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Classifying Bacteria
• Bergey’s Manual of Systematic
Bacteriology
– Classifies bacteria via evolutionary or genetic
relationships.
• Bergey’s Manual of Determinative
Bacteriology
– Classifies bacteria by cell wall composition,
morphology, biochemical tests, differential
staining, etc.
Prokaryotic Organisms
• Prokaryotic-means pre-nucleus.
– Genetic material not enclosed in a special
nuclear membrane.
– What are the other differences between
Prokaryotic and Eukaryotic organisms.
• Prokaryotic organisms are split into two
Domains.
– Bacteria
– Archaea
The Prokaryotes
Domain Bacteria
• Phylum Proteobacteria
– Contains most of the gram negative bacteria.
– Relationships have been put together via
Ribosomal RNA studies.
– Split up into five classes.
– Alpha, beta, gamma, delta, and epsilon
Alphaproteobacteria
• The Alphaproteobacteria contain many
bacteria that are capable of nitrogen
fixation in symbiosis with plants.
– What is nitrogen fixation?
• Also includes several plant and human
pathogens.
The Alphaproteobacteria
• Human pathogens
– Bartonella
• B. hensela: Cat-scratch disease
– Brucella: Brucellosis
• Can survive phagocytosis, an important element of the
body’s defense against bacteria.
The Alphaproteobacteria
• Obligate intracellular parasites
– Rickettsia: Arthropod-borne, spotted fevers
• R. rickettsii: Rocky Mountain spotted fever
The Alphaproteobacteria
• Plant pathogen
– Agrobacterium:
Insert a
plasmid into
plant cells,
inducing a
tumor
Figure 9.19
The Alphaproteobacteria
• Nitrogen-fixing
bacteria
– Rhizobium
• Fix nitrogen in the
roots of plants
Figure 27.5, step 5
The Betaproteobacteria
• Neisseria
– Usually inhabit the
mucous membranes
of mammals.
– N. meningitidis
– N. gonorrhoeae
Figures 11.4, 11.6
The Gammaproteobacteria
Pseudomonas
• Opportunistic
pathogens
• Metabolically
diverse
• Polar flagella
Figure 11.7
The Gammaproteobacteria
Legionella
• Found in streams, warm-water pipes, cooling
towers
• L. pneumophilia
• Legionellosis or legionaire’s disease
Figure 24.15b
Enteric Bacteria Genera
• Escherichia-Very commonly found in human
intestines. Known for its ability to cause very
serious food-borne disease.
• Salmonella-Almost all members of this genera
are potential pathogens.
• Serratia-Can be found on catheters, in saline
irrigation solutions, and in other supposedly
sterile situations.
• Proteus-very motile genera, many flagella, can
cause UTI’s or wound infections.
The Epsilonproteobacteria
• Helicobacter
– Multiple flagella
– Peptic ulcers
– Stomach cancer
Figure 11.12
Cyanobacteria
• Oxygenic photosynthesis
• Heterocysts-specialized cells that fix
nitrogen.
Firmicutes
• Low G + C ratio-Guanine and cytosine
bases in DNA.
• Gram-positive bacteria.
Clostridiales
• Clostridium
– Endospore-producing
– Obligate anaerobes
C. tetani- tetanus,
C. Botulinum- Botulism
C. perfringens- gas
gangrene,
C. difficile- serious diarrhea,
Especially when undergoing
Antibiotic therapy.
Figures 11.15, 11.16
Bacillales
• Bacillus
– Endospore-producing rods
– B. anthracis –cause anthrax
Figure 11.17b
Bacillales
• Staphylococcus
– S. aureus-cause a lot of hospital infection.
MRSA- methicillin resistant S. aureus.
Figure 11.18
StreptococcusMembers of this genus are probably
responsible for more
Diseases than any other
group of bacteria.
Pneumonia, strep throat,
cavities, scarlet fever.
Figure 11.19
Actinobacteria
• High G + C-guanine and cytosine levels in
DNA.
• Gram-positive
Important Genera
• Mycobacterium
– M. tuberculosis
– M. leprae-causes leprosy.
• Propionibacterium-Some species help make
swiss cheese, others cause acne.
• Streptomyces-produce a a large number of
antibiotics.
Figure 11.21b
Phylum Spirochaetes
• Treponema
– T. pallidum is the cause of syphilis.
Figure 11.24
Domain Archaea
• Hyperthermophiles
– Pyrodictium
– Sulfolobus
• Methanogens
– Methanobacterium
• Extreme halophiles
– Halobacterium
Figure 11.26
Homework
• Write a few sentences
about the difference
between gram positive
cell walls and gram
negative cell walls, and
how the gram stain came
about.
• Also define:
• Nitrogen fixation
• Plasmids
• Diseases
• Rocky Mountain Spotted
fever
• Legionellosis
• MRSA
• Scarlet Fever
• Cat-scratch disease
• Brucellosis
• Peptic Ulcers
(Helicobacter)
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