Lecture 1 Flashcards
what is the path of a microbial culture ? What do we not see in textbooks ?
sample -> incubation -> isolation of one culture and incubation -> further experiments.
- medium preparation and choice
- sterilisation of materials
- waste management
what are the 3 ways to classify media ?
1) physical : liquid, semi-solid, solid
2) chemical : complex or defined
3) function : basal, enrichment, selective, differential (metabolic capacity), minimal
what must a medium contain and provide ?
carbon source + nitrogen source + energy source + terminal electron acceptor
provide good pH, salinity and trace elements.
what are some media related problems that can happen ? (3 examples)
- clumping / dehydrated
- caramelization
- tubidity / precipitation
what is the problem if the sugar and the amino acid react together ? (browning reactions)
they become unavailable for the bacteria
How do we sterilize growth medium ?
Most of the time autoclave.
Sometimes :
- autoclave separately
- sterile filtration
- chemical sterilization
What is the difference between enrichment media and selective media ?
enrichment = promote growth of microbe we want to extract by giving them an advantage, usually liquid media before plating on solid
selective = select organism of interest by inhibiting the other organisms present (with antimicrobials for example)
Difference between enriched and enrichment media ?
enriched = comprises all the nutrients needed for growth of different organisms
enrichment = growth of only some kind of microbes
Are there a lot of bacteria that are culturable ? why ?
only 1% of prokaryotes may be grown under standard lab conditions. Failure to replicate essential aspects of their environment.
what is culturomics ?
An attempt to vary all the growth conditions in a multidimensional matrix of possibilities -> takes a lot of work compared to metagenomics.
what happens in co-cultures ?
The presence of one bacteria type can influence the growth of another type.
What is the main target in medical antibacterials ?
cell wall
what is the MIC ? and the MBC ?
minimum inhibitory concentration = lowest concentration of antibacterial which prevents VISIBLE growth (not killing)
Minimum bactericidal concentration = lowest concentration of antibacterial required to KILL a bacterium over a fixed period.
What is the disc diffusion method ?
antibiotis discs on inoculated plate -> size of zone of inhibition tells us if bacterium is resistant or sensitive
