1. Growth requirements

2. Optimal Conditions – A. Warmth B. Moisture C. Food
Conditions in witch bacteria thrive.
A. Warmth
B. Moisture
C. Food
D. Gases – usually oxygen

3. How Bacteria Feed

4. B. Chemo Autotrophs – These use chemicals to form nutrients.
Photo Autotrophs – using light to form sugar
B. Chemo Autotrophs – These use chemicals to form nutrients.
- Chemicals: H2, H2S, Sulfur, or Iron
*Examples: Methanogens + Ocean Vent Bacteria

5. Figure 6.1 Four basic groups of organisms

7. D. Parasites – Feed off live host
C. Saprobes – Feed on dead stuff
D. Parasites – Feed off live host
E. Heterotrophs – diffusing nutrients from environment

8. Growth Requirements Oxygen requirements
Aerobes - are completely dependent on atmospheric O2 for growth
Anaerobes - do not tolerate O2 and die in its presence
Facultative anaerobes - do not require O2 for growth, but do grow better in its presence
Aerotolerant anaerobes - ignore O2 and grow equally well whether it is present or not
Microaerophiles - are damaged by the normal atmospheric level of O2 (20%) but require lower levels (2 to 10%) for growth 8

9. Figure 6.3 Oxygen requirements of organisms-overview

10. Growth Requirements Nitrogen requirements
Nitrogen fixation by certain bacteria is essential to life on Earth
Nitrogen acquired from organic and inorganic nutrients
Key bacteria for nitrogen cycle
Nitrosomonas convert ammonia to nitrite
Nitrobacter convert nitrite to nitrate.
Pseudomonas convert nitrate to nitrogen gas.
Azotobacter and Rhizobium are nitrogen-fixing bacteria which fix nitrogen from the atmosphere and make it available to leguminous plants 10

11. Growth Requirements Other chemical requirements Phosphorus Sulfur
Trace elements
Required only in small amounts
Growth factors
Necessary organic chemicals that cannot be synthesized by certain organisms 11

12. Growth Requirements Physical Requirements Temperature
Effect of temperature on proteins
Effect of temperature on membranes of cells and organelles
If too low, membranes become rigid and fragile
If too high, membranes become too fluid 12

14. Figure 6.4 Microbial growth-overview

15. Mesophile - moderate temp, between 20 and 45°C
Psychrophile -  cold‐loving, having an optimal temp. at about 15°C or lower
max temperature = about 20°C
Mesophile - moderate temp, between 20 and 45°C
Thermophile -  high temperatures, between 41 and 122 °C
Hyperthermophile -  extremely hot environments, from 60 °C (140 °F) upwards
optimal temperature  is above 80 °C

16. Thermophiles Mesophiles Hyperthermophiles Growth rate Psychrophiles
Figure 6.5 Four categories of microbes based on temperature ranges for growth
Thermophiles
Mesophiles
Hyperthermophiles
Growth rate
Psychrophiles
Temperature (°C)

17. Figure 6.6 An example of psychrophile-overview

18. Growth Requirements Physical Requirements pH
Organisms are sensitive to changes in acidity
H+ and OH– interfere with H bonding
Neutrophiles grow best in a narrow range around neutral pH (5.5 – 8.0)
Acidophiles grow best in acidic habitats
pH between 0-5.5
Alkalinophiles live in alkaline soils and water
pH between 8.5 and 11.5 18

19. Growth Requirements Physical Requirements - water
Most cells die in absence of water
Some have cell walls that retain water
Endospores and cysts cease most metabolic activity
Hydrostatic pressure
Water exerts pressure in proportion to its depth
Barophiles live under extreme pressure
Their membranes and enzymes depend on pressure to maintain their shape 19

20. Growth Requirements Physical Requirements - water Osmotic pressure
Hypotonic - osmotic lysis can occur
Hypertonic - cell shrinkage called plasmolysis
the addition of salts or other solutes to a solution inhibits food spoilage by bacteria
as occurs when meats or fish is salted
Restricts organisms to certain environments
halophiles 20

21. Associations and Biofilms
Organisms live in association with different species
Antagonistic relationships
Synergistic relationships
Symbiotic relationships 21

22. Associations and Biofilms
Biofilms – complex relationships among many microorganisms
Develop an extracellular matrix
Adheres cells to one another
Allows attachment to a substrate
Sequesters nutrients
May protect individuals in the biofilm
Form on surfaces often as a result of quorum sensing
a system of stimulus and response correlated to population density
coordinate gene expression according to the density of their local population
Many microorganisms more harmful as part of a biofilm 22

23. Figure 6.7 Plaque (biofilm) on a human tooth

24. Bacteria Reproduction
A. Asexual – Binary fission(Mitosis= Clones)
*Every 20 minutes with optimal conditions
B. Sexual – Conjunction using pili – DNA exchanges

25. Prokaryotic reproduction
binary fission - this process involves copying the chromosome and separating one cell into two
asexual form of reproduction
Transformation - the prokaryote takes in DNA found in its environment that is shed by other prokaryotes.
transduction - bacteriophages, the viruses that infect bacteria, sometimes also move short pieces of chromosomal DNA from one bacterium to another
Conjugation - DNA is transferred from one prokaryote to another by means of a pilus

27. Binary Division Generation Time
Time required for a bacterial cell to grow and divide
Dependent on chemical and physical conditions
Chapter 6

28. Phases of Growth Lag Log Stationary Death
Adapt to nutrients
Log
Active growth
Stationary
Death = Growth rate
Death
Nutrients consumed
pH too low (why?)
Optimize curves in production
Chapter 6

29. Chapter 6

30. Bacteria and the Human Host
Bacteria living in/on humans may be: Beneficial, harmful or neutral
B. Resident Flora – Microbes which normally live with humans
1.Human sites with a
normal Flora of bacteria
a. Skin – Mouth
b. Upper respiratory
c. Digestive tract
d. Vagina
e. Urethra Opening
f. External eye
g. External ear

32. 2. Sterile Human Sites c. Urine in bladder d. Amniotic fluid
a. Internal organs except the digestive tube
b. Blood
c. Urine in bladder
d. Amniotic fluid
3. Humans first exposed to bacteria at birth – then at 1st milk feeding

33. 4. Saliva has a high Bacteria count
*Human bite is very dangerous because of:
a. Many dangerous bacteria in saliva/mouth
b. Jagged deep wound favorable to anaerobes

34. 5. Large Intestine: Many anaerobic Bacteria
a % of fecal mass is bacteria
b. These bacteria digest cellulose
and produce vitamins and gas