Requirements for Growth Effect of pH and temperature on microbial ...

Include most pathogens <strong>and</strong> common spoilage organisms.
Best growth between 25 to 40 o C.
Optimum <strong>temperature</strong> commonly 37 o C.
Many have adapted to live in the bodies <strong>of</strong> animals.
C. Thermophiles: “Heat loving”.
Optimum growth between 50 to 60 o C.
Many cannot grow below 45 o C.
Adapted to live in sunlit soil <strong>and</strong> hot springs.
Some thermophiles <strong>for</strong>m heat resistant endospores.
Extreme Thermophiles (Hyperthermophiles): Optimum growth at 80 o C or higher.
Archaebacteria. Most live in volcanic <strong>and</strong> ocean vents.
Organism Minimum Optimum Maximum
Bacillus cereus 5 28 - 40 55
Campylobacter spp. 32 42 - 45 45
Clostridium botulinum 10 - 12 30 - 40 50
Clostridium perfringens 12 43 - 47 50
Enterotoxigenic Escherichia coli 7 35 - 40 46
Listeria monocytogenes 0 30 - 37 45
Salmonella spp. 5 35 - 37 45 - 47
Staphylococcus aureus 7 35 - 40 48
Shigella spp. 7 37 45 - 47
Vibrio cholerae 10 37 43
Vibrio parahaemolyticus 5 37 43
Vibrio vulnificus 8 37 43
Yersinia enterocolitica -1 28 - 30 42
2. <strong>pH</strong>:
<strong>pH</strong> dramatically affects bacterial growth, this is because that <strong>pH</strong> affects the activity <strong>of</strong> enzymes
those that are involved in biosynthesis <strong>and</strong> growth.
Each microbial species possesses a definite <strong>pH</strong> growth range <strong>and</strong> a distinct <strong>pH</strong> growth
optimum.