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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 GammaproteobacteriaPseudomonas
• Opportunistic
pathogens• Metabolically
diverse• Polar flagella
Figure 11.7
The GammaproteobacteriaLegionella
• 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 anaerobesC. tetani- tetanus, C. Botulinum- BotulismC. 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
Streptococcus-
Members 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)