This document discusses new trends in using microbes to monitor toxic environmental hazards. It describes how microbial biosensors can detect various pollutants by immobilizing microorganisms onto transducers. There are three main types of microbial biosensors: optical biosensors which detect changes in light properties, electrochemical biosensors which track electron transfer, and microbial fuel cell biosensors which convert substrates to electricity. Microbial biosensors are useful for environmental monitoring because microbes can thrive in harsh conditions and don't require expensive purification.

1. New trends in the monitoring of toxic
environmental hazards by microbes
Presented to: Dr Humaira Yasmeen
Presented by Minahil Khalid
Roll no :MP-MMG-21-12

2. Environmental Hazard.
❑ A substance that has the potential to threaten
the surrounding natural environment or
adversely affect people's health.
❑ It includes pollution and natural disasters such
as storms and earthquakes.

3. What are the toxic environmental
pollutants?

4. Environmental Monitoring:
❑ It involves the assessment of the quality of the
environment in order to control the risk of
pollution.
❑ Several microbial biosensors are used for the
detection of organic and inorganic toxicities.

5. Biosensors
❑ Biosensors are described as analytical
devices capable of sensing substances with
the help of some specific biological
reactions.
❑ The sensing elements are usually enzymes,
receptors, antibodies, or a whole cell
including unicellular microorganism.

6. Biosensors

7. Microbial biosensors
❑ A microbial biosensor is an analytical
device that immobilizes
microorganism(s) as a sensing element
onto a transducer for the detection of
target analytes
❑ Microbial biosensors are used
environmental monitoring, toxins
detection, etc.

8. Microbial biosensors

9. Microbial biosensors
❑ Divies in 1975 designed the first
microbial biosensor using Acetobacter
xylinum and oxygen electrode.
❑ Bacteria and yeast are the most popular
type of microorganisms used as
recognition elements.

10. TypesofMicrobial
biosensors(Transducers).

11. 1. Optical
2. Electrochemical
3. Microbial fuel cells types

12. Optical biosensor:
It is a device that makes use of an optical transducer to produce
changes in diverse optical properties (such as adsorption,
fluorescence, luminescence) which are proportional to the
concentration of the analytes.

13. 1. Optical biosensor:
Optical biosensors are classified on the basis of
their properties of compactness, selectivity,
sensitivity, and flexibility as :
❑ Fluorescent Microbial Biosensor.
❑ Bioluminescent microbial biosensor.
❑ MFC Biosensor.

14. Fluorescent Microbial Biosensor.
❑ Fluorescent Microbial biosensors can emit
fluorescent light that is directly proportional to the
concentration of the analyte at a low level.
❑ They are widely used in analysis processes
❑ By expressing green fluorescent proteins
recombinant yeast has the ability to emit
fluorescence when it is exposed to
genotoxins.

15. Bioluminescent microbial
biosensor:
❑ Bioluminescence-based microbial biosensors have
been extensively used in environmental monitoring for
the detection of toxicity.
❑ The changes in the density of the bioluminescence
emitted by the living cells can be measured by the
bioluminescent microbial biosensor.

16. Bioluminescent microbial
biosensor:
• The method of bioluminescence production can be divided
into two manners:
Constitutive manner. Inducible manner.
Lux gene-coded
luciferase exists
constitutively as
long as the organism
is active.
Toxicity can be used
as a parameter that
affects the density
of bioluminescence.
The Lux gene is fused
with a promoter
regulated by the
concentration of the
analytes.
Bioluminescence can
not be detected until
the concentration of
the analytes
approaches a critical
value.

17. Colorimetric microbial biosensor:
❑ It involves the changes in the color of the
special compound to determine the
concentration of the target analytes.
❑ By the immobilization of Flavobacterium
sp. in glass fiber, and Sphingomonas
bacteria onto the surface of the 96 wells
microplate a colorimetric microbial
biosensor is constructed for the
detection of methyl parathion.

18. 2. Microbial Electrochemical
biosensor:
❑ Microbial electrochemical sensors employ
electrode-biofilm as the sensing element.
❑ It detects biotoxicity by tracking the electron transfer
of microorganisms and electrodes under toxic stress.

19. 3. MFC Biosensor:
o MFC Biosensors have the ability to convert
organic substrates into electricity through
microbial catabolism.
Anodic Chamber Cathodic Chamber

20. MFC Biosensor:
❑ MFCs have been used as biosensors, for
measuring biochemical oxygen demand
and water toxicity.
❑ However, MFC biosensors suffer from
low sensitivity because the power
generated from MFCs is very low.

21. Applications of Microbial
biosensors
They can thrive in adverse environmental
conditions.
They do not require high costs of purification as in
enzymes.
Some of the main applications of Microbial
Biosensors are:
❑ BOD detection.
❑ Surfactant detection.
❑ Metal ion detection.
❑ Hydrocarbons detection.

22. Conclusion:
❑ Although microbial biosensors have some limitations, their usage in
environmental monitoring is widespread.
❑ The reusability of a microbial biosensor is one of the main concerns
in continuous environmental monitoring.
❑ Considering all the drawbacks microbial biosensor still offers
significant advantages over conventional sensing techniques.