Week 1

Koch’s Postulate

1. Pathogen = in disease, not healthy

2. Grown in pure culture (isolated)

3. Isolated culture = infect healthy

4. Can be reisolated

Issues with Koch’s Postulate

1. Many organisms = do not fulfill all of Koch’s postulates (viruses) but are still known to be causal

2. There are asymptommatic carriers

3. Requires specific conditions

4. Requires specific healthy organisms (i.e. humans, not cows)

5. Some individuals = not susceptible, such as those w/ strong immune systems

Bacteroidetes

Gram negative

• major vertebrate colonizer

• digests complex carbohydrates

• modulate host immjune responses

• includes Bacteroides

Proteobacteria

Gram negative

• very diverse

• numerous pathogens

• includes Escherichia and Yersinia

Firmicutes

mostly Gram positive

• many produce endospores

• includes Clostridia and Bacilli

Actinomycetota

Gram positive

• major contributors to

decomposition of organic matter

• includes Streptomycetes and

Mycobacteria

Bright Field Microscopy

• bright background

• dark specimen

• with stain

Phase-contrast Microscopy

• cells = motile

• grey/ green background

• see internal structure

• fluorescence microscopy

• colourful

• shining light

Confocal (fluorescence) microscopy

• more focused than normal fluorescence

• see fibers

Transmission (electron) microscopy

• high quality

• can see inside

• uniform grade background

Scanning (electron) microscopy

• only see surface

acellular

• no cell

• can’t do life processes on own

• require a host

viroids

• do RNA replication

• don’t have protein coat

viruses

• RNA and DNA

• Do have protein coat

• have membrane

prions

• proteins that help misshapen other proteins

• no nucleic acids

nucleoids

carry chromosomes

plasmids

extra chromosomal material

protozoa

free living and parasitic microorganisms that feed on organic matter

Vertical Gene transfer

Adult → kids

Horizontal Gene transfer

organism → organism

ribozymes

catalytic RNA

Endosymbiotic theory

1. Mitochondria and chloroplasts = free living (have own DNA, ribosomes and can replicated independently)

2. Take by larger cell

3. Entered host cell as muralist or pathogen

4. became permanent

Endsymbiots

organisms = live inside another but help each other

Endosymbiotic theory importance

refers to the separation between Archaeoeukarya (how eukarya evolved)

importance of kochi postulate

demonstrated that particular microorganism cause particular diseases