Food Protection with High Temperatures
433
Table 17–14 Maximal Growth Temperatures and Ribosome Melting
Organism and Strain Number
Maximum Growth Temperature (
◦ C)
Ribosome T m (
◦ C)
1. V. marinus (15381)
18
69
2. 7E-3
20
69
3. 1–1
28
74
4. V. marinus (15382)
30
71
5. 2–1
35
70
6. D. desulfuricans (cholinicus)
∗
40
73
7. D. vulgaris (8303)
∗
40
73
8. E. coli (B)
45
72
9. E. coli (Q13)
45
72
10. S. itersonii (SI–1)
†
45
73
11. B. megaterium (Paris)
45
75
12. B. subtilis (SB-19)
50
74
13. B. coagulans (43P)
60
74
14. D. nigrificans (8351)
‡
60
75
15. Thermophile 194
73
78
16. G. stearothermophilus (T-107)
73
78
17. G. stearothermophilus (1503R)
73
79
18. Thermophile (Tecce)
73
79
19. G. stearothermophilus
73
79
∗ Desulfovibrio.
† Spirillum.
‡ Desulfotomaculum.
Source: From Pace and Campbell. 43
Oxygen Tension
Thermophilic growth is affected by oxygen tension. As the temperature of incubation is increased,
the growth rate of microorganisms increases, thereby increasing the oxygen demand on the culture
medium while reducing the solubility of oxygen. This is thought by some investigators to be one of
the most important limiting factors of thermophilic growth in culture media. Downey
15 has shown
that thermophilic growth is optimal at or near the oxygen concentration normally available in the
mesophilic range of temperatures—143 to 240 µM. Although it is conceivable that thermophiles are
capable of high-temperature growth due to their ability to consume and conserve oxygen at high
temperatures, a capacity that mesophiles and psychrophiles lack, further data in support of this notion
are wanting.
Cellular Lipids
The state of cellular lipids affects thermophilic growth. Because an increase in degree of unsaturation
of cellular lipids is associated with psychrotrophic growth, it is reasonable to assume that a reverse effect
occurs in the case of thermophilic growth. This idea finds support in the investigations of many authors.
Gaughran
19 found that mesophiles growing above their maximum range showed decreases in lipid
433
Table 17–14 Maximal Growth Temperatures and Ribosome Melting
Organism and Strain Number
Maximum Growth Temperature (
◦ C)
Ribosome T m (
◦ C)
1. V. marinus (15381)
18
69
2. 7E-3
20
69
3. 1–1
28
74
4. V. marinus (15382)
30
71
5. 2–1
35
70
6. D. desulfuricans (cholinicus)
∗
40
73
7. D. vulgaris (8303)
∗
40
73
8. E. coli (B)
45
72
9. E. coli (Q13)
45
72
10. S. itersonii (SI–1)
†
45
73
11. B. megaterium (Paris)
45
75
12. B. subtilis (SB-19)
50
74
13. B. coagulans (43P)
60
74
14. D. nigrificans (8351)
‡
60
75
15. Thermophile 194
73
78
16. G. stearothermophilus (T-107)
73
78
17. G. stearothermophilus (1503R)
73
79
18. Thermophile (Tecce)
73
79
19. G. stearothermophilus
73
79
∗ Desulfovibrio.
† Spirillum.
‡ Desulfotomaculum.
Source: From Pace and Campbell. 43
Oxygen Tension
Thermophilic growth is affected by oxygen tension. As the temperature of incubation is increased,
the growth rate of microorganisms increases, thereby increasing the oxygen demand on the culture
medium while reducing the solubility of oxygen. This is thought by some investigators to be one of
the most important limiting factors of thermophilic growth in culture media. Downey
15 has shown
that thermophilic growth is optimal at or near the oxygen concentration normally available in the
mesophilic range of temperatures—143 to 240 µM. Although it is conceivable that thermophiles are
capable of high-temperature growth due to their ability to consume and conserve oxygen at high
temperatures, a capacity that mesophiles and psychrophiles lack, further data in support of this notion
are wanting.
Cellular Lipids
The state of cellular lipids affects thermophilic growth. Because an increase in degree of unsaturation
of cellular lipids is associated with psychrotrophic growth, it is reasonable to assume that a reverse effect
occurs in the case of thermophilic growth. This idea finds support in the investigations of many authors.
Gaughran
19 found that mesophiles growing above their maximum range showed decreases in lipid