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Copyright © 2013 Pearson Education, Inc.

Lectures prepared by Christine L. Case

Chapter 11

The Microbial World and You

© 2013 Pearson Education, Inc.

Lectures prepared by Christine L. Case

© 2013 Pearson Education, Inc.

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The Prokaryotes

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Domain Bacteria

  • Proteobacteria
  • From the mythical Greek god Proteus, who could assume many shapes
  • Gram-negative
  • Chemoheterotrophic

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The Alphaproteobacteria

  • Pelagibacter ubique
  • Discovered by FISH technique
  • 20% of prokaryotes in oceans
  • 0.5% of all prokaryotes
  • 1354 genes

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The Alphaproteobacteria

  • Human pathogens
  • Bartonella
  • B. henselae: cat-scratch disease
  • Brucella: brucellosis
  • Ehrlichia: tickborne

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The Alphaproteobacteria

  • Obligate intracellular parasites
  • Ehrlichia: tickborne, ehrlichiosis
  • Rickettsia: arthropod-borne, spotted fevers
  • R. prowazekii: epidemic typhus
  • R. typhi: endemic murine typhus
  • R. rickettsii: Rocky Mountain spotted fever

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Figure 11.1 Rickettsias.

Slime layer

Scattered rickettsias

Chicken embryo cell

Nucleus

Masses of rickettsias in nucleus

A rickettsial cell that has just been released from a host cell

Rickettsias grow only within a host cell, such as the chicken embryo cell shown here. Note the scattered rickettsias within the cell and the compact masses of rickettsias in the cell nucleus.

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The Alphaproteobacteria

  • Wolbachia: live in insects and other animals

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Applications of Microbiology 11.1a Wolbachia are red inside the cells of this fruit fly embryo.

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Applications of Microbiology 11.1b In an infected pair, only female hosts can reproduce.

Neither infected

Uninfected offspring

Male infected

No offspring

Female infected

Infected offspring

Both infected

Infected offspring

Unfertilized female infected

Infected female offspring

Wolbachia

Females

Males

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The Alphaproteobacteria

  • Have prosthecae
  • Caulobacter: stalked bacteria found in lakes
  • Hyphomicrobium: budding bacteria found in lakes

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Insert Fig 11.2b

Figure 11.2b Caulobacter.

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Figure 11.3 Hyphomicrobium, a type of budding bacterium.

Hypha

Bud

Bud

Holes in

filter

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The Alphaproteobacteria

  • Plant pathogen
  • Agrobacterium: insert a plasmid into plant cells,
    inducing a tumor

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Figure 9.19 Crown gall disease on a rose plant.

Crown gall

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The Alphaproteobacteria

  • Chemoautotrophic
  • Oxidize nitrogen for energy
  • Fix CO2
  • Nitrobacter: NH3  NO2–
  • Nitrosomonas: NO2–  NO3–

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The Alphaproteobacteria

  • Nitrogen-fixing bacteria
  • Azospirillum
  • Grow in soil, using nutrients excreted by plants
  • Fix nitrogen
  • Rhizobium
  • Fix nitrogen in the roots of plants

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Figure 27.5 The formation of a root nodule.

An infection thread is

formed, through which

bacteria enter root cells.

Enlarged root cells

form a nodule.

Bacteria change into bacteroids; packed root cells enlarge.

Rhizobia attach

to root hair.

Pea plant

Root

hairs

Rhizobia

Infection

thread

Bacteroids

Root

Nodules

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The Alphaproteobacteria

  • Produce acetic acid from ethanol
  • Acetobacter
  • Gluconobacter

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Chapter 11, unnamed figure, page 303.

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The Betaproteobacteria

  • Thiobacillus
  • Chemoautotrophic; oxidize sulfur: H2S  SO42–
  • Sphaerotilus
  • Chemoheterotophic; form sheaths

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Figure 11.5 Sphaerotilus natans.

Bacterial cell

Sheath

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Figure 11.6 The gram-negative coccus Neisseria gonorrhoeae.

Capsule

Fimbriae

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Figure 11.4 Spirillum volutans.

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The Betaproteobacteria

  • Bordetella
  • Chemoheterotrophic; rods
  • B. pertussis
  • Burkholderia
  • Nosocomial infections

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Figure 24.7 Ciliated cells of the respiratory system infected with Bordetella pertussis.

B. pertussis

Cilia

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Figure 27.19 Floc formed by an activated sludge system.

Bacterial cells

embedded in

particles of floc

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The Gammaproteobacteria

  • Pseudomonadales
  • Pseudomonas
  • Opportunistic pathogens
  • Metabolically diverse
  • Polar flagella

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Figure 11.7 Pseudomonas.

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The Gammaproteobacteria

  • Pseudomonadales
  • Moraxella
  • Conjunctivitis
  • Azotobacter and Azomonas
  • Nitrogen-fixing

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The Gammaproteobacteria

  • Legionellales
  • Legionella
  • Found in streams, warm-water pipes, cooling towers
  • L. pneumophilia
  • Coxiella
  • Q fever transmitted via aerosols or milk

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Figure 24.14b Coxiella burnetii, the cause of Q fever.

This cell has just divided; notice the endospore-like body (E), which is probably responsible for the relative resistance of the organism.

E

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The Gammaproteobacteria

  • Vibrionales
  • Found in coastal water
  • Vibrio cholerae causes cholera
  • V. parahaemolyticus causes gastroenteritis

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Figure 11.8 Vibrio cholerae.

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The Gammaproteobacteria

  • Enterobacteriales (enterics)
  • Peritrichous flagella; facultatively anaerobic
  • Enterobacter
  • Erwinia
  • Escherichia
  • Klebsiella
  • Proteus
  • Salmonella
  • Serratia
  • Shigella
  • Yersinia

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Figure 11.19 Streptomyces.

Filaments

Filament

Conidiospores

Drawing of a typical streptomycete showing filamentous, branching growth with asexual reproductive conidiospores at the filament tips.

Coils of conidiospores supported by filaments of the streptomycete.

Conidiospores

in coils

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The Gammaproteobacteria

  • Pasteurellales
  • Pasteurella
  • Cause pneumonia and septicemia
  • Haemophilus
  • Require X (heme) and V (NAD+, NADP+) factors

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The Gammaproteobacteria

  • Beggiatoa
  • Chemoautotrophic; oxidize H2S to S0 for energy
  • Francisella
  • Chemoheterotrophic; tularemia

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Figure 11.10 Bdellovibrio bacteriovorus.

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The Deltaproteobacteria

  • Desulfovibrionales
  • Use S instead of O2 as final electron acceptor

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Figure 11.11 Myxococcales.

Myxospores

Myxospores are resistant resting cells released from sporangioles upon favorable conditions.

Germination

Myxospores germinate and form gram-negative vegetative cells, which divide to reproduce.

Vegetative growth cycle

Vegetative myxobacteria are motile by gliding, forming visible slime trails.

Aggregation

Under favorable conditions, the vegetative cells swarm to central locations, forming an aggregation.

Mounding

Aggregations of cells heap up into a mound, an early fruiting body.

Mounds of myxobacteria differentiate into a mature fruiting body, which produces myxospores packed within sporangioles.

Sporangiole

Myxobacteria fruiting body

Myxospores

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The Epsilonproteobacteria

  • Campylobacter
  • One polar flagellum
  • Gastroenteritis
  • Helicobacter
  • Multiple flagella
  • Peptic ulcers
  • Stomach cancer

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Figure 11.12 Heliobacter pylori.

Flagella

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Firmicutes

  • Low G + C
  • Gram-positive

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Clostridiales

  • Clostridium
  • Endospore-producing
  • Obligate anaerobes
  • Epulopiscium

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Figure 11.13 Clostridium difficile.

Endospore

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Figure 11.14 A giant prokaryote, Epulopiscium fishelsoni.

Epulopiscium

Paramecium

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Bacillales

  • Bacillus
  • Endospore-producing rods
  • Staphylococcus
  • Cocci

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Figure 11.15 Bacillus.

This Bacillus cereus cell is shown emerging from the

endospore.

Endospore case

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Figure 11.16 Staphylococcus aureus.

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Lactobacillales

  • Generally aerotolerant anaerobes; lack an
    electron transport chain
  • Lactobacillus
  • Streptococcus
  • Enterococcus
  • Listeria

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Figure 11.17 Streptococcus.

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Mycoplasmatales

  • Wall-less; pleomorphic
  • 0.1–0.24 µm
  • M. pneumoniae

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Actinobacteria

  • High G + C
  • Gram-positive

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Actinobacteria

  • Actinomyces
  • Corynebacterium
  • Frankia
  • Gardnerella
  • Mycobacterium
  • Nocardia
  • Propionibacterium
  • Streptomyces

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Figure 11.19a Streptomyces.

Filaments

Drawing of a typical streptomycete showing filamentous, branching growth with asexual reproductive conidiospores at the filament tips.

(a)

Conidiospores

in coils

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Figure 11.19b Streptomyces.

Filament

Conidiospores

Coils of conidiospores supported by filaments of the streptomycete.

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Figure 11.20 Actinomyces.

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  • Oxygenic photosynthesis
  • Anoxygenic photosynthesis

Phototrophic

2H2O + CO2

light

(CH2O) + H2O + O2

2H2S + CO2

light

(CH2O) + H2O + 2S0

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Oxygenic Photosynthetic Bacteria

  • Cyanobacteria
  • Gliding motility
  • Fix nitrogen

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Figure 11.21 Cyanobacteria.

Heterocysts

(b) A unicellular, nonfilamentous cyanobacterium, Gloeocapsa. Groups of these cells, which divide by binary fission, are held together by the surrounding glycocalyx.

(a) Filamentous cyanobacterium showing heterocysts, in which nitrogen-fixing activity is located.

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Chlamydias

  • Chlamydia trachomatis
  • Trachoma
  • STI, urethritis
  • Chlamydophila pneumoniae
  • Chlamydophila psittaci
  • Psittacosis

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Figure 11.22a Chlamydias.

The bacterium’s infectious form, the elementary body, attaches to a host cell.

The host cell phagocytizes the elementary body, housing it in a vacuole.

The elementary body reorganizes to form a reticulate body.

The reticulate body divides successively, producing multiple reticulate bodies.

The reticulate bodies begin to convert back into elementary bodies.

The elementary bodies are released from the host cell.

Reticulate body

Host cell

Nucleus

Vacuole

Elementary body

Vacuole forming

Life cycle of the chlamydias, which takes about 48 hours to complete.

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Planctomycetes

  • Gemmata obscuriglobus
  • Double internal membrane around DNA

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Figure 11.23 Gemmata obscuriglobus.

Nucleoid

Nuclear envelope

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Nonproteobacteria Gram-Negatives

  • Bacteroidetes
  • Anaerobic
  • Bacteroides are found in the mouth and large intestine
  • Cytophaga: degrade cellulose in soil
  • Fusobacterium
  • Are found in the mouth
  • May be involved in dental diseases

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Anoxygenic Photosynthetic Bacteria

  • Purple sulfur
  • Purple nonsulfur
  • Green sulfur
  • Green nonsulfur

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Figure 11.25 Purple sulfur bacteria.

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Figure 11.26 Spirochetes.

This cross section of a spirochete shows numerous axial filaments between the dark cell and the outer sheath.

This micrograph of a portion of Treponema pallidum shows the sheath, which has shrunk away from the cell, and two axial filaments attached near one of the cell under the sheath.

Axial filaments

Sheath

Axial filaments

Sheath

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Deinococci-Thermus

  • Deinococcus radiodurans
  • More resistant to radiation than are endospores
  • Thermus aquaticus
  • Hot spring in Yellowstone National Park
  • Source of Taq polymerase

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Domain Archaea

Extremophiles

  • Hyperthermophiles
  • Pyrodictium
  • Sulfolobus
  • Methanogens
  • Methanobacterium
  • Extreme halophiles
  • Halobacterium

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Figure 11.27 Archaea.

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Microbial Diversity

  • Bacteria size range
  • Thiomargarita (diameter of 750 µm)
  • Carsonella ruddii (182 genes)
  • Metagenomics
  • PCR
  • GeoChip

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Figure 11.28 Thiomargarita namibiensis.

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Microbial Diversity

  • PCR indicates up to 10,000 bacteria per gram of soil
  • Many bacteria have not been identified because they
  • Have not been cultured
  • Need special nutrients
  • Are a part of complex food chains requiring the products of other bacteria
  • Need to be cultured to understand their metabolism and ecological role