18.4 Bacteria and Archaea KEY CONCEPT Bacteria and archaea are both single-celled prokaryotes.
Chapter 11 The Prokaryotes: Domains Bacteria and Archaea Part 2.
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Transcript of Chapter 11 The Prokaryotes: Domains Bacteria and Archaea Part 2.
Chapter 11
The Prokaryotes: Domains Bacteria and Archaea
Part 2
The Nonproteobacteria Gram-Negative Bacteria
• Not closely related to the gram-negative proteobacteria
• Several physiological and morphologically distinctive photosynthesizing bacteria
• Phyla Cyanobacteria, Chlorobi (green sulfur bacteria) & Choloroflexi (green nonsulfur bacteria)
The Nonproteobacteria Gram-Negative Bacteria
Photosynthetic Bacteria
Photosynthetic Bacteria
• Phyla Cyanobacteria, Chlorobi, Chloroflexi, photosynthetic purple sulfur bacteria (-proteobacteria), and purple nonsulfur bacteria (-proteobacteria)
• Photoautotrophs and chemoheterotrophs
• Photosynthetic purple and green sulfur bacteria are generally anaerobic and usually found in deep sediments of lakes and ponds
• Oxygenic (oxygen-producing) photosynthetic bacteria– Produce O2 from H2O using light energy
• Characteristic blue-green (cyan) pigmentation
• Gliding motility or gas vacuoles
• Fix nitrogen (into ammonium) from atmosphere in specialized cells called heterocysts
• Morphologically varied (Unicellular to colonial form)
Cyanobacteria
Cyanobacteria
Figure 11.12a-c
• Anoxygenic photosynthesis (does not produce O2)
– carry out photosynthesis to make carbohydrates – Possess chlorophyll
Purple and Green Photosynthetic Bacteria
2H2S + CO2
light(CH2O) + H2O + 2S0
2H2O + CO2
light(CH2O) + H2O + O2
Oxygenic
Anoxygenic (purple sulfur and green sulfur bacteria)
• Do not contain peptidoglycan in cell walls– Chlamydia: intracellular parasite; a unique
developmental cycle (elementary body is the infective agent); gram-negative coccoid
– Transmitted via interpersonal contact or by airborne respiratory routes
• C. trachomatisTrachoma, STD, urethritis
• C. pneumoniae Mild form of pneumoniae
• C. psittaci Causes psittacosis (ornithosis)
Phylum Chlamydiae
In Bergey's Manual, Volume 5
Figure 11.22a
In Bergey's Manual, Volume 5
Figure 11.22b
Phylum Spirochaetes
Figure 11.23
• Coiled morphology; outer sheath; axial filaments (endoflagella) for motility– many are found in oral cavity
• Borrelia Relapsing fever and Lyme disease
• Leptospira leptospirosis
• Treponema syphilis (T. pallidum)
• Anaerobic Bacteria– Bacteroides: nonmotile; in mouth (gingival
crevice) and large intestine; also recovered frequently from deep tissue infections
– Cytophaga: degrade cellulose and chitin in soil; gliding motility
Phylum Bacteroidetes
• Often pleomorphic, may be spindle-shaped– Fusobacterium:
found in mouth (gingival crevice); may be involved in dental diseases
Phylum Fusobacteria
Figure 11.24
Gram-Positive Bacteria
• Two groups: – high G + C ratios (above 50%)
e.g. Phylum Actinobacteria (mycobacteria, corynebacteria,and actinomycetes)
– low G + C ratios (below 50%)
e.g. Phylum Firmicutes (common soil bacteria, lactic acid producing bacteria, and several human pathogens)
• Low G + C
• Gram-positive
Phylum Firmicutes
Order Clostridiales
Figure 11.14 & 15
• Clostridium– Form endospores– Obligate anaerobes
• C. botulinum Botulism
• C. tetani Tetanus
• C. perfringens Gas gangrene Food
diarrhea
• C. difficile Severe diarrhea
• Epulopiscium– Giant prokaryote; symbiotic
in the gut of surgeonfish
• Important genera of gram-positive rods and cocci
• Bacillus– Rod-shaped bacteria that
form endospores – Common in soils
• B. anthracis: Anthrax
• B. thuringiensis: Microbial insect pathogen
• B. cereus: Occasional food poisoning
Order Bacillales
Figure 11.16b
• Staphylococcus– Cocci in clusters
• S. aureus: facultative anaerobes; can tolerate high osmotic pressure and low moisture; produce many toxins (e.g. enterotoxin); toxic shock syndrome, food poisoning
Order Bacillales
Figure 1.17
• Generally aerotolerant anaerobes, lack an electron-transport chain
• Lactobacillus– produce lactic acid (industrial and commercial
application); found in vagina, intestinal tract, and oral cavity
• Enterococcus– facultative anaerobes; found in GI tract, vagina, and
oral cavity; leading cause of nosocomial infection
Order Lactobacillales
Order Lactobacillales
– E. faecalis & E. faecium: infect surgical wounds & urinary tract
• Listeria: facultative anaerobes– L. monocytogenes: contaminate food (dairy
products); can grow in refrigeration temperature
• Streptococcus– Usually cocci in chains; human pathogens– Have hemolytic activity (alpha hemolysis,
beta hemolysis, and no hemolysis)
Order Lactobacillales
– S. pyogenes: scarlet fever, pharyngitis, impetigo, and rheumatic fever
– S. mutans: dental carries
– S. pneumoniae: most common cause of pneumonia
Figure 11.18
• Wall-less and highly pleomorphic
• Very small (0.1 - 0.25 µm)
• Degenerative evolution– M. pneumoniae:
common form of mild pneumonia
– Spiroplasma: plant pathogens and common parasites of plant-feeding insects
Order Mycoplasmatales
Figure 11.19a, b
Actinobacteria
• High G + C
• Gram-positive; highly pleomorphic; tend to be filamentous; very common inhabitants in soil
Phylum Actinobacteria
• Mycobacterium– Aerobic, acid-fast (contains mycolic acids
which forms waxy, water resistant layer in cell wall); slow grower (may take weeks for visible colonies to appear)
– Found in soil and water; occasional pathogens– Human pathogens
• M. tuberculosis Tuberculosis• M. leprae Leprosy
Phylum Actinobacteria
• Nocardia– Aerobic; filamentous morphology– Reproduction by forming rudimentary
filaments which fragment into short rods– Cell wall resemble mycobacteria; often acid-
fast• N. asteroides Mycetoma and occasionally cause a
chronic, difficult-to-treat pulmonary infection
Phylum Actinobacteria
• Corynebacterium– Tend to be pleomorphic; morphology varies
with the age of the cells• C. diphtheriae Diphtheria
• Propionibacterium– Form propionic acid; fermentation of Swiss
cheese• P. acnes Common on human skin, cause acne
• Frankia– Form nitrogen-fixing nodule in alder tree roots
Phylum Actinobacteria
• Gardenella– Gram-variable; highly pleomorphic– Cause of one of the most common forms of
vaginitis
• Actinomyces– Facultative anaerobe; filamentous morphology– Found in the mouth and throat of humans and
animals• A. israelii actinomycosis
• Streptomyces– One of the most commonly isolated bacteria from
soil; responsible for the musty odor of soil– Strict aerobes; filamentous bacteria– Produce most of our commercial antibiotics
Phylum Actinobacteria
Figure 11.20b
• Bacteria size range– Thiomargarita
(750 µm) to nanobacteria (0.02 µm) in rocks
Microbial Diversity
Figure 11.26
• PCR indicates up to 10,000 bacteria/gm of soil. Many bacteria have not been identified or characterized because they:– Haven't been able to culture (need to develop special
media/nutrients and cultivation condition)– Are part of complex food chains requiring the
products of other bacteria– Need to be cultured to understand their metabolism
and ecological role
Microbial Diversity
Chapter Review
• Prokaryotic organisms are classified into 2 domains: Archaea & Bacteria based on rRNA sequences– Each domain is further subdivided into phylum,
class, order, family, genus, and species
• Domain Bacteria– Relatively few species cause disease in humans,
animals, plants or any other organisms– Essential part of life on Earth
Domain Bacteria
• Phylum: Proteobacteria (gram-negative bacteria)1) Alpha- (α-) proteobacteria– Includes most of the proteobacteria that are
capable of growth at very low levels of nutrients; nitrogen –fixing bacteria & several plant & human pathogens
– Some bacteria with unusual morphology such as prosthecae
– Prosthecae: a stalk or bud protruding from a prokaryotic cell
Domain Bacteria
2) Beta- (-) proteobacteria– Often use nutrient substances that diffuse away
from areas of anaerobic decomposition of organic matter
– Considerable overlap between the α- & -proteobacteria, especially among the nitrifying bacteria; some human pathogens in this group
– Spirillum helical shaped bacteria, but use flagella for motility (not axial filament)
Domain Bacteria3) Gamma- (-) proteobacteria– Constitute the largest subgroup of proteobacteria;
many are human & plant pathogens (e.g. Order Pseudomonadales, Legionellales, Vibrionales, Enterobacteriales, & Pasteurellales)
4) Delta (-) proteobacteria– Include some bacteria that are predators of other
bacteria and important contributors to the sulfur cycle (e.g. Bdellovibrio, Desulfovibrio, and Myxococcus)
– Myxococcus form fruiting bodies under low nutrients condition
Domain Bacteria
5) Epsilon- (-) proteobacteria– Slender gram-negative rods that are helical or
vibrioid (e.g. Campylobacter & Helicobacter)– Vibrioid: helical bacteria that do not have a
complete turn
• Gram-negative Nonproteobacteria – Include several photosynthetic bacteria: Phyla
cyanobacteria, green sulfur bacteria, & green nonsulfur bacteria (Table 11.2)
Domain Bacteria
– Purple sulfur (α-proteobacteria) & purple nonsulfur (-proteobacteria) also included in this section
– Cyanobacteria carry out oxygenic (oxygen-producing) photosynthesis and fix nitrogen gas (in specialized cell called heterocyst) from the atmosphere into ammonium
– Green & purple photosynthetic bacteria carry out anoxygenic photosynthesis (generally anaerobic)
Domain Bacteria
• Gram-positive bacteria– 2 groups based on G + C ratio1) Firmicutes (low G + C ratio)– Includes important endospore forming bacteria
(e.g. Bacillus & Clostridium), medically important bacteria (e.g. Staphylococcus, Enterococcus, & Streptococcus), industrially important bacteria (e.g. Lactobacillus), and wall-less Mycoplasma
Domain Bacteria
2) Actinobacteria (high G + C ratio)– Highly pleomorphic, but tend to be fimalentous– Common inhabitants in soil– e.g. acid-fast group (e.g. Mycobacterium &
Nocardia), and antibiotic producing Streptomyces.
• Assorted Phyla– Chlamydiae: no peptidoglycan in cell wall;
intracellular parasite (human pathogen); has unique developmental cycle (elementary body = infectious)
Domain Bacteria
– Spirochaetes: coiled morphology; motility by axial filament; many found in human oral cavity & in environment; some human pathogens
– Bacterioidetes: several genera of anaerobic bacteria
– Fusobacteria: anaerobic bacteria, spindle-shaped (often pleomorphic); can cause dental diseases
Domain Archaea
• Cell wall lacks peptidoglycan; a few lack cell wall
• Frequent inhabitants of exceptional extreme environment (heat, cold, acidity, & pressure)
• 3 major groups:– Extreme halophiles: survive in very high
concentrations of salt; found in Great Salt Lake, solar evaporating ponds, salinas, & Dead Sea
Domain Archaea
– Extreme thermophiles: thrive in high temperature (above 70 oC) or sulfur rich environment; found in acidic, sulfur rich hot springs or deep ocean hydrothermal vents
– Methanogens: obligately anaerobic methane producing bacteria; found in human intestines and used in sewage-treatment processes
• Microbial Diversity– Various sizes: nanobacteria (0.02 – 0.03 μm) to
giant bacteria (750 μm)
Microbial Diversity
• Many bacteria in the environment have not been identified or characterized due to:– Lack of culture method – Some bacteria are part of complex food chains
and can only grow in the presence other microbes that provide specific growth requirements
• PCR can be used to reveal the presence of bacteria that cannot be cultured in the laboratory
Chapter Review
• Know these terms: prosthecae, vibrioid, and oxygenic
• Know different groups of proteobacteria (and some examples) given in the chapter review section
• Know the names of different photosynthesizing bacteria and their mode of photosynthesis
Chapter Review
• Know characteristics of 2 groups of gram-positive bacteria and some of the examples listed in the chapter review
• Know characteristics of Arhaea, and its 3 major groups (characteristics and where they are found) given in the chapter review
• Know why many bacteria have not been classified and identified (2 main reasons) & use of PCR to detect them without culturing them