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)