Cheatography
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Cheat sheet to refer before Microbiology examination
This is a draft cheat sheet. It is a work in progress and is not finished yet.
The Importance of Microorganisms
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Who are the members of the microbial world? - Cellular and acellular microorganisms too small to be clearly seen by the unaided eye
- Organisms with no highly differentiated tissues
- Relatively simple in their constructions
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What are the types of microorganisms 1. Cellular - Includes Fungi, Protists, Bacteria and Archaea
2. Acellular (Not made up of cells/divided into cells) - Includes Virus, Viroids, Satellites and Prions
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Describe prokaryotic cells Their contents are not divided into compartments by membranes
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Describe eukaryotic cells - Have a membrane-enclosed organelles
- More complex morphologically
- Usually larger than prokaryotes
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What are the three domain systems? - Bacteria
- Archaea
- Eukaryotes
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Describe the domain bacteria - Usually single-celled organism
- Contain peptidoglycan in their cell wall
- Most lack membrane bounded nucleus
- Ubiquitous and some live in extreme environments
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Describe the domain archaea - Distinguished from bacteria by unique rRNA sequences
- Have unique membrane lipids
- Lack peptidoglycan in their cell walls
- Many live in extreme environments
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Describe the domain eukarya - Include plants, animals, protists and fungi
- Protists are generally larger than bacteria and archaea
- Fungi have metabolic capabilities
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What are the differences between organisms' rRNA? - Archaea SSU rRNA are more similar to eukaryotes compared to bacteria
- Prokaryotes have tRNA on their rRNA
- Prokaryotes have longer rRNA compared to eukaryotes
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Describe viruses - Smallest of all microbes
- Require host cell to infect
- Consist of nucleic acid and protein
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Describe viroids and satellites Composed of RNA only but some have DNA
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Describe prions - Infectious proteins
- Lack nucleic acid
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How did the methods used to classify microbes changed? Before
- Organisms were classified into five kingdoms ( Monera, Protista, Fungi, Animalia, Plantae)
- All organisms with prokaryotic cell structures are under Monera
- Prokaryotes are too diverse to be grouped together in a single kingdom so this is invalid
After
- Recent discoveries on rRNA lead to classification into three domains (Bacteria, Archaea, Eukaryotes)
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Different characteristic that distinguish microorganisms from the other - Bacteria: Contain peptidoglycan in their cell walls
- Archaea: Have unique membrane lipid
- Protists: Usually larger than bacteria and archaea
- Fungi: Have metabolic capabilities
- Viruses: Composed of nucleic acid and proteins
- Viroids: Composed of RNA only
- Satellites: Composed of RNA/DNA
- Prions: Composed of infectious protein only
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Microbiology and Its Origins
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Explain the endosymbiotic hypothesis Over time the bacterial endosymbiont of ancestral cell in the eukaryotic lineage lost its ability to live independently, becoming either a mitochondrion if it used aerobic respirations or chloroplasts if it was a photosynthetic bacterium
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What are the evidences to support endosymbiotic hypothesis? - Mitochondria and chloroplasts have similar SSU rRNA with bacteria:Mitochondria - proteobacteria while chloroplast and green algae - cyanobacterium
- Peptidoglycan found in chloroplasts
- Mitochondria and chloroplast have similar DNA and ribosomes with Bacteria's
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Explain the hyrogen hypothesis - The endosymbiont was an anaerobic bacterium that produces hydrogen and carbon dioxide as end products of its metabolism
-Over time, the host become dependent to the hydrogen produced by the endosymbiont thus it evolved into several organelles
- Perform aerobic respiration: Mitochondria
- Produce ATP through fermentation: Hydrogenosome
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Describe Koch's Postulates 1. The microorganism must be present in every case of the disease but absent from healthy organisms
2. The suspected microorganism must be isolated and grown in a pure culture
3. The same disease must result when the microorganism is inoculated into a healthy host
4. The same microorganism must be isolated from the infected host
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What is a pure culture? A medium used to isolated suspected bacterial pathogens
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Why are pure cultures important to Koch's postulates? - To isolate suspected bacterial pathogens
- Agar is not broken down by most bacteria
- Agar will not melt until it reach 100c and will only solidify if it reach 50c
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