Microbiology 4 Flashcards
what is carbons % dry weight, its source and its function?
50%
- organics / CO2
- main constituent of cell, cell material and water
what is oxygens % dry weight, its source and its function?
20%
- H2O, organics, CO2 and O2
- electron acceptor in aerobic respiration
what is nitrogens % dry weight, its source and its function?
14%
- NH3, NO3, organics, N2
- amino acids, nucleotides & coenzymes
what is hydrogens % dry weight, its source and its function?
8%
- H2O, organics, H2
- organic compounds and cell water
what is phosphorous’ % dry weight, its source and its function?
3%
- inorganic phosphates
- nucleic acids, nucleotides & phospholipids
what is sulphurs % dry weight, its source and its function?
1%
- SO4, H2S, S^o and organic sulphur compounds
- proteins & several coenzymes
what is potassiums % dry weight, its source and its function?
1%
- potassium salts
- main inorganic cation & enzymatic cofactor
what is magnesiums % dry weight, its source and its function?
- 5%
- magnesium salts
- inorganic cation & enzymatic cofactor
what is calciums % dry weight, its source and its function?
- 5%
- calcium salts
- inorganic cation, enzymatic cofactors & endospores
what is irons % dry weight, its source and its function?
- 2%
- iron salts
- cytochrome component, enzymatic cofactor
carbon source trophs?
- autotrophs
- heterotrophs
energy source trophs?
- phototrophs
- chemotrophs
electron source trophs?
- lithotrophs
- organotrophs
autotrophs?
CO2 sole / principle carbon source
heterotrophs?
obtained from other organism
phototrophs?
light
chemotrophs?
compound oxidation
lithotrophs?
reduced inorganic compounds
organotrophs?
organic molecules
what are the 2 ways to culture microorganism?
- liquid media (broth)
- solid media (agar plates)
who was in vitro microorganism culture originally grown by?
koch (late C19th) on potato slices and gelatine
in liquid media, how do bacteria grow?
as individual cells until available nutrients exhausted
- makes suspension of cells (can’t differentiate between different cell types without further testing)
on solid media, how does bacteria grow?
bacteria and fungi form colonies with distinctive appearances
- each colony comes from single cells
what can the formula of media influence?
colony appearance (selective and differential media)
what is the difference between solid and liquid media?
solid has addition of gelling agent (agar)
undefined media?
contains chemically undefined yeast/veg/meat extracts and digested proteins
- batch-batch variation and reproducibility
- useful for routine growth applications
defined media?
(synthetic media) all components chemically define
- highly reproducible
- can = rich/minimal depending on requirements
obligate aerobe?
e.g. mycobacterium tuberculosis
cannot survive without oxygen
obligate anaerobe?
e.g. clostridium difficile
cannot survive in presence of oxygen
facultative aerobe?
e.g. staphylococcus aureus
can grow in presence of oxygen / produce energy by fermentation
microaerophile?
e.g. campylobacter jejuni
needs reduced oxygen content (inc CO2) in order to survive
aerotolerant anaerobe?
e.g. streptococcus mutans
can tolerate oxygen in air but makes energy in fermentation
what are the methods for anaerobic/aerotolerant culture?
- anaerobic cabinet
- gaspak sachets
- candle extinction
anaerobic cabinet?
- big isolates cabinet
- 95% N2, 5% H2 with palladium catalyst
- under positive pressure
gaspak sachets?
produces CO2 & H2 from breakdown of citric acid, cobalt chloride and NaBH4
candle extinction?
uses up oxygen by burning of candle in jar
what 2 methods rarely produce a true anaerobic enviro?
gaspak and candle methods
most bacteria reproduce by binary fission, what do other reproduce by?
budding
what is the generation time?
time taken to reproduce
how does the generation time vary?
- e.coli: 30 mins
- mycobacterium leprae: 14 days
how many distinct phases are there in bacterial growth?
4
lag phase
- no immediate increase in cell number
- old cells depleted & need time for synthesis of new cell components/metabolites
exponential (log) phase
- growth & division at max possible rate five genetic potential & enviro conditions
- regular doubling time
stationary phase
- in closed system nutrients = depleted & waste products build up
- growth ceases (or balanced by death)
- morphological and metabolical changes (e.g. secondary metabolism)
death phase (senescence)
- severe nutrient deprivation
- build-up of toxic waste products
- viable cell numbers decline at exponential rate
primary metabolism
includes major metabolic pathways
- energy production and release
- cell component synthesis
- enzyme production
secondary metabolism
non-essential metabolic pathways
- includes production of natural products e.g. antibiotics
- production of secondary metabolites in disease states —> inc pathogenicity (e.g. pyocyanin)
what kind of system are flask cultures?
closed systems
flask/batch cultures
- used for optimisation
- nutrient availability limited
- atmosphere limited due to diffusion at liquid surface
- limited product production (not suitable for industry, lab scale only)
what kind of systems are chemostats?
open systems
chemostats/ continuous cultures
- allows for highly controlled growth
- nutrients supplied at constant rate
formula for steady state?
Mew = D = F/V
what are the 3 growth modes in bulk culturing?
- batch - full at start
- fed batch - fill until vessel full
- continuous - fill and overflow
what is the important criteria in bulk culturing?
- maintain adequate mixing
- maintain high oxygen levels - if aerobic
- control pH
- control temp
- control foam
- initial starting conc
what does viral replication rely on?
subversion of host replication machinery
in both prokaryotic and eukaryotic viruses
in bacteriophages what does subversion lead to?
- cell destruction
- lytic replication
in eukaryotes what do viruses tend to do?
bud rather than destroy cell
e.g. influenza, HIV
give examples of viruses which lie dormant and cause human disease?
- herpes simplex virus
- human papilloma virus
what is lysogenic replication?
when bacteriophages integrate genome into host and replicate alongside host
what is evolution?
change in population over time
how does evolution arise?
- acquisition of new genes
- mutation of existing genes
results of bacterial evolution can = good/bas
give examples of this?
- inc product yield
- become pathogenic
- inc in resistance to treatment
more complex the organism ….
slower rate of evolution
what is a mutation and give examples of how mutations can arise?
permanent change in single cell (not necessarily cause any noticeable change/get passed on)
- UV irradiation
- chemical exposure
- poor genome copy
a harmful or deleterious mutation decreases…
organism fitness
a beneficial/advantageous mutation increases ….
organism fitness
also include mutations that promote desirable traits
what kind of effect does a neutral mutation have?
no harmful / beneficial effect
such mutations occur at steady state
what are the 3 main mechanisms through which bacteria can evolve?
- transformation
- transduction
- conjugation
transformation?
direct uptake of DNA through cell membrane
transduction?
introduction of genetic material via viral vector
conjugation?
transfer of genetic material between 2 directly connected bacteria
antibiotic usage can as what on bacteria?
selective pressure
removes competition for resistant cells by killing susceptible cells
how can bacterial strains be improved naturally?
spontaneous mutation (random & infrequent)
give examples how can exposure to mutagens increase frequency of mutations?
- uv/chemical exposure
- random mutagenesis
- mutants can be picked and assessed for increased production
what is targeted mutagenesis?
add/remove/alter genes to improve overall yield
what is production measured in?
activity/mL
