Response Of Saccharomyces Cerevisiae And Yarrowia Lipolytica On The Stimulation Of Lipopolysacchairdes

Lipopolysaccharide (LPS), known as endotoxin, is an important component of the outermembrane in most Gram-negative bacteria. LPS can be recognized by TLR4/MD-2receptorcomplex to induce serious immune response that is closely related to some human diseases.Some plant cells can also sense LPS and resist pathogenic bacteria invasion through plantdefense. However, similar LPS-infected mechanism has not been clarified in lower eukaryotessuch as yeast. In this study, Saccharomyces cerevisiae and Yarrowia lipolytica are chosen toinvestigate the response of yeast on the stimulation of LPS, by using methylene blue staining,flow cytometry and transcriptome analysis. The major results are listed below:(1) Using the method of KDO quantification to screen LPS-absorbed strains isolatedfrom fermented food, we found strains CSW1and CSW2could absorb LPS, and theabsorbability of CSW1is stronger than that of CSW2. Based on the sequence analysis of18srDNA, CSW1and CSW2were identified as Yarrowia lipolytica and Zygosaccharomycesrouxii, respectively. Using the fluorescence tracer (FITC-LPS), we compared that theabsorbability of different yeast strains.(2) Yeast cells such as S. cerevisiae, Y. lipolytica and Z. rouxii can be stained bymethylene blue after co-incubated with LPS. Generally, number of cells stained by methyleneblue increased with the increase of LPS concentration. Interestingly, all of the cells survivedthe staining of methylene blue.(3) Based on the analysis of flow cytometry, phosphatidylserine exposure happened inboth LPS-stimulated S. cerevisiae and Y. lipolytica cells, but metacaspase activation was notobserved. In LPS-stimulated S. cerevisiae cells, mitochondrial membrane potential increasedwithout obvious ROS abundance; by contrast, in LPS-stimulated Y. lipolytica cells, the ROSaccumulation was detected, but mitochondrial membrane potential was not increased.(4) Transcriptome analysis was performed for S. cerevisiae cells cultivated with orwithout LPS. The results showed that cell wall and membrane component, antioxidant activity,peroxisome and lipid metabolism were significantly affected in LPS-stimulated cells. Inaddition, LPS can induce signal transduction or vesicular transport related to apoptosis orautophagy, involving membranous organelles such as mitochondria, endoplasmic reticulumand vacuole.In summary, stress restoration or cell defense-like pathways might be the survivalmechanism for S. cerevisiae and Y. lipolytica cells under apoptosis-like signal transductionstimulated by LPS. This study provides experimental evidence for the research of yeastresponse to LPS stimulation, and the results should be useful for LPS-related immuneresearch.