content during the fermentation process (R² = 0.772, P < 0.01). Differences in urea production and degradation were found at both species and functional gene levels by metatranscriptomic sequencing and culture-dependent analysis. Lactobacillus spp. could competitively degrade arginine through the arginine deiminase pathway with yeasts, and most Lactobacillus species were capable of degrading urea. Some dominant nonconventional yeasts, such as Pichia, Schizosaccharomyces, and Zygosaccharomyces species, were shown to produce low amounts of urea relative to Saccharomyces cerevisiae. Moreover, unusual urea degradation pathways (urea carboxylase, allophanate hydrolase, and ATP-independent urease) were identified. Our results indicate that EC precursor levels in the solid-state fermentation can be controlled using lactic acid bacteria and nonconventional yeasts.

Nic1p, a relative of bacterial transition metal permeases in Schizosaccharomyces pombe, provides nickel ion for urease biosynthesis

The Schizosaccharomyces pombe genome sequencing project identified an open reading frame (O74869 and O74912, named Nic1p in the present study) with significant similarity to members of a family of bacterial transition metal permeases. These uptake systems transport Ni(2+) ion with extremely high affinity across the bacterial cytoplasmic membrane, but they differ in selectivity toward divalent transition metal cations. An S. pombe mutant harboring an interrupted nic1 allele (nic1-1) was strongly impaired in (63)Ni(2+) uptake in the presence of a high molar ratio of Mg(2+) relative to Ni(2+), conditions that reflect the natural situation. Under these conditions, the nic1-1 mutant contained only background activities of the nickel-dependent cytoplasmic enzyme urease and could not catabolize urea. Among a series of divalent transition metal cations tested (Cd(2+), Co(2+), Cu(2+), Mn(2+), and Zn(2+)), only Co(2+) caused considerable inhibition of Nic1p-mediated Ni(2+) uptake. On the other hand, experiments with (57)Co(2+) (at nm concentrations) did not show significant differences in Co(2+) uptake between the nic1-1 mutant and the parental strain. Our data suggest that Nic1p acts as a plasma-membrane nickel transporter in fission yeast, a finding that invites searches for isologous counterparts in higher eukaryotes.