L9: Bacterial Diversity and Human Health

T or F: Not all bacteria species are believed to be named

• True

• 16,000 have been named

• 700,000 to 1.4 million are believed to exist

What is used to identify species of bacteria?

• 16S rRNA

Proteobacteria

• Gram negative

• Very diverse

• Photoautotrophs or chemoheterotrophs

• Ancestors of eukaryotic mitochondria via endosymbiosis

Cyanobacteria

• Gram negative

• ONLY bacteria photoautotroph that does oxygen photosynthesis

• Ancestors of eukaryotic chloroplasts via endosymbiosis

Gram-positive bacteria

• very diverse

• Mainly chemoheterotrophs

• Examples: Staphylococcus aureus, Bacillus anthracis, Bacillus subtilis

Chlamydia

• “gram negative”- no peptidoglycan cell wall

• Obligate parasites, survived inside host

Spirochetes

• gram negative

• some live on own, some symbiotic

Symbiosis

• 2 species living together in close relationship

Symbiont

• Usually smaller specie that lives with host

Mutalism

• Type of symbiosis

• Both benefit

Commensalism

• type of symbiosis

• One benefits, one not harmed

Parasitism

• type of symbiosis

• one benefits, one harmed

• commonly cause diseases

Fact about symbiote bacteria and human cells

• Estimated that amount of symbiote bacteria is equal to or greater than human cells

Disease

• disturbance in normal function of organism

Infectious disease

• any disease caused by a microorganism

• bacteria, eukaryotic protists, fungi, and viruses

• only archaea is not know to cause disease in humans

Pathogen

• bacteria that causes a disease

Pathogenesis

• process where pathogen causes a disease

5 things that make bacteria a pathogen

1. enters host

2. attaches and invades host cells/tissues

3. evades host defenses

4. obtains nutrients and reproduces in host

5. exits original point of infection and spreads

How does biofilm help pathogens?

• capsule/slime layer form structures to support bacterial communities to co-exist

• helps with attachment and evasion of host defense

Bacteria named after disease

• Bacillus anthracis causes anthrax

Obligate pathogens

• will (high chance) of causing disease

Oppurtunistic pathogens

• co-exist as normal microbiome

• only cause disease after being triggered (such as decrease in host immune system)

Shipping fever

• caused by Mannheimia haemolytica

• gram negative bacillus

• live in upper respiratory tract (nose/mouth)

• BPP (Bovine pneumonic pasteurellosis) occurs when cows are under stress (being shipped long distances)

• stress compromises immune system

• Fever, nasal discharge, loss of appetite, lack of movement

• opportunist pathogen

Escherichia coli

• gram negative

• Escherichia coli O157:H7 (o-antigen 157 and h-antigen 7)

  • commonly causes food poisoning

  • normal in cows (bovine intestine)

  • severe, causes acute hemorrhagic diarrhea and abdominal cramps

• two categories of toxins

  • endotoxin: outer member (LPS) gets released when cell is killed

  • exotoxin: toxins produced by bacteria (shiga toxins)

Bacillus antracis

• gram positive

• causation agent of athrax, skin/lung infection that can be fatal if left untreated

• forms spores (like a lot of bacillus)

• ONLY obligate pathogen in the genus

• Has been used for bioterrorism in 2001 where it was mailed leaving 5 people dead

What are the 8 techniques to suppress microbial growth in food?

1. storage in antimicrobial chemicals, sugar/salt causes water to travel out of the microbial cell preventing their growth (osmosis)

2. Fermentation, produce antimicrobial chemicals such as acids and alcohols

3. Drying, removal of water to prevent growth (especially UV radiation)

4. Smoking, smoke is antimicrobial (combined with drying and salting)

5. Canning, prevents growth (can boiled to kill pre-existing microbials)

6. Cooling/freezing, inhibits growth of bacteria, freezing causes ice crystals to form inside cell killing bacteria

7. Boiling/cooking, cannot survive intense heat

8. Pasteurization, low heat for short amount of time, kills most pathogens, used to preserve heat-sensitive products such as milk and wine