Chapter 27 Bacteria and Archaea Halobacterium an archaeon 3 Domains of Life Bacteria Archaea Eukarya Polytomy COMMON ANCESTOR OF ALL LIFE Euglenozoans Forams Diatoms Ciliates Red algae Green algae Plants Tubulinids Fungi Animals Euryarcheotes Thaumarchaeotes Crenarcheotes Proteobacteria Mitochondria Chlamydias Spirochetes Gram positive bacteria Cyanobacteria Chloroplasts 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success Bacteria and archaea are prokaryotes which evolved 3 5 billion years ago Characteristics of prokaryotes nucleus and membrane bound organelles size unicellular multicellular both chromosome reproduction motility cell wall simple or complex 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Prokaryotes dominate the biosphere a combined mass 10X than all eukaryotes combined b exhibit all 4 nutritional modes c found everywhere some thrive in extreme habitats of temperature and salinity d most are benign or beneficial but some cause illness Examples of beneficial prokaryotes a intestine provide important vitamins b mouth prevent harmful fungi from growing there c source of some antibiotics d return nutrients back to environment 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Prokaryotic shapes 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Typical prokaryotic cell Fimbriae Cell wall Circular chromosome Sex pilus Capsule Internal organization Flagella 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Cell Surface Structures 1 Cell wall Functions Most bacterial cell walls are composed of sugars cross linked with polypeptides Archaeal cell walls contain polycasacharides and proteins Eukaryotic cell walls are made of or The Gram stain is a valuable tool for identifying specific bacteria based on differences in cell wall composition 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Cell Surface Structures cont 1 Cell Wall cont Gram positive bacteria peptidoglycan traps crystal violet Gram negative bacteria crystal violet is easily rinsed away revealing red dye Gram positive bacteria Cell wall Peptido glycan Plasma membrane 10 m Carbohydrate portion of lipopolysaccharide Gram negative bacteria Cell wall Outer membrane Peptido glycan Plasma membrane 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Cell Surface Structures cont 2 Capsule sticky layer of polysaccharide or protein enable prokaryotes to adhere to substrate or other individuals to form a colony protect against dehydration or shield pathogenic species from host s immune system Bacterial capsule Tonsil cell Bacterial cell wall 200 nm Streptococcus 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Cell Surface Structures cont 3 Endospore Some bacteria can withstand harsh conditions ex lacking an essential nutrient by forming resistant cells called endospores Endospores can withstand boiling water and can remain dormant for centuries Endospore Coat Bacterium 0 5 m Bacillus anthracis 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Cell Surface Structures cont 4 Fimbriae and Pili Some prokaryotes stick to their substrate or to one another by means of hair like appendages called fimbriae Longer structures called pili can pull two cells together such as in conjugation Fimbriae Pilus 1 m 1 m 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Motility Many prokaryotes exhibit taxis the ability to move in response to a stimulus Prokaryotes can move themselves via Flagellum Bacterial flagella are composed of a motor hook and filament Cell wall Hook Motor Filament 20 nm Plasma membrane Peptidoglycan layer Rod 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Internal Organization Some prokaryotes have specialized membranes that perform metabolic functions Respiratory membrane ETC for ATP synthesis like cristae of mitochondria Thylakoid membrane pigments for photosynthesis like those of chloroplasts 0 2 m 0 5 m Respiratory membrane Thylakoid membrane a Aerobic prokaryote b Photosynthetic prokaryote 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Internal Organization cont Differences exist between prokaryotes and eukaryotes in DNA replication transcription and translation The ribosomes of prokaryotes are smaller and differ in protein and RNA content 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont DNA The chromosome is located in the nucleoid region Some species also have one or more plasmids Chromosome Plasmids 1 m 27 1 Structural and Functional Adaptations Contribute to Prokaryotic Success cont Reproduction Prokaryotes reproduce quickly asexually by binary fission Typically divide every 1 3 hours some can divide every 20 minutes At optimal conditions with unlimited resources growth is geometric Key features of prokaryotic reproduction small binary fission short generation times 27 2 Rapid Reproduction Mutation and Genetic Recombination Promote Genetic Diversity in Prokaryotes Factors that contribute to genetic diversity Rapid Reproduction and Mutation Reproduction by binary fission results in daughter cells being generally identical with low mutation rates However because of rapid reproduction mutations can accumulate rapidly in a population Their short generation time allows prokaryotes to evolve quickly 27 2 Rapid Reproduction Mutation and Genetic Recombination Promote Genetic Diversity in Prokaryotes cont Genetic Recombination Horizontal lateral gene transfer is the movement of genes from one organism to another that does not involve descent Prokaryotes do so by transformation transduction conjugation Pilus 1 m 27 3 Diverse Nutritional and Metabolic Adaptations Have Evolved in Prokaryotes Prokaryotes can be categorized by Energy and Carbon 27 3 Diverse Nutritional and Metabolic Adaptations Have Evolved in Prokaryotes cont Oxygen Requirements require O2 for cellular respiration are poisoned by O2 and use fermentation or anaerobic respiration ex Clostridium tetani C botulinum C perfringens C difficile can survive with or without O2 Nitrogen Metabolism Nitrogen is essential for the production of amino acids and nucleic acids In nitrogen fixation some prokaryotes convert atmospheric nitrogen N2 to ammonia NH3