Pichia membranifaciens

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1. Classification

a. Higher order taxa

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2. Description and significance

Describe the appearance, habitat, etc. of the organism, and why you think it is important.

• Include as many headings as are relevant to your microbe. Consider using the headings below, as they will allow readers to quickly locate specific information of major interest*

3. Genome structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence?

4. Cell structure

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5. Metabolic processes

Describe important sources of energy, electrons, and carbon (i.e. trophy) for the organism/organisms you are focusing on, as well as important molecules it/they synthesize(s).

6. Ecology

P. membranifaciens can be found in a various types of environments. While Pichia membranifaciens are most notably known for creating biofilms on various alcohol products, they can also be found in fruit skins, cheese, olive brines, and baking products4,17, 18. With an ethanol tolerance of 11%, they often reside in alcohol distilleries and are involved in all stages of the fermentation process2. Considering the fact that this yeast is commonly found in outdoor environments, it is a mesothermophile which has an optimal growth temperature of 20℃5. P. membranifaciens is a well-known halotolerant for it optimally grows at a sodium chloride concentration of 3M5. For this reason, Pichia membranifaciens is commonly found in olive brines16. The following species is also osmotolerant and acidophilic, with its optimal pH conditions being around a 4.05. It has also been demonstrated that P. membranifaciens is capable of growing in the presence of common growth inhibitors such as acetate10.

7. Pathology

Pichia membranifaciens, like many species in the Pichia genus, is capable of secreting toxins which kill other yeasts species that are sensitive to these toxins. Pichia membranifaciens themselves are immune to the lethality of these toxins, allowing them to thrive5. These killer toxins, PKMT and PKMT2, help eliminate similar yeast species that compete with P. membranifaciens17. Because of this adaptation, P. membranifaciens remains a dominant yeast in many different fermentation processes, especially in grapes and olives6,16. PMKT and PMKT2 kill other yeast and filamentous fungi by binding to β-D-glucans and mannoproteins respectively on the host cell’s surface12,13. PMKT also triggers a secondary receptor called Cwp2p (a plasma membrane receptor) in the cytoplasm of sensitive cells12. These toxins act by lowering the intracellular pH, hence triggering the High Osmolarity Glycerol (HOG) pathway, which in turn creates pores that allow for an influx of ions into the cytoplasm12 . Low concentrations of either toxin (PMKT/PMKT2) results in cell death; however, high concentrations of PMKT2 does not trigger apoptosis but arrests yeast cells in early S-phase instead12. Contrary to the species’ high halotolerance, P. membranifaciens’ killer activity correlates with significantly lower salt concentrations, with its optimal killer activity being at a salt concentration of 0-0.5M5. Pichia membranifaciens is also sensitive to the toxins of various other killer yeasts. Some of these killer yeasts include Pichia jadinii, Kluyveromyces lactis, and Pichia anomala, all of which are considered highly active killer yeasts5.

8. Current Research

Include information about how this microbe (or related microbes) are currently being studied and for what purpose

9. References

It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.