Microbiology Module One: Microbial Cell Structure and Function

Microorganisms “Microbes”

-organisms that are too small to be clearly seen without a microscope

-lack differentiated tissues

-Most numerous organisms on Earth

-Found in diverse habitats

*More microbial cells in the human body than human cells*

Cellular Organisms

Fungi, protists, Bacteria, Archaea

Fungi

-pathogenic

-yeast (sourdough, beer, wine)

-Molds

Protists

-“diarrhea lettuce”

-eukaryotic microbe

-Algae

-Protozoa

-Slime molds

Bacteria

Escherichia coli

Archaea

-Closely related to bacteria

-not really associated with disease but with extreme habitats

-Methanogens

Acellular Organisms (Do not replicate independently)

Viruses, Viroids, Satellites, Prions

Viruses

-composed of protein and nucleic acid

-named based on the illness caused, the infection caused, or the type of replication system

Viroids

-Infectious RNA

-affects plants

-composed of RNAatS

Satellites

-virus of a virus

-composed of nucleic acid enclosed in a protein shell

Prions

-A misfolded protein turns other proteins into misfolded proteins

-composed of protein

Carl Woese

-Established the three-domain system for classifying cellular life (1970s)

-Bacteria, Archaea, Eukarya

Domain Bacteria

-Unicellular

-Prokaryotes (lack a membrane-bound nucleus)

-E.Coli, Cyanobacteria

-Have peptidoglycan cell walls

-Microbiomes

-Diverse environments

-ester-linked phospholipids

Domain Archaea

-Based on ribosomal RNA sequencing

-Similar to bacteria, with some features similar to Eukarya

-Unicellular

-Prokaryotes

-Methanobacteriota (can survive off methane)

-Can survive in extremely harsh environments (hot springs, salt flats)

-Unusual metabolic characteristics

-extremophiles

-Glycerol diethers and diglycerol tetraethers

-Do NOT directly cause disease in humans (can be associated with some conditions)

Domain Eukarya

-Plants, Animals, Fungi(Yeast & Mushrooms), Protists(Algae & Protozoa)

-Unicellular and multicellular

-Eukaryotic cells (have a membrane-bound nucleus)

-ester-linked phospholipids

Microbial taxonomy involves multiple orders of classifications

Domain(classification), Phylum, Class, Order, Family, Genus, Species (defined by unique metabolic capabilities)

Proper microbe classification formation

-Genus first, capitalized, and italicized

-Species second, lowercase, and italicized

-Strain last

*Genus can be abbreviated after the full spelling of the name has been established*

Microbes evolve and diversify all the time via

-Mutation (division errors, mutagens in the environment)

-New genes and phenotypes (bacteria exchange DNA material)

-Horizontal gene transfer

-Eukaryotic sexual reproduction

Phylogentic Trees

display evolutionary relationships between organisms using genetic sequencing comparisons

16S rRNA

-structural component

-key component in bacteria (has 1 to 5 copies)

-diverse

-used to analyze microbial community composition and phylogeny

-an important function in translation

-mixture of variable regions

-contains conserved regions (design different primer combinations that amplify some variable regions)

-different components of the sequence can yield different relationships

Germ Theory

-Microbes causing disease were not always apparent

-thought sickness came from dirty air and water

Koch’s Postulates

-can be used to identify the causative agent of a microbial disease

What’s wrong with this? One may be immune to the variableescribD

Postulate #1

The suspected causative agent must be absent from all healthy organisms but present in all diseased organisms

Postulate #2

The causative agent must be isolated from the diseased organism and grown in pure culture (recall TopHat)

Postulate #3

The cultured agent must cause the same disease when inoculated into a healthy susceptible organism

Postulate #4

The same causative agent must then be reisolated from the inoculated diseased organism