Chapter 19 The Diversity of Prokaryotes and Viruses Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc Chapter 19 At a Glance 19 1 Which Organisms Are Members of the Domains Archaea and Bacteria 19 2 How Do Prokaryotes Survive and Reproduce 19 3 How Do Prokaryotes Affect Humans and Other Eukaryotes 19 4 What Are Viruses Viroids and Prions Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 1 Which Organisms Are Members of the Domains Archaea and Bacteria Earth s first organisms were prokaryotes single celled microbes that lacked organelles Prokaryotes are still abundant forming two of life s three domains bacteria archaea Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 1 Which Organisms Are Members of the Domains Archaea and Bacteria Bacteria and Archaea are fundamentally different They have some similarities They are both prokaryotic They are both single celled organisms Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 1 Which Organisms Are Members of the Domains Archaea and Bacteria Differences between Bacteria and Archaea Structural and biochemical features Bacteria have peptidoglycan in their cell walls Archaea don t There are also differences in the plasma membrane composition ribosomes and RNA polymerases between the two domains Differences in transcription and translation also exist between the two Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 1 Which Organisms Are Members of the Domains Archaea and Bacteria Classification of prokaryotes within each domain is difficult Prokaryotes are very small and structurally simple Prokaryotes do not have a huge array of anatomical differences that can be used to distinguish between groups Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 1 Which Organisms Are Members of the Domains Archaea and Bacteria Classification of prokaryotes within each domain is difficult continued Features used in prokaryotic classification are Shape Means of locomotion Pigments Nutrient requirements Colony appearance Gram staining characteristics Nucleotide sequences Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 1 Which Organisms Are Members of the Domains Archaea and Bacteria Prokaryotes differ in shape and structure Both bacteria and archaea are very small ranging from 0 2 to 10 micrometers in diameter Prokaryotes have three common shapes Spherical Rod like Corkscrew shaped Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Some prokaryotes are motile Flagella are the primary means of locomotion in prokaryotes Flagella are found singly in pairs as a tuft at one end of the cell or scattered over the entire cell surface In bacteria a wheel and axle arrangement anchors the flagellum within the cell wall and plasma membrane enabling the flagellum to rotate rapidly The archaeal flagella are thinner than those of bacteria and are made of different proteins Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Many bacteria form films on surfaces Some bacteria secrete sticky layers of polysaccharide or protein slime Aggregates communities of slime secreting bacteria are called biofilms dental plaque is a biofilm Bacteria embedded in biofilms are protected from disinfectants and antibiotics Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Protective endospores allow some bacteria to withstand adverse conditions Endospores are thickly wrapped particles of genetic material and a few enzymes Endospores form inside some bacteria under inhospitable environmental conditions When the endospores form the bacterium breaks open releasing the endospores When a hospitable environment is found metabolism resumes and the endospore develops into a fully functioning bacterium Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Protective endospores allow some bacteria to withstand adverse conditions continued Endospores are resistant even to extremely harsh conditions including boiling for an hour Endospores found sealed within a rock for 250 million years produced live bacteria when incubated in a test tube Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Prokaryotes are specialized for specific habitats Each species is specialized for certain environmental conditions and usually cannot survive outside a narrow range around those conditions Prokaryotes occupy a wide range of habitats Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Prokaryote habitats High pressure underground environments Cold environments the Antarctic sea ice High salt environments the Dead Sea Acidic or alkaline environments vinegar ammonia Moderate environments the human body Hot environments deep sea vents hot springs Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Prokaryotes exhibit diverse metabolisms Anaerobic metabolism Some bacteria such as the tetanus bacterium are anaerobes and live without oxygen and are poisoned by it Some bacteria can switch between aerobic and anaerobic respiration For example Escherichia coli in our large intestines Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Prokaryotes exhibit diverse metabolisms continued Prokaryotes can extract their energy from familiar organic compounds Sugars carbs fats and proteins Prokaryotes can also extract energy from compounds poisonous to humans Petroleum methane benzene toluene Prokaryotes can even extract energy from inorganic molecules such as hydrogen sulfur ammonia iron and nitrite Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Prokaryotes exhibit diverse metabolisms continued Some bacteria get energy from sunlight cyanobacteria perform photosynthesis Sulfur bacteria use H2S instead of water in photosynthesis Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 19 2 How Do Prokaryotes Survive and Reproduce Prokaryotes reproduce by binary fission which is simpler than mitotic division Asexual cell division produces identical copies Binary fission can occur every 20
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