ESPM 131 Lecture Notes - Lecture 15: Aerotolerant Anaerobe, Heterotroph, Auxotrophy
14 May 2018
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Lecture 15: Cultivation Methods
●Growth media:
○Complex : most heterogeneous, grow most heterotrophs
○Defined : grow specific heterotrophs, known quantities of ingredients, oten mandatory
for chemo/photoautotrophs
○Selective : suppress unwanted microbes and encourage desired, use inhibitors
○Diferential : distinguish colonies of specific microbes, diferential growth
○Enrichment : increases number of desired to detectable level without stimulating others,
similar to selective
○Reducing : increases number of obligate anaerobes
●Methods:
○Spread plates with dilution :
■Isolate and enumerate (basic method)
■Too numerous to count (TNTC) : when not dilute enough
■Serial dilutions
○Pour plates : inoculum added to molten agar
■Increased diversity - surface and subsurface colonies
■Less O2 dif inside media
■Some orgs grow better when surrounded by matrix
○Gradient plates : define inhibition concentration/concentration niche
■Tilt plate
■Add agar and antibiotic w/ range of concentrations
○Roll tubes : with or without reducing agents
■O2 conditions
■Facultative, microaerophiles, obligate, aerotolerant
■Where they grow determines what their O tolerance/prefs are
○Enrichment cultures : select specific metabolism
■Sequential: lose orgs you don’t want over time
■Has specific nutrients
○For strict anaerobes:
■Special jars with gas pak
■Catalyst chamber: 2H2 + O2 → 2H2O
●Plate counting & the Great Plate Count Anomaly :
○Microscopy vs isolates :
■Discrepancy btw viable plate count and direct microscopic count
■Winogradsky : growing particular groups, missing other orgs
○Only 0.1-1% of total bacteria can be enumerated
○Og 61 phyla, 32 have no cultivated reps
○Why?
■Picky
■phys/chem heterogeneity
■Microbe-microbe interactions, signaling
○Alterations:
Document Summary
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