Nitric oxide increases biofilm formation in by activating the transcriptional factor Mac1p and thereby regulating the transmembrane protein Ctr1.

BACKGROUND

Biofilms with immobilized cells encased in extracellular polymeric substance are beneficial for industrial fermentation. Their formation is regulated by various factors, including nitric oxide (NO), which is recognized as a quorum-sensing and signal molecule. The mechanisms by which NO regulates bacterial biofilms have been studied extensively and deeply, but were rarely studied in fungi. In this study, we observed the effects of low concentrations of NO on biofilm formation in Transcriptional and proteomic analyses were applied to study the mechanism of this regulation.

RESULTS

Adding low concentrations of NO donors (SNP and NOC-18) enhanced biofilm formation of in immobilized carriers and plastics. Transcriptional and proteomic analyses revealed that expression levels of genes regulated by the transcription factor Mac1p was upregulated in biofilm cells under NO treatment. promoted yeast biofilm formation which was independent of flocculation gene . Increased copper and iron contents, both of which were controlled by Mac1p in the NO-treated and -overexpressing cells, were not responsible for the increased biofilm formation. , one out of six genes regulated by , plays an important role in biofilm formation. Moreover, and contributed to the cells' resistance to ethanol by enhanced biofilm formation.

CONCLUSIONS

These findings suggest that a mechanism for NO-mediated biofilm formation, which involves the regulation of expression levels by activating its transcription factor Mac1p, leads to enhanced biofilm formation. The role of protein in yeast biofilm formation may be due to the hydrophobic residues in its N-terminal extracellular domain, and further research is needed. This work offers a possible explanation for yeast biofilm formation regulated by NO and provides approaches controlling biofilm formation in industrial immobilized fermentation by manipulating expression of genes involved in biofilm formation.