bacteria cultivation Flashcards
what are the 4 phases of bacterial growth and what happens in each l
lag - metabolism to acquire essential nutrients ready to divide
exponential - binary fission
stationary- essential nutrients depleted and toxic metabolic products accumulate
decline - old cells die rapidly followed by young cells
ways to count bacteria
microscopic counting
colony counting
opacity/turbidity
bacterial nutrition requirements
raw materials essential for growth
large quantities of C and N
peptones = meat, protein, amino acids
phosphates - nucleic acid production
sulphur= amino acid production
Ca, Fe, Mg, K= important enzyme co-factors
temperature range of mesophilic bacteria
20 - 45
temperature psycrophiles prefer
15
temperature thermofiles prefer
60
oxygen requirements of aerobes
obligate
oxygen requirements of microaerophiles
small amounts
oxygen requirements of anaerobes
do not require
obligate anaerobes
killed/inhibited by oxygen
aerotolerant anaerobes
killed by oxygen
facultive anaerobes
can grow with/without oxygen
why are micro-organisms preserved
vaccine production
research and teaching
how are micro-organisms preserved
freezing in liquid nitrogen at -190
dessication - freeze drying then stored as ampoules in dark
methods to prevent food spoilage/limit pathogens
refrigeration at 4 degrees = prevents microbe multiplication as slows enzymatic reactions (listeria still grows)
freezing at -20 (survivors multiplied rapidly if thawed)
boiling at 100 - inactivation of bacteria/fungi (endospores may still survive)
vacuum packing - oxygen removal prevents aerobe growth
pasteurization - flash and ultra high temperatures
