Chapter 10: Classification of Prokaryotes
Principles of Taxonomy
Taxonomy is the science of classifying organisms. Provides universal names for organisms. Provides a
reference for identifying organisms. Allows organisms to be arranged into similar, or related groups
Placing Bacteria
1735 Kingdoms Plantae and Animalia
1857 Bacteria and fungi put in the Kingdom Plantae –“Flora”
1866 Kingdom Protista proposed for bacteria, protozoa, algae, and fungi
1937 Prokaryote introduced for cells "without a nucleus"
1961 Prokaryote defined as cell in which nucleoplasm is not surrounded by a nuclear membrane
1959 Kingdom Fungi
1968 Kingdom Prokaryotae proposed
1978 Two types of prokaryotic cells found
Scientific Nomenclature
Common names: Vary with languages. Vary with geography
Binomial Nomenclature (genus + specific epithet). Used worldwide
 Escherichia coli
 Homo sapiens
Taxonomic Hierarchy
Domain – Kingdom – Phylum – Class – Order – Family – Genus – Species
Classification of Prokaryotes
 Prokaryotic species: A population of cells with similar characteristics
 Culture: Grown in laboratory media
 Clone: Population of cells derived from a single cell
 Strain: Genetically different cells within a clone
Domain Bacteria
Proteobacteria – From the mythical Greek god Proteus, who could assume many shapes. Gram-negative and
chemoheterotrophic
1. The Alphaproteobacteria – Human pathogens
o Bartonella - B. henselae: Cat-scratch disease
o Brucella: Brucellosis
o Ehrlichia: Tickborne
o Plant pathogen
o Agrobacterium: Insert a plasmid into plant cells, inducing a tumor
o Nitrogen-fixing bacteria
o Azospirillum – Grow in soil, using nutrients excreted by plants. Fix nitrogen
o Rhizobium – Fix nitrogen in the roots of plants
2.
The Betaproteobacteria
o Neisseria - Chemoheterotrophic; cocci (N. meningitidis and N. gonorrhoeae)
o Spirillum - Chemoheterotrophic; helical
o Bordetella - Chemoheterotrophic; rods (B. pertussis)
o Burkholderia – Nosocomial infections
3. The Gammaproteobacteria
o Pseudomonadales (Pseudomonas). Opportunistic pathogens. Metabolically diverse. Polar flagella.
o Legionellales (Legionella) - Found in streams, warm-water pipes, cooling towers (L. pneumophilia)
o Coxiella –Q fever transmitted via aerosols or milk
o Vibrionales – Found in coastal water. Vibrio cholerae causes cholera and V. parahaemolyticus causes
gastroenteritis
o Enterobacteriales (enterics). Peritrichous flagella; facultatively anaerobic
o Pasteurellales (Pasteurella) Cause pneumonia and septicemia
o
Haemophilus – Require X (heme) and V (NAD+, NADP+) factors
4. The Deltaproteobacteria
o Bdellovibrio – Prey on other bacteria
o Campylobacter – One polar flagellum. Causese gastroenteritis
5. The Epsilonproteobacteria
o Helicobacter – Multiple flagella. Peptic ulcers and Stomach cancer
o Oxygenic Photosynthetic Bacteria (Cyanobacteria) – Gliding motility. Fix nitrogen
o Clostridiales (Clostridium) – Endospore-producing. Obligate anaerobes
o Bacillales (Staphylococcus)
o Lactobacillales – Generally anaerobes; lack an electron-transport chain (Lactobacillus, Streptococcus,
Enterococcus, and Listeria)
o Mycoplasmatales – Wall-less; pleomorphic 0.1 - 0.24 µm
Phylum Actinobacteria
 Actinomyces - A group of nonmotile, non spore producing, aerobic or anaerobic bacteria that are pathogenic to
humans. The pathogenic type are usually present in the mouth and throat. Gram Positive
 Corynebacterium (suborder) Gram Positive, rod-shaped bacteria. Usually a curved bacilli. Most common are C.
acnes, which is found in acne lesions, and C. diphtheriae, that causes diphtheria
 Frankia (family) Gardnerella (genus)
 Mycobacterium
 Nocardia
 Propionibacterium
 Streptomyces (family) Chiefly saprophytic forms found in soil and used to make antibiotics
Genus Chlamydia
Chlamydia trachomatis – Trachoma. STI, urethritis (Chlamydophila pneumonia)
o Chlamydophila psittaci - Psittacosis
Spirochetes (Borrelia, Leptospira, Treponema)
Fusobacteria (Fusobacterium). Are found in the mouth. May be involved in dental diseases
Domain Archaea – Extremophiles
 Hyperthermophiles – Pyrodictium, Sulfolobus
 Methanogens - Methanobacterium
 Extreme halophiles - Halobacterium
Microbial Diversity
Bacteria size range: Thiomargarita (750 µm) to Nanobacteria (0.02 µm) in rocks
PCR indicates up to 10,000 bacteria per gram of soil. Many bacteria have not been identified because they
haven't 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