1. Overview of Gram-Positive and Other Bacteria
Bacteria has many phyla other than Proteobacteria, including
Gram-positive bacteria
Large group of mostly chemoorganotrophs
Cyanobacteria
Oxygenic phototrophs that have evolutionary roots near those of gram-positive bacteria
Phylogenetically early-branching phyla
Such as Aquifex
Other morphologically distinct groups
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2. I. Firmicutes, Mollicutes, and Actinobacteria
Gram-positive bacteria are a large and diverse group
Divided into three groups:
Firmicutes
Mollicutes
Actinobacteria
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3. 18.1 Nonsporulating Firmicutes
Key genera: Staphylococcus, Streptococcus, Lactobacillus, Sarcina
Staphylococcus and Micrococcus (Figure 18.1)
Aerobic, cocci
Resistant to reduced water potential
Tolerate high salt
Many species are pigmented
Staphylococcus aureus
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4. Figure 18.1
Figure 18.1 Staphylococcus.
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5. 18.1 Nonsporulating Firmicutes
Streptococcus
Play important roles in production of buttermilk, silage, and other products
Some species are pathogenic
Lactococcus: genera of dairy significance (Figure 18.3)
Enterococcus: genera of fecal origin
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6. Figure 18.3 Figure 18.3 Gram-positive cocci.
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7. 18.2 Endospore-Forming Firmicutes
Key genera: Bacillus & Clostridium
Distinguished on the basis of cell morphology, and the shape and cellular position of endospore
Generally found in soils
Endospores are advantageous for soil microorganisms
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8. Figure 18.5 Figure 18.5 Clostridium species and endospore location.
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9. 18.2 Endospore-Forming Firmicutes
Bacillus
Many produce extracellular hydrolytic enzymes that break down polymers
Many bacilli produce antibiotics
Bacillus thuringiensis produces insect larvicides (Figure 18.6)
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10. Endospore Crystal Figure 18.6
Figure 18.6 The toxic parasporal crystal in the insect pathogen Bacillus thuringiensis.
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11. 18.2 Endospore-Forming Firmicutes
Clostridium
Lack a respiratory chain, anaerobic
Mainly found in anaerobic pockets in the soil
Also live in mammalian intestinal tract
Some cause diseases such as botulism, tetanus, and gangrene
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12. 18.3 Mollicutes: The Mycoplasmas
Key genera: Mycoplasma
Lack cell walls
Some of the smallest organisms capable of autonomous growth
Parasites that inhabit animal and plant hosts
Key components of peptidoglycan are missing
Mycoplasma cells are pleomorphic
Cells may be cocci or filaments of various lengths
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13. Figure 18.9 Figure 18.9 Mycoplasma mycoides.
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14. 18.4 Actinobacteria: Coryneform & Mycobacteria
Key genera: Corynebacterium & Mycobacterium
Actinobacteria form their own phylum
Over 30 taxonomic families
Rod-shaped to filamentous, usually aerobic
Mostly harmless commensals (Mycobacterium are exceptions)
Valuable for antibiotics and certain fermented dairy products
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15. 18.4 Actinobacteria: Coryneform & Propionic Acid Bacteria
Corynebacterium
Gram-positive, aerobic, nonmotile, rod-shaped
Form club-shaped, irregular-shaped, or V-shaped cell arrangements
Extremely diverse
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16. Figure 18.12 Figure 18.12 Snapping division in Arthrobacter.
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17. 18.5 Actinobacteria: Mycobacterium
Rod-shaped organisms, exhibit acid-fastness (Figure 18.15)
First discovered by Robert Koch
Not readily stained by Gram stain because of high surface lipid content
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18. Figure 18.16
Figure Characteristic colony morphology of mycobacteria.
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19. 18.6 Filamentous Actinobacteria: Streptomyces & Relatives
Key genera: Streptomyces, Actinomyces (Figure 18.18)
Filamentous, gram-positive bacteria
Produce mycelium analogous to mycelium of fungi
Over 500 species of Streptomyces
Streptomyces spores are called conidia (Figure 18.19)
Primarily soil microorganisms, responsible for earthy odor of soil (geosmins)
Strict aerobes that produce many extracellular enzymes
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20. Figure 18.18
Figure Nocardia.
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21. 18.6 Filamentous Actinobacteria: Streptomyces & Relatives
Streptomyces (Figure 18.22)
50% of all isolated Streptomyces produce antibiotics (Figure 18.23)
Over 500 distinct antibiotics produced by Streptomyces
Some produce more than one antibiotic
Genomes are typically quite large (8 Mbp and larger)
Knowledge of the ecology of Streptomyces remains poor
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22. Figure 18.22 Figure 18.22 Streptomycetes.
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23. Figure 18.23 Figure 18.23 Antibiotics from Streptomyces.
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24. 18.7 Cyanobacteria Phototrophic
Gas vesicles are found in many cyanobacteria
Help maintain buoyancy
Keep cell in water column where there is light
Heterocysts are rounded, enlarged cells
Anoxic environment inside heterocyst
Site for nitrogen fixation
Nitrogenase is sensitive to oxygen
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25. Figure 18.24
Figure Cyanobacteria: the five major morphological types of cyanobacteria.
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26. Figure 18.26 Heterocyst Glutamine Heterocyst Vegetative cells
Figure Heterocysts.
Glutamine
Heterocyst
Vegetative cells
Vegetative cells
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27. 18.9 The Chlamydia Key genera: Chlamydia
Obligately parasitic with poor metabolic capacities
Some of the simplest biochemical capacities of all known bacteria
Currently one of the leading sexually transmitted diseases
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28. Figure 18.30
Figure Chlamydia.
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29. Figure 18.31 Elementary bodies Elementary body Reticulate body
Release of elementary bodies
Elementary bodies
Conversion to elementary bodies
Elementary body
Elementary body attacks host cell
Reticulate body
Phagocytosis of elementary body
Multiplication of reticulate bodies
Figure The infection cycle of a chlamydia.
Conversion to reticulate body
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30. 18.10 Planctomyces: A Phylogenetically Unique Bacterium
Key genera: Planctomyces
Planctomyces is a budding bacterium
Facultative aerobic chemoorganotroph
Stalked
Primarily aquatic
Extensive cell compartmentalization including a membrane-enclosed nuclear structure
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31. Flagellum Pilus Stalk Stalk Figure 18.32
Figure Planctomyces maris.
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32. Nucleoid Nuclear envelope Figure 18.33
Figure Gemmata: a nucleated bacterium.
Nuclear envelope
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33. Bacteroides Key genera: Bacteroides Obligately anaerobic
Numerically dominant bacterium in human intestinal tract
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34. 18.15 Chlorobium and Other Green Sulfur Bacteria
Key genera: Chlorobium
Phylogenetically distinct, nonmotile, anoxygenic phototrophs
Utilize H2S as an electron donor and oxidize it to SO42
Have chlorosomes bacteriochlorophyll-rich bodies bounded by a thin membrane
Green- and brown-colored species exist
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35. Figure 18.39
Figure The thermophilic green sulfur bacterium Chlorobaculum tepidum.
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36. 18.15 Chlorobium and Other Green Sulfur Bacteria
Green sulfur bacteria inhabit anoxic environments rich in H2S
Some green sulfur bacteria form consortia
Involves the green sulfur bacterium and a chemoorganotrophic bacterium
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37. 18.16 Spirochetes
Key genera: Spirochaeta, Treponema, Leptospira, Borrelia
Gram-negative, motile, and coiled
Widespread in aquatic environments and in animals
Have endoflagella: located in the periplasm of the cell
Also found in the rumen of animals
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38. Figure 18.42 Figure 18.42 Morphology of spirochetes.
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39. Outer sheath (flexible) Endoflagellum
Figure 18.43
Endoflagellum (rigid, rotates, attached to one end of protoplasmic cylinder)
Outer sheath (flexible)
Endoflagellum
Protoplasmic cylinder
Outer sheath
Figure Motility in spirochetes.
Protoplasmic cylinder (rigid, generally helical)
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40. 18.16 Spirochetes Spirochaeta Treponema (Figure 18.45a)
Free-living, anaerobic and facultatively anaerobic spirochetes
Treponema (Figure 18.45a)
Anaerobic host-associated spirochetes that are commensal or parasites of humans
Borrelia (Figure 18.45b)
Majority are human or animal pathogens
Borrelia burgdorferi is the causative agent of Lyme disease
B. burgdorferi has a linear chromosome
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41. Deinococcus Deinococcus Gram-positive, aerobic, organotrophic
Most are red or pink due to carotenoids
Resist UV radiation, gamma radiation, and desiccation
Resistant to most mutagenic agents
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42. 18.20 Aquifex Key genera: Aquifex Aquifex
Obligately chemolithotrophic hyperthermophile
Most thermophilic of all Bacteria (can grow at 95C)
1.55-Mbp genome
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