1. Online Counseling Resource YCMOU ELearning Drive…
8-Apr-17
Online Counseling Resource YCMOU ELearning Drive…
School of Architecture, Science and Technology
Yashwantrao Chavan Maharashtra Open University, Nashik – , India
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2. OC-SEP041-CP01-05 Introduction
8-Apr-17
OC-SEP041-CP01-05 Introduction
Programmes and Courses
SEP – SBT041 – Unit 01
SEP – SBI041 – Unit 01
SEP – SGS041 – Unit 01
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8-Apr-17
Credits
Academic Inputs by
Mrs. Rasika Bhore
M.sc (Microbiology)
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4. How to Use This Resource
8-Apr-17
How to Use This Resource
Counselor at each study center should use this presentation to deliver lecture of minutes during Face-To-Face counseling.
Discussion about students difficulties or tutorial with assignments should follow the lecture for about minutes.
Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.
Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.
Appear several times, for all the Self-Tests, available for this course.
Student can use handouts for last minutes preparation just before end exam.
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Learning Objectives
After studying this module, you should be able to:
Discuss the struggle for existence by the formation of Endospores by bacteria.
Describe the germination of endospore back to vegetative form.
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6. © 2007, YCMOU. All Rights Reserved.
Introduction
A bacterial structure sometimes observed as an inclusion is actually a type of dormant cell called an endospore.
Endospores are formed by a few groups of bacteria as intracellular structures, but ultimately they are released as free endospores, a fascinating type of cell.
Endospores exhibit no signs of life, being described as cryptobiotic.
Although cryptobiotic, they retain viability indefinitely such that under appropriate environmental conditions, they germinate back into vegetative cells.
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Endospores
Endospores are probably the most durable cell produced in nature.
They are formed by vegetative cells in response to environmental signals that indicate a limiting factor for vegetative growth, such as depletion of an essential nutrient.
They are highly resistant to environmental stresses such as high temperature, irradiation, strong acids, disinfectants, etc.
Endospores are commonly found in soil and water, where they may survive for long periods of time.
Some bacteria produce exospores or cysts instead.
Endospores germinate and become vegetative cells when the environmental stress is relieved.
Hence, endospore formation is a mechanism of survival rather than a mechanism of reproduction.
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8. Endospore Forming Bacterial Genera
Bacillus(B.anthracis, B.cereus, B. subtilis)
Clostridium (Cl.tetani)
Desulfotomaculum
Sporolactobacillus
Sporosarcina
Thermoactinomyces
Endospores of different species
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9. Stages of Endospore Formation
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10. Stages of Endospore Formation-2
When the environmental conditions becomes unfavorable bacteria starts sporulation, which takes about eight hours.
The DNA is replicated and a membrane wall known as a spore septum begins to form between it and the rest of the cell.
The plasma membrane of the cell surrounds this wall and pinches off to leave a double membrane around the DNA, and the developing structure is now known as a forespore.
Calcium dipicolinate is incorporated into the forespore during this time.
Next the peptidoglycan cortex forms between the two layers and the bacterium adds a spore coat to the outside of the forespore.
Sporulation is now complete, and the mature endospore will be released when the surrounding vegetative cell is degraded.
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Mature Endospore
The spore has a core wall of unique peptidoglycan surrounded by several layers, including the cortex, the spore coat and the exosporium.
The dehydrated core contains the bacterial chromosome and a few ribosomes and enzymes to jump-start protein synthesis and metabolism during germination.
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12. Functions of Structural Components
Spore coat is impermeable to many toxic molecules and contain enzymes that are involved in germination.
The core has normal cell structures, such as DNA and ribosomes, but is metabolically inactive.
The spore cell also contains small acid-soluble spore proteins (SASPs) to protect DNA from UV radiation, desiccation and dry heat, and they also serve as a carbon and energy source during the germination process.
Up to 15% of the dry weight of the endospore consists of calcium dipicolinate within the core, which is thought to stabilize the DNA.
Dipicolinic acid believed to responsible for the heat resistance of the spore, and calcium may aid in resistance to heat and oxidizing agents but mutants resistant to heat but lacking dipicolinic acid have been isolated.
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Types of Endospores
Various types of endospores are accounted depending on their positions.
The main types within the cell are: terminal, lateral and centrally placed endospores.
Terminal endospores are seen at the poles of cells (1,4)
Central endospores are more or less in the middle (2,3,5)
Lateral endospores are those between these two extremes, usually seen far enough towards the poles but close enough to the center so as not to be considered either terminal or central (6)
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14. Bacteria Having Different Endospores
Bacteria having terminal endospores include Clostridium tetani, the pathogen which causes the disease tetanus.
Bacteria having a central endospore include Bacillus cereus, and
Those having a subterminal endospore include Bacillus subtilis.
Sometimes the endospore can be so large the cell can be distended around the endospore, this is typical of Clostridium tetani.
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15. Destruction of Endospores
Alkylating agents such as ethylene oxide, is effective against endospores.
Though resistant to extreme heat and radiation, endospores can be destroyed by burning or autoclaving.
Exposure to extreme heat for a long enough period will generally have some effect, though many endospores can survive hours of boiling or cooking.
Prolonged exposure to high energy radiation, such as x-rays and gamma rays, will also kill most endospores.
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16. Germination of Endospores
When conditions are favorable reactivation of endospore starts involves activation, germination, and outgrowth.
Even if an endospore is located in plentiful nutrients, it may fail to germinate unless activation has taken place which may be triggered by heating the endospore.
Germination involves the dormant endospore starting metabolic activity and thus breaking hibernation.
It is characterised by rupture or absorption of the spore coat, swelling of the endospore, an increase in metabolic activity, and loss of resistance to environmental stress.
Outgrowth involves the core of the endospore manufacturing new chemical components and exiting the old spore coat to develop into a fully functional vegetative bacterial cell.
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17. Differences Between Endospore & Vegetative Cell
Property
Vegetative cells
Endospores
Surface coats
Typical Gram-positive murein cell wall polymer
Thick spore coat, cortex, and peptidoglycan core wall
Microscopic appearance
Nonrefractile
Refractile
Calcium dipicolinic acid
Absent
Present in core
Cytoplasmic water activity
High
Very low
Enzymatic activity
Present
Macromolecular synthesis
Heat resistance
Low
Resistance to chemicals and acids
Radiation resistance
Sensitivity to lysozyme
Sensitive
Resistant
Sensitivity to dyes and staining
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18. What We Learn………….
Endospores are cryptobiotic & highly resistant to heat & radiations.
Commonly found in soil & water.
Early stage of endospore formation involves partition of chromosome & ribosome in mother cell.
Late stage involves formation of several layers i.e. cortex, spore coat, spore wall.
Mature endospore contain calcium dipicolinic acid supposed to role in heat resistance.
Three types of endospores are terminal, subterminal & central.
Endospore germination is carried our by rupture of spore coat & manufacturing of new chemical components.
Differences between endospores & vegetative cell.

19. Critical Thinking Questions
8-Apr-17
Critical Thinking Questions
What is the medical significance of endospore forming bacteria?
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20. Tips For Critical Thinking Questions
Treatment of bacterial infection depend on whether the infecting pathogen is able to form spores.

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8-Apr-17
Study Tips
Book
Title: Microbiology
Author: L. M. Prescott
Book
Title: Introduction to Microbiology
Author: J. L. Ingraham
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8-Apr-17
Study Tips
Endospores
Bacterial endospores
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23. End of the Presentation
8-Apr-17
End of the Presentation
Thank You !
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