Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – , India

OC-SEP041-CP01-03 Introduction Programmes and Courses  SEP – SBT041 – Unit 01  SEP – SBI041 – Unit 01  SEP – SGS041 – Unit 01

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.3 Credits  Academic Inputs by Mrs. Rasika Bhore  M.sc (Microbiology)

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.4 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.

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Discuss the locomotory organ of bacteria. Describe the arrangement & mechanism of locomotory organ.

School of Science and Technology, Online Counseling Resource… 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. © 2007, YCMOU. All Rights Reserved.6

School of Science and Technology, Online Counseling Resource… 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. © 2007, YCMOU. All Rights Reserved.7

School of Science and Technology, Online Counseling Resource… 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. © 2007, YCMOU. All Rights Reserved.8

School of Science and Technology, Online Counseling Resource… 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. © 2007, YCMOU. All Rights Reserved.9

School of Science and Technology, Online Counseling Resource… 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. © 2007, YCMOU. All Rights Reserved.10

School of Science and Technology, Online Counseling Resource… 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. © 2007, YCMOU. All Rights Reserved.11

School of Science and Technology, Online Counseling Resource… 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. © 2007, YCMOU. All Rights Reserved.12

School of Science and Technology, Online Counseling Resource… 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. © 2007, YCMOU. All Rights Reserved.13

School of Science and Technology, Online Counseling Resource… 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. © 2007, YCMOU. All Rights Reserved.14

School of Science and Technology, Online Counseling Resource… 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.

School of Science and Technology, Online Counseling Resource… Critical Thinking Questions  How could you distinguish between a prokaryotic flagellum & eukaryotic flagellum just by watching it move? © 2007, YCMOU. All Rights Reserved.16

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved. Tips For Critical Thinking Questions  Prokaryotic flagellum moves by rotation while eukaryotic flagellum moves by rhythmic sliding back & forth.

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.18 Study Tips  Book Title: Methods In Cell Biology Author: David M. Prescott  Book Title: Methods In Cell Biology Author: William Dentlar  Book Title: Cell Movements Author: Dennis Bray

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.19 Study Tips Structure & functions of prokaryotes Flagellum

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