12 The History of Life

UNIT 4 BIOZINEFighting BackSome scientists are trying to develop ways to treatpatients without killing the bacteria that are makingthem sick. Instead, they target the toxins produced bybacteria. If the bacteria are not harmed by thetreatment, no selective pressure is produced. Scientistshope that by using this approach, bacteria willbe slower to evolve defense mechanisms against theantibiotics. Other scientists hope to fight back byusing bacteria’s ancient rival, bacteriophages, whichare viruses that infect bacteria.CAREERSEvolutionary Biologistin ActionDR. RICHARD LENSKITITLE Professor, Microbial Ecology,Michigan State UniversityEDUCATION Ph. D., Zoology, Universityof North Carolina, Chapel HillIf you want to observe evolution in action, you mustfind populations that reproduce quickly. Dr. RichardLenski, a professor at Michigan State University, hasdone just that. Dr. Lenski studies populations of E. colibacteria, which he grows in flasks filled with a sugarybroth. These bacteria produce about seven generationseach day. Dr. Lenski has now observed more than30,000 generations of E. coli.The rapid rate of E. coli reproduction allows Dr.Lenski to watch evolution take place. Dr. Lenski cansubject each generation of bacteria to the sameenvironmental stresses, such as food shortages orantibiotics. He can then compare individuals from morerecent generations with their ancestors, which he keepsin his laboratory freezer. By comparing generations inthis way, Dr. Lenski can study how the population hasevolved.When Dr. Lenski began his research in 1988, watchingevolution in action was still new. Now, manyevolutionary biologists are following in his footsteps. at CLASSZONE.COMTECHNOLOGYNew Drug Delivery SystemResearchers at the University ofSouth Florida decided to takeon one of the most difficultbacterial infections of all,methicillin-resistant staph.They have developed a newclass of antibiotics along witha new way to deliver it tothe bacteria.• Antibiotics are bonded to nano-sized plastic balls.(One nanometer is one millionth of a millimeter.)• The “nanoballs” are dissolved in water, and thesolution is released into the patient’s bloodstream.When the nanoballs reach the bacteria, the bacteriaeat them.• Nanoballs release antibiotics inside bacterial cells.Because the bacteria are “eating” the nanoballs, cell walladaptations that once kept antibiotics out are nolonger an obstacle. at CLASSZONE.COMUnanswered QuestionsSome important research questions involving drugresistantbacteria include the following:• Can plasmids or bacteriophages be used in vaccinesto fight bacteria?• Are bacteria being exposed to antibiotics in sewagesystems and evolving resistant strains there?• How do antibacterial soaps and household cleanerscontribute to the evolution of drug-resistantbacteria?• Can drug-resistant bacteria be transferred fromdomestic animals to humans through food? at CLASSZONE.COMstaph bacteria392 Unit 4: Evolution