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Transcript
The effects of Antibiotics on the growth of bacteria intro http://outreach.mcb.harvard.edu/animations/resistance7.swf How do bacteria reproduce? • Binary fission: to divide in half http://www.ryancshaw.com/Files/micro/Animations/BacterialGrowth/PLAY _bacterial_growth.html How do bacteria reproduce? How do bacteria reproduce? • Parent cell produces genetically identical daughter cells –unless mutation changes DNA (rare but happens) How do bacteria reproduce? • Exponential growth –bacteria at appropriate temperature w/ nutrients can reproduce every 20 minutes How do bacteria reproduce? • Exponential growth –In 24 hours 1 cell --> 4,722,400,000,000,000,000,000 How do scientists grow bacteria? • Petri Dish with solid agar nutrition How do scientists grow bacteria? • Flask or test tube with liquid nutrients Antibiotics • Drugs produced by bacteria or fungi to treat people with bacterial infections (does not treat viral infections) Antibiotics • Most antibiotics come from microorganisms –chemical warfare to keep foreign microbes out of territory and away from food Antibiotics • Example: different Streptomyces strains which naturally grow in soil produce: streptomycin, erythromycin and tetracyline Antibiotic resistant bacteria • Bacteria that have a gene or genes that allow them to survive the antibiotic Antibiotic resistant bacteria • How do individual bacteria develop resistance? –Random mutation hidden in genes Antibiotic resistant bacteria • And “bacteria sex”– conjugation: bacteria of different or same species can exchange pieces of DNA sometimes including mutation If mobile plasmid Includes an antibiotic resistance Gene, then the recipient bacterium Will transform into An antibiotic resistant strain http://highered.mcgrawhill.com/sites/9834092339/student_view0/chapte r28/bacterial_conjugation.html Antibiotic resistant bacteria • Resistance not always 100% Antibiotic resistant bacteria • 2 types of bacteria –gram (+): stain violet because of cell wall components – http://www.microbelibrary.org/microbelibrary/files/ccIm ages/Articleimages/keen/Gramstainkeen.htm Antibiotic resistant bacteria • 2 types of bacteria –gram (-): stain red because of cell wall components. This cell wall can be toxic and more resistant to antibiotics Antibiotic resistant bacteria Lab Purpose: to determine which antibiotic is the most effective in limiting the growth of the bacterial species Bacillus subtilis (that was grown from a peppercorn source) BioRad Modified Kirby-Bauer Test http://www.cleanvideosearch.com/media/action/yt/watch?videoId=CaeQaAuG9pU