Effect of Temperature on Microbial Growth

Topics: Bacteria, Model organism, Osmosis Pages: 3 (756 words) Published: July 13, 2012
PROCEDURE:
Part A (Effect of temperature on growth)
1) 15 tubes of glucose broth are provided and one set of 3 tubes are inoculated with each of the following cultures; Escherichia coli, Pseudomonas fluorescens, Micrococcus luteus and Saccharomyces cerevisiae. The last served as control. 2) One of the three tube of each culture is incubated at each of the following temperature: * 4°C

* 37°C
* 55°C
3) All the tubes are incubated within 5 minutes after inoculating. The turbidity of the broth is observed and compared with the control after 24 hours. Part B ( Effect of osmotic pressure on growth)

1) Label four plates of glucose agar containing varying concentrations of NaCl (0.5%, 5%, 15%, and 25%) and three plates of glucose agar containing varying concentrations of sucrose (0.5%, 15%, and 30%). 2) Escherichia coli, Pseudomonas fluorescens, Micrococcus luteus, and Saccharomyces cerevisiae were inoculated into each plate. 3) The petri plates were then incubated at 37°C 24 hours.

RESULTS:
Part A) Effect of temperature on growth
At 4° C
M. Luteus| E. coli| P. fluorescens| S. cerevisiae| At 37° C
M. Luteus| E. coli| P. fluorescens| S. cerevisiae| At 55 °C
M. Luteus| E. coli| P. fluorescens| S. cerevisiae|

Result
Temperature(°C) Microbes| E.coli| P. fluorescens| M. luteus| S. cerevisiae| control| 4| -| -| ++| -| -|
37| ++| -| +| +++| -|
55| -| -| -| -| -|

Part B) Effect of osmotic pressure on growth

Sucrose concentration| E. coli| P. fluoresces| M. luteus| S. cerevisiae| 0.5%| ++| ++| ++| +|
15%| ++| ++| +| +|
30%| -| -| -| ++|

Nacl concentration| E. coli| P. fluoresces| M. luteus| S. cerevisiae| 0.5%| +++| ++| ++| +|
5%| ++| +| +| +|
15%| -| -| -| -|
25%| -| -| -| -|

KEY:
-| No growth|
+| Slight growth|
++| Moderate growth|
+++|...
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