Role of immune system in health & Diseases

Presented by:Ms. Smita Shukla

Assistant Professor

Classification of Microbes

What are Microbes?

A microbe is any living thing that spends its life at a size visible sometimes only with a microscope.

It is too tiny to be seen with the naked eye. Microbes are the oldest form of life on Earth.

Prokaryotes (Bacteria)Eubacter "True" bacteria

Human pathogens Clinical or environmental One kingdom

Archaea Environmental organisms Second kingdom

Here is an outline of the major groups of microorganisms:

VirusesBacteriaAlgaeFungiProtozoa

BacteriaBacteria consist of only one cell, but they're a very complex

group of living things.

There are thousands of species of bacteria, but all of them are basically one of three different shapes.

Some are rod- or stick-shaped; others are shaped like little balls.

Others still are helical or spiral in shape.

Classification of bacteria

There are several approaches to bacterial classification

A. Morphological classsification.Based on morphology bacteria are divided into various groups

1. Filamentous or higher bacteria- Actinomycetes

2. True or lower bacteria

I. Gram positive bacilli Aerobes- corynebacterium, bacillus Anaerobes-Clostridium, lactobacillusII. Gram positive cocciIII. Gram negative cocciIV. Gram negative bacilli or rods

Gram-positive rods

Gram-negative rods

Gram-positive cocci

Gram-negative cocci

B.Nutritional classification

I. Based on Energy requirementsPhototrophs: Derive energy from sunlightChemotrophs: Use Chemicals

II. Based on ability to synthesize essential metabolitesAutotrophs: Synthesize organic compounds from carbon dioxide and nitrogenHeterotrophs: Depend on preformed organic

compounds eg. pathogens

III. Based on oxygen requirementsAerobesAnaerobes

Gram-positive cocci

AnaerobicGram-positive rods

AnaerobicGram-negative rods

AnaerobicGram-positive cocci

AnaerobicGram-negative cocci

C. Based on temperature

Psychrophiles: Below 20°C

Mesophiles: 25-40°C

Thermophiles: 55-80°C

D. Classification based on staining reaction:

Based on Grams stain:

Gram positive bacteria

Gram negative bacteria

Bacterial Pathogenicity

Microbial Mechanisms of Pathogenicity: How Microorganisms Cause Disease

How do Bacterial Pathogens penetrate Host Defenses?

1. Adherence - almost all pathogens have a means to attach to host tissue

Binding Sites

Adhesins

Ligands

Some cells use fimbriae to adhere.

Fimbriae can play a role in tissue tropism.

Adhesins and ligands are usually on Fimbriae

• Neisseria gonorrhoeae• ETEC (Entertoxigenic

E. coli)

• Bordetello pertussis

Bacteria typically employ proteins known as Adhesins to attach to host tissues, which usually are located on ends of fimbriae.

Alternatively, adhesins can consist of glycocalyx.

2. Capsules• Prevent phagocytosis• Attachment• Streptococcus

pneumoniae• Klebsiella

pneumoniae• Haemophilus

influenzae• Bacillus anthracis K. pneumoniae

Avoidance of Phagocytosis

Capsules are Involved in avoidance of phagocyte-mediated recognition and

attachment.

Cell Wall Components

M protein: Found on cell surface and fimbriae of Streptococcus pyogenes. Mediates attachment and helps resist phagocytosis. M-protein is heat and acid resistant.

Waxes [ Mycolic Acid]: In cell wall of Mycobacterium tuberculosis helps resist digestion after phagocytosis and can multiply inside WBC.

3. Enzymes

• Many pathogens secrete enzymes that contribute to their pathogenicity

A. Leukocidins• Attack certain types of WBC’s

• 1. Kills WBC’s which prevents phagocytosis• 2. Releases & ruptures lysosomes

– lysosomes - contain powerful hydrolytic enzymes which then cause more tissue damage

B. Hemolysins - cause the lysis of RBC’s

Streptococci

C. Coagulase - cause blood to coagulate

• Blood clots protect bacteria from phagocytosis from WBC’s and other host defenses

• Staphylococcus aureus - are often coagulase positive

Fibrinogen ----------------- Fibrin ( Clot)

D. Kinases - enzymes that dissolve blood clots

• 1. Streptokinase - Streptococci• 2. Staphylokinase - Staphylococci

• Helps to spread bacteria - Bacteremia

E. Hyaluronidase

• Breaks down Hyaluronic acid (found in connective tissues)

• “Spreading Factor”• mixed with a drug to help spread the drug

through a body tissue• Streptococci, Staphylococci, Clostridia and

pneumococci.

F. Collagenase

• Breaks down collagen (found in many connective tissues)

• Clostridium perfringens - Gangrene– uses this to spread through muscle tissue

H. Lecithinase

• Destroys lecithin ( phosphatidylcholine) component of plasma membrane.

• Allowing pathogen to spread

• Clostridium perfringens

Summary of How Bacterial Pathogens Penetrate Host Defenses• 1. Adherence• 2. Capsule• 3. Enzymes

– A. leukocidins B. Hemolysins– C. Coagulase D. Kinases– E. Hyaluronidase F. Collagenase– G. Necrotizing Factor H. Lecithinase

Generalized Stages of Infection

1. Entry of Pathogen – Portal of Entry

2. Colonization – Usually at the site of entry

3. Incubation Period– Asymptomatic period – Between the initial contact with the microbe

and the appearance of the first symptoms

4. Prodromal Symptoms– Initial Symptoms

5. Invasive period– Increasing Severity of Symptoms – Fever – Inflammation and Swelling – Tissue Damage – Infection May Spread to Other Sites

6. Decline of Infection

5. Convalescence

Course of Infectious Disease

Incubation period is the interval between

exposure and illness onset.

Convalescence is a time of recuperation and recovery from

illness.

Depending on various factors an individual may still be infectious

during either incubation or convalescence.

USEFUL MICROORGANIS

M

ROLE OF MICROORGANISM

Roles microorganism in digestion

ONE OF THE MAIN COMPONENT OF PLANT IS CELLULOSE

BACTERIA THAT HELP IN DIGESTION

1.Lactobacillus acidophilus2.Bifidobacteria 3.Streptococus thermophilus4.Lactobacilus bulgaricus

Where can we find these bacteria except in intestines ?

MEDICINE• Some type of microorganism produce

important drugs called ANTIBIOTICS..• Functions of antibiotics….

• Weaken • Destroy other microorganism

• Penicillium notatum is a GREEN MOULD

• Its produces antibiotic called PENICILLIN

AGRICULTURE

• Bacteria play important roles to promote the plant growth..

• Bacteria• Break down dead plants and dead animals by

releasing AMMONIA

AMMONIA

• Adds nitrogen into the soil• The nitrogen fixing bacteria in the soil change

the ammonia into nitrates.

• This nitrates will be used by plants

Ammonia Nitrates

nitrogen fixing bacteria

INDUSTRY

• Bacteria are used in the production of• Milk• Yogurt• Cheese • Vinegar • Soy sauce • Chocolate • Certain vitamin B• Citric acids

VIRUSES

Living or Non-Living?Infectious particles of nucleic acid and proteins

Cannot “live” (reproduce) outside a host

1st virus discovered-Tobacco Mosaic Virus (TMV)

Are viruses alive?

Prokaryotes Vs. Eukaryotes Vs. Viruses• No membrane

bound nucleus• Has a cell wall• Only a few

organelles or none at all.

• Has a capsule surrounding it

• Three main types.

• Nucleus with membrane

• Only plants have cell wall

• Contains many organelles

• Has a lipid bi-layer membrane surrounding it.

• Specialized by thousands of different sizes and shapes.

• No nucleus• No membranes• No organelles• Cannot

reproduce on its own

• Generally not considered alive by most standards

VIRUS STRUCTURE

Adenovirus, a naked virus, with a polyhedral capsid and a fiber at each corner

Influenza virus, surrounded by an envelope with spikes

Virion Structure

Nucleic Acid

Spike Projections

ProteinCapsid

Lipid Envelope

VirionAssociatedPolymerase

Polyhedral capsid attached to a helical tail.

T4 Bacteriophage

Head

Tail fiber

DNA

Tail

Viral Infection

Viruses and Living Cells• Viruses must infect a living cell in order to

grow and reproduce

• They also take advantage of the host’s respiration, nutrition and all the other functions that occur in living things

• Therefore, viruses are considered to be parasites

Viral Reproduction

• Steps of Lytic Cycle–Attachment–Entry–Replication–Assembly–Lysis/Release (lyses the cell)

In the lytic cycle, the virus reproduces itself using the host cell's chemical machinery.

The red spiral lines in

the drawing indicate the virus's genetic material.

The orange portion is the outer shell that protects it.

Viruses Enter Living Cells

Viruses enter plant cells through tiny rips in the cell wall.

Viruses enter animal cells by endocytosis.

Viriods• Much smaller than viruses• Just consist of small sRNA molecule• No protein coat• Infect plants

Protozoa

Protozoa

Protozoa:

• The word protozoa is come from Greek protozoon word meaning “First Animal”.

• Protozoa are unicellular (may be Multicellular) Eukaryotic microorganism.

Characteristics

• Mostly Unicellular organism with fully functional cell

• Live freely, may be parasitic or symbiotic

• Protozoa are chemo-hetrotrops

• They are motile have locomotive organelles. E.g. Flagella and Cilia for movement

Nutrition• Mostly protozoa feed on dead plants and

animal debris while some (trophozoites) feed on bacteria and Algae.

• Parasitic Protozoa feeds on the fluids and tissues of their host(e.g. Plasma and blood cells)

• Some Protozoa live in symbiotic relationship with other plants and animals

Reproduction in Protozoa• Protozoa can reproduce their off spring by both

Sexual and Asexual methods

• Asexual methods of reproduction are:– Budding– Binary Fission– Schizogony or Multiple Fission

• Sexual Methods– Conjugation– Gametogony

Disease Caused ProtozoaDisease Causative Agent

Malaria Plasmodium (P. Falciparum, P. Oval,P. Vivax,

P.malariae)

Giardiasis (diarrhea) Giardia intestinalis

Amoebic Dysentery Entamoeba histolytica

Toxoplasmosis (immune deficiency )

Toxoplasma gondii

Cryptosporidiosis Cryptosporidia

Sleeping sickness Trypanosoma

Leishmmaniasis (kala-azar) Leishmania

Antiprotozoal Drugs

• Examples of antiprotozoal drugs include: Chloroquine Mefloquine and Pyrimethamine. These are used in malaria treatment.

• Metronidazole was developed as an antiprotozoal drug. It induces strand breaks in the DNA of sensitive organisms and also disrupts membrane integrity.

FUNGI

Characteristics of Fungi• Body form

– unicellular – filamentous (tube-like strands called hypha

(singular) or hyphae (plural)

mycelium = aggregate of hyphae

sclerotium = hardened mass of mycelium that generally serves as an overwintering stage.

• Heterotrophy - 'other food' – Saprophytes or saprobes - feed on dead

tissues or organic waste (decomposers)

– Symbionts - mutually beneficial relationship between a fungus and another organism

– Parasites - feeding on living tissue of a host. • Parasites that cause disease are called

pathogens.

Fungi as Saprobes and Decomposers

Mycorrhizae• “Fungus roots”• Mutualism between:

– Fungus (nutrient & water uptake for plant)– Plant (carbohydrate for fungus)

• Extremely important ecological role of fungi!

Lichens

• “Mutualism” between– Fungus – structure– Algae or

cyanobacterium – provides food

Fungi are Spore-ific!!!

• Spores - asexual (product of mitosis) or sexual (product of meiosis) in origin.

• Purpose of Spores – Allows the fungus to move to new food source. – Resistant stage - allows fungus to survive periods

of adversity.– Means of introducing new genetic combinations

into a population

HUMAN-FUNGUS INTERACTIONS

• Beneficial Effects of Fungi – Decomposition - nutrient and carbon recycling.

– Biosynthetic factories. Can be used to produce drugs, antibiotics, alcohol, acids, food (e.g., fermented products, mushrooms).

– Model organisms for biochemical and genetic studies.

Harmful Effects of Fungi

– Destruction of food, lumber, paper, and cloth.

– Animal and human diseases, including allergies.

– Toxins produced by poisonous mushrooms and within food (e.g., grain, cheese, etc.).

– Plant diseases.