FMB - Lecture 5 Flashcards
Factors affecting the growth of bacteria:
Physical
- pH
- Temperature
- Oxygen concentration
- Moisture
- Hydrostatic pressure
- Osmotic pressure
- Radiation
Nutritional
- Carbon
- Nitrogen
- Sulfur
- Phosphorus
- Trace elements
- Vitamins
A measure of how acidic/basic water is.
pH
____ ranges from 0 to 14, with 7.0 being neutral.
pH
Acidity is inversely related to pH.
- A system with high acidity has a low pH.
- A system with low acidity has a high pH.
Most bacteria grow between pH _______.
pH 6.5 AND 7.5
Molds and yeast grow between pH _______.
pH 5 and 6
They grow in acidic enviroment.
Acidophiles
Examples of acidophiles.
- Sulfolobus spp.
- Lactobacillus spp.
Examples of neutrophiles.
- Escherichia coli
- Salmonella
They grow at a pH level of 7.0 - 11.5, 12.0
Alkaliphiles
Example of alkaliphiles.
- Vibrio cholerae
- Alcaligenes faecalis (9.0 - higher)
- Agrobacterium (soil microorganisms, 12.0 pH)
Cause peptic ulcer.
Helicobacter pylori
_____ is neutrophile, however, its ability to survive low pH of the stomach would seem to suggest that it is an extreme acidophile.
H. pylori
The ammonium ion raises the pH of the immediate environment (NH4+ and CO2).
H. pylori
Effects of pH in growth of bacteria:
- Protection.
- Inhibits growth.
- Denaturation of enzymes and other proteins.
- Metabolic by-products.
It is a major environmental factor controlling microbial growth and is accomplished through enzymatic reactions.
Temperature
Because _____________ influences enzyme reactions, it has an important role in microbial growth in food.
Temperature
Must meet required environmental conditions.
Obligate
Adjust and tolerate / thrive in other environmental conditions, and can adapt.
Facultative
Cold loving microorganisms (cold temperature optima). Most extremes representative inhabit permanently in cold environments.
Psychrophiles
Growth temperature of 15 - 20 degree celsius and 0 - 20 degree celsius.
Psychrophiles
Example of obligate psychrophiles.
Bacillus globisporus - 20 degree celsius.
Example of facultative psychrophiles.
Xanthomonas pharmicola - below 20 degree celsius but can grow above 20 degree celsius.
Moderate loving microorganisms (midrange temperature optima). Found in warm-blooded animals and in terrestrial and aquatic environments in temperature and tropical latitudes.
Mesophiles
Growth temperature of 20 - 45 degree celsius / 25 - 40 degree celsius. Also considered as human pathogen because it grow best in human temperature (37 degree celsius).
Mesophiles
Growth temperature optima between 45 - 80 degree celsius / 50 - 60 degree celsius / 50 - 80 degree celsius.
Thermophiles
It can be seen in compost pits and hot springs. They are also called as heat loving microorganisms.
Thermophiles
Obligate thermophiles temperature:
Above 37 degree celsius
Facultative thermophiles temperature:
Both above and below 37 degree celsius.
Example of thermophiles.
Bacillus stearothermophilus
Optima greater than 80 degree celcius. These organisms inhabit hot environments including boiling hot springs, as well as undersea hydrothermal vents that can have temperature in excess of 100 degree celcius.
Hyperthermophiles
Example of hyperthermophiles:
Thermus aquaticus
Live as mesophiles but can live at a higher temperature for a short period of time.
Thermoduric
Growth temperature of 0 - 30 degree celcius. Cannot grow in 4. degree celcius. Low temperature food spoilage.
Psychrotrophs
Three cardinal temperature.
- Minimum Temperature
- Optimum Temperature
- Maximum Temperature
Temperature below which growth ceases, or lowest temperature at which microbes will grow.
Minimum Temperature
Temperature at which its growth rate is the fastest.
Optimum Temperature
Temperature above which growth ceases, or highest temperature at which microbes will grow.
Maximum Temperature
Effects of temperature in growth of bacteria:
- Enzyme activity.
- Preventing growth.
- Preservations
Microbes that use molecular oxygen produce more energy from nutrients
Aerobes (Oxygen)
Microbes that do not use oxygen.
Anaerobes (Oxygen)
Require an atmosphere oxygen in concentrations comparable to 20%–21%.
Obligate aerobes
Example of Obligate aerobes:
Pseudomonas
Not require oxygen for life and reproduction.
Obligate anaerobes