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.

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

10. CAMPARSION OF CELL CROPS OR AMOUNT OF
GROWTH AT TIME A,B AND C :