Lecture 10 - Bacterial Transcription.docx

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University of Toronto St. George
Cell and Systems Biology
William Navarre

MGY377H © Lisa | Page 13 L E C T U R E 1 0 : B A C T E R I A L T R A N S C R I P T I O N 1. gnotobiotic (germ-free) mice in microbiota studies 1. don’t have a microbiota 2. enables him to put in exogenous bacteria from other species 3. and study the effect on the physiology & biology of the mouse 4. early study: take poop from obese ppl and lean ppl and put into mice 1. found obese microbiota mice gained weight 2. lean microbiota mice gained little weight 5. criticism: twins are not involved 6. he has subsequent studies w twins w discordance in obesity (one was obese one was not) 1. took poop from discordant twins into qnotobiotic mice 2. lean – mice no difference in BMI 3. obese – mice increased in BMI 7. mice are cobrophagic (eat their own poop), if you cohouse mice, they eat each other’s poop 8. he paired mice that received Ob microbiota ,and they were obese 9. lean mice together stayed lean 10. ob + ln – mice that strated w Ln stayed lean, ob who also ate ln microbiota started to lose weight 1. thus this is a transferable phenotype 2. less fiversity in Ob microbiota (due to i.e. antibiotics used, diet had nutrients that absorbed in small intesting and starved large intestine bacteria) 3. Ob mice that ate Ln gained flora that it didn’t have before 2. cellulose has only beta-bonds (no alternating alpha bonds) 3. DNA doesn’t do much, it only does something when it is transcribed into RNA and translated to protein 4. DNA to RNA is two-way, ribosome to protein is a one-way path 5. a genomes doesn’t have all genes expressed all the time in a cell, one cell may be expressing one gnese and others may be expressing thougsands of genes 6. this requires gene regulateion (turning on and off genes) 7. bacterial genes can be clusetered in operons 1. bacterial genomes don’t have a lot of junk DNA 2. gene 2, 3, 4 are all encoded by same mRNA (very close ORFs together) 3. operon: genes close toether that are regulated by the same promoter 4. gnee 2, 3, 4 maybe coregulated by the presence of glucose 8. regulons: a few operons that scatter aroudnthe chromosome that respond to the same signal (same transcription factor ex.presence of glucose – part of the glucose regulon), these genes are coordinated regulated in response to the same signal 9. promoters: regions of DNA that control the transcription o adjacent genes that don’t… 1. binds RNA polymerase to initiate the trancrition of an adjacent gene 10. bacteria promotes have common distinguisihign characteristics 1. -10 element 2. element upstream of - 10 (short “extended -10” sewuenct) 3. -35 element 4. UP element 11. reminder: transcription doenst always start when translation starts 1. translation may start hundreds of nucleotides down from site of initial transcription 12. if you align all of these, together,69 = at this position, 69%, a T would be found MGY377H © Lisa | Page 23 1. percentatge of time you would find that base 2. no naturally occurring promoter that matches the consensus perfectly has ever been found (no bacteria has that exact sequence) 13. recA promoter comes close to being the same as consensus 14. araBAD (controls arabinose utilization) a lot of mismatches and bad spacing (suboptimal) why is uit supobtimla? 1. something that is suboptimal give you a place where you can regulate it 2. also give chance to finetune the expression of each gene by playing with each elements 3. .. 15. why aren’t all promoters opti
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