Microbial Growth Flashcards
Important for energy and construction
microbial nutrition
substances used in biosynthesis energy production
nutrients
Biochemical Components of Cells
Water-
Protein-
Nucleic acid-
Lipid-
Water-80%
Protein- 40-70%
Nucleic acid- 13-34%
Lipid-10-15%
Refers to an increase in cell number, not in cell size.
microbial growth
Bacteria grow and divide by _______ a rapid and relatively simple process.
binary fission
“Cold-loving”. Can grow at 0oC
Psychrophiles
Psychrophiles two groups
True Psychrophiles
Psychrotrophs
Sensitive to temperatures over 20oC. Optimum growth at 15oC or below. Found in very cold environments (North pole, ocean depths). Seldom cause disease or food spoilage.
True Psychrotrophs
Optimum growth at 20 to 30oC. Responsible for most low temperature food spoilage.
Psychrotrophs
Requirements for Growth
Physical Requirements
Temperature
pH
Osmotic Pressure
Middle loving”. Most bacteria.
mesophiles
include most pathogens and common spoilage organisms.
mesophiles
Mesophiles best growth between
25° to 40°C
mesophiles optimum temperature commonly is
37°
Heat loving
thermophiles
Thermophiles optimum growth is
50° to 60°C
Adapted to live in sunlit soil, compost piles, and hot springs.
Thermophiles
Optimum growth at 80oC to 140o C. Archaebacteria. Most live in volcanic and ocean vents.
extreme thermophiles (hyoerthermophiles)
Most bacteria prefer _____ pH (6.5-7.5)
neutral
_____ and ____ grow in wider pH range, but prefer pH between 5 and 6.
molds and yeast
inhibits most microbial growth and is used frequently for food preservation
acidity
inhibits microbial growth, but not commonly used for food preservation
alkalinity
inhibits microbial growth, but not commonly used for food preservation
alkalinity
“Acid loving”
acidophiles
Grow at pH 5.4 to 8.5.
neutrophiles
“Alkali loving”
alkaliphiles
Grow at alkaline or high pH (7 to 12 or higher)
alkaliphiles
High osmotic pressure removes water from cell, causing shrinkage of cell membrane (plasmolysis)
hypertonic solutions
