MORPHOLOGY OF BACTERIA

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MORPHOLOGY OF BACTERIA:

MORPHOLOGY OF BACTERIA BY S.KRITHIKAA I Yr MD MICROBIOLOGY

CLASSIFICATION OF MICROORGANISMS:

CLASSIFICATION OF MICROORGANISMS MICROORGANISMS PLANTS PROTISTA ANIMALS PROKARYOTES EUKARYOTES Bacteria & blue green fungi, algae, slime algae moulds& protozoa

PROPERTIES OF PROKAYOTIC &EUKARYOTIC CELLS:

PROPERTIES OF PROKAYOTIC &EUKARYOTIC CELLS

MORPHOLOGY OF A BACTERIAL CELL:

MORPHOLOGY OF A BACTERIAL CELL SIZE SHAPE & ARRANGEMENT ANATOMICAL STRUCTURES - CELL WALL - CELL MEMBRANE - CYTOPLASM - SLIME LAYER & CAPSULE APPENDAGES- FLAGELLA & FIMBRIAE SPORES

SIZE:

SIZE 3-5 *0.2-1.5 µm EPULOPISCIUM FISHELSONII- largest bacterium of size 600* 80 µm DEMONSTRATION- electron microscopy

SHAPE :

SHAPE COCCI- spherical or oval cells BACILLI- rod shaped COCCOBACILLI-length is same as width SPIROCHAETES- slender flexuous spiral forms VIBRIOS- comma shaped SPIRILLA- rigid spiral forms ACTINOMYCETES- branching filamentous bacteria resembling fungi MYCOPLASMA- round or oval bodies & interlacing filaments (cell wall deficient)

ARRANGEMENT:

ARRANGEMENT STREPTO- chains DIPLO- pairs STAPHYLO- clusters TETRADS- groups of four SARCINA- groups of eight CUNEIFORM- chinese letter pattern DEMONSTRATION- simple & differential staining – grams stain & acid fast staining

ANATOMY :

ANATOMY

CELL WALL:

CELL WALL Tough & rigid structure Made of peptidoglycan – mucopeptide ( murein ) composed of N-acetyl muramic acid & N- acetyl glucosamine alternating in chains cross linked by peptide subunits

GRAM POSITIVE CELL WALL:

GRAM POSITIVE CELL WALL tightly cross linked peptides- d- alanine & d- glutamic acid Thickness- 18-80 nm & constitutes 40-80% of the dry weight Techoic acid- water soluble polymers of glycerol phosphate or ribitol phosphate residues two types – wall techoic acid- ribitol & membrane techoic acid- glycerol functions- cell wall stability, association of wall with membrane, adherence, reproduction Polysaccharides- mannose, arabinose , rhamnose , glucuronic acid & mannuronic acid Thick peptidoglycan layer

CONTD…:

CONTD… S LAYER- protein or glycoprotein molecules that self assemble on the outer surface of the organism. Protect from stressful environments, inhibit phagocytosis , contribute to virulence

GRAM NEGATIVE CELL WALL:

GRAM NEGATIVE CELL WALL Thickness- 3-4 nm Loosely crosslinked by d- diaminipimelic acid or lysine Outer membrane- bilayered LPS containing OMPs – porins , OmpC , D, F, PhoE , LamB,Tsx contains 3 regions- I- polysaccharide determining O ag specificity II- core polysaccharide containing 3-deoxy-D- mannulooctulusonate (KDO) & heptose III- glucolipid responsible for endotoxicity

CONTD...:

CONTD... Lipoprotein layer- connects peptidoglycan to outer membrane & stabilizes the outer membrane Periplasmic space- space between inner& outer membranes containing the peptidoglycan layer and gel like solution of proteins & membrane derived oligosaccharides Thin peptidoglycan layer

ACID FAST CELL WALL:

ACID FAST CELL WALL Lipids constitute 60% of the dry weight & are made of mycolic acid also known as cord factor Responsible for virulence, cytotoxicity , granuloma formation, adjuvanticity Also contains phosphatidylinositol mannosides & lipoarabinimannan Polysaccharide- arabinogalactans Trehalose sulpholipid - 2,3,6,6’ tetracylhelose-2 sulphate - prevents phagosome lysozyme fusion fusion following phagocytosis Proteins- act as porins & involved in biosynthesis of cell wall polymers

FUNCTIONS OF CELL WALL:

FUNCTIONS OF CELL WALL Accounts for the shape of the cell Protects the cell against osmotic damage Confers rigidity Cell division Target site for antibiotics, lysozymes , bacteriophages Carries bacterial antigens

DEMONSTRATION OF CELL WALL:

DEMONSTRATION OF CELL WALL Plasmolysis Microdissection Differential staining Raection with specific antibody Electron microscopy Indirect methods- grams staining & acid fast staining, flurochrome staining for acid fast bacteria

GRAMS STAINING:

GRAMS STAINING MECHANISM- permiability of bacterial cell wall integrity of cell wall METHOD- to a heat fixed smear add gentian violet-1min grams iodine-1 min acetone-2-3sec saffranin - 1min MODIFICATIONS- Kopeloff and Beerman’s method for films & sections, Jensons , Preston & Morrel , quick gram, multiple slide

ZIEHL NEELSON METHOD:

ZIEHL NEELSON METHOD PRINCIPLE- mycolic acid, lipds , fatty acids& higher alchols integrity of the cell wall METHOD- to a heat fixed smear add carbol fuschin - 5-7min and apply gentle heat 20% sulphuric acid- 2-3sec methylene blue 1-2min MODIFICATIONS- cold method, 5%sulphuric acid

CELL WALL DEFICIENT FORMS:

CELL WALL DEFICIENT FORMS MYCOPLASMA- stable oval or round forms L- FORMS- observed in streptobacillus monoliformis . Induced by penicillin PROTOPLASTS- gram positive bacteria when placed in hypertonic saline SPHEROPLASTS- gram negative bacteria when subjected to penicillin. Some cell wall material is retained PLEIOMORPHIC & INVOLUTION FORMS- swollen & aberrant forms resulting from ageing

CELL MEMBRANE:

CELL MEMBRANE 5-10nm thick elastic membrane beneath the cell wall separating it from cytoplasm Composed of lipoprotein. Sterols absent except in mycoplasma Permeases - membrane associated carrier proteins FUNCTIONS- selective permiability and transport of solutes electron transport and oxidative phosphorylation excretion bearing the enzymes and carrier molecules for biosynthesis

CYTOPLASM:

CYTOPLASM Colloid of organic and inorganic solutes in viscous watery solution RIBOSOMES- centres of protein synmthesis . Composed of rRNA of size 10 - 20nm with a sedimentation constant of 70S MESOSOMES- vesicular, convoluted invaginations from plasma membrane. more prominent in GPB principal site of respiratory enzyme site of synthesis of cross wall septa during binary fission

INCLUSIONS:

INCLUSIONS VOLUTIN- highly refractile , strongly basophilic bodies consisting of polymetaphosphate . stained by Albert or Neisser stain present in diphtheria bacilli reserve of energy POLYSACCHARIDE- stained with iodine LIPIDS- stained with sudan black VACUOLES- fluid filled cavities covered by a membrane

NUCLEUS:

NUCLEUS Contains the cell’s genome made of a single molecule of double stranded DNA arranged in the form of a circle . Measure about 1mm long May possess extranuclear genetic material called as plasmids DEMONSTRATION- acid or ribonuclease hydrolysis and subsequent staining of nuclear material. appear as oval or elongated bodies FUNCTIONS- binary fission

SLIME LAYER & CAPSULE:

SLIME LAYER & CAPSULE Amorphous viscid bacterial secretion surrounding the cell wall Loose undemarcated secretion – slime layer or glycocalyx Sharply defined structure- capsule Homo or hetero Polysaccharides made of hexose and pentose sugars plus ribitol , glycerol and other sugar alchohols synthesised by the cell membrane with enzymes- glucosyl and fructosyl transferases producing an insoluble glucan matrix

CONTD…:

CONTD… FUNCTIONS- enhances virulence, protective covering, increases invasiveness, adhesion, capsular antigen for identification of bacteria DEMONSTRATION- Negative staining S erological methods- Quellung phenomenon

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