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Anthrax Cutaneous anthrax Bacillus anthracis Microbial Diversity Chapt. 27 – Prokaryotes and the Origins of Metabolic Diversity & Chapt. 28 – The Origins of Eukaryotic Diversity What are microbes? Single-celled organisms and some non-cellular parasites Kinds of microbes Non-cellular, parasitic molecules Viruses Viroids Prions Prokaryotes Domain Bacteria Domain Archaea Eukaryotes Several Kingdoms in Domain Eukarya Nonliving parasitic molecules Viruses Single or double stranded RNA or DNA with a protein coat Common cold, Ebola, HIV HIV Nonliving parasitic molecules Viruses Single or double stranded RNA or DNA with a protein coat Common cold, Ebola, HIV Viroids Short, single strand of RNA w/o protein coat Primarily infect plants Prions Protein particles w/o genetic material Kuru, mad cow, chronic wasting disease Kinds of microbes Non-cellular, parasitic molecules Viruses Viroids Prions Prokaryotes Domain Bacteria Domain Archaea Eukaryotes Several Kingdoms in Domain Eukarya Carl Woese’s 3 Domains of Life See Fig. 27.12 Based primarily on genetic sequence data; e.g., small subunit ribosomal RNA – present in all organisms Carl Woese’s 3 Domains of Life Prokaryotes Eukaryotes NOTE: “Microbes” and “Prokaryotes” are not taxonomic categories See Fig. 27.12 Carl Woese’s 3 Domains of Life Prokaryotes Eukaryotes NOTE: Eukarya & Archaea are more closely related than either is to Bacteria See Fig. 27.12 Carl Woese’s 3 Domains of Life Prokaryotes See Fig. 27.12 Eukaryotes Even so, Archaea & Bacteria share more structural & functional properties than either does with Eukarya Microbes are microscopic, but very diverse & extremely abundant Bacteria on the tip of a pin Relative sizes of microbes Prokaryotes Domains Bacteria & Archaea Simple cells – with no nucleus or membrane-bound organelles Prokaryotes Domains Bacteria & Archaea Simple cells – with no nucleus or membrane-bound organelles First organisms on Earth – at least 3 billion years ago The oldest known fossils Cyanobacteria > 3 billion years old Prokaryotes Domains Bacteria & Archaea Simple cells – with no nucleus or membrane-bound organelles First organisms on Earth – at least 3 billion years ago Distributed globally – including many extremophiles Extreme Thermophiles “Heat-loving” Archaea Extreme Halophiles “Salt-loving” Archaea pink color due to halophiles Australian Salt Lake Methanogens Methane-generating Archaea Occur in oxygen-free habitats E.g., swamp mud, guts of ruminant animals Ice Bacteria & Archaea Cave Bacteria Sometimes reaching acidity of pH 0.5 Prokaryotes Domains Bacteria & Archaea Simple cells – with no nucleus or organelles First organisms on Earth – at least 3 billion years ago Distributed globally – including many extremophiles Nutrition – autotrophs & heterotrophs Prokaryote Nutrition All organisms require a source of energy & carbon Autotrophs can obtain all their C from CO2 Prokaryote Nutrition All organisms require a source of energy & carbon Heterotrophs require at least one organic nutrient, e.g., glucose Prokaryote Nutrition All organisms require a source of energy & carbon Phototrophs obtain their energy from the sun Prokaryote Nutrition All organisms require a source of energy & carbon Chemotrophs obtain their energy from chemical compounds Bacteria Structure Systematic / phylogenetic relationships among bacteria are based on genetic data, but structural properties are indispensable for identifying them Bacteria Structure Cell wall – unique, peptidoglycan Peptidoglycan - structural polysaccharides (sugars) cross-linked by peptides (chains of amino acids) Two biochemical groups of bacteria: peptidoglycan outer membrane Two biochemical groups of bacteria: peptidoglycan outer membrane will stain will not stain Gram positive bacteria Gram negative bacteria Gram stain Distinguishes different cell wall types Gram positive Staphylococcus aureus Gram negative Escherichia coli 3 common bacterial shapes: Cocci- spheres Spirilli- spirals Bacilli- rods Bacteria Structure Cell wall – unique, peptidoglycan Capsules or slime layer E.g., slime layer allows bacteria to cling to tooth enamel or other substrates Bacteria Structure Cell wall – unique, peptidoglycan Capsules or slime layer Pili & Flagella Pili (singular: pilus) Protein filaments that attach bacteria to other cells & substrates pili Some prokaryotes have flagella (singular: flagellum) Used for locomotion flagella Base of a bacterial flagellum… …the only known wheel in nature 50 nm Fig. 27.6 What is “taxis”? Motility allows some bacteria to move towards or away from stimuli Phototaxis Chemotaxis Magnetotaxis Bacteria Structure Cell wall – unique, peptidoglycan Capsules or slime layer Pili & Flagella Circular DNA molecule & plasmids Bacteria Reproduction Asexual, through binary fission Binary fission Daughter cells are identical copies Chromosome (1) (4) Plasma membrane (2) (5) (3) (6) Neither mitosis nor meiosis occurs in prokaryotes Binary fission E. coli DNA cell wall Bacteria Reproduction Asexual, through binary fission No true sexual reproduction, since neither mitosis nor meiosis exist in prokaryotes Bacteria Reproduction Asexual, through binary fission No true sexual reproduction, since neither mitosis nor meiosis exist in prokaryotes Horizontal transfer of genetic material Uptake of genetic material Transformation from the environment Bacteria Reproduction Asexual, through binary fission No true sexual reproduction, since neither mitosis nor meiosis exist in prokaryotes Horizontal transfer of genetic material Transformation Transfer of genetic Transduction material between prokaryotes by viruses Bacteria Reproduction Asexual, through binary fission No true sexual reproduction, since neither mitosis nor meiosis exist in prokaryotes Horizontal transfer of genetic material Transformation Transduction Direct transfer of genetic Conjugation material from one prokaryote to another Conjugation in E. coli Sex pilus connects cells and draws them together Conjugation tube then forms Sex pilus Bacteria Surviving harsh conditions Endospore – forms inside a bacterium and then persists through inhospitable conditions endospore Bacteria – Impacts on other organisms, including Human Society Decomposition Bacteria – Impacts on other organisms, including Human Society Decomposition Louis Pasteur’s observations (1860s) on decomposition disproved spontaneous generation Bacteria – Impacts on other organisms, including Human Society Decomposition Louis Pasteur’s observations (1860s) on decomposition disproved spontaneous generation Bacteria – Impacts on other organisms, including Human Society Decomposition Louis Pasteur’s observations (1860s) on decomposition disproved spontaneous generation Bacteria – Impacts on other organisms, including Human Society Decomposition Photosynthesis Especially common in the cyanobacteria Bacteria – Impacts on other organisms, including Human Society Decomposition Photosynthesis Especially common in the cyanobacteria Bacteria – Impacts on other organisms, including Human Society Decomposition Photosynthesis N-fixation Bacteria – Impacts on other organisms, including Human Society Decomposition Photosynthesis N-fixation Symbiosis Mutualism Rhizobium in the roots of a soybean plant Bacteria – Impacts on other organisms, including Human Society Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism Bacteria – Impacts on other organisms, including Human Society Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism, parasitism Bacteria are often agents of disease by producing toxins E.g., Clostridium tetani, the species that causes tetanus by producing a toxin that interferes with nerve impulses and causes muscles to spasm Bacteria are often agents of disease by producing toxins Robert Koch (late 1800s) was the first person to link diseases to specific species of bacteria The “Germ Theory” revolutionized medicine in the early 20th century Koch’s Postulates guide the identification of disease agents: 1. Find the same pathogen in each victim 2. Isolate the pathogen & grow it in pure culture 3. Induce the disease in a healthy individual from culture 4. Isolate the same pathogen after disease occurs Bacteria – Impacts on other Organisms, including Human Society Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism, parasitism What type of symbiont is Escherichia coli? Normal strains provide K & B-complex vitamins Bacteria – Impacts on other Organisms, including Human Society Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism, parasitism What type of symbiont is Escherichia coli? Some infectious strains cause disease Bacteria – Impacts on other Organisms, including Human Society Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism, parasitism Bioremediation Oil spills, mine tailings, heavy metal dumps, etc. Archaea Structure Several basic biochemical differences distinguish them from Bacteria E.g., No peptidoglycan in their cell walls Archaea Archaea Many are extremophiles… Archaea Even so, archaea are not restricted to extreme habitats Archaea account for 20-30% of marine microbial cells
