Part II BACTERIOLOGY

1. Part II BACTERIOLOGY Yang Haibo

2. PROKARYOTES Structure: • have a nucleoid containing DNA surrounded by cytoplasm • proteins can be synthesized • energy can be generated • have cell wall containing peptidoglycan 肽聚糖

3. Method of replication: by binary fission can replicate extracellulary except rickettsiae，chlamydiae

4. Nature of the nucleic acid contain both DNA and RNA

5. Chapter 7 Morphology and Structure of Bacteria

6. Size and shape • Unit for measurement : Micron or micrometer, μm: 1μm=10-3mm

7. Size: • Varies with kinds of bacteria, and also related to their age and external environment. • range from 0.1--10μm in their largest dimension • Approximate 1μm

9. Shape • Three basic groups: 1.cocci: round 2.bacilli: rods 3. spiral B.: spiral-shape pleomorphic: variable shape • The shape is determined by its rigid cell wall • Microscopic appearance: identification

10. Coccobacilli: very short rods • Spiral-shaped: • Spirilla: the cells are rigid • Spirochetes: the cells are mor flexible and undulating

12. arrangement • cocci diplococci: in pairs streptococci: in chains staphylococci: in grapelike clusters • bacilli Some arrange in chains

13. Structure • Basic structure • Cell wall • Cytoplasmic membrane • Cytosol 胞液 • nucleiod • Specific structure • Capsule 荚膜 • Endospores 芽胞 • Flagella 鞭毛 • Pili 菌毛

15. Basic structure cell wall • The outermost component common to all bacteria (except mycoplasma) • In gram-positive B. : peptidoglygan teichoic acids • In gram-negative B. : peptidoglycan outer membrane

16. The Cell Envelope Gram Stain Gram Positive Gram Negative

21. Functions of cell wall • Osmotic protection • maintains the characteristic shape of the cell • The sites of major antigenic determinants • Endotoxin activity of Gram-negative B.

22. 1. Peptidoglycan layer • It is found only in B. cell walls. • provides rigid support for the cell • important in maintaining the characteristic shape of the cell • allows the cell to withstand media of low osmotic pressure • A good target for antibacterial drugs

23. Three parts of peptidoglycan layer Carbohydrate backbone: composed of alternating N-acetylglucosamine molecules and N-acetylmuramic acid Tetrapeptide side chains: attached to each of the muramic acid molecules Peptide cross-bridges: between the two tetrapepteds

24. The backbone is the same in all B. species • The tetrapeptide side chains and the peptide cross-bridge vary from species to species • The cross-bridge of G- B. consists of a direct peptide linkage between two side chains

25. In G+ B.: • About 40 sheets of peptidoglycan • Comprise 50% of the cell wall material in G- B.: • Only 1 or 2 sheets • Comprise 5%--10% of the cell wall material

28. 2. Special components of G+ cell walls • Teichoic and teichuronic acids 磷壁酸 • Polysaccharides 多聚糖

29. GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur Gln-Mur Gln-Mur Gln-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GRAM POSITIVE CELL WALL secrete exoenzymes and perform extracellular digestion Peptidoglycan-teichoic acid Lipoteichoic acid Cytoplasmic membrane Cytoplasm

30. (1) Teichoic and teichuronic acid • Wall teichoic acid : linked to peptidoglycan • lipoteichoic acid: linked to the lipid in the cytoplasmic membrane • are antigenic and induce antibodies that are species-specific • mediate adherence

31. 3. Special components of G- cell wall 3 components: • Lipoprotein 脂蛋白 • Outer membrane 外膜 • Lipopolysaccharide 脂多糖

32. GlN-Mur GlN-Mur GlN-Mur GlN-Mur GRAM NEGATIVE CELL WALL Outer Membrane (Major permeability barrier) Lipopolysaccharide Porin Braun lipoprotein degradative enzyme Periplasmic space Inner (cytoplasmic) membrane Cytoplasm

33. (1) lipoprotein • Cross-link the outer membrane and peptidoglycan layers • Stabilize the outer membrane and anchor it to the peptidoglycan layer

34. (2) Outer membrane • Asymmetrical bilayered structure • Contain prorins 孔蛋白 • Large antibiotic molecules penetrate the outer membrane relatively slowly

35. (3) Lipopolysaccharide (LPS) • Attached to the outer membrane • It is endotoxin of gram-negative B. • the effects are similar irrespective of the organism from which it is derived

36. GlN-Mur GlN-Mur GlN-Mur GlN-Mur GRAM NEGATIVE CELL WALL Outer Membrane (Major permeability barrier) Lipopolysaccharide Porin Braun lipoprotein degradative enzyme Periplasmic space Inner (cytoplasmic) membrane Cytoplasm

37. Three units • Lipid A 脂质A: responsible for the toxic effects • Core polysaccharide: link to lipid A • Outer polysaccharide: the important somatic antigen of several G- B.

38. (4) The periplasmic space 周浆间隙 • Between the inner and outer membranes • Hydrolytic enzymes: breakdown nontransportable substrates into transportable ones • Detoxifying enzymes: inactivate certain antibiotics

39. GlN-Mur GlN-Mur GlN-Mur GlN-Mur GRAM NEGATIVE CELL WALL Outer Membrane (Major permeability barrier) Lipopolysaccharide Porin Braun lipoprotein degradative enzyme Periplasmic space Inner (cytoplasmic) membrane Cytoplasm

41. GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur Gln-Mur Gln-Mur Gln-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GlN-Mur GRAM POSITIVE Lipoteichoic acid Peptidoglycan-teichoic acid Cytoplasmic membrane Cytoplasm GRAM NEGATIVE Lipopolysaccharide Porin Outer Membrane Braun lipoprotein Periplasmic space Inner (cytoplasmic) membrane Cytoplasm

42. 4. L forms • Removal of the B. cell wall, in osmotically protective media, they can grow and divide • May produce chronic infection • Relatively resistant to antibiotic treatment • Can revert to the normal bacillary form

43. Cytoplasmic membrane Functions: 1. selective permeability and transport of solutes 2. electron transport and oxidative phosphorylation 磷酸化作用 3. Excretion of hydrolytic exoenzymes 4. Secretion of enzymes and toxins

44. cytosol • Bounded by the cell membrane • Contain plasmid

45. plasmids • Are extrachromosomal, double- stranded, circular DNA molecules • are capable of replicating independently of the bacterial chromosome • can be integrated into the bacterial chromosome

46. plasmids • More than one type of plasmid or several copies of a single plasmid may be present in the cell • Can be lost and transfer • Many plasmids carry genes coding for different functions nucloid plasmids

47. Functions and structures 1. Antibiotic resistance 2. Resistance to heavy metals 3. resistance to ultraviolet light 4. pili (fimbriae) 5. Exotoxins

48. Nucleoid: • the area in which DNA is located • the DNA is a double strand, circular molecule • the nucleoid contains no nuclear membrane, no nucleolus, no mitotic spindle, and no histones

49. Specific structure of B. • Capsule • Endospores • Flagella • Pili

50. A. capsule: • a gelatinous extracellular layer • Synthesized when growing in natural environments • composed of polysaccharede • Capsule: condensed, closely surrounding the cell • Glycocalyx: loose meshwork of fibrils extending outward from the cell