Transcript Modelling microbial growth

Modelling Bacterial
Growth
Thinking Activity
It takes 20 minutes for one E. coli
bacterium to divide to make two
bacteria.
Assuming there is nothing to limit their
growth, how many bacteria would
there be after eight hours?
More than 16 million!
Lesson Objectives
 To state the scientific unit for
temperature is Kelvin.
 To use modelling software to investigate
how temperature affects the growth of
bacteria.
 To suggest reasons why fridge
temperature should be set at a
maximum of 5°C.
Measuring Temperature
Celsius or oC is a unit of
temperature. So is
Fahrenheit or oF.
But scientists use
another based on
particle vibrations...
How are particles
arranged in solids,
liquids and gases?
Absolute zero – when particles stop
vibrating.....
That is where the Kelvin scale starts, and it is
equivalent to -273.15 oC
Try these examples
To convert Celsius to
Kelvin add 273
e.g. 36oC is 309K
 To convert Kelvin
to Celsius
subtract 273
 e.g. 400K is
127oC
40oC
313K
0K
-273oC
0 oC
273K
55K
-218oC
100oC
373K
400K
127oC
Go to www.combase.cc and follow the
instructions on the lab sheet. You will
use the research database to
investigate bacteria.
Plenary
Using the ‘MicroTrumps’ cards, play
using temperature as your category.
Stretch and challenge:
Use the Kelvin scale, converting in
your heads from the temperature in °C
on the card.
Plenary
Why is a fridge
set at 5°C?
What be the
effect of leaving
the fridge door
open?
Hint: think about
the shelf life and
bacterial growth