MMG301 1nd Edition Lecture 11 Outline of Last Lecture I. Growth mediumsOutline of Current Lecture II. Generation timeIII. Population growth in batch cultureIV. VBNCCurrent Lecture-generation time: the time that it takes a population to double-varies per species and conditions (ie temperature, pH)-takes much longer in nature than in a lab (lab provides perfect conditions for growth that do not exist in nature)-population growth in batch culture-batch culture: culture in a closed container, the top can be open to air if aerobic, but has some type of cap; growth medium not renewed during growth-nutrients: consumed (run out after time)-waste products: accumulate in the medium, can become toxic if accumulate too much-four distinct phases:-1. lag: metabolic adjustment-length of lag phase depends on how healthy the cells are and on the content of the medium-if you go from complex to defined medium, you will have a long lag phase-if you go from defined to complex medium, you will have a short lag phaseThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-2. exponential: cell and mass double in each generation-very uniform population-faster growth rate (higher slope) in rich/complex medium than in minimal or defined medium-exponential growth rates vary-microbial growth is under precise control-3. stationary: balance between cell division and death-metabolically active, non dividing-cause: nutrients ran out or waste accumulation became toxic-physiological adaptations to survival-cells become smaller-4. death: cells start dying -death phase is also exponential-viable count declines faster than turbidity (still counts dead cells)-surviving cells resume growth in fresh medium-viable but non-culturable (VBNC)-loss of ability to grow-still metabolically active and structurally intact-considered a survival mechanism-abundant in environments with nutrient limitations-human pathogens may exist as VBNC -examples: E. coli, Helicobacter pylori, Klebsiella pneumoniae, Salmonella spp., Shigella spp. Vibrio cholerae (all Gram-negative)-studies are being done to resuscitate VBNC species (bring them back to
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