L9: Bacterial diversity and human health

number of names and estimated bacteria

• 16000 named

• 700000 - 1.4 million estimated

proteobacteria

• gram negative

• very diverse

• E. coli, vibrio cholerae

• ancestor of mitochondria

cyanobacteria

• gram negative

• only bacteria to photosynthesize

• ancestor of chloroplasts

spirochetes

• gram negative

• some free living

• some symbiotic

• Borrelia burgdorferi (lyme disease)

chlamydias

• gram negative

• obligate parasites

• survive inside hosts

• no cell wall

gram positive

• very diverse

• mostly chemoheterotrophs

• Staph A, bacillus subtilis, Lactobacillus bulgaricus

• M. TB but doesnt have a cell wall

draw phylogenetic tree: eukaryote, archae, proteobacteria, chlamydia, spirochete, cyanobacteria, gram positive bacteria

h

symbiosis

2 species live together in close relationship

symbiont

lives with host

types of symbiosis

• mutualism

• commensalism

• parasitism

mutualism

both host and symbiont benefit

commensalism

one benefits, other is unharmed

parasitism

one harms the other

disease

disturbance in normal functioning

infectious disease

• disease caused by microorgs

• mostly by bacteria, fungi, virus, eukaryotic protists

• archaes are yet to be linked

pathogens

microorgs that cause a specific disease

pathogenesis

process by which pathogen causes disease

requirements for pathogenesis

• enter host

• attach/invade host cell

• evade defenses

• obtain nutrients and reproduce

• exit from original point and spread

bubonic plague

• Yersinia pestis

• gram negative

• non motile, coccobacillus

• transmission via fleas

obligate pathogens

will cause disease

opportunistic pathogens

will only cause disease if triggered

Mannheimmia haemolytica

• gram negative bacillus

• live in upper respiratory tract of healthy farm animals

Bovine pneumonic pasteurellosis

• shipping fever

• pneumonia accompanied by fever, nasal discharge

• occurs when animals are stressed

M. haemolytica pathogen type

opportunistic

healthy vs BPP calf flowchart

h

escherichia coli

• gram negative bacillus

• live in intestines, most are non pathogenic

food poisoning e coli serotype

O antigen 157 and H antigen 7

how is e coli transmitted to humans and symptoms

• contaminated food

• diarrhea

• cramps

2 categories of toxins

• exotoxin

• endotoxin

exotoxin and example

• produced by bacteria to attack host

• shiga toxins produced by e coli

endotoxin

• lipopolysaccharide

• outermost layer of gram negative bacteria

• gets released when the cell is killed and causes an immune response

• sugars on the further end are called O-antigen

• worsens exotoxins

Bacillus antraxis

• gram positive streptobacillus

• causes anthrax

• spore forming

• only obligate pathogen in the genus

anthrax

skin infection via contact, lung infection via inhalation

storage in antimicrobial chemicals

• vinegar, oil, alcohol

• sugar and salts make water move outwards due to osmotic pressure

fermentation

produce antimicrobial chemicals such as acids and alcohols

drying

removal of water prevents microbial growth

smoking

• smoke is an antimicrobial

• usually combined with drying/salting

cooling and freezing

• cooling inhibits microbial growth

• freezing kills microorganisms

pasteurization

• exposes samples to low heat for a short amount of time

• kills off most problematic pathogens