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BIOL 205
Ian D Chin- Sang

BIOL205:week 4, lecture 12 Everything you wanted to know about bacteria sex but were afraid to ask… Why study bacteria? • cheap, abundant, fast life cycle! • Biologically important, most numerous organism on the planet • Contribute to recycling of nutrients eg. Nitrogen, Sulfur, Carbon • Agents of human, animal and plant disease. • Non harmful bacteria part of our bodily function (probiotics). • Useful in the synthesis of a wide range of organic products. • Basic understanding of molecular biological processes: • Replication, transcription, translation. • How genes work? Gene regulation and gene products. • Modern DNAtechnologies are all derived from bacteria and their viruses. Bacteria exchange DNAby several processes Ifcompetent:cantake up DNAfrom envmt (transformation) donatingplasmid:extra donating chromosomalDNA chromosomalDNA virus infects w/ some ofbacterial genome Bacterial colonies, each derived from a single cell w/ nutrients Bacterial phenotypes • wild-type bacteria are prototrophs—they can grow on minimal media (just a carbon source for energy and water) • auxotrophic mutants can be obtained—they can grow only when supplemented with certain cellular components: i.e. amino acids (eg. Met,Arg, Pro, Thr, Gly, His), vitamins (eg. Biotin and thiamine) • carbon sources (eg. Lactose) • colony shape, size and color • resistance or sensitivity to antibiotics (Streptomycin) r • resistance to bacteriophange (Ton) Distinguishing lac+ and lac- by using a red dye Red:wild type Yellow:cannot process lactose → can't cleave lactose whencleaved:red How would you isolate a bacteria mutant that can’t grow on minus Arginine media ? • colonies that fail to grow on the minus arginine plates are potential arginine auxotrophs (mutant) Discovery of Bacterial conjugation: • do bacteria possess any process similar to sexual reproduction and recombination? • Joshua Lederberg and Edward Tatum (1946) discovered a sex-like process in what became the main model of bacterial genetics. Mixing bacterial
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