BIO 1150 1st Edition Lecture 17Chapter 27 Topic Discussed: Bacteria and ArchaeaThree domains: Eukarya, Bacteria and ArchaeaTable 27.2 is important to reviewStructural and functional adaptations contribute to prokaryotic success- Unicellular- Small- Variety of shapes- Well organizedArchaea- “extremophiles”- Extreme halophiles- Halobacterium- Extreme thermophiles- Thermophilusaquaticus- Methanogens- responsible for methane output- Archaea - have polysaccharides and proteins but lack peptidoglycan in their wallsProteobacteria- Subgroups: Alpha, Beta, Gamma, Delta and Epsilon ProteobacteriaOther Bacteria- Spirochetes- Chlamydias- Cyanobacteria- Gram-Positive BacteriaCell-Surface Structures- Cell wall- Bacteria have peptidoglycan in their walls- All proteobacteria are gram negativeGram-positive bacteria include:- Actinomycetes- decompose soil- Bacillus anthracis- causes of anthrax- Clostridium botulinum- causes of botulism- Some Staphylococcus and Streptococcus- can be pathogenic- Mycoplasmas- the smallest known cells Gram positive- peptidoglycan traps crystal violet, stain stays purple after rinsedGram negative- ends up deep red, has two plasma membraneCell surface structures- Capsule (slime layer)- Fimbriae- receive tactile stimulus- Pili- long hairsMotility- Taxis- propeller- Chemotaxis-movement in a direction due to chemical stimulus- Flagella –Evolutionary “exaptations” from secretory protein systemInternal Organization and DNA- Lack compartmentalization- specialmembranes perform metabolic functions- DNA packaged in a circular chromosome in the nucleoid region- Additional rings of DNA called plasmidsReproduction and Adaptation- Reproduce by binary fission- short generation times- form metabolically inactive endospores, which can remain viable in harsh conditions for centuriesGenetic Variation of Prokaryotes- Rapid reproduction- Mutation- Genetic recombinationTransformation and Transduction- Transformation: incorporating foreign DNA from the surrounding environment- Transduction: movement of genes between bacteria by bacteriophages (viruses that infectbacteria)Conjugation and Plasmids- Conjugation- process where genetic material is transferred between prokaryotic cells- F (fertility) - required for the production of piliR Plasmids and Antibiotic Resistance- Antibiotics kill sensitive bacteria, but not bacteria with specific R plasmids carrying genes for antibiotic resistance- natural selection- the fraction of bacteria with genes for resistance increases in a population repeatedly exposed to antibiotics- Antibiotic-resistant strains of bacteria are becoming more
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