1. Prokaryotic Profiles: the Bacteria and the Archaea

2. 2 Characteristics of Cells Eucaryotic cells: animals, plants, fungi, and protists –contain membrane-bound nucleus with DNA as chromosomes –contain membrane-bound organelles that compartmentalize the cytoplasm and perform specific functions Procaryotic cells: bacteria and archaea –no nucleus or other membrane-bound organelles

3. 3 Prokaryotic Profiles

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5. 5 External Structures Appendages –Two major groups of appendages: Motility – flagella and axial filaments (periplasmic flagella) Attachment or channels – fimbriae and pili Glycocalyx – surface coating

6. 6 Flagella 3 parts –filament – long, thin, helical structure composed of proteins –hook- curved sheath –basal body – stack of rings firmly anchored in cell wall Rotates 360 o 1-2, or many distributed over entire cell Functions in motility

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8. 8 Flagellar Function Guide bacteria in a direction in response to external stimulus: chemical stimuli – chemotaxis; positive and negative light stimuli – phototaxis Signal sets flagella into rotary motion clockwise or counterclockwise: counterclockwise – results in smooth linear direction – run clockwise - tumbles

9. 9 Chemotaxis in bacteria

10. 10 Fimbrae Fine hairlike bristles from the cell surface Function in adhesion to other cells and surfaces

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12. 12 Pili Rigid tubular structure made of pilin protein Found only in Gram negative cells Functions –joins bacterial cells for DNA transfer (conjugation) –adhesion

13. 13 Conjugation

14. 14 Glycocalyx Coating of molecules external to the cell wall, made of sugars and/or proteins 2 types 1.capsule - highly organized, tightly attached 2.slime layer - loosely organized and attached Functions –Attachment and formation of biofilms –inhibits killing by white blood cells –protect cells from dehydration and nutrient loss

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16. 16 Biofilms

17. 17 Biofilm on a Catheter

18. 18 The Cell Envelope Composed of two basic layers: –cell wall and cell membrane Maintains cell integrity Two generally different groups of bacteria demonstrated by Gram stain: –Gram-positive bacteria: thick cell wall composed primarily of peptidoglycan and cell membrane –Gram-negative bacteria: outer cell membrane, thin peptidoglycan layer, and cell membrane

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20. 20 Peptidoglycan Unique macromolecule composed of a repeating framework of long glycan chains cross-linked by short peptide fragments Provides strong, flexible support to keep bacteria from bursting or collapsing because of changes in osmotic pressure

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22. 22 4 Bacterial Groups Based on Cell Wall Composition 1.Gram positive cells 2.Gram negative cells 3.Bacteria without cell walls 4.Bacteria with chemically unique cell walls

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25. 25 Gram Positive Cell Wall Consists of –a thick, homogenous sheath of peptidoglycan 20-80 nm thick –tightly bound acidic polysaccharides, including teichoic acid and lipoteichoic acid –cell membrane Retain crystal violet and stain purple

26. 26 Gram Negative Cell Wall Consists of –an outer membrane containing lipopolysaccharide (LPS) –thin shell of peptidoglycan –periplasmic space –inner membrane Lose crystal violet and stain red from safranin counterstain

27. 27 Cell Membrane Structure Phospholipid bilayer with embedded proteins – fluid mosaic model Functions in: –providing site for energy reactions, nutrient processing, and synthesis –transport into and out of the cell

28. 28 Cell Membrane Structure

29. 29 Cytoplasm Dense gelatinous solution of sugars, amino acids, & salts 70-80% water serves as solvent for materials used in all cell functions

30. 30 “Chromosome” Single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell DNA is tightly coiled around protein, aggregated in a dense area called the nucleoid

31. 31 Plasmids Small circular, double-stranded DNA Free or integrated into the chromosome Duplicated and passed on to offspring Not essential to bacterial growth & metabolism May encode antibiotic resistance, tolerance to toxic metals, useful enzymes & toxins Used in genetic engineering- readily manipulated & transferred from cell to cell

32. 32 Ribosomes Made of 60% ribosomal RNA & 40% protein Consist of 2 subunits: large & small Procaryotic differ from eucaryotic ribosomes in size, and number of proteins Site of protein synthesis All cells have ribosomes

33. 33 Ribosomes

34. 34 Endospores Resting, dormant cells Produced by some G+ genera: Clostridium, Bacillus & Sporosarcina Have a 2-phase life cycle – vegetative cell & an endospore Sporulation -formation of endospores Germination - return to vegetative growth Hardiest of all life forms Withstand extremes in heat, drying, freezing, radiation & chemicals

35. 35 Sporulation Cycle

36. 36 Endospores Environmental resistance linked to high levels of calcium & dipicolinic acid Dehydrated, metabolically inactive Thick coat Longevity verges on immortality, 25-250 million years Pressurized steam at 121 o C for 20-30 minutes will destroy

37. 37 3 Basic Shapes of Bacteria Cocci - spherical Bacilli - rod Spiral - helical, comma, twisted rod, spirochete

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39. 39 Methods in Bacterial Identification 1.Microscopic morphology 2.Macroscopic morphology – colony appearance 3.Physiological / biochemical characteristics 4.Serological analysis 5.Genetic & molecular analysis G + C base composition DNA analysis using genetic probes Nucleic acid sequencing & rRNA analysis

40. 40 Major Taxonomic Groups of Bacteria Domain Archaea – primitive, adapted to extreme habitats and modes of nutrition Domain Bacteria - –Phylum Proteobacteria – Gram-negative cell walls –Phylum Firmicutes – mainly Gram- positive with low G + C content –Phylum Actinobacteria – Gram-positive with high G + C content

41. 41 species –a collection of bacterial cells which share an overall similar pattern of traits in contrast to other bacteria whose pattern differs significantly strain or variety – a culture derived from a single parent that differs in structure or metabolism from other cultures of that species (biovars, morphovars) type – a subspecies that can show differences in antigenic makeup (serotype or serovar), susceptibility to bacterial viruses (phage type) and in pathogenicity (pathotype) Bacterial Naming Conventions

42. Procaryotes with Unusual Characteristics

43. 43 Rickettsias Very tiny, gram-negative bacteria Most are pathogens that alternate between mammals and fleas, lice or ticks Obligate intracellular pathogens Cannot survive or multiply outside of a host cell Cannot carry out metabolism on their own Rickettsia rickettisii – Rocky Mountain spotted fever Rickettsia prowazekii – epidemic typhus Coxiella burnetti – Q fever

44. 44 Chlamydias Tiny Obligate intracellular parasites Not transmitted by arthropods Chlamydia trachomatis – severe eye infection and one of the most common sexually transmitted diseases Chlamydia psittaci – ornithosis, parrot fever Chlamydia pneumoniae – lung infections

45. 45 Mycoplasmas Naturally lack a cell wall Membranes stabilized by sterols, resistant to lysis Extremely small Range in shape from filamentous to coccus or doughnut shaped Mycoplasma pneumoniae – causes atypical pneumonia in humans

46. 46 Variations in the Shape of Mycoplasma pneumoniae

47. 47 Free-living Nonpathogenic Bacteria Photosynthetic bacteria –Cyanobacteria –Green & purple sulfur bacteria Gliding, fruiting bacteria Appendaged bacteria –produce an extended process of the cell wall in form of a bud, stalk or long thread

48. 48 Archaea Constitute third Domain Appear more closely related to Domain Eucarya than to bacteria Contain unique genetic sequences in their rRNA Have unique membrane lipids & cell wall construction Live in the most extreme habitats in nature, extremophiles Includes: methane producers, hyperthermophiles, extreme halophiles, and sulfur reducers