1. 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

2. Matter and energy
In order to grow, bacteria need a source of raw materials and energy
Source can be the same (e.g. glucose) or different (e.g. carbon dioxide and sunlight).
Living things can extract energy from matter
Living things can’t turn energy into matter
Living things can use energy to assemble raw materials.
Bacteria can’t grow on nothing!

3. 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
Auto=self; hetero=other; troph=feeding.
Autotrophs use carbon dioxide
Heterotrophs use pre-formed organic compounds (molecules made by other living things).
Humans and medically important bacteria are heterotrophs.

4. Essentials of Bacterial nutrition
Macronutrients: needed in larger amounts
Needed in large quantities: CHONPS
Carbon, hydrogen, oxygen, nitrogen, phosphorous, and sulfur. H and O are common. Sources of C, N, P, and S must also be provided.
Macronutrients needed in smaller amounts:
Mineral salts such as Ca+2, Fe+3, Mg+2, K+
Micronutrients = trace elements;
needed in very tiny amounts; e.g. Zn+2, Mo+2, Mn+2

5. http://textbookofbacteriology.net/nutgro.html 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
Potassium salts
Magnesium
0.5
Magnesium salts
Calcium
Calcium salts
Iron
0.2
Iron salts

6. Chemical form must be appropriate
Not all bacteria can use the same things
Some molecules cannot be transported in
Enzymes for metabolizing it might not be present
Chemical may be used, but more expensive
These differences are used for identification
Some chemicals are inert or physically unusable
Relatively few bacteria (and only bacteria) use N2
Diamonds, graphite are carbon, but unusable
P always in the form of phosphate

7. 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, blood, 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.

8. Feast or famine: normal is what’s normal for you: Oligotrophs vs
Feast or famine: normal is what’s normal for you: Oligotrophs 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.

9. Selective and differential
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.

10. Defined Medium for Cytophagas/Flexibacters
Component grams
K2HPO
KH2PO
MgCl
NaHCO
{CaCl2 1 ml*
{BaCl2.2H2O
Na acetate
FeCl.7H2O 0.2 ml*
RNA
alanine
arginine
aspartic acid
glutamic acid 0.55
glycine
histidine 0.20
isoleucine 0.30
leucine
lysine
phenylalanine 0.30
proline
serine
threonine 0.50
valine

11. Physical requirements for growth
Prefixes and suffixes:
Bacteria are highly diverse in the types of conditions they can grow in.
Optimal or required conditions implied by “-phile” meaning “love”
Some bacteria prefer other conditions, but can tolerate extremes
Suffix “-tolerant”
Note the difference!

12. 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.

13. 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.
Fe3+ -SOD + O2- → Fe2+ -SOD + O2
Fe2+ -SOD + O2- + 2H+ → Fe 3+ -SOD + H2O2

14. Relation to Oxygen Aerobes: use oxygen in metabolism; obligate.
Microaerophiles: require oxygen (also obligate), but in small amounts.
Anaerobes: grow without oxygen; SEE NEXT
A: aerobe B: microaerophile
Capnophiles: require larger amounts of carbon dioxide than are found normally in air.

15. Anaerobes grow without O2
Classifications vary, but our definitions:
Obligate (strict) 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
C: could be facultative or aerotolerant. D: strict anaerobe

16. Effect of temperature Low temperature High 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.

17. 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.

18. Classification of bacteria based on temperature

19. Terms related to temperature
Special cases:
Psychrotrophs: bacteria that grow at “normal” (mesophilic) temperatures (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.

20. pH Effects pH = -log[H+]
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

21. Low water activity: halophiles, osmophiles, and xerotolerant
Water is critical for life; remove some, and things can’t 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; grandma’s wax over jelly.
Xerotolerant: dry. Subject to desiccation. Fungi best
Bread, dry rot of wood
Survival of bacterial endospores.

22. 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.