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
virus infects w/
genome Bacterial colonies, each derived from a single cell
• 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
• carbon sources (eg. Lactose)
• colony shape, size and color
• resistance or sensitivity to antibiotics (Streptomycin)
• resistance to bacteriophange (Ton)
Distinguishing lac+ and lac- by using a red dye
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