Growth requirements

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

How Bacteria Feed

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

Figure 6.1 Four basic groups of organisms

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

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

Figure 6.3 Oxygen requirements of organisms-overview

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

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

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

Figure 6.4 Microbial growth-overview

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

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)

Figure 6.6 An example of psychrophile-overview

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

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

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

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

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

Figure 6.7 Plaque (biofilm) on a human tooth

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

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

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

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

Chapter 6

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

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

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

5. Large Intestine: Many anaerobic Bacteria a. 10-30% of fecal mass is bacteria b. These bacteria digest cellulose and produce vitamins and gas