Transcript Online Counseling Resource YCMOU ELearning Drive…

Online Counseling Resource
YCMOU ELearning Drive…
School of Architecture, Science and Technology
Yashwantrao Chavan Maharashtra
Open University, Nashik – 422222, India
OC-SEP041-CP01-03
Introduction
Programmes and Courses
 SEP – SBT041 – Unit 01
 SEP – SBI041 – Unit 01
 SEP – SGS041 – Unit 01
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Credits
 Academic Inputs by
 Mrs. Rasika Bhore
 M.sc (Microbiology)
 [email protected]
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How to Use This Resource

Counselor at each study center should use this presentation to deliver
lecture of 40-60 minutes during Face-To-Face counseling.

Discussion about students difficulties or tutorial with assignments should
follow the lecture for about 40-60 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 locomotory organ of bacteria.
 Describe the arrangement & mechanism of
locomotory organ.
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Introduction
 Mesosomes are complex, localized in
foldings of the cell membrane. Although
also found in gram negative bacteria,
they are more frequently observed in
gram positive bacteria.
 A flagellum is a tail-like structure that
projects from the cell body of certain
prokaryotic cells, functions in locomotion.
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Mesosomes
 The plasma membrane of prokaryotes may invaginate into the
cytoplasm or form stacks or vesicles attached to the inner
membrane surface.
 These structures are sometimes referred to as mesosomes.
 Such internal membrane systems may be analogous to the
cristae of mitochondria or the thylakoids of chloroplasts which
increase the surface area of membranes to which enzymes are
bound for specific enzymatic functions.
 The photosynthetic apparatus of photosynthetic prokaryotes is
contained in these types of membranous structures.
 Mesosomes may also represent specialized membrane regions
involved in DNA replication and segregation, cell wall
synthesis, or increased enzymatic activity.
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Flagella
 Flagella are filamentous protein structures attached to the cell
surface that provide the swimming movement for most motile
prokaryotes.
 Prokaryotic flagella are much thinner than eukaryotic flagella,
and they lack the typical "9 + 2" arrangement of microtubules.
 The diameter of a prokaryotic flagellum is about 20
nanometers.
 The flagellar filament is rotated by a motor apparatus in the
plasma membrane allowing the cell to swim in fluid
environments.
 Bacterial flagella are powered by proton motive force
(chemiosmotic potential) established on the bacterial
membrane.
 About half of the bacilli and all of the spiral and curved
bacteria are motile by means of flagella.
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Ultrastructure of Flagellum
 The flagellar apparatus
consists of several
distinct proteins:
 A system of rings
embedded in the cell
envelope (the basal
body).
 A hook-like structure
near the cell surface.
 The flagellar
filament.
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Arrangement of Flagellum
 The innermost rings, the M and S rings, located in
the plasma membrane, comprise the motor
apparatus.
 The outermost rings, the P and L rings, located in
the periplasm and the outer membrane
respectively, function as bushings to support the
rod where it is joined to the hook of the filament on
the cell surface.
 As the M ring turns, powered by an influx of
protons, the rotary motion is transferred to the
filament which turns to propel the bacterium.
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Types of Flagella

Flagella are of four types:
1.
Monotrichous: single flagellum
at one pole.
2.
Lophotrichous: two or more
flagella at one or both poles.
3.
Amphitrichous: single flagellum
at each pole.
4.
Peritrichous: flagella all over
the surface of the cell.
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Mechanism of Flagellar Movement
 Prokaryotes are known to exhibit a variety of types of tactic
behavior, i.e., the ability to move in response to
environmental stimuli.
 Chemotaxis a bacterium can sense the quality and quantity
of certain chemicals in its environment and swim towards
them (if they are useful nutrients) or away from them (if they
are harmful substances).
 Phototaxis a photosynthetic bacteria swim to regions of
optimal light intensity & quality.
 Aerotaxis, they swim to regions that contain favorable
concentrations of dissolved oxygen.
 Magnetotaxis. allows them to travel along magnetic lines of
force. In doing so they enter sediments at the bottoms of
marine or fresh waters, in favorable conditions.
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Fimbriae & Pili
 Fimbriae and pili are interchangeable terms used to
designate short, hair-like structures on the surfaces of
prokaryotic cells.
 Like flagella, they are composed of protein.
 Fimbriae are shorter and stiffer than flagella, and slightly
smaller in diameter.
 Generally, fimbriae is not involved in bacterial movement .
 Fimbriae are very common in Gram-negative bacteria, but
occur in some archaea and Gram-positive bacteria as well.
 Fimbriae are most often involved in adherence of bacteria to
surfaces, substrates and other cells or tissues in nature.
 In E. coli, a specialized type of pilus, the F or sex pilus,
apparently stabilizes mating bacteria during conjugation, but
the function of common pili is quite different.
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Common Pili
 Common pili (fimbriae) are usually involved in specific
adherence of prokaryotes to surfaces in nature.
 In medical situations, they are major determinants of bacterial
virulence because they allow pathogens to attach to tissues or
to resist attack by phagocytic white blood cells.
 For example,
 Pathogenic Neisseria gonorrhoeae adheres specifically to
the human cervical or urethral epithelium by means of its
fimbriae.
 Enterotoxigenic strains of E. coli adhere to the mucosal
epithelium of the intestine by means of specific fimbriae.
 The M-protein and associated fimbriae of Streptococcus
pyogenes are involved in adherence and to resistance to
engulfment by phagocytes.
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What We Learn………….
 Mesosomes are the vesicles attached to the inner
membrane of bacterial cell.
 Flagella are of four types, monotrichous,
lophotrichous, amphitrichous & peritrichous.
 Flagella gives mobility to bacteria which is
generated by proton motive force.
 Tactic behavior of prokaryotes.
 Fimbriae & common pili are the structures which
are involved in attachment of bacterial cell to host
surface.
 Sex pili stabilizes mating during conjugation.
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Critical Thinking Questions
 How could you distinguish between a
prokaryotic flagellum & eukaryotic
flagellum just by watching it move?
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Tips For Critical Thinking Questions
 Prokaryotic flagellum moves by rotation
while eukaryotic flagellum moves by
rhythmic sliding back & forth.
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Study Tips
 Book
 Book


Title: Methods In Cell
Biology
Author: David M. Prescott

Title: Methods In Cell
Biology

Author: William Dentlar
 Book

Title: Cell Movements

Author: Dennis Bray
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Study Tips
www.textbookofbacteriology.com
Structure & functions of prokaryotes
www.wikepedia.org
Flagellum
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End of the Presentation
Thank You !