Module 4 pt. 2 Flashcards
Acidophiles
Neutrophiles
Alkaliphiles
< pH 5.4
pH 5.4 - 8.5
pH 7.5 – 11.5
– acid-loving organisms
– can be found in acidic lakes, gastrointestinal tract
– most fungi (acid-tolerant; optimum temperature 5 or below)
– some algae, bacteria, and several Archaea
– high H+ concentration is required to maintain cell membrane stability
acidophiles
most human disease-causing bacteria
(human blood and tissues pH = 7.2 – 7.4)
protozoans and most bacteria (pH 6.5-7.5)
neutrophiles
base-loving organisms
live in soda lakes, high-carbonate soils
i.e. Bacillus, Vibrio cholerae (pH 9), Alcaligenes
faecalis (>pH 9), Agrobacterium (pH 12)
some produce hydrolytic enzymes (proteases and
lipases)
alkaliphiles
one of the most, if not the most, important
environmental factors affecting growth and
survival of microorganisms
Temperature
lowest temperature at which cells can divide
temperature at which cells divide most rapidly
highest temperature at which cells can divide
minimum growth temperature
optimum growth temperature
maximum growth temperature
Temperature Classes of
Microorganisms
Psychrophiles <0 to 20 C 15 C
Mesophiles 10 to 48 C 37 C
Thermophiles 40 to 72 C 60 C
Hyperthermophiles 65 to 110 C 80 C
“cold-loving organisms”
grow best at -10˚ to 20˚C
live mostly in cold water and soil (Arctic and
Antarctic regions) and can cause spoilage of
refrigerated food
psychrophiles
Organism found in raw milk
Listeria monocytogenes
➢ most bacteria including pathogens
➢ most common group of microorganisms
➢ 25 ˚to 40˚C
➢ found in warm-blooded animals
mesophiles
➢ “heat-loving organisms”
➢ 40 ˚ to 72˚C
➢compost heaps, hot springs
➢contaminants in dairy products
➢can be categorized into:
* obligate thermophiles
– temperatures above 37 ˚C
– Geobacillus stearothermophilus (65-75 ˚C)
- facultative thermophiles (moderate thermophiles)
– can grow both above and below 37 ˚C
thermophiles
➢ extreme heat-loving organisms
➢ 65 to 110 ˚C
➢ boiling hot springs, geysers, hot-water vents
hyperthermophiles
At 4 C reduces growth of psychrophiles; prevents growth of other microorganisms
continuously -30 C
Prevent bacterial growth
refrigeration
Long-time storage
High temperatures
Tolerance of psychrophiles
unsaturated (polyunsaturated) fatty acids in phospholipids
Tolerance of thermophiles
saturated fatty acids in phospholipids
heat-stable proteins and enzymes
