About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.
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What are the differences between the petite and grande strain of Brewer's yeast (S. cerivisiae)?
I can only find the lack of mitochondria and hence anaerobic metabolism of petite strain as a difference.
Are there any more?
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with the 1,500 species currently describe estimated to be only 1% of all yeast species. Most reproduce asexually by budding, although a few do so by binary fission. Yeasts are unicellular, although some species with yeast forms may become multicellular through the formation of a string of connected budding cells known as pseudohyphae, or false hyphae, as seen in most molds. Yeast size can vary greatly depending on the species, typically measuring 3–4 µm in diameter, although some yeasts can reach over 40 µm.
The yeast species Saccharomyces cerevisiae has been used in baking and fermenting alcoholic beverages for thousands of years. It is also extremely important as a model organism in modern cell biology research, and is one of the most thoroughly researched eukaryotic microorganisms. Researchers have used it to gather information about the biology of the eukaryotic cell and ultimately human biology. Other species of yeast, such as Candida albicans, are opportunistic pathogens and can cause infections in humans. Yeasts have recently been used to generate electricity in microbial fuel cells, and produce ethanol for the biofuel industry.
The of active mitochondria and oxidative metabolism is shown to be essential to maintain low inhibition levels by ethanol of the growth rate ( ), fermentation rate (v) or respiration rate ( ) of Saccharomyces cerevisiae wild type strain S288C. Cells which have respiratory metabolism show K i (ethanol inhibition constant) values for , v and , higher (K i>1 M) than those of petite mutants or grande strains grown in anaerobiosis (K i=0.7 M). In addition, the relationship between or v and ethanol concentration is linear in cells with respiratory metabolism and exponential in cells lacking respiration. When functional mitochondria are transferred to petite mutants, the resulting strain shows K i values similar to those of the grande strain and the inhibition of and v by increasing ethanol concentrations becomes linear.
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