This document discusses several techniques for quantitatively measuring microbial growth, including determining nitrogen content, dry weight, and colony counts. Determining nitrogen content involves harvesting and washing cells for chemical nitrogen analysis, and is useful for concentrated populations but laborious. Dry weight determination directly measures cell mass in dense suspensions after washing, but does not indicate living material; reserves can accumulate. Colony counts reflect only viable populations and are widely used, but discrepancies may occur compared to other methods. No single technique can universally measure all growth; the appropriate method depends on the situation and measurements allow interpreting growth under different conditions.
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1. TOPICS
DETERMINATION OF NITROGEN CONTENTS
DETERMINATION OF DRY WEIGHT IF CELL
THE SELECTION OF PROCEDURE TO
MEASURE GROWTH
IMPORTANCE OF QUANTATIVE
MEASUREMENT OF GROWTH
Subject : Microbiology
Roll No: 16251514-014
Presented by: Khadija Akram
Group 1
BS (Zoology) 7th (2016)
2. DETERMINATION OF NITROGEN CONTENTS :
Major Constituent of cell material is protein
Charaterstics part of protein
Measurement of cell crop and bacterial population
Dry weight basis of Nitrogen is 14%
This figure is responsilbe for variation by cultural
condition or difference b/w sp.
3. MEASURE GROWTH BY THIS TECHNIQUE :
First harvest the cell and wash them free of medium
Then perform Quantative chemical analysis for
nitrogen
These determinations are laborious
This is only perform on specimen free of all other
source of nitrogen
This method is only applicable only for
concentrated population
This procedure used in research
4. DETERMINATION OF DRY WEIGHT OF CELL :
Direct approach to Quantative Measurement of the
mass of cell
Used in dense suspension
The cell must washed free of extraneous matter
Dry weight does not indicative of the amount of
living material in cell
For Example:
The intercellular reserve material
Poly-8-hydroxybutyrate can accumulate in
Azotobacter beijerinckii at the end or Log phase
of growth
During the stationary phase and finally can
comprise upto 74% of dry weight of cell
5. CONTINUED……
The Dry weight may increase without cell growth
For many Organisms the determination of dry
weight is an accurate and reliable way to measure
growth
It is widely used in research
6. THE SELECTION OF A PROCEDURE TO
MEASURE GROWTH :
Each measurement procedure have its particular
advantages and limitation
No one method can be recommended universally
The Colony count is the most widely used
procedure for general microbial work
The complete familiarity is essential for both
principle and practice.
The Colony count is theoretically is the only
technique that reflect the viable population
Discrepancies may occur in growth of bacterial
population when measured with two different
methods
7. FOR EXAMPLE :
A Microbial count of a culture in stationary phase
would include all cells,Viable and Nonviable
Whereas, The Colony Count would reveal only
viable population
8. IMPORTANCE OF QUANTATIVE MEASUREMENT
OF GROWTH :
We can Elevate and Interpret growth responses of
bacteria in different media or under various
conditions, growth must expressed in quantative
terms
Growth is a term used in several ways
For Example :
We may judge condition being good or not
If Good bacteria grow rapidly but the total cell crop
may be may not be large under another set of
condition
In another condition the proceed at slower rate but
contine to increase for longer time period
9. GROWTH OF SAME BACTERIAL SPECIES IN
COMPARED IN TWO DIFFERENT MEDIA :
1. If we measure the growth at Time A we conclude
that growth is best in Medium II
2. If we measure the growth at Time B we conclude
that growth would be equally good in Both Media
(I & II)
3. And, If we measure the growth at Time C growth
would be better in Medium I