Microbiologie: Les grands groupes de microorganismes (monde microbien) Flashcards
What are the steps for the classification of living beings?
D, K, P, C, O, F, G, S (sub-s)
Domaine, règne (not defined for bacteria), embranchement, classe, ordre, famille, genre, espèce —> souche (sous-espèce)
What is the classification for E. Coli? (D, K, G, S, S)
D: Bacteria
K: N/A
G: Escherichia
S: coli
sub-S: Sakai (sérotype O157:H7)
What are the classification types according to domain?
- Bacteria —> procaryotes (no nucleus/sophisticated organelles)
- Archaea —> procaryotes (no nucleus/sophisticated organelles)
- Eukaryotes —> have nucleus
What is the most evolved plyla of bacteria?
Proteobacteria —> most pathogens belong in this phylum
What is believed to be the origin of mitochondria and chloroplasts?
Mitochondria: endosymbiotic bacteria
Chloroplasts: chloroplasts
Where are most archaea found?
Extreme environments except for methanogens which are in the gut
What are the kingdoms (règnes) in pro and eukaryotes?
Prokaryotes: N/A
Eukaryotes: protists (unicellular eukaryotes), *fungi* (mycètes), plants (*Algus vertes*) and animals
How are viruses and prions categorized?
They are not considered living, but are associated to all other branches of living things
Although their specific hosts are usually limited to certain taxonomic ranks and sometimes even limited to one species
How do viruses work?
They are semi-autonomous replicons that need to infect host in order to replicate using the hosts own “machinery”, once replicated they can leave host and infect others
Why are viruses so hard to treat?
They use our own bodies mechanisms so it would be hard to treat them without killing our own cells
How do prions work?
They are misfolded proteins that work as pathogenic agents able to cause a cascade of conformational changes in healthy proteins that can lead to damage within cells and tissues
**DO NOT REPLICATE —> CAUSE A CASCADE**
What does the word microorganism mean?
Term representing bacteria, viruses, fungi, and protozoa
What do bacteria, viruses, fungi, and protozoa have in common? (7)
- Small size, need a microscope to see them
- Omnipresent/abundant in nature
- Unicellular (some fungi can be uni and pluricellular)
- Simple organization/structure
- Includes prokaryotes and eukaryotes
- Able to accomplish metabolic processes (except viruses)
- Capable to reproduce autonomously (except viruses)
What are the different ways to classify and identify bacteria?
Classification: taxonomy
Identification: knowing what it is
- Genotype: genetic constitution
- Phenotype: observable characteristics
What are the 5 tools used for classification and identification?
- Morphology: form, elevation, border, colour, transparency, and surface aspect
- Biochemical
- Serological (antibodies)
- Physico-chemical
- Genetics
What are the 4 most common ways to name/refer to a bacteria?
- following latin root
- following greek root
- named after a person
- using the common name
What are the different shapes and spatial arrangements of bacteria called?
Shapes:
- Rod: bacilla, coccobacilla (sometimes)
- Sphere: cocci
- Spiral: vibrio (comma-shaped), spirochaetes (corkscrew)
- “Difforme”: pléïomorphes
Spatial arrangement:
- Individual
- Pairs: diplo
- Chains: strepto
- Mass: organized or not
What are the 3 different cellular envelopes for bacteria?
- Capsule (or glycocalyx)
- Cell wall (rigid)
- Cell membrane (all bacteria have this)
What is the function of a capsule?
Added pathogenic protection against phagocytosis —> makes it “slippery”
Made of polysaccharides —> Antigène K
There are 83 different variants of the capsule for pneumococcal bacteria
What is a glycocalyx?
Intercellular capsule forming agglutinating biofilms that promote adhesion to materials and make it much harder to penetrate/kill bacteria by antibiotics or the immune system
What is the cell wall?
Rigid envelope that ensures the form of the bacteria
What are the two different structures of cell walls?
Gram-positive: thick layer of peptidoglycan with one internal membrane
Gram-negative: thin layer of peptidoglycan with an additional external envelope with Lipopolysaccharides (LPO) —> antigen O
What is the cell membrane and what are its functions (3)?
Phospholipid bilayer with transmembrane proteins
Function:
- osmotic barrier to control ionic levels
- transport: regulate exchanges
- enzymes for metabolism
What are the internal constituents of a bacteria?
- Cytoplasm containing DNA and ribosomes
- DNA: double-stranded DNA
- Plasmids: circular extra-chromosomal DNA, with autonomous replication
What do plasmids do?
Code for properties to help with survival including genes for antibacterial resistance
What are the potential external appendages of bacteria?
Flagellum Pili/fimbraea
What are the flagella?
Assure motility —> antigène H
Number and positioning depend on genus
What are the pili/fimbrae?
Hairlike structures used for: movement, reproduction, conjugaison, transfer of DNA/plasmids
What is a spore?
Only in genus Bacillus and Clostridium
Helps with survival in unfavourable conditions (lack of H2O/organic material)
Their volume and position are distinguishing characteristics for species types
Illnesses associated to sporulated bacteria: gangrene, tetanus, botulism, anthrax
What are the steps of sporulation and germination?
What are the three bacterial antigens?
H: Flagella
K: Capsule
O: Gram +, gram -
What are the “obligatoire” and “facultative” components of bacteria?
Obligatoires (5): paroi cellulaire, membrane plasmique, cytoplasme, chromosome, ribosomes
Facultatives (6): capsule, endotoxines, plasmide, flagelle, pili, spore
How are bacteria identified?
Simple colouration
GRAM staining
Optic microscope
Fluorescent microscope: lasers, immunofluorescence, 3D reconstruction (computer), can use to film interactions between living species
Electronic microscope: transmission (2D), scan (3D), diamond knife (sectioning and cutting things)
Atomic force microscopy and tunnelling probe microscopy
Biochemical tests
How does gram staining work?
What are the different available biochemical tests to identify bacteria?
Carbon source, aerobic, anaerobic, ability to ferment, terminal metabolic products, tolerance to metabolic and antibiotic inhibitors
Micro-Scan: points depending on positive reactions to certain things
- rangée 1:4, rangée 2:2, rangée 3:1 —> final number corresponds to genus and species of bacteria
Serological antigen/antibody tests
Antigen: ELISA TEST… limited number and sensitivity
Diagnostic test using DNA detection:
- Detection kits to test for the presence of suspected pathologies
- Used when you don’t have enough time to grow something or the right conditions
