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BIO 325 September 23rd Lecture Notes

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BIO 325
Sanghamitra Mohanty

9/23 Lecture Monday, September 23, 2013 1:39 AM Since 1940s, many bacterial genes have been studied in details! Few reasons as to why we use bacteria: 1. Easy to grow in multiples in short time with many offsprings 2. Genomes are pretty simple and mostly it's single chromosome 3. Bacteria reproduces asexual 4. Genome is haploid (1 copy of each gene --- and if it has any mutations it will be easily seen) 5. They're medically important o Produced many diseases in us so it's important for us to learn about them --- DRUG RESISTANT BACTERIA Minimal medium - has just the water, a little bit of sugar and mineral salts  Wild-types can grow well on this (prototroph)  Auxotroph - lost the ability to synthesize one or more essential compounds, and must be provided with them in the medium if it's to grow o Can't grow in minimal medium  Additional nutrients must be added in order to grow on the minimal medium  Or you can use supplement minimal medium or complex medium Selection - growth of the organism under conditions in which only the mutant of interest grows well, whereas the wild type does not Adaptation hypothesis - proposes that the interaction of bacteriophage and bacterium is essential to the bacterium's acquisition of immunity to the phage Spontaneous mutation - occurs in the presence or absence of phage is considered the primary source of genetic variation in bacteria  Rate is slow  Mutation usually happens at one loci (doesn't happen simultaneously) Induced mutation - can happen at any rate at any loci  Stress factors: bacteriophage, antibiotics (specifically for bacteria), and disinfectants o Ex: bacterial wipes nurses use o Induces resistance in bacteria! o Physicians are advised not to prescribe antibiotics Bacteria has THREE GROWTH PHASES:  Lag phase o Proteins and enzymes made in order to use for growth  Log phase o Transformation - process of genetic exchange between the bacteria  Stationary phase o Threshold of 10 /mL  Overcrowding  Depletion of nutrients  Depletion of oxygen  NO ACTIVE GROWTH IS SEEN!!!  When depletion is complete, that's when the down hill slope comes in *there's actually a 4th phase called death phase where it starts slopping downwards after stationary phase How do you count the number of cells? COUNT THE COLONIES  Each colony is taken as one bacteria cells  Countable plate - 30-300 colonies per plate o You have to serially dilute your suspension o You have to see which dilution gives you the countable plate MEANS OF GENETIC RECOMBINATION IN BACTERIA: *normally these are done in the lab but it happens inside nature and the human body  Conju
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