The effects of Antibiotics on the

growth of bacteria introhttp://outreach.mcb.harvard.edu/animations/resistance7.swf

How do bacteria reproduce?

• Binary fission: to divide in halfhttp://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 plasmidIncludes an antibiotic resistanceGene, then the recipient bacteriumWill transform into An antibiotic resistant strain

http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter28/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/ccImages/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

LabPurpose: 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 Testhttp://www.cleanvideosearch.com/media/action/yt/watch?videoId=CaeQaAuG9pU