Lecture_2.ppt

Beneficial Uses of Microbes
Extraction of copper from ore

Synthesis of drugs, hormones and enzymes

Bioremediation is the use of microbes to degrade organic
matter in sewage and detoxify pollutants such as oil spills.

Photosynthetic Microbes
Microbes are involved in photosynthesis and accounts for
>50% of earth’s oxygen.
Also involved in decomposition and nutrient recycling.

Modern Uses of Microbes
 Biotechnology, the use of microbes as miniature
biochemical factories to produce food and chemicals is
centuries old.
 Genetic engineering makes use of molecular biology
and recombinant DNA techniques as new tools for
biotechnology.
 Gene therapy replaces missing or defective genes in
human cells through genetic engineering.
 Genetically modified bacteria are used to protect crops
from pests and freezing.

General Characteristics
 Prokaryotes no nucleus and organelles
 Eukaryotes membrane bound nucleus
and organelles
 Acellular agents genomes contain either
DNA or RNA; newer agent
is proteinaceous

Cell Types
Comparative cellular structures of microbes

The Microbes
viruses protozoa
bacteria
bacteriophage
algae
spirochaetes
cyanobacteria
fungi

Size of Microbes
Microbes vary in size ranging
from 10 nm (nanometers) to
100 mu (micrometers) to the
macroscopic.
Viruses in nm = 10-9 m (meter)
Bacteria in um = 10-6 m
Helminths in mm = 10-3 m

Bacteria
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Prokaryotes
Peptidoglycan cell walls
Binary fission
Example: Escherichia coli

Fungi
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Eukaryotes
Chitin cell walls
Molds and mushrooms
are multicellular
Yeasts are unicellular

Protozoa
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Eukaryotes
Mostly saprobes and
commensals
May be motile by means
of pseudopod, cilia or
flagella

Algae
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Eukaryotes
Cellulose cell walls
Photosynthetic
Produce molecular oxygen
and organic compounds
Part of food chain

Helminthes
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Eukaryotes
Multicellular animals
Parasitic flatworms and
roundworms called
helminths
Microscopic stages in life
cycles

Viruses
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Acellular
Obligate intracellular parasites
Genome consist of DNA or
RNA called Core
Core surrounded by protein
coat called Capsid
Virion may be enclosed in lipid
envelope

Prions
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Proteinaceous infectious
agents
Causes Bovine Spongiform
Encephalopathy (BSE)
Also causes Creutzfeldt-
Jacob Disease (CJD)
An Emerging Infectious
Disease (EID)

Emerging Infectious Diseases
 Occurrence of new diseases and increasing incidence of
old ones (EID)
 Factors:
(a) evolutionary changes in existing organisms
(b) spread of known diseases into new
geographic areas by modern transportation
(c ) ecological changes resulting in introduction of
unusual agents
(d) emergence of antimicrobial resistance

Examples of Emerging Infectious Diseases
 West Nile Encephalitis, first diagnosed in Uganda in 1937;
appeared in New York City in 1999.
 Invasive Group A Streptococcus, also known as the “flesh eating
bacteria”
 Escherichia coli 0157:H7, causes “bloody diarrhea” and
hemorrhagic uremic syndrome (HUS)
 Bovine Spongiform Encephalopathy (BSE) or “mad cow” disease
caused by prions
 Acquired Immunodeficiency Syndrome (AIDS) caused by HIV and
 Anthrax caused by Bacillus anthracis was sensationalized in 2001
when spores were disseminated via the mail

Overview of Normal Flora, Pathogenic
Organisms
• Definitions of Terms
• Normal floras: Are bacteria, fungi, and protozoa that
live on or within the bodies of animals and plants
without doing any harm in healthy individuals. o
They may be commensalists or mutualists with
regard to the host. o Basically they do not harm the
host; however they can even do some good.
• Pathogen: Is an organism which is capable to cause
pathological condition to another organism. Invasion
of the body by pathogenic organism is called
infection

Normal Flora Found in the Body and their
Importance
• Normal flora tends to be commensal or mutual
symbionts adapted to the special conditions found
in various body locations.
• Normal flora are found mostly: On skin, in eyes,
in the nose, in mouth and pharynx, in urethra, in
lower GIT, in vagina and in external ear

Bacterial Normal Flora of Different Parts
of the Body
Types of Normal Flora
• Transient flora: Members of the normal flora
that are not always present or present for only a
few days, weeks, or months before disappearing.
• Resident flora: Members of the normal flora that
are always present at their specific site of the
body or re-establishes after being eliminated by
antibiotics

Importance of Normal Flora
• They compete for space and nutrients with
pathogens (microbial antagonism)
• They are protective against pathogens
hence they add up to the immunity of the
body
• Some of them synthesize vitamins
• Enteric normal flora help with digestion

Types of Pathogens and Vectors
• Types of Pathogens
• Microbiological pathogens
These are the pathogens of microscopic size and
include viruses, bacteria and fungi.
• Parasitological pathogens
These are the pathogens which are larger in size
as compared to microbiological pathogens and
include protozoans and helminthes (worms).

Types of Vectors
• Biological vectors
These are vectors which can support life and/ or
development of pathogenic organisms in their
tissues and transmit. E.g. mosquitoes, tsetse flies
• Mechanical vectors
These are Vectors which transmit pathogens
mechanically (no development of the pathogens
take place). Examples, houseflies & cockroaches.

Characteristics of Pathogens and Vectors
Characteristics of Pathogens
• All are living organisms
• They all cause disease by various mechanisms
• Can be found inside or outside the human body
• Some of them reproduce while in the human host,
some of them in the vector (intermediate host)
and some of them outside the host

Characteristics of Vectors
• They are all arthropods however snails which are
intermediate hosts are conveniently considered
vectors.
• They are invertebrates.
• They are capable of transmitting diseases.
• Biological vectors can support development of
pathogenic organisms in their tissues then transmit
the pathogens.
• Mechanical vectors cannot support development of
the pathogenic organisms but can transmit
pathogens mechanically.

• The biological vectors feed on the host. For the
pathogenic transmission to occur the vector has
to come in contact with the host looking for blood.
Key Points
• Normal flora is bacteria, fungi, and protozoa that
live on or within the bodies of animals and plants
without doing any harm in healthy individuals.
• Pathogens are organisms which are capable of
causing pathological condition to other organisms.

• Pathogens are classified into different
groups like viruses, bacteria, fungi,
protozoa and helminthes based on their
different characteristics.
• Vectors also bear different characteristic,
therefore they are also classified into
different groups like mechanical and
biological vectors respectively.

Lecture_2.ppt

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