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. The First Law of Thermodynamics
Energy cannot be created or destroyed.
It is interchangeable with matter.
Chemical energy; nuclear energy: E = mc2
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’t turn energy into raw materials, only use it 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. Responses of microbes to nutritional deficiency
Extracellular molecules collect nutrients
Siderophores, hemolysins collect iron
extracellular enzymes break down polymers
Cells enter Semi-starvation state:
slower metabolism, smaller size.
Sporulation and “resting cells”:
cells have very low metabolic rate
Some cells change shape, develop thick coat
Endospores form within cells; very resistant.
Spores are for survival, triggered by low nutrients

10. Endospore formation

11. 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.

12. 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.

13. 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

14. 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!

15. 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.

16. 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

17. 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.

18. 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