Transcript Prokaryotes and bacterial growth curves

Prokaryotes and bacterial growth
curve
This lab
•Bacteria, Archea
•Bacterial morphology, reproduction and growth curve
•How to calculate generation time
•How to draw a growth curve
•Exercise on phase contrast microscope
•Inoculating some plates
Domains of life
Domains of life
Blue green bacterium
Chlo.A
Eukarya
Archaea
chloroxybacteria
schizomycetes
Muramic
acid
Intracellular
organelles
Chlo. A&B
Nuclear mem.
DNA transcription factors
DNA
RNA
ATP
Bacteria and Archea
• Bacteria and Archea are unicellular organisms.
• For long time, Archea used to be grouped with
bacteria
• but it was separated later on. Generally Archea
can be described as bacteria able to grow and
multiply in extreme environmental conditions
(high temperature, high salinity,….)
Why to study Bacteria and
Archea
• Many of them produce diseases (HUS
caused by E. coli O157).
• Others are beneficial (lactobacillus species
is used in yogurt, bacteria in association
with plant roots supply nitrogen).
• Archea is good source for restriction
enzymes
Bacterial morphology
• Bacteria has many shapes
• B.subtilis is bacilli (rod shaped)
Bacterial reproduction
• Simple binary fission (Asexual)
• The bacterium double its content then
divide into two
• Bacterial motility
http://www.bme.jhu.edu/~skuo/emph_ListSte
ps.html#Relevance
Bacterial growth curve
• Bacteria grow in population called Culture
• Binary fission result in “geometric
progression in number” which is termed
exponential growth
• 1-> 2-> 4-> 8->16 -> 2n….
• Generation time (doubling time):time
needed for division
Growth curve
How to calculate generation time
from data set
• n = 3.3 x log (P/p)
n= number of generations
P= final population number
p= original population number
•Generation time = time elapsed to reach “P”
minute/generation
n
*example page 38
How to calculate generation time
•How to determine the population number?
•By using
light
spectrophotometer (A600)
Detector….reading
600nm
Different reading
How to calculate generation time
time
8:20
Time
elapsed
0
8:50
30 m
9:20
60 m
9:50
90 m
10:20
120 m
A600
Log A600
What to do
1- mark your tubes (on the upper part) 25C and
37C
2- using the Blank tube adjust your machine to
zero absorbance (on the lower scale using right knob). You
do not have to do this step again
3- aseptically (using pasteure pipette) take 4 ml
from each culture into each tube then take the
reading.
4- return the the 4ml back to the culture and turn on the
shaker
5- repeat step 3 and 4 every 30 minutes
P.S make sure that you return it to the correct culture
otherwise it will spoil all the work
How to draw a growth curve at
the exponential phase
* Plot you A600 or log A600 against your time point
A600
Log A600
Log A600
A600
Time in minutes
How to calculate generation time
from a growth curve
* If you have the growth curve of certain bacteria
(exponential phase), you can calculate the generation time
by this equation
*generation time= time elapsed x log2
logA600
*example in page 38
Microscope
* Staining of biological specimen enhance visibility
*What you should do
1- mount the slid on the stage
2- chose the low power lens and start to focus using
the coarse focusing the fine focusing.
3- chose another objective lens and repeat
4- your goal is to have clear sharp view of what you
are examining
Lab report on bacteria
and
c
bacterial growth curve
•Worth 15 point .due next week in class
•Topics to be covered
1- title :chose suitable title from your creation (1)
2-abstract: summary of the report (3)
3-introduction:background (3)
4-experimental procedures (1)
5-results : include page 39&40 from the manual as attachments)(3)
also include tables (A600 readings)
6-discussion (4)
7-references: cite any references you used in you report
There is a handout on what is expected in lab. report.
There is a handout on group members participation.
I will post an example Lab report (on a different topic)
today.