learning objectives for chapter 4

Define symbiotic relationships and identify examples

Mutualism: Both partners benefit. Bacteroids (human gut bacteria) digesting plant matter

Commensalism: One benefits, the other is unharmed. Staphylococcus on human skin.

Parasitism: One benefits, the other is harmed. Borrelia burgdorferi causes lyme disease.

Amensalism: Pseudomonas aeruginosa releases a toxin that damages other bacteria. P. aeruginosa is unaffected.

Neutralism: E. coli and pseudomonas might sit unaffecting each other because resources are not limited.

Define microbial ecology and recognize cooperative and competitive interactions

Cooperative: microbes work together.

Competitive: microbes fight for the same space or food.

Compare normal/commensal/resident microbiota to transient microbiota

Normal/commensal/resident microbiota: Permanent microbes that live in or on the body for a long time without causing disease. Example: bacteroids that live in the gut or staphylococcus aureus that live on the skin.

Transient: temporary. Example: pseudomonas aeruginosa that causes UTI.

Explain how prokaryotes are classified

Prokaryotes are classified using shape, staining patterns, metabolic traits, and genetic analysis.

Describe the unique features of each class within the phylum proteobacteria.

Alphaproteobacteria: oligotrophs. Many are obligate intracellular parasites that must live in a host.

Betaproteobacteria: require many nutrients. Found in environments with high organic matter.

Gammaproteobacteria: Largest and most diverse class. Many are human pathogens or normal gut flora.

Deltaproteobacteria: Includes sulfate-reducing bacteria and predatory bacteria.

Epsilonproteobacteria: Smallest group, microaerophiles, which require little oxygen

Give examples of bacteria in each class of proteobacteria

Alphaproteobactreria: R. Prowazekii: causes epidemic typhus

Betaproteobacteria: Bordetella pertussis: causes whooping cough

Gammaproteobacteria: Haemophilus influenza: causes upper and lower respiratory infections as well as burn wound infections

Deltaproteobacteria: Bdellovibrio: parasitic

Epsilonproteobacteria: Helicobacter pylori: stomach ulcers

Describe the unique features of nonproteobacteria gram-negative bacteria.

Spirochetes: long, spiral shaped bodies. They use axial filament.

CFB group: rod-shaped anaerobes, ferment sugar or break down tough plant fibers

Phototrophic bacteria: Uses sunlight for energy

Chlamydia: Live entirely inside host cells to survive

Give examples of nonproteobacteria bacterium in each category.

Spirochetes: Treponema pallidum (causes syphilis)

CFB group: bacteroids melaninogenicus: breaks down food

Phototrophic bacteria: anabaena: cyanobacteria, uses the sun to make food

Chlamydia: lymphogranuloma venereum

Describe the unique features of each category of high G+C and low G+C gram-positive bacteria

Actinobacteria: has thick cell walls and soil dwelling habits. Major antibiotic producers and can cause severe respiratory diseases.

Firmicutes: has thick cell walls (or no cell wall at all). Includes endospore formers (survives harsh conditions) and beneficial lactic acid bacteria.

Give examples of bacteria of high G+C and low G+C group commonly associated with each category

Actinobacteria: Mycobacterium tuberculosis (causes TB)
Firmicutes: Bacillus anthracis (causes anthrax) or Lactobacillus (yogurt bacteria)