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Prokaryotes They’re Everywhere!
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References • Bergey’s Manual of Determinative Bacteriology
Provides identification schemes for identifying bacteria and archaea Morphology, differential staining, biochemical tests • Bergey’s Manual of Systematic Bacteriology Provides phylogenetic information on bacteria and archaea Based on rRNA sequencing • Approved Lists of Bacterial Names Lists species of known prokaryotes Based on published articles
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Pokaryota Overview They’re (Almost) Everywhere!
Most prokaryotes are microscopic But what they lack in size they more than make up for in numbers The number of prokaryotes in a single handful of fertile soil Is greater than the number of people who have ever lived
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Prokaryotes thrive almost everywhere
Including places too acidic, too salty, too cold, or too hot for most other organisms Figure 27.1
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Themes in the Diversification of Bacteria and Archaea
Morphological Diversity Metabolic Diversity Cellular Respiration: Variation in Electron Donors and Electron Acceptors Fermentation Photosynthesis Pathways for Fixing Carbon
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Numbers Total number alive today 5 1030
As much carbon in these cells as in all of the plants on Earth More living on a single person than number of people alive in the world
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Prokaryotic Cells Size Smallest of living cells Most eukaryotes bigger
0.2 to 2.0 μm in diameter 2 to 8 μm in length Most eukaryotes bigger Viruses much smaller
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Two of the Three Domains
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Prokaryote vs Eukaryote Overview
Prokaryote or “before nucleus” no membrane-bound nucleus no other membrane-bound organelles DNA not associated with histones cell walls almost always contain peptidoglycan 70s ribosomes Largest about size of smallest eukaryote Eukaryote or “true nucleus” membrane bound nucleus many other membrane-bound organelles DNA associated with histones cell walls never contain peptidoglycan 80s ribosomes Smallest about size of largest prokaryote
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Bacteria Cell walls made of peptidoglycan
Plasma membranes similar to those of eukaryotes Distinct ribosomes and RNA polymerase.
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Archea Extreme environments Call walls made of polysaccharides
High heat High Salt Concentration High Acid Concentration Call walls made of polysaccharides unique plasma membranes Ribosomes and RNA polymerase similar to those of eukaryotes.
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Major nutritional modes in prokaryotes
Table 27.1
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The Requirements for Growth: Chemical Requirements
Oxygen (O2) obligate aerobes Faultative anaerobes Obligate anaerobes Aerotolerant anaerobes Microaerophiles
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Cyanobacteria Photosynthetic bacteria
first organisms to perform oxygenic (oxygen-producing) photosynthesis Once oxygen was common in the oceans, aerobic respiration became possible.
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Changed the Earth’s Atmosphere
From one dominated by nitrogen gas and carbon dioxide To one dominated by nitrogen gas and oxygen.
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Nitrate Pollution Use of ammonia fertilizers Nitrate may cause
serious pollution problems Releasing nitrate by-product of bacterial ammonia metabolism Nitrate may cause cancer decrease oxygen of aquatic systems anaerobic “dead zones” to develop
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Study of Bacteria and Archaea
Our understanding of the Bacteria and Archaea domains is advancing more rapidly now than at any time during the past 100 years—and perhaps faster than our understanding of any other lineages on the tree of life.
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Enrichment Culture Media with specific growing conditions
Used to isolate new bacteria and archea
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Direct Sequencing a strategy for documenting the presence of bacteria and archaea that cannot be grown in culture
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Direct sequencing has been used to discover a new lineage of Archaea called the Korarchaeota
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Bacteria NOT Closely Related to Archea
The first lineage to diverge from the common ancestor of all living organisms was the Bacteria Archaea and Eukarya are more closely related to each other than to the Bacteria.
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How the Major Clades are Related
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Themes in the Diversification of Bacteria and Archaea
Bacteria and Archaea diversified Hundreds of thousands of distinct species 3.4 billion years Metabolic Diversity Produce ATP in different ways Obtain carbon in diverse ways
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Microbial Growth and Cell Division
Increase in mass Increase in cell numbers Mitosis in most eukaryotes Budding in yeasts Fragmentation in filamentous fungi Binary fission in bacteria and archea
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Steps in Binary Fission
Chromosome replication Chromosome attachment to cell membrane. Chromosomal segregation Septum formation Inward movement of cell wall and cell membrane dividing daughter cells Wall Elongation
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Binary Fission
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Plasmids Figure 8.29
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Conjugation Figure 8.27a
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Conjugation Figure 8.27b
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Conjugation Figure 8.27c
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Cellular Respiration A molecule with high potential energy serves as an electron donor is oxidized, A molecule with low potential energy serves as a final electron acceptor is reduced Potential energy difference is converted into ATP
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Exploit a Wide Variety of Electron Donors and Acceptors
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Typical Bacterial Cell
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Common Bacterial Shapes
Cocci - spherical Bacilli – rods Spirillum - spiral
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Other, Less Common Shapes
Vibrio – comma Coccobacillus - Square Star
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Common Cell arrangements
Cocci Bacilli
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Bacterial Anatomy from the Outside In
Glycocalyx Appendages Cell Wall Bacterial Cell Membranes Inside the Cell
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Glycocalyx Composition varies with species Function
Sticky substances that surround cells Firmly attached = capsule Loosely attached = slime layer Composition varies with species Polysaccharides Polypeptides Both Function Protect cell from phagocytosis and dehydration Aid in attachment to various surfaces May inhibit movement of nutrients from cell
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Appendages Flagella Tail-like structures extending out from glycocalyx
Functions in movement of the bacterial cell Complex structure
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Structure of Flagella Filament Hook Basal body Long tail-like region
Constant diameter Made of protein Hook Filament attachment Basal body Small central rod inserted into a series of rings
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Cell Wall Rigid Composed mostly of peptidoglycan
Found only in bacterial cell walls Amount differs in gram+ and gram- cells Protects cell in environments with osmotic pressures
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Peptidoglycan Glycan portion Peptide portion NAG NAM
N-acetylglucosamine NAM N-acetylmuramic acid Linked in rows of sugars Peptide portion Adjacent rows are linked by polypeptides
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Gram+ Cell Wall
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Gram – Cell Wall
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Gram Stain The Gram Stain is the single most important test in microbiology. The principal utility of the Gram Stain rests on its speed and simplicity. Most bacteria may be divided in two groups by this procedure developed by the Danish physician Hans Christian Gram to differentiate pneumococci from Klebsiella pneumonia difference between Gram-positive and Gram-negative bacteria is in the structure of the cell wall
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Results G+ cocci G- rods
Websites with more samples of gram stained bacteria GRAM STAINED IMAGES OF MEDICALLY IMPORTANT BACTERIA Loyola University Medical Center GRAM STAIN TUTORIAL
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Atypical Cell Walls Mycoplasmas Archea L-forms Lack cell wall
Smallest known bacteria Archea Cell walls contain pseudomurein rather than peptidoglycan Lacks D-amino acids found in bacteria L-forms Tiny mutant bacteria with defective cell walls Just enough material to prevent lysis in dilute environments
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There are at least 14 major lineages (phyla) of bacteria.
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Microbial Diversity PCR indicates up to 10,000 bacteria/gm of soil. Many bacteria have not been identified or characterized because they: Haven't been cultured Need special nutrients Are part of complex food chains requiring the products of other bacteria Need to be cultured to understand their metabolism and ecological role
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Spirochetes Spirochetes are distinguished by their corkscrew shape and unusual flagella
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Spirochaetes Borrelia Leptospira Treponema Figure 11.23
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Chlamidiae Chlamydiaeare spherical and very tiny.
They live as parasites inside animal cells
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Chlamydiae C. trachomatis C. pneumoniae C. psittaci Trachoma
STD, urethritis C. pneumoniae C. psittaci Causes psittacosis
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In Bergey's Manual, Volume 5
Figure 11.22b
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In Bergey's Manual, Volume 5
Figure 11.22a
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High-GC (guanine and cytosine) Gram-positive bacteria have various shapes, and many soil-dwelling species form mycelia (branched filaments)
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Actinobacteria Actinomyces Corynebacterium Frankia Gardnerella
Mycobacterium Nocardia Propionibacterium Streptomyces Figure 11.20b
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Cyanobacteria Cyanobacteria dominate many marine and freshwater environments. They produce much of the oxygen and nitrogen, as well as many organic compounds, that feed other organisms in freshwater and marine environments
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Cyanobacteria Oxygenic photosynthesis Gliding motility Fix nitrogen
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Low-GC Gram-positive bacteria cause a variety of diseases including anthrax, botulism, tetanus, gangrene, and strep throat. Lactobacillus is used to make yogurt.
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Clostridiales Clostridium Endospore-producing Obligate anaerobes
Figure & 15
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Bacillales Bacillus Endospore-producing rods Figure 11.16b
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Bacillales Staphylococcus Cocci Figure 1.17
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Lactobacillales Generally aerotolerant anaerobes, lack an electron-transport chain Lactobacillus Streptococcus Enterococcus Listeria Figure 11.18
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Mycoplasmatales Wall-less, pleomorphic 0.1 - 0.24 µm M. pneumoniae
Figure 11.19a, b
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Proteobacteria Large group
Cause Legionnaire’s disease, cholera, dysentery, and gonorrhea. Certain species can produce vinegars. Rhizobium can fix nitrogen.
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The (alpha) Proteobacteria
Human pathogens: Bartonella B. hensela Cat-scratch disease Brucella Brucellosis
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The (alpha) Proteobacteria
Wolbachia. Live in insects and other animals
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The (alpha) Proteobacteria
Nitrogen-fixing bacteria: Azospirillum Grow in soil, using nutrients excreted by plants Fix nitrogen Rhizobium Fix nitrogen in the roots of plants Figure 27.5
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The (alpha) Proteobacteria
Produce acetic acid from ethyl alcohol: Acetobacter Gluconobacter
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The (beta) Proteobacteria
Thiobacillus Chemoautotrophic, oxidize sulfur: H2S SO42– Sphaerotilus Chemoheterotophic, form sheaths Figure 11.5
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The (beta) Proteobacteria
Neisseria Chemoheterotrophic, cocci N. meningitidis N. gonorrhoeae Spirillum Chemoheterotrophic, helical Figure 11.4 & 6
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The (beta) Proteobacteria
Bordetella Chemoheterotrophic, rods B. pertussis Burkholderia. Nosocomial infections Zoogloea. Slimy masses in aerobic sewage-treatment processes
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The (gamma) Proteobacteria
Pseudomonadales: Pseudomonas Opportunistic pathogens Metabolically diverse Polar flagella Azotobacter and Azomonas. Nitrogen fixing Moraxella. Conjunctivitis Figure 11.7
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The (gamma) Proteobacteria
Legionellales: Legionella Found in streams, warm-water pipes, cooling towers L. pneumophilia Coxiella Q fever transmitted via aerosols or milk Figure 24.15b
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The (gamma) Proteobacteria
Vibrionales: Found in coastal water Vibrio cholerae causes cholera V. parahaemolyticus causes gastroenteritis Figure 11.8
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The (gamma) Proteobacteria
Enterobacteriales (enterics): Peritrichous flagella, facultatively anaerobic Enterobacter Erwinia Escherichia Klebsiella Proteus Salmonella Serratia Shigella Yersinia
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The (delta) Proteobacteria
Bdellovibrio. Prey on other bacteria Desulfovibrionales. Use S instead of O2 as final electron acceptor Myxococcales. Gliding. Cells aggregate to form myxospores
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The (delta) Proteobacteria
Figure 11.10a
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The (delta) Proteobacteria
Figure 11.1b
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The (epsilon) Proteobacteria
Campylobacter One polar flagellum Gastroenteritis Figure 11.1a
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The (epsilon) Proteobacteria
Helicobacter Multiple flagella Peptic ulcers Stomach cancer Figure 11.1b
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Extremophiles Some archaea Extreme thermophiles Extreme halophiles
Live in extreme environments Extreme thermophiles Thrive in very hot environments hot springs at the bottom of the ocean, where water as hot as 300°C emerges Extreme halophiles Live in high saline environmentsMethanogens Live in swamps and marshes Produce methane as a waste product
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Extremophiles Methanogens Low-temperature
Live in swamps and marshes Produce methane as a waste product Low-temperature High-pressure habitats Are of commercial interest enzymes that function at low temperature or high temperature may be useful in industrial processes Model organisms in the search for extraterrestrial life
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Extreme Halophiles Figure 27.14
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Prokaryotes play crucial roles in the biosphere
Prokaryotes are so important to the biosphere that if they were to disappear The prospects for any other life surviving would be dim Continual recycling of chemical elements function as decomposers Corpses, dead vegetation, and waste products Symbiotic Relationships mutualism, commensalism, parasitism
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The Nitrogen Cycle Molecular nitrogen (N2) is abundant in the atmosphere most organisms cannot use All eukaryotes and many bacteria and archaea must obtain their nitrogen from ammonia (NH3) or nitrate (NO3).
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Nitrogen Metabolism Prokaryotes can metabolize nitrogen
In a variety of ways In a process called nitrogen fixation Some prokaryotes convert atmospheric nitrogen to ammonia Redox reactions
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Nitrogen Fixing Organisms
Species of cyanobacteria bacteria Land Live in close association with plants often in nodules
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Pathogenic Prokaryotes
Prokaryotes cause about half of all human diseases Lyme disease is an example 5 µm Figure 27.16
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Pathogenic Prokaryotes
Pathogenic prokaryotes typically cause disease By releasing exotoxins or endotoxins Many pathogenic bacteria Are potential weapons of bioterrorism Also cause other animal and plant diseases
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Bioremediation Prokaryotes are the principal agents in bioremediation
The use of organisms to remove pollutants from the environment Figure 27.17
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Bioremediation Some of the most serious pollutants in soils, rivers, and ponds organic compounds originally used as solvents or fuels leaked or were spilled into the environment Sediments where these types of compounds accumulate become anoxic Use bacteria and archaea to degrade pollutants fertilizing contaminated sites to encourage the growth of existing bacteria that degrade toxic compounds adding specific species of bacteria to contaminated sites
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Prokaryotes in Research and Technology
Experiments using prokaryotes Have led to important advances in DNA technology
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Other Contributions Prokaryotes are also major tools in Mining
The synthesis of vitamins Production of antibiotics, hormones, and other products
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