Bacteria and Environmental Conditions

1. Bacteria and Environmental Conditions Patricia Sidelsky Microbiology 156- Class 10

2. Energy for the Cell • The energy currency of the cell is ATP • ATP is adenosine tri phosphate • Adenosine tri phosphate is used by the cell for the completion of all cellular process that have energy requirements

3. Oxygen • Aerobic bacteria – Do oxidative phosphorylation( production of ATP) • Tolerate oxygen in the environment • Have mechanisms for tolerating an oxygen rich environment

4. Energy pathways- with oxygen • Sugars and other molecules are broken down into intermediate molecules • Glucose may be broken down into pyruvic acid • 2C fragment from pyruvic acid( Acetyl COA) is fed into Kreb’s Cycle and Electron transport chain to produce ATP

5. Anaerobic pathways • Use alternate sources of electrons and hydrogen • Oxygen is a poison • No tolerance of oxygen in the environment • Break down sugars into smaller carbon fragments and generally carry out a type of fermentation

6. Terminology • Aerobe – An organism that can grow in oxygen • Obligate aerobe- An organism that requires oxygen as the terminal electron acceptor in the electron transport chain • Anaerobe – Cannot grow in the presence of oxygen • Aerotolerant – Like Enterococcus – oxygen is not a factor in the growth of these organiss • Capnophile – Likes high levels of carbon dioxide • Facultative anaerobe – Do not require oxygen but grow better in its presence • Microaerophile – prefers levels of oxygen below 10%

7. Free radicals • Aerobic bacteria make free radicals during aerobic respiration • Free radicals can be damaging to the cell • The aerobic bacteria have the capacity to break down the free radicals • Obligate aerobes make catalase or superoxide dismutase that breaks down free radicals

8. Halophiles • Grow in the presence of NaCl or other salts at levels greater than 0.2M • These organisms have adjusted their membranes and metabolism to a hypertonic environment • Their proteins and biochemistry have also adapted to this environment

9. Halotolerant • These orgnisms can tolerate lower levels of salt • They are osmotolerant and can adapt to a varying level of salt in their environment by accumulating potassium inside of their cells

10. pH • pH is a measure of the hydrogen ion activity of a solution • The pH scale extends from 0-14 • 0-7 is the acidic side of the scale • 7-14 is the basic side of the scale • 7 is neutral

11. Acidophiles • Prefer an environment of 0-5.5 • The lower the number the more acidic the pH

12. Neutrophiles • Have a pH preference for levels between 5.5 and 8 • Many pathogens fall in this group • Bacteria that can adapt to varying levels of pH are many of the enteric pathogens • E. coli and Salmonella have adapt by altering the proton pumps and other mechanisms for the movement of ions and molecules across their membrane

13. Waste products • Some bacteria give off waste by products that alter the environment and therefore adjust their environment • Fermentative microbes produce acids which in fact change their environment in the small intestine and large intestine

14. Alkalophiles • Alkalophiles prefer environments with high pH. • This environment is basic or alkaline

15. Temperature preferences( cold) • Psychrophiles – Live on the ice in Anarctica • These organisms can survive extreme conditions and even grow in the cold • Psychrotrophs – Live and grow in the refrigerator. • These organisms can grow at temperatures of 7oC, but optimally can grow at temperature up to 30oC

16. Mesophiles • Prefer temperatures 25-40oC • Human pathogens are mesophiles because human body temperatures fall within this range

17. Thermophiles • These organisms can grow at temperatures higher than 55oC • The may be found in compost heaps or piles of hay • They may also be found in hot water lines • Their proteins have more stable structures at higher temperature

18. Hyperthermophiles • These microbes can survive in boiling water • They can be found in the geysers of Yellowstone Part • They tolerate these high temperatures

19. New Work - Table • Plate bacteria on different pH concentrations, acidic, neutral, and alkaline. Place in the holder • Plate bacteria. Place in incubators at varying temperature levels • Plate bacteria. Place one set in incubator( oxygen) • Plate bacteria. Place the set in the anaerobic container and incubate.