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Functional Anatomy of Prokaryotic Cells 1 All living cells can be classified into two groups based on certain structural & functional characteristics Prokaryotes • Eukaryotes • • They are chemically similar in the sense that they both contain nucleic acids proteins lipids carbohydrates The distinguishing characteristic of prokaryotes & eukaryotes * 0.2-2.0 microm • • *DNA is not enclosed within a • membrane (singularly arranged chromosome) Proka. *DNA is not associated with • histones=special chromosomal proteins found in euk • *no membrane-enclosed • organelles • *cell wall almost always • contain the complex polysaccharide peptidoglycan • *divided by binary fission(DNA • is copied & the cell splits into two cells The distinguishing characteristic of prokaryotes & eukaryotes *10-100microm. • • *DNA is found in cells nucleus • which is separated from the cytoplasm by nuclear membrane (DNA is found in multiple chromosomes) • *DNA is associated with • histones Euka. *the have a number of membrane- • enclosed organelles(mitochondria , endoplasmic reticulum Golgi complex lysosomes) • *cell wall is chemically simple • • *cell division usually involves • mitosis 8 EUKARYOTES PROKARYOTES BACTERIA ARCHAEA 9 BACTERIA Naming and Classifying Microorganisms The system for nomenclature for microorganisms • The scientific name is binomial • The First is the genus name The Second is the species name The first letter of the genus name is always capitilized Staphylococcus (genus) aureus (species) Both are underlined or italicized Staphylococcus aureus Staphylococcus aureus Identification of bacteria Thousands of bacteria species are differentiated by many factors including: **morphology (shape , size & arrangement) • **Chemical composition (staining) **Nutritional requirements **Biochemical activities **Source of energy • Morphology Size -- Shape -- & Arrangement Size = 0.2 – 2.0 micrometer in diameter 2.0 -- 8.0 micrometer in length Bacterial shapes are determined by heredity Shapes & Arrangements of Bacteria cocci Coccus=spherical =round or oval • Diploccoci=pairs • Streptococci=chainlike • Staphylococci=groups (grapelike) • Bacilli Bacilli= rode shape • mostly Single Diplobacilli=pairs • Streptobacolli=chais • Coccobacilli=oval • spiral Have one or more • twists----never straight Vibrios=curved rods • Spirilla=helical • Spirochetes=helical • & flexible Structure of Bacteria Essential structures cell wall cell membrane Cytoplasm & nuclear material Particular structures capsule flagella pili spore 18 STRUCTURE OF BACTERIAL CELL 19 19 Structures structures external to the cell wall cell wall itself structures internal to the cell wall structures external to the cell wall glycocalyx (capsule) flagella axial filaments fimbriae pili GLYCOCALYX Glycocalyx=sugar • coat=sub.that surround cells=sticky=external to cell wall Polysaccharide , • polypeptide or both If attached to cell wall • =capsule (well defined) or slim layer(not defined) GLYCOCALYX Capsule or slime layer • Functions: – Help adherence & attachment of bacterial cells to surfaces. – Provide nutrients – Protect bacterial cells against dehydration – Increase virulence of bacteria Protect the pathogenic bacteria. From phagocytosis by host The degree of which WBC bac. Cause disease • 23. 23 Streptococcus pneumoniae pneumonia respiratory tract FLAGELLA Some bacteria are motile • Locomotory organelles- • flagella=long filamentous appendages • External to cell wall 25 Flagellar arrangements outside bacterial cell Atrichous –lack flagella 26 Monotrichous – single flagellum at one end 27 Lophotrichous-2 or more arising from one end of bacterial cell Amphitrichous- flagella at both end of bacterial Peritrichous – Flagella distributed over the entire surface, low motility Motility=is the ability of bac. to move itself one direction different directions waves toward a favorable environment or away from an adverse conditions chemotaxis=away from chemicals light=phototaxis Advantages of flagella Identification of Bacteria • H-antigen = flagellar protein is • useful for distinguish variations within species Motility of bacteria Axial filaments similar to flagellum • =bundles of fibrils that arise at the • end of bacterial cell **Spiral motion • **Snake-like movement • –spirochetes have unique structure & motility 30 Pili (fimbriae) hair-like projections of the cell• (shorter and thinner than flagella) Occur at the poles or can evenly distributed on bacterial cell Fibriae are involve in bacterial attachment to surfaces and resistance to phagocytosis === cause disease Neisseria gonorrhoeae gonorrhea 31 Pili Chemical nature is pilin bacterial conjugation Sex pili effect the transfer of conjugative plasmids 32 FIMBRIE FLAGELLA SEX PILI EXTRACELLULAR APPENDAGES 33 33 STRUCTURE OF BACTERIAL CELL 34 34 Composition & structure of cell wall Bacterial cell wall All prokaryotes have cell wall • The cell wall of bacterial cell is • Complex • Surround the fragile plasma membrane • (cytoplasmic) Protect the interior of cell • The major functions of cell wall Prevent bacterial cells from rupturing, when water pressure inside the cell is greater than that outside the cell , so it is essential for bacterial viability Countering the effects of osmotic pressure Providing a rigid platform for surface appendages- flagella, fimbriae, and pili all originate from the wall and extend beyond it Cell wall major functions Site of action of antibiotics, the most important one Resistance of Antibiotics • Shape of bacteria Functions of cell wall The chemical composition of cell wall is used to differentiate major types of bacteria. Be the sites of major antigenic determinants of the cell surface Provide the immunological distinction among bacteria Bacterial cell wall is composed of • macromolecular net work = peptidoglycan Peptidoglycan = peptide + glycan Peptidoglycan consists of repeating disaccharide attached by polypeptides , that surrounds & protects bacterial cell Disaccharide portion is mad up of Monosaccharides = N-acetylglucosamine (NAG) & N-acetylmuramic acid= (NAM) 5/23/2017 CELL WALL 41 41 Alternating (NAG) &( NAM) molecules are linked in rows to from a carbohydrate backbone (glycan portion ) Adjacent rows are linked by polypeptides CELL WALL (peptide portion) 42 5/23/2017 42 5/23/2017 Penicillin interferes with final linking of the peptidoglycan rows by peptide =bac.cell wall is weakened & the cell undergoes lysis = this destruction caused by rupture of the CELL WALL plasma membrane & the 43 loss of cytoplasm 43 Gram positive bacteria cell wall consists of many layers of peptidiglycan forming a thick , rigid structure Cell wall of Gram positive bac. Contain • Teichoic acids= consist primarily of • • an alcohol (glycerol or ribitol) • & • phosphate • Teichoic acid classes Wall teichoic acid = linked to the peptidoglycan Lipoteichoic acid= spans the peptidoglycan layer & is linked to the plasma membrane Special components of Gram positive cell wall Teichoic acid SPA / M POTEIN 46 Teichoic acid = • Regulate the movement of cations (+ve • ions) into & out of the cell Assume in cell growth • Provide wall s antigenic specificity = • diagnosis Gram negative bacteria cell wall Consist of one layer of peptidoglycan • & • an outer membrane • Do not contain teichoic acid • the peptidoglycan is bonded to • lipoproteins (=lipids linked to proteins) in the • outer membrane The outer membrane of Gm.-ve bac, consists of Lipopolysaccharides lipoproteins • & • phospholipids • • Lipopolysaccharides O polysaccharides antigen Lipid portion Lipid A endotoxin Porin = is a proteins in the outer membrane which is important in the permeability of outer membrane CELL WALL OF G+VE AND G-VE BACT. GRAM STAIN TECHNIQUE CELL WALL STRUCTURE AND GRAM STAIN 53 53 ATYPICAL CELL WALLS 1- No or very little cell wall material: Mycoplasma = are the smallest bacteria that can & reproduce outside living cell (sterols in the plasma membranes for protection) 2- Archaea: unusual wall-- No peptidoglycan, , proteins and polysaccharides. 3- Acid-fast cell walls: contain high constration (60%) of Waxy material outside the peptidoglycan. = Mycolic acids prevent uptake of stains. 54 54 Damage to the cell wall Chemicals that damage bact. Cell wall often do not harm the cells of an animal host .Why?? When bacteria are treated with 1) enzymes that are lytic for the cell wall e.g. lysozyme (tears,mucus, saliva) Active on major cell wall components of most Gram +ve bact. **back bone disaccharide wall-less cell (protoplast) When Gram –ve bact. Treated with lysozyme cell wall is not destroyed to the same extant as in Gram +ve bact. Why ?? (outer membrane) (spheroplast) 55 Effect of "lysozyme", which is found • naturally in tears, mucus, and saliva. -Gram positives are most susceptible and typically they burst (lyse) or, in favorable environments, they may form "protoplasts", which have no cell wall. -Gram negatives are less susceptible and some of the cell wall material remains (spheroplasts)--> Can only survive in .favorable conditions as they are weak Damage to the cell wall 2) antibiotics that interfere with biosynthesis of peptidoglycan, wall-less bacteria are often produced. antibiotics that damage bact. Cell wall often do not harm the cells of an animal host .Why?? 58 STRUCTURE OF BACTERIAL CELL 59 59 Structures internal to the cell wall Structures internal to the cell wall Plasma or cytoplasmic membrane **Is a thin structure lying inside the cell wall & • enclosing the cytoplasm **consist primarily of phospholipids & proteins • Functions of Plasma membrane Selective permeability = certain molecules & ions pass through the membrane , but others prevented from passing through it • Breakdown of nutrients and the production of • energy ( contain enzymes catalyzing the chemical reaction) Some antibiotics and antibacterial agents kill • bacteria by attacking the plasma membrane Damage of plasma membrane Many antibiotics have effect on plasma • membrane Polymyxins = disrupting phospholipids of • the plasma membrane Alcohols & ammonium compounds = • used as disinfectants Structures within the bacterial cell • Cytoplasm: thick aqueous (80% water) semitransparent. • Contains organic molecules and inorganic ions. Proteins(enzymes) , carbohydrates , & lipids • The major structures in the cytoplasm are: • Nucleoid, ribosomes, inclusions 64 The major structures in the cytoplasm are: Nucleoid,= nuclear area • containing DNA Ribosomes • Inclusions = reserve • deposits NUCLEAR MATERIAL Plasmids: . Single, long, double stranded circular DNA=bacterial chromosome. Carry all the genetic information required for cell structure & function 66 66 extra-chromosomal DNA • PLASMID Small,circular,doubl-stranded • DNA .not connected to bact. Chromosome, replicate independently May be gained or lost. Without • harming bact. Can be transfer from one bact. • To other (biotechnology) Plasmids: Cary genes for: )5-100 genes) • antibiotic resistance, • . tolerance to toxic metals, • production of toxins and • synthesis of enzymes 67 67 Nuclear material • No nuclear membrane, absence of nucleoli, hence known as nucleic material or nucleoid, one to few per bacterium. 68 Ribosomes Sites of protein synthesis Composed of two subunits made of protein and ribosomal RNA. Prokaryotic ribosomes are 70S while Eukaryotic ribosomes are 80S. 69 Erythromycin and chloramphenicol attach to 50 S subunit Streptomycin and gentamicin attach to 30 S subunit and inhibit protein synthesis. Bacterial cell can be killed by antibiotic while eukaryotic cell remains unaffected. Why??? 70 • Inclusions Several kinds of reserve deposits within the cytoplasm Cells may accumulate certain • nutrients when they are plentiful & use them when the environment is deficient Their number depend on bact. Species == identification • • Inclusions • Reserve deposits • Metachromatic granules. • Polysaccharide granules = carbohydrate • Lipid inclusions = lipid storage material • Sulphur granules = energy server • Carboxyzomes = enzymes ** photosynthesis • Gas Vacuoles • Magnetosomes 72 Inclusions Metachromatic granules =large = • inclusions some time stain red with blue dye • have diagnostic significance =stores inorganic phosphate Corynebacterium diphtheriae Endospores (spores) Resting structures • Clostridium= tetanus – gas gangrene – • food poisoning Bacillus = anthrax • Highly durable dehydrated cells with thick • walls & additional layers which formed internal to the bact. cell membrane Endospores when released into • environment they survive • -- extreme heat • • --lack of water • • --exposure to many toxic chemicals & • radiation Sporulation = sporogenesis • formation of endospore • (endospre forming bact.) • This occur when nutrient • (carbon , nitrogen source ) becomes unavailable or scarce Germination = formation of • vegetative form Endospores (spores) Identification of Bacteria Pathogenesis Resistance 77 One vegetative cell endospore Sporulation Single endospore germination cell single • one vegetative • Not a means of reproduction • protection • • Endospores are clinically important • Food industry • Resist heating • Freezing • Desiccation • Use of chemicals & radiation • Some bact. Produce toxins • BACILLUS ANTHRAX BACTERIAL SPORES 80 80 First Term Exam. Good Luck