BIO 226 Lecture Notes - Lecture 5: Organic Growth, Microorganism, Methylene Blue
20 Sep 2016
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When microbes grow, looking for number of cells (not their size) The more a microbe gets something that it loves (-phile), the more it becomes tolerant of it. Different microbes have different growth requirements, like temp, ph, osmotic pressure (salt concentration) o. Oxygen (some in atmospheric oxygen at 21% but some others live under different oxygen) o. Psychrotrophs: can grow in refrigerator (main one is listeria munocytogenes that gets in lunch meats or cheeses that can cause problems for pregnant women but isn"t that bad) Optimum growth temperature (mesophiles that are pathogens like e. coli or. Some can grow in a ph of 1 which is crazy! Hypertonic environments increase salt or sugar, cause plasmolysis. Addition of salts (or other solutes) can be used to preserve foods: halophiles salt loving. Extreme or obligate halophiles require high osmotic pressure. Organisms in the dead sea require 30% salt. Able to grow at 2% salt; a few can tolerate 15% salt o.
