Microorganism

1. INTRODUCTION
Microorganisms:-Organisms found in surface water
and wastewater include bacteria, fungi, algae,
protozoa, plants and animals and viruses which can
only be observed microscopically.

2. Microorganisms
Prokaryote
(Simplest cell structure
Size: 0.2 -3.0µm)
Eukaryote
(more complex
Size: 2-100 µm)
(e.g. bacteria, blue-
green algae and
archaea)
(e.g. protozoa, fungi,
rotifers, green algae,
plants & animals)

4. DETECTION TECHNIQUES

5. Why Detect Microorganisms?
• Determine cause of infection
• Appropriate treatment (antibiotics,
antivirals, vaccination )
 Rapid detection leads to earlier intervention
 Exclusion of infectious causes

6. Three Major Steps Involved
Recovery
&
Concentration
Purification
&
Separation
Assay
&
Characterization

7. Methods for Identification of bacteria
1. Direct microscopic count
2. Pour & spread plate counts
3. Membrane filtration (MF)
4. Multiple tube fermentation

8. Direct Microscopic Count
1. Microscopically by using Petroff-Hauser
counting chamber
• Difficult to differentiate b/w live & dead
cells
• Acridine orange (Vital) stain to
differentiate b/w live & dead cells
2. Electronic particle counter is an alternative

10. • Used to culture, identify & enumerate the
bacteria
• Sample of wastewater to be tested is diluted
• Small amount of dilution is mixed with a warned
liquid (agar) culture, poured into a culture dish,
allowed to solidify and incubated under
controlled conditions
• Finally separate distinct bacterial colonies are
formed on the plates after incubation and the
results reported as colony-forming unit per unit
volume (cfu/ml)
Pour & Spread Plate Counts

12. Membrane-Filter (MF) Technique
• Known volume of water is passed through a
membrane filter
• Bacteria are retained on filter
• Membrane filter is placed in contact with an agar for
growth of specific bacteria
• After incubation, colonies are formed and then
counted

14. • This method is based on the principle of dilution to extinction
• Concentration of total coliform bacteria are reported as most
probable number per 100ml (MPN/100ml)
Multiple-Tube Fermentation
 Other methods of bacteria identification
1. Presence – absence test
2. Heterotrophic Plate Count

15. Identification of Specific Bacteria & Protozoa
1. Fluorescence method
2. Nucleic acid probe method

16. end