L29 - Bacterial Growth And Replication Flashcards
Where do bacteria form biofilms?
On any surface where there is moisture
What do bacteria attach to? What happens afterwards?
- bacteria attach to surface
- grow and become enveloped in extracellular matrix (ECM) (polysacch, proteins and DNA)
What are the stages of biofilm formation? (5)
- inital attachment
- irreversible attachment
- maturation 1
- maturation 2
- dispersal
What happens during initial attachment?
Individual bacteria attach weakly to a surface
What happens during irreversible attachment?
Attachment becomes irreversible using fimbrae and pilli
What do bacteria do after attachment?
Multiply, attract other microbes to attach
What happens during maturation 1? (2)
- bacteria secrete a sticky, protective ECM
- contiue to join and multiply
What happens during maturation 2?
Biofilm grows in size and structure form large 3D colony
What happens during dispersal?
Sections of the biofilm break off - cells can go and colonise new areas
What do biofilms protect against? (3)
- phagocytosis
- antibiotics
- disinfectants
How are biofilms a huge problem in healthcare?
Growth on medical devices
What are examples of biofilm in healthcare? (4)
- dental plaque
- urinary catheter
- heart valve - endocarditis, enterococcus sp
- lung tissue - cf, pseudomonas aeruginosa
How do nutrients affect growth of biofilm? (3)
- required for cellular biosynthesis and energy generation
- macroelements - C, H, O, N, water, S, P, K, Ca, Mg, Fe
- trace elements - Mn, Co, Mo, Ni, Cu vits, gf
How does iron affect growth of biofilm? (5)
- used for energy generation
- iron in body not available
- withing mammalian cells (90% stored in ferritin/haem group, 8% stored elseqhere)
- outside mammalian cell (1-2% attached to transporters
- non complexed iron exists as Fe3+, insoluble
What is the bacterial iron transport system?
Siderophores
What are siderophores? (4)
- low MW compounds with high affinity for iron
- produced and exported from some bacteria when iron low
- bind iron and allow uptake into the cell
- -remove iron complexed with transferrin, uptake
How does oxygen affect growth of biofilm? (2)
- aerobe (with O) - microaerophile - can grow in low conc
- anaerobe (w/o O) - obligate anaerobe - cannot grow in O, faculative anaerobe - can grow in O if available
How does temperature affect growth of biofilm? (3)
- psychrophiles - -40C to 20C, optimum <15C // lysteria monocytogene
- thermophiles - 45 to 100C // thermophilus aquaticus
- mesophiles - 20 to 40C, organisms of med and pharm importance
How does pH affact growth of biofilm?
Most organisms or medical importance are neutrophiles - pH6.5-7.5
What are the different ways of growing bacterial culture? (2)
- suspension
- colony
What are bacterial cultures in suspension? Why?
- Bacteria grown in complex liquid media as batch culture
- to determine growth rate/ effect of antimicrobial agents
What are bacterial cultures in colonies ilke? Why?
- bacteria grown on complex media solidified with agar
- to obtain pure culture/ viable count/ assess diversity/ aid identification
What is the bacterial replication?
Binary fission - one bacteria cell grows and divides to 2 identical daughter cells
How does binary fission happen? (5)
- cell elongage ~ double
- cell copies chromosome
- septum beings to form
- 2 copies of chromosome pulled apart
- septum formation continues until 2 cells formed
