Bacterial Growth and Physiology – Flashcards
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Differential Media Example |
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-MacConkey -Lactose utilization -Bacteria import lactose (a disaccharide); metabolize glucose using fermentation, producing acid -Dye shows change in pH, indicating fermentation of lactose |
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Liquid Media |
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-Good for growing specific amounts of bacteria and for growing large amounts of bacteria Types of liquid media (also applies to solid media) -Complex -Defined |
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Media Classifications |
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Complex : contains uncharacterized mixtures of compounds. -Usually used for routine growth (cheap, easy to make) -Defined : uses specific chemicals -Used for nutritional studies -Requires knowledge (or trial and error) of requirements of bacteria Minimal: only has the minimal components for growth of a particular bacterium |
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‘Heterotroph |
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-(short for chemoheterotroph) or ‘Organotroph’ refer to bacteria that use organic C as both energy and C source -Most pathogenic bacteria fall into this category |
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Basic Growth Requirements for Bacteria |
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Inorganic -N, C, O, H -S -P -K, Na (some), Cl (some) -Mg, Ca (some) -Trace elements (Fe, Cu, Zn, Mn, etc.) -Vitamins and growth factors (some bacteria) |
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Environmental Requirements for Bacteria |
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-Temperature -pH -Oxygen -Salt |
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Atmospheric Requirements |
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Anaerobes -Obligate (i.e. intestinal bacteria) -Aerotolerant- does not use oxygen but tolerates it Utilize fermentative metabolism or ’anaerobic respiration’: use of electron acceptors other than O2 Aerobes Obligate aerobes Microaerophiles -Require low oxygen tensions; harmed by oxygen concentrations that are too high. Both utilize respiratory metabolism (O2) Facultatives (aerobic or anaerobic) Utilize respiratory or fermentative metabolism (respiratory preferred if oxygen present) – ex: E. coli
Aerotolerant anaerobes Can grow in the presence of oxygen but do not utilize respiratory metabolism (utilize fermentative metabolism under all conditions. ex: Streptococcus pyogenes |
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Generation Time |
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Generation Time -Cells divide by binary fission at a constant rate -Period between the time that a new cell arises and the time that this cell completes division into two new daughter cells is known as the generation time |
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Catabolism of Carbohydrates |
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Glycolysis Followed by -Fermentation or Respiration Goals: ATP generation Generation of metabolic building blocks
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Basic Facts of Glycolysis |
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-Substrate level phosphorylation -Not very efficient -Lots of C utilized -Lots of energy remains in the end products -Different bacteria utilize different glycolytic pathways! |
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Embden-Meyerhof-Parnas Pathway |
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-Net ATP yield = 2 moles of ATP per mole of glucose fermented -Not very energy efficient -Lots of energy remaining -Need to further metabolize pyruvate -Fermentation used (see below) |
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HexoseMonophosphateGlycolytic Pathway |
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-Provides NADPH and pentoses for biosynthesis -Pathway for utilization of pentoses as C and energy sources -Makes ribose-5-phosphate, key intermediate for production of nucleotides -Also called Pentose phosphate pathway (PPP) |
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Entner-Doudoroff (ED) glycolytic pathway |
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-Replaces the EMP pathway in many pseudomonads. -Less energy efficient than EMP pathway (1 ATP/mole glucose). -Usually utilized under aerobic conditions. |
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Fermentation |
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-Used by anaerobic bacteria or by facultatives under anaerobic conditions -These organic end products are used as electron acceptors to recycle NADH, which is produced during glycolysis, to NAD+ -End product depends on bacterial species -Identification of bacteria -Industrial value -Stinks! |
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Anaerobic respiration |
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-Electrons transferred from reduced carbon compound (acetate, fumarate) and NADH (which are oxidized to NAD+) through electron carriers similar to aerobic electron transport chain (but distinct carriers) to various electron sinks (which are reduced) -ATP generated in the process, but <38 ATP that is seen in aerobic respiration; yields vary nSO42- H2S Sulfate reductase nNO3- NO2- Nitrate reductase nHCO3- CH4 Methyl Co-M reductase |
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Energy Yields |
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From Most to Least:
-Glycolysis+TCAcycle+electron transport 38 ATP/mole glucose -Glycolysis+Anaerobic respiration Variable ATP yield, but more than fermentation -Glycolysis+fermentation -EMP 2 ATP/mole of glucose -HMP & ED -1 ATP/mole glucose |
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Anabolic reactions |
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-E. coli can synthesize all cellular components from glucose, N, S, P source, some trace metals, and some salts! |
