Bacterial Growth and Nutrition

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Bacterial Growth and Nutrition

• Bacterial nutrition and culture media
• Chemical and physical factors affecting growth
• The nature of bacterial growth
• Methods for measuring population size

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Where do raw materials come from?

• Bacteria acquire energy from oxidation of organic
  or inorganic molecules, or from sunlight.
• Growth requires raw materials some form of
  carbon.
• Autotrophs vs. heterotrophs
• Autoself heteroother trophfeeding.
• Autotrophs use carbon dioxide
• Heterotrophs use pre-formed organic compounds
  (molecules made by other living things).
• Humans and medically important bacteria are
  heterotrophs.

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Essentials of Bacterial nutrition

• Six elements needed in large quantities by all
  living things CHONPS
• Carbon, hydrogen, oxygen, nitrogen, phosphorous,
  and sulfur. H and O are common. Sources of C,
  N, P, and S must also be provided.
• Other macronutrients not as much needed
• Mineral salts such as Ca2, Fe3, Mg2, K
• Micronutrients trace elements needed in very
  tiny amounts things like Zn2, Mo2, Mn2
• Elements must be in the correct chemical form!
• Diamonds, graphite no good. N2 used by very few
  bacteria.

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Element dry wgt Source
Carbon 50 organic compounds or CO2
Oxygen 20 H2O, organic compounds, CO2, and O2
Nitrogen 14 NH3, NO3, organic compounds, N2
Hydrogen 8 H2O, organic compounds, H2
Phosphorus 3 inorganic phosphates (PO4)
Sulfur 1 SO4, H2S, So, organic sulfur compounds
Potassium 1 Potassium salts
Magnesium 0.5 Magnesium salts
Calcium 0.5 Calcium salts
Iron 0.2 Iron salts
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Make it, or eat it?

• Some bacteria are remarkable, being able to make
  all the organic compounds needed from a single C
  source like glucose. For others
• Vitamins, amino acids, etc. added to a culture
  medium are called growth factors.
• Bacteria that require a medium with various
  growth factors or other components and are hard
  to grow are referred to as fastidious.

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Feast or famine normal is whats normal for
youOligotrophs vs. copiotrophs

• Oligo means few oligotrophs are adapted to life
  in environments where nutrients are scarce
• For example, rivers, other clean water systems.
• Copio means abundant, as in copious
• The more nutrients, the better.
• Medically important bacteria are copiotrophs.
• Grow rapidly and easily in the lab.

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Responses of microbes to nutritional deficiency

• Siderophores and hemolysins
• For collecting iron. (e.g. electron transport
  systems)
• Extracellular enzymes leave cell, go out into
  medium, break down polymers, release LMW
  compounds.
• Genetic regulation cell uses other nutrient
  sources.
• Semi-starvation state slower metabolism, smaller
  size.
• Sporulation cells form environmentally resistant
  resting state. Endospores form within cells
  others become spores.

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Responses of microbes to other environmental
stresses

• Compatible solutes small neutral molecules
  accumulated in cytoplasm when external
  environment is hypertonic.
• Heat shock proteins and other stress proteins
• Bacteria express additional genes that code for
  protective proteins.

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Culture Medium

• Defined vs. Complex
• Defined has known amounts of known chemicals.
• Complex hydrolysates, extracts, etc.
• Exact chemical composition is not known.
• Selective and differential
• Selective media limits the growth of unwanted
  microbes or allows growth of desired ones.
• Differential media enables differentiation
  between different microbes.
• A medium can be both.

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Defined Medium for Cytophagas/Flexibacters
Component grams K2HPO4 0.10 KH2PO4 0.05 MgCl2
0.36 NaHCO3 0.05 CaCl2 1 ml BaCl2.2H2O Na
acetate 0.01 FeCl.7H2O 0.2 ml RNA 0.10
alanine 0.15 arginine 0.20 aspartic acid
0.30 glutamic acid 0.55
glycine 0.02 histidine 0.20 isoleucine 0.30 le
ucine 0.20 lysine 0.40 phenylalanine 0.30 pro
line 0.50 serine 0.30 threonine 0.50 valine
0.30
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Physical requirements for growth

• Prefixes and suffixes
• Bacteria require wide ranges of conditions
• Optimal conditions implied by -phile meaning
  love
• Some bacteria prefer other conditions, but can
  tolerate extremes
• Suffix -tolerant

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Oxygen friend or foe?

• Early atmosphere of Earth had none
• First created by cyanobacteria using
  photosynthesis
• Iron everywhere rusted, then collected in
  atmosphere
• Strong oxidizing agent
• Reacts with certain organic molecules, produces
  free radicals and strong oxidizers
• Singlet oxygen, H2O2(peroxide), O3- (superoxide),
  and hydroxyl (OH-) radical.

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Protections of bacteria against oxygen

• Bacteria possess protective enzymes, catalase and
  superoxide dismutase.
• Catalase breaks down hydrogen peroxide into water
  and oxygen gas.
• Superoxide dismutase breaks superoxide down into
  peroxide and oxygen gas.
• Anaerobes missing one or both slow or no growth
  in the presence of oxygen.

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Relation to Oxygen

• Aerobes use oxygen in metabolism obligate.
• Anaerobes grow without oxygen
• Microaerophiles require oxygen, but in small
  amounts.
• Capnophiles require larger amounts of carbon
  dioxide.

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Oxygen and microbes continued

• Classifications vary, but our definitions
• Obligate anaerobes killed or inhibited by
  oxygen.
• Aerotolerant anaerobes do not use oxygen, but
  not killed by it.
• Facultative anaerobes can grow with or without
  oxygen

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Effect of temperature

• Low temperature
• Enzymatic reactions too slow enzymes too stiff
• Lipid membranes no longer fluid
• High temperature
• Enzymes denature, lose shape and stop functioning
• Lipid membranes get too fluid, leak
• DNA denatures
• As temperature increases, reactions and growth
  rate speed up at max, critical enzymes denature.

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Bacteria and temperature

• Bacteria have temperature ranges (grow between 2
  temperature extremes), and an optimal growth
  temperature. Both are used to classify bacteria.
• As temperature increases, so do metabolic rates.
• At high end of range, critical enzymes begin to
  denature, work slower. Growth rate drops off
  rapidly with small increase in temperature.

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Classification of bacteria based on temperature
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Terms related to temperature

• Special cases
• Psychrotrophs bacteria that grow at normal
  temperature ranges (e.g. room temperature but
  can also grow in the refrigerator responsible
  for food spoilage.
• Thermoduric more to do with survival than
  growth bacteria that can withstand brief heat
  treatments.

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pH Effects

• pH -logH
• Lowest 0 (very acid) highest 14 (very basic)
  Neutral is pH 7.
• Acidophiles/acidotolerant grow at low pH
• Alkalophiles/alkalotolerant grow at high pH
• Most bacteria prefer a neutral pH
• What is pH of human blood?
• Some bacteria create their preferred conditions
• Lactobacillus creates low pH environment in vagina

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Low water activityhalophiles, osmophiles, and
xerotolerant

• Water is critical for life remove some, and
  things cant grow. (food preservation jerky,
  etc.)
• Halophiles/halotolerant relationship to high
  salt.
• Marine bacteria archaea and really high salt.
• Osmophiles can stand hypertonic environments
  whether salt, sugar, or other dissolved solutes
• Fungi very good at this grandmas wax over
  jelly.
• Xerotolerant dry. Subject to dessication. Fungi
  best
• Bread, dry rot of wood
• Survival of bacterial endospores.

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Miscellaneous conditions

• Radiation (solar, UV, gamma)
• Can all damage cells bacteria have pigments to
  absorb energy and protect themselves.
• Endospores are radiation resistant.
• Deinococcus radiodurans extremely radiation
  resistant
• Extremely efficient DNA repair, protection
  against dessication damage to DNA.
• Barophiles/barotolerant microbes from deep sea
• Baro- means pressure. Actually require high
  pressure as found in their environment.