Component 1 - Microbiology Flashcards
(29 cards)
Label the structure of bacteria
What is the plasma membrane and what is its function?
Barrier between the environment and the cytoplasm - controls entry and exit of substances into and out of the cell
What is the function of the cell wall and what is it made out of?
Prevents lysis in a hypotonic solution
Peptidoglycan/murein
What is the function of the circular DNA?
Contains the genes necessary for normal functioning of the bacterium
What is the purpose of the capsule?
Outer layer of mucopolysaccharide slime which can glue bacteria together, stick them to surfaces and protect the bacteria from attack by other cells
What are the function of the ribosomes?
Synthesis of proteins (smaller than eukaryotic ribosomes)
What is the function of the pili?
For attaching to surfaces and for transferring plasmids by conjugation
What is the function of the flagellum?
For motility
What is the function of the plasmid?
Circular DNA which contains extra bacterial genes including genes for antibiotic resistance
What are the 3 shapes of bacteria?
Bacillus - rod shaped
Coccus - spherical
Spirillum - spiral
What are the properties of prokaryotes?
They have no membrane bound nucleus instead have a large circular piece of DNA in a region called a nucleoid (and many small circular fragments called plasmids)
No membrane bound organelles
Smaller ribosomes than eukaryotes
Cell wall which is made up of peptidoglycan
Very small
Reproduce bi binary fission
What is meant by gram positive bacteria?
These bacteria have a cell wall with a THICK layer of peptidoglycan
Holds onto the dye crystal violet
Dye is not washed out by ethanol
Appear purple
What are some examples of gram positive bacteria?
Staphylococcus
Streptococcus
Bacillus
What is meant by gram negative bacteria?
They have a complex cell wall with a thin layer of peptidoglycan and a thick outer layer of lipopolysaccharide
Crystal violet is removed when rinsed with ethanol
They appear pink
E.coli
What are the physical conditions for microbes to function?
Suitable temperature
Suitable pH
Oxygen
What are the some of the nutrients microbes require for function
Carbon source - usually organic - eg glucose - energy source
Nitrogen source - inorganic (nitrate) or organic (amino acids)
Inorganic ions and vitamins - growth factors
What temperature do pathogens often grow best at?
37C
What temperature do you incubate bacteria at and how long for?
25C
For 24-48 hrs
Why do we seal the agar plate with 4 pieces of tape?
To allow oxygen into to the plat
Why do we use specific these conditions for pathogenic bacteria?
To ensure that the growth rate is low
Tend to grow at a fast rate in anaerobic conditions and at 37C
What is the name given to bacteria which require oxygen?
Obligate aerobes
What are facultative anaerobes?
Able to survive in the absence of oxygen but grow and divide faster in the presence of oxygen
Q
Why do we use aseptic techniques when culturing bacteria?
To prevent contamination of the environment by the microbes being handled
And contamination of microbial cultures by unwanted microbes from the environment
