Microbilogy ..microbial toxin

1. Microbial Toxin-BIOC 422
Lecture-1

2. They are toxins produced by microbes and have the
ability to promote infection and disease by directly
damaging host tissues and disabling the immune
system.

3.  Microbe is a microscopic living organism, which may be single-cell or multicellular;
[tiny organisms—too tiny to see without a microscope, yet they are abundant on
Earth].
 They live everywhere—in air, soil, rock, and water.
The term is very general. It is used to describe many different types of life forms,
with dramatically different sizes and characteristics:
*Viruses *Bacteria *Fungi *Protozoa *Microscopic Algae

4. They are poisonous chemical compounds produced by or derived from
microorganisms that can cause some disorders/diseases when present at low
concentration in the body in human health.
“synthetic toxins created by artificial processes are thus excluded”

5. We have become obsessed with eliminating bacteria, attacking with
gels and wipes the microbes we associate with infection, illness and
death.
But not only are many types of bacteria actually helpful, some strains
may hold the key to fighting global warming, cleaning up pollution,
breaking down plastic and even developing a cure for cancer.

6. Some Examples of the beneficial roles of microbial toxins:
Maintain balance of environment (microbial ecology)
Basis of food chain
Nitrogen fixation
Photosynthesis
Digestion, synthesis of vitamins
Manufacture of food and drink
Genetic engineering
Recycling sewage
Bioremediation: (waste management technique)
use microbes to remove toxins (oil spills)
Use of microbes to control crop pests
http://webecoist.momtastic.com/2011/09/26/beneficial-bacteria-12-ways-microbes-help-the-environment/

7.  Poison: toxins that, in small amounts, cause immediate death.
 Toxicant: is a man-made “artificial” products introduced into the environment due to
human activity; examples are industrial waste products and pesticides capable of
causing a harmful effect to living organisms.
 Toxin: is a toxicant produced by a living organism (floral or fungal , including
bacteria); that is, naturally produced toxicants.
All toxins are toxicants, but not all toxicants are toxins.
 Xenobiotic: is a man-made substance found within an organism that is not normally
naturally produced by or expected to be present within. Principal xenobiotics include:
drugs, carcinogens and various compounds that have been introduced into the
environment by artificial mean.
 Hazard: the adverse or undesirable effect resulting from exposure to a particular
toxicant or physical agent.

8.  Toxicity : is the degree to which a substance can damage an organism.
 Dose: the amount of a chemical that gains access to the body.
Types of doses:
Exposure dose: amount of toxin found in the environment.
Administered dose: The quantity of the toxin given.
Absorbed dose: The actual quantity of a toxicant that is absorbed into the
organism and distributed systematically through the body.
Total dose: The sum of all individual doses which may be received over
a period of time.

9.  For administered dose: mg/ Kg/ Day
 For environmental exposure:
>>For Liquids: mg/ liter
>>For Solid: mg/gram
>>For Air: mg/m3
• Smaller units are needed for substances in the environment or media are parts per million(ppm) or per
billion (ppb) and per trillion (ppt).

10. Q. “Which group of chemicals do we consider to be toxic?”
A. All chemicals
 For even relatively safe, chemicals can become toxic if the dose is high enough,
and even potent highly toxic chemicals may be used safely if exposure is kept
low enough.
 Paracelsus (1493–1541) stated stated this concept as : “All substances are
poisons; there is none which is not a poison. The right dose differentiates a
poison and a remedy.”
 Consequently, another way of viewing all chemicals is that provided by Emil
Mrak, who said “There are no harmless substances, only harmless ways of
using substances.”

11. Lethal median dose- LD50
The value of LD50 for a substance is the dose required to kill half the members of a
tested population after a specified test duration. It is expressed as mg/kg
(milligrams of substance per kilogram of animal body weight)
Lethal concentration-LC50
The concentration of a chemical in an environment (generally air or
water) which produces death in 50% of an exposed population of test
animals in a specified time frame.
Some chemicals are rapidly detoxified by the human body. So, in these cases, the
lethal concentration may be given simply as LC50 and qualified by a duration of

12. First, cross-match the doses listed in column A of Table 1.1, doses that produce lethality in 50 percent
of the animals (LD50), to the correct chemical listed in column B. The chemicals listed in column B are
a collection of food additives, medicines, drugs of abuse, poisons, pesticides, and hazardous
substances for which the correct LD50 is listed somewhere in column A
muscle relaxant
neurotoxic protein  causes flaccid paralysis
medicine  treat and prevent anaemia
pain medication  directly on CNS to decrease pain
highly toxic chemical compounds  reproduction, development, and
the immune system

13. To perform this cross-matching, first photocopy Table 1.1 and simply mark the ranking of the dose (i.e., the number
corresponding next to the dose in column A) you believe correctly corresponds to the chemical it has been measured
for in column B. [Note: The doses are listed in descending order, and the chemicals have been listed alphabetically. So,
the three chemicals you believe to be the safest, should have the three largest doses (you should rank them as 1, 2, and
3), and the more unsafe or dangerous you perceive the chemical to be, the higher the numerical ranking you should
give it

14. • Ingestion (water and food)
• Absorption (through skin)
• Injection (bite, puncture, or cut)
• Inhalation (air)

15. Duration and frequency are also important components of exposure and
contribute to dose
1. Acute exposure -- exposure over a brief period of time; generally less than 24 h.
“Often it is considered to be a single exposure (or dose) but may consist of repeated exposures within a short
time period”.
2. Subacute exposure—resembles acute exposure except that the exposure duration is
greater, from several days to one month.
3. Subchronic exposure—exposures repeated or spread over an intermediate time
range, 1–3 months.
4. Chronic exposure—exposures (either repeated or continuous) over a long period of
time, greater than 3 months.

16. 1- Clinical toxicology is the diagnosis and treatment of human poisoning.
2. Veterinary toxicology is the diagnosis and treatment of poisoning in animals.
3. Forensic toxicology concerns the medicolegal aspects, including detection of
poisons in clinical and other samples.
4- Environmental toxicology is concerned with the movement of toxicants and their
metabolites and degradation products in the environment and in food chains and
with the effect of such contaminants on individuals and, especially, populations.
5. Industrial toxicology is a specific area of environmental toxicology that deals with
the work environment and constitutes a significant part of industrial hygiene.
*Toxicologists are scientists who study the chemical or agent in depth for the purpose of gaining an understanding of how the chemical or agent
initiates those biochemical or physiological changes within the cell or tissue that result in the toxicity.
**Applied toxicologists are scientists concerned with the use of chemicals in a “real world” or nonlaboratory setting.