microbiology basics

8/8/2019 Microbiology Basics

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MICROBIOLOGY BASICS

ByPradip Sarate

Amarjitsingh Lohiya


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What is Microbiology ?

The study of organisms that are usually too small to be

seen with the naked eye.

The branch of biology that studies microorganisms and

their effects on humans.

Microbiology is the study of microorganisms, which are

unicellular or cell-cluster microscopic organisms. Thisincludes eukaryotes such as fungi and protists, and

prokaryotes. ...


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Types of Microorganisms

Bacteria Algae

Yeast Fungi Virus

Protozoa


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TYPICAL BACTERIAL CELL STRUCTURE

Cell Components Cell Wall

Pili

Capsule

Flagella

Cytoplasm

Plasma Membrane

Ribosomes

Nucleoid


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Classification of Bacteria (Gram Staining)

Bacteria

Gram positive Gram negative

Gram Staining Procedure


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Classifying Bacteria

Gram-Positive

Peptidoglycan is the thick,outermost layer of the cell wall.

About 90% of the Gram-positive

cell wall is made of

peptidoglycan.

Gram-Negative

The cell walls of gram-negative bacteria aremore chemically complex, thinner and less

compact.

Peptidoglycan only 5 20% of the cell wall.

Peptidoglycan is not the outermost layer,

but between the plasma membrane and theouter membrane.

Not accessible to the action of antibiotics.

Outer membrane is similar to the plasma

membrane, but is less permeable and

contains lipopolysaccharides (LPS).

LPS is a harmful substance classified as an

endotoxin.


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Forms of Bacteria

Vegetative cell A vegetative cell is one which is capable of actively growing.

Endospore

Tough, dormant state of certain bacterial cell that is veryresistant to desiccation, heat, and a variety of chemical and

radiation treatments that are otherwise lethal to non-

endospore bacterial cells.

Only some bacteria produce endospores. Eg. Bacillus spp.,

Clostridium spp.

(Endospores of some bacteria can last so long under proper

conditions that various endospores found in such things as

Egyptian mummies are likely the oldest living things.)


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Life Cycle of Bacterial Spore


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What is Endospore ?

Endospores are dormant alternate life forms produced by the genus

Bacillus, the genus Clostridium, and several other genera of bacteriaincluding Desulfotomaculum, Sporosarcina, Sporolactobacillus,Oscillospira, and Thermoactinomyces.

Bacterial endospores are resistant to antibiotics, most disinfectants, andphysical agents such as radiation, boiling, and drying.

The impermeability of the spore coat is thought to be responsible for theendospore's resistance to chemicals. The heat resistance ofendospores is due to a variety of factors:

1. Calcium-dipicolinate, abundant within the endospore, may stabilizeand protect the endospore's DNA.

2. Specialized DNA-binding proteins saturate the endospore's DNA andprotect it from heat, drying, chemicals, and radiation.3. The cortex may osmotically remove water from the interior of theendospore and the dehydration that results is thought to be veryimportant in the endospore's resistance to heat and radiation.4. DNA repair enzymes contained within the endospore are able to

repair damaged DNA during germination.


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Structure ofEndospore


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Formation of Spore (Sporulation)


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Stages of endospore formation (Sporulation)

Stage I An axial filament of nuclear material is formed

Stage II Cell membrane invaginates to enclose part of theDNA and to form forespore septum

Stage III Membrane continues to grow and engulf theforespore in a second membrane

Stage IV Primordial cortex develops between the twomembranes and the exsporium becomes apparent.

Stage V SASPs (small acid--soluble spore proteins) andsipicolinic acid produced. The latter forms calcium-dipicolinate-comples with Ca++Protein coat layers are formed around the

cortex.

Stage VI Maturation of the spore takes place and theresistance to heat and chemicals is developed.

Stage VII Endospore-producing cell is destroyed (lysed) bylytic enzymes and the spore becomes free.


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Germination of Spore


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Germination of Spore

Spore Germination is the process by which a dormant

spore develops into an activity metabolising vegetativecell and this involves the process of activation triggeringof germination, initiation of germination and fianlly,outgrowth.

The process of activation involves the breaking of the

dormant stage partially but is reversible. During this process, rearrangement not structural

components occurs preparing the spore to proceed intothe germination process. A variety of chemical andphysical agents are known to cause activation of

bacteria spores. For example Heavy metals, heat (65C for several

hours) hydrostatic pressure etc,. Activation however,does not result in any detectable changes either in thespore Structure or composition.


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microbiology basics

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