The document discusses bacteria, including that they were the first life forms on Earth, are unicellular prokaryotic cells typically 0.5-1.5 μm in length that can have rod, spiral or other shapes. It classifies bacteria according to their shape (coccus, bacillus, spirillum) and arrangement (diplococci, streptococci, tetracocci, staphylococci, sarcinae). The document also discusses how different types of bacteria are adapted to different temperature ranges (psychrophiles, mesophiles, thermophiles, hyperthermophiles) and defines D-value, Z-value and F-value which relate to the thermal destruction of

1. By Sayanta Mitra
Bacteria According
To The
Temperature

2.  First life forms to appear on the earth.
 Unicellular prokaryotic biological cell.
 0.5µm to 1.5µm in length.
 Have numbers of shapes like rod, spiral.
 Inhibit in soil, water.
 Live in symbiotic and parasitic relationship with
plants and animals.
What is bacteria?

3. Classification of bacteria
(According to shapes & size)
Bacteria
Coccus Bacillus Spirillum
(Spherical) (Dot) (Helical)
e.g. e.g. e.g.
Staphylococcus Aquospirillum
lactobacillus
Aquospirillum

4. Classification of bacteria
(According to arrangement of cocci)
Bacteria
Diplococci Tetracocci
Streptococci Staphyllococci
Sarcinae

5.  Diplococci : Cells divide in one plane and remain
attached in pair forms.
 Streptococcus : Cells divide in one plane and
remain attach to form chain.
 Tetracocci : Cells divide in two planes and forms
groups of four cells.
 Staphyllococci : Cells divide in three planes and
irregular pattern producing branches of cocci.
 Sarcinae : Cell divide in three planes in a regular
pattern producing a cubical arrangement.

6. 120
110
100
90
80
70
60
50
40
30
20
10
0
-10
Effect of temperature on bacterial
growth
Temperature (ºC)
Growth
rate
Psychrophiles
Example :
Polaromonas
Mesophiles
Example :
Escherichia coli
Thermophiles
Example :
Geobacillus
Hyperthermophile
Psychrotrophs stearothermophilus
vacuolata
Example :
Example :
Thermococcus
celer
Pyrolobus
fumarii
4º
39º
60º
88º
106º
Freezing
point
Room
temperature
Boiling
temperature

7. D- value :
10
100
1000
10000
D
log
t
Constant
temperature
Number
of
microorganism
N
N
Time (t)
Exponential decrease
Survivor curve
Time needed at a constant temperature to
kill 90% of microorganism population.
D- value :
Thermal destruction of microorganism

8. Z - value :
Z
100
10
D
Temperature (T)
Z - value :
Resistance of a microorganism to different
temperature.

9. F- value :
10
100
1000
10000
D
F- value :
Numbers of minutes required to kill
microorganisms at a certain temperature.
Time (T)
Microbial
population 1000 to 100 » F= 1*D
10000 to 100 » F= 2*D
10000 to 10 » F= 3*D