Growth requirements Optimal Conditions Conditions in witch bacteria

Growth requirements

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

How Bacteria Feed

A. Photo Autotrophs – using light to form sugar B. Chemo Autotrophs – These use chemicals to form nutrients. ‐ Chemicals: H 2, H 2 S, Sulfur, or Iron *Examples: Methanogens + Ocean Vent Bacteria

Figure 6. 1 Four basic groups of organisms

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 O 2 for growth – Anaerobes ‐ do not tolerate O 2 and die in its presence – Facultative anaerobes ‐ do not require O 2 for growth, but do grow better in its presence – Aerotolerant anaerobes ‐ ignore O 2 and grow equally well whether it is present or not – Microaerophiles ‐ are damaged by the normal atmospheric level of O 2 (20%) but require lower levels (2 to 10%) for growth

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

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

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

Figure 6. 4 Microbial growth-overview

• 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

Figure 6. 5 Four categories of microbes based on temperature ranges for growth Growth rate Thermophiles Mesophiles Psychrophiles Temperature (°C) Hyperthermophiles

Figure 6. 6 An example of psychrophile-overview

Growth Requirements • Physical Requirements – p. H • Organisms are sensitive to changes in acidity – H+ and OH– interfere with H bonding • Neutrophiles grow best in a narrow range around neutral p. H (5. 5 – 8. 0) • Acidophiles grow best in acidic habitats – p. H between 0‐ 5. 5 • Alkalinophiles live in alkaline soils and water – p. H between 8. 5 and 11. 5

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

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

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

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

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 – Adapt to nutrients • Log – Active growth • Stationary – Death = Growth rate • Death – Nutrients consumed – p. H too low (why? ) • Optimize curves in production Chapter 6

Chapter 6

Bacteria and the Human Host A. 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 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 1 st 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