T3: Introduction and Classification of human microbiota Flashcards
How are microorganisms classified?
Life, Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
What is the role of flagella? Give examples of number and location.
These are long protruding structures that allow bacteria to swim. Bacteria can have multiple flagella which can be organised in different ways. Flagella protein is also used in identification (H antigen) of bacteria.
These can be:#
- Monotrichous (A) - single flagella
- Lophotrichous (B) - multiple flagella at a single point
- Amphitrichous (C) - flagella at both poles
- Peritrichous (D) - Flagella all over
What is the role of fimbriae/pilli?
Pilli/Fimbriae - theses are structures exposed to the extracellular space. Useful in adhesion. Can lead to a bacteria having a preference to a particular cell - tissue tropism.
Examples:
- Pili/opacity protein of Neisseria gonorrheae
- P/pap pili in uropathogenic E. coli
What is the difference between a capsule and slime layer?
Capsule/Slime layer - Capsule is tightly adhered to the cell. The slime layer is loosely adheres. These are protective layers - protect them form the environment (drying out), chemicals and immune system). Made up of polysaccharides.
What are endospores? Give examples of bacteria that produce them.
Some bacteria have the ability to form spores - allow them to persists. They are metabolically inert forms of bacteria. They are resistant to many forms of environmental stress:
- Desiccation
- UV radiation
- Temperature extremes
- Certain antiseptic agents
C. Difficle, for example is resistant to antibiotic gel
Examples of endospore-producing bacteria:
- Genus Bacillus
- Genus Clostridium
How are bacteria sorted according to there reaction to gram staining?
A cell wall is made up of peptidoglycan in the majority - they can be gram positive or gram negative. This is to with the arrangement of the peptidoglycan in the cell wall. Some have atypical cell walls without this sugar - this is a minority.
We differentiate them using gram staining. Gram positive retain the complex and appear blue/purple when visualised (the stain cant leave the bacteria as the peptidoglycan is less tightly packed). Gram negative bacteria loose their complex and appear red/pink.
Gram-positive bacteria: Staphylococcus, Streptococcus, Bacillus, Clostridium
Gram-negative bacteria: E. coli, Acinetobacter, Klebsiella, Neisseria
How can bacteria be sorted according to there shape and size?
Can be divided into cocci (circular shaped), bacillus (rod shaped), spirillum (spiral), filamentous and budding.
How do yeast replicate?
Replication by be asexual or sexual. Mostly they replicate by budding. A smaller yeast cell will start to grow, genetic information is transferred and you end up with a smaller daughter cell. Can get sexual reproduction where cells fuse into diploid cells, this allows mixing of the genetic information.
Give examples of parasites.
Can be protozoa which are unicellular eukaryotes such as plasmodium, entamoeba and giardia. Can also be helminths which are multicellular eukaryokes such as euterobius (pinworm), taenia (tapeworm) and ascaris (roundworm) .
How do parasites replicate?
ave asexual and sexual forms. Often need multiple hosts to complete the life cycle.
How do viruses replicate?
- Attachment is via specific receptors (tropism) - viruses are specific to certain cells.
- Penetration via endocytosis or membrane fusion
- Uncoating > genetic material targeted to nucleus
- Early viral proteins produced:
- Polymerase
- Integrase
- Allows genome replication
Late viral proteins produced : Structural proteins
- Capsid
- Surface proteins
- Assembly of virion - Release via budding, or cell lysis
What are pions?
They are not living organisms - they are a misfolded protein. They can be inherited or spread by contaminated material. It can also occur spontaneously. They aggregate ad cause misfolding of native proteins - chain reaction.
These are responsible for:
- Creutzfeldt-Jakob Disease
- Bovine spongiform encephalopathy
- Scrapie
- Kuru
What is a biofilm?
A community of bacteria surrounded by a polylactide layer.
Give an example of a bacteria with an atypical cell wall/
Tuberculosis, chlamydia and mycoplasma. Mycobacterium and Rhodococcus have acid cell walls.
What is the main method of bacterial replication?
The main method of replication in bacteria is binary fission. They will replicate the DNA and then the cell will separate. This is asexual. This is why we get the exponential growth curve in bacteria number. There is a real variation in this speed e.g. E. coli time is 17 minutes and M. tuberculosis is 792 minutes. Bacterial replication is an important target in antibiotics.
