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Characterizing and Classifying Prokaryotes
11 Characterizing and Classifying Prokaryotes
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General Characteristics of Prokaryotic Organisms
Prokaryotes Most diverse group of cellular microbes Thrive in various habitats Only a few capable of colonizing humans and causing disease
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Coccus Spirillum Coccobacillus Spirochete Bacillus Pleomorphic Vibrio
Figure Typical prokaryotic morphologies. Coccus Spirillum Coccobacillus Spirochete Bacillus Pleomorphic Vibrio Star
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General Characteristics of Prokaryotic Organisms
Endospores Produced by Gram-positive bacteria Bacillus and Clostridium Each vegetative cell transforms into one endospore Each endospore germinates to form one vegetative cell Defensive strategy against unfavorable conditions Concern to food processors, health care professionals, and governments
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Vegetative cell Endospore Endospore
Figure Locations of endospores. Vegetative cell Endospore Endospore
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General Characteristics of Prokaryotic Organisms
Reproduction of Prokaryotic Cells All reproduce asexually Three main methods: Binary fission (most common) Snapping division Budding
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Bacterial Growth: Overview
PLAY Bacterial Growth: Overview
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Cell wall Cytoplasmic membrane Replicated DNA Cell replicates its DNA;
Figure Binary fission. Cell replicates its DNA; both molecules are attached to the cytoplasmic membrane. Cell wall Cytoplasmic membrane Replicated DNA The cytoplasmic membrane elongates, separating DNA molecules. Cross wall forms; membrane invaginates. Cross wall forms completely. Daughter cells may separate.
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Newer, inner portion of cell wall Older, outer portion of cell wall
Figure Snapping division, a variation of binary fission. Newer, inner portion of cell wall Older, outer portion of cell wall Ruptured remains of old cell wall Hinge
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Filamentous vegetative cells Spores
Figure Spores of actinomycetes. Filamentous vegetative cells Spores
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DNA, which is attached to the cytoplasmic membrane, is replicated
Figure Budding. DNA, which is attached to the cytoplasmic membrane, is replicated Cell elongates to form a bud; the expanding cytoplasmic membrane carries one attached DNA molecule into the bud Young bud Daughter cell
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General Characteristics of Prokaryotic Organisms
Reproduction of Prokaryotic Cells Epulopiscium and its relatives have unique method of reproduction Live offspring emerge from the body of the dead mother cell (viviparity) First noted case of viviparous behavior in prokaryotic world
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Figure 11.7 Viviparity in Epulopiscium.
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General Characteristics of Prokaryotic Organisms
Arrangements of Prokaryotic Cells Result from two aspects of division during binary fission: Planes in which cells divide Separation of daughter cells
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Figure 11.8 Arrangements of cocci.
Plane of division Diplococci Streptococci Tetrads Sarcinae Staphylococci
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Figure 11.9 Arrangements of bacilli.
Single bacillus Diplobacilli Streptobacilli Palisade V-shape
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General Characteristics of Prokaryotic Organisms
Dr. Bauman's Microbiology Video Tutor For more information, listen to Dr. Bauman describe the basic shapes of prokaryotic cells and how cell division determines cellular arrangements.
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Modern Prokaryotic Classification
Currently based on genetic relatedness of rRNA sequences Three domains: Archaea Bacteria Eukarya
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BACTERIA ARCHAEA Figure 11.10 Prokaryotic taxonomy. PHYLUM CHLOROFLEXI
(green nonsulfur) Thermophilic bacteria PHYLUM DEINOCOCCUS-THERMUS DEEPLY BRANCHING BACTERIA GRAM-NEGATIVE BACTERIA PHYLUM PROTEOBACTERIA Rickettsias (α) Purple nonsulfur (α) Nitrifying (β) PHYLUM AQUIFICAE Nitrogen fixing (α) PHYLUM CHLOROBI (green sulfur) Myxobacteria (δ) Zetaproteobacteria (ζ) Campylobacteria (ε) Gammaproteobacteria (γ) PHYLUM CYANOBACTERIA Neisserias (β) PHYLUM FIBROBACTERES ARCHAEA PHYLUM BACTEROIDETES PHYLUM CHLAMYDIAE PHYLUM KORARCHAEOTA PHYLUM THAUMARCHAEOTA PHYLUM PLANCTOMYCETES PHYLUM SPIROCHAETES PHYLUM NANOARCHAEAOTA PHYLUM EURYARCHAEOTA Low G+C Gram-positive Methanogens PHYLUM CRENARCHAEOTA PHYLUM FIRMICUTES PHYLUM FUSOBACTERIA Clostridia Halophiles Mycoplasmas Selenomonas Bacilli, lactobacili, cocci Streptomyces Atopobium Arthrobacter Corynebacterium Mycobacterium Nocardia Thermophilic archaea PHYLUM ACTINOBACTERIA GRAM-POSITIVE BACTERIAHigh G+C Gram-positive
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Survey of Archaea Common features:
Lack true peptidoglycan Cell membrane lipids have branched hydrocarbon chains AUG codon codes for methionine Two phyla: Crenarchaeota, Euryarchaeota Reproduce by binary fission, budding, or fragmentation Are cocci, bacilli, spirals, or pleomorphic Not known to cause disease
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Figure Archaea.
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Survey of Archaea Extremophiles Require extreme conditions to survive
Temperature, pH, and/or salinity Prominent members are thermophiles and halophiles
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Survey of Archaea Extremophiles Thermophiles
DNA, RNA, cytoplasmic membranes, and proteins do not function properly below 45ºC Hyperthermophiles — require temperatures over 80ºC Two representative genera: Thermococcus Pyrodictium
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Figure 11.12 Some hyperthermophilic archaea live in hot springs.
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Survey of Archaea Extremophiles Halophiles
Inhabit extremely saline habitats Depend on greater than 9% NaCl to maintain integrity of cell walls Many contain red or orange pigments May protect from sunlight Most studied — Halobacterium salinarium
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Figure 11.13 The habitat of halophiles: highly saline water.
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Survey of Archaea Methanogens Largest group of archaea
Convert carbon dioxide, hydrogen gas, and organic acids to methane gas Convert organic wastes in pond, lake, and ocean sediments to methane Some live in colons of animals One of primary sources of environmental methane Have produced ~10 trillion tons of methane that is buried in mud on ocean floor
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Survey of Bacteria Deeply Branching and Phototrophic Bacteria
Deeply Branching Bacteria Scientists believe these organisms are similar to earliest bacteria Autotrophic Live in habitats similar to those thought to exist on early Earth Aquifex Considered to represent earliest branch of bacteria Deinococcus Has outer membrane similar to Gram-negatives, but stains Gram-positive
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Survey of Bacteria Deeply Branching and Phototrophic Bacteria
Phototrophs that contain photosynthetic lamellae Autotrophic Divided into five groups based on pigments and source of electrons for photosynthesis: Blue-green bacteria (cyanobacteria) Green sulfur bacteria Green nonsulfur bacteria Purple sulfur bacteria Purple nonsulfur bacteria
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Vegetative cell Akinete Heterocyst Sheath (glycocalyx)
Figure Examples of cyanobacteria with different growth habits. Vegetative cell Akinete Heterocyst Sheath (glycocalyx)
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Figure 11.15 Deposits of sulfur within purple sulfur bacteria.
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Table 11.1 Characteristics of the Major Groups of Phototrophic Bacteria
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Photosynthesis: Comparing Prokaryotes and Eukaryotes
PLAY
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Survey of Bacteria Low G + C Gram-Positive Bacteria Clostridia
Rod-shaped, obligate anaerobes Important in medicine and industry Microbes related to Clostridium include Epulopiscium, sulfate-reducing microbes, and Selenomonas
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Survey of Bacteria Low G + C Gram-Positive Bacteria Mycoplasmas
Facultative or obligate anaerobes Lack cell walls Smallest free-living cells Colonize mucous membranes of the respiratory and urinary tracts
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Figure 11.16 The distinctive "fried egg" appearance of Mycoplasma colonies.
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Survey of Bacteria Low G + C Gram-Positive Bacteria
Other Low G + C Gram-Positive Bacilli and Cocci Bacillus Many are common in soil Bacillus thuringiensis toxin used by farmers and gardeners as an insecticide Bacillus anthracis causes anthrax
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Bacillus thuringiensis
Figure Crystals of Bt toxin, produced by the endospore-forming Bacillus thuringiensis. Bt toxin Bacillus thuringiensis
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Survey of Bacteria Low G + C Gram-Positive Bacteria
Other Low G + C Gram-Positive Bacilli and Cocci Listeria Contaminates milk and meat products Capable of reproducing under refrigeration Can cross the placenta in pregnant women Lactobacillus Grows in the body but rarely causes disease Used in the production of various foods
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Survey of Bacteria Low G + C Gram-Positive Bacteria
Other Low G + C Gram-Positive Bacilli and Cocci Streptococcus and Enterococcus Cause numerous diseases Various strains of multi-drug-resistant streptococci Staphylococcus One of the most common inhabitants of humans Produces toxins and enzymes that contribute to disease
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Table 11.2 Characteristics of Selected Gram-Positive Bacteria
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Survey of Bacteria High G + C Gram-Positive Bacteria Corynebacterium
Pleomorphic aerobes and facultative anaerobes Produces metachromatic granules Mycobacterium Aerobic rods that sometimes form filaments Slow growth partly due to mycolic acid in its cell walls Actinomycetes Form branching filaments resembling fungi Important genera include Actinomyces, Nocardia, Streptomyces
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Figure 11.18 The branching filaments of actinomycetes.
Spores
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Survey of Bacteria Gram-Negative Proteobacteria
Largest and most diverse group of bacteria Six classes of proteobacteria: Alphaproteobacteria Betaproteobacteria Gammaproteobacteria Deltaproteobacteria Epsilonproteobacteria Zetaproteobacteria
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Survey of Bacteria Gram-Negative Proteobacteria
Class Alphaproteobacteria Nitrogen fixers Grow in association with the roots of plants Two genera important to agriculture Azospirillum Rhizobium
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Figure A prostheca. Flagellum Prostheca
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Figure 11.20 Nodules on pea plant roots.
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Survey of Bacteria Gram-Negative Proteobacteria
Class Alphaproteobacteria Nitrifying bacteria Oxidation of nitrogenous compounds provides electrons Important in the environment and agriculture Nitrobacter Purple nonsulfur phototrophs Grow at the bottom of lakes and ponds
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Survey of Bacteria Gram-Negative Proteobacteria
Class Alphaproteobacteria Pathogenic alphaproteobacteria Rickettsia Transmitted through bite of an arthropod Causes several human diseases Brucella Causes brucellosis
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Survey of Bacteria Gram-Negative Proteobacteria
Class Alphaproteobacteria Other alphaproteobacteria Acetobacter Gluconobacter Caulobacter
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Rock or other substrate
Figure Growth and reproduction of Caulobacter. Rock or other substrate Prostheca Flagellum Swarmer cell Cell doubles in size or pf s Rosette
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Figure A plant gall.
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Survey of Bacteria Gram-Negative Proteobacteria
Class Betaproteobacteria Pathogenic betaproteobacteria Neisseria Inhabits mucous membranes of mammals Causes numerous diseases Bordetella Causes pertussis Burkholderia Colonizes moist environmental surfaces and respiratory passages of cystic fibrosis patients
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Survey of Bacteria Gram-Negative Proteobacteria
Class Betaproteobacteria Other betaproteobacteria Thiobacillus Recycles sulfur in the environment Zoogloea Forms flocs that assist in the treatment of sewage Sphaerotilus Flocs impede flow of waste in treatment plants
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Figure 11.23 Flocs—slimy, tangled masses of bacteria and organic matter.
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Survey of Bacteria Gram-Negative Proteobacteria
Class Gammaproteobacteria Largest and most diverse class of proteobacteria Divided into subgroups: Purple sulfur bacteria Intracellular pathogens Methane oxidizers Glycolytic facultative anaerobes Pseudomonads
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Figure 11.24 Purple sulfur bacteria.
Roundworm
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Survey of Bacteria Gram-Negative Proteobacteria
Class Gammaproteobacteria Intracellular pathogens Legionella Causes Legionnaires' disease Coxiella Causes Q fever Methane oxidizers Use methane as a carbon and energy source Inhabit anaerobic environments
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Survey of Bacteria Gram-Negative Proteobacteria
Class Gammaproteobacteria Glycolytic facultative anaerobes Catabolize carbohydrates by glycolysis and the pentose phosphate pathway Divided into three families
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Table 11.3 Representative Glycolytic Facultative Anaerobes of the Class Gammaproteobacteria
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Survey of Bacteria Gram-Negative Proteobacteria
Class Gammaproteobacteria Pseudomonads Break down numerous organic compounds Important pathogens of humans and animals Pseudomonas causes urinary tract, ear, and lung infections Azotobacter Azomonas
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Figure 11.25 Pseudomonas is notable for its polar flagella.
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Survey of Bacteria Gram-Negative Proteobacteria
Class Deltaproteobacteria include a wide variety of metabolic types Desulfovibrio Bdellovibrio Myxobacteria
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Figure 11.26 Bdellovibrio, a Gram-negative pathogen of other Gram-negative bacteria.
bacterial prey Outer membrane 10 minutes Periplasmic space 10 seconds later Cytoplasmic membrane 20 minutes later 20 minutes later 150–210 minutes later
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Figure 11.27 Life cycle of myxobacteria.
Mounding when nutrients are depleted Binary fission (nutrients plentiful) Vegetative cells Mound of cells Slime trail Formation of fruiting body Sporangium Myxospores Sporangium Myxospores germinate to form vegetative cells once nutrients are restored Myxospores Fruiting body
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Survey of Bacteria Gram-Negative Proteobacteria
Class Epsilonproteobacteria Important genera include Campylobacter Helicobacter
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Survey of Bacteria Gram-Negative Proteobacteria
Class Zetaproteobacteria First discovered based on DNA sequences DNA of zetaproteobacteria is common in oceans Only two organisms have been cultured Mariprofundus ferrooxydans is the only species to be formally named
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Survey of Bacteria Other Gram-Negative Bacteria Chlamydias
Grow intracellularly in mammals, birds, and some invertebrates Some are smaller than viruses Most common sexually transmitted bacteria in the United States
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Survey of Bacteria Other Gram-Negative Bacteria Spirochetes
Motile bacteria that move in a corkscrew motion Have diverse metabolism and habitats Treponema and Borrelia both cause disease in humans
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Survey of Bacteria Other Gram-Negative Bacteria Bacteroids Bacteroides
Inhabit digestive tracts of humans and animals Some species cause infections Cytophaga Aquatic, gliding bacteria Important in the degradation of raw sewage
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