MI 1.1 Morphology of Bacteria - Part one

MI 1.1 Morphology of Bacteria

1. Morphology of Bacteria DR RANU SONI MD, DNB, MNAMS ASSISTANT PROFESSOR DEPARTMENT OF MICROBIOLOGY MMCMSR, SADOPUR, AMBALA

2. Learning Objectives At the end of the session, the students will know 1. To know the classification of microorganisms 2. To understand the principles of staining techniques 3. Differentiate between Gram-positive and Gram-negative bacterial cell wall

3. Characteristics of Prokaryotes and Eukaryotes Characteristics Prokaryotes Eukaryotes Major groups Bacteria, blue green algae Fungi, parasites, other algae, plants and animals Nucleus Diffuse Well defined   Nuclear membrane Absent Present   Nucleolus Absent Present   Ribonucleoprotein Absent Present   Cell division Binary fission Mitosis, Meiosis   Chromosome One, circular Many, liner   Extrachromosomal DNA Found in plasmid Found in mitochondria

4. Characteristics of Prokaryotes and Eukaryotes Characteristics Prokaryotes Eukaryotes Cell membrane Doesn’t contain sterols except in mycoplasma Contain sterols Cellular organelles like mitochondria, golgi apparatus etc Absent (except ribosome) Present Ribosome 70s in size 80s in size Site of respiration Mesosome Mitochondria Pinocytosis Absent Present

5. Microscopy of Bacteria in Living State Unstained (Wet) Preparations Vital Stains - Used to differentiate living cells from dead cells. Examples of vital stains include eosin, propidium iodide, trypan blue, erythrosine, and neutral red.*

6. Morphology of B acteria Bacteria Example Gram positive cocci arranged in   Cluster Staphylococcus   Chain Streptococcus   Pairs, lanceolate shaped Pneumococcus   Pair or in short chain, spectacle eyed shape Enterococcus   Tetrads Micrococcus   Octate Sarcina Gram negative cocci arranged in   Pairs,lens shaped Meningococcus     Pairs, kidney shaped Gonococcus

7. Morphology of Gram-Positive /Negative B acteria Bacteria Example Gram positive bacilli arranged in   Chain(bamboo stick appearance) Bacillus anthracis     Chain Streptobacillus   Chinese letter or cuneiform pattern Corynebacterium diphtheriae   Palisade pattern Diphtheroids   Branched and filamentous form Actinomyces and Nocardia

8. Morphology of Gram- Negative B acteria Bacteria Example Gram negative bacilli arranged in   Pleomorphic (various shapes) Haemophilus, Proteus   Thumb print appearance Bordetella pertussis   Comma shaped (fish in stream appearance) Vibrio cholerae   Curved Campylobacter (Gull-wing shaped) and Helicobacter   Spirally coiled, flexible Spirochetes   Rigid spiral forms Spirillum   Bacteria that lack cell wall Mycoplasma

9. M orphology of bacteria and gram staining property

10. Structure of Bacterial C ell

11. Bacterial Cell Wall

12. Gram Positive C ell W all

13. Gram-positive cell wall Teichoic acid: Teichoic acids are of two types: Cell wall teichoic acid- covalently linked to NAM molecules of peptidoglycan. Lipoteichoic acid attached to lipid groups of the cell membrane.

14. Gram-negative cell wall Peptidoglycan layer : Skinny (1-2 layer, 2nm thick). Composed of a mucopeptide chain similar to a Gram-positive cell wall, consisting of alternate NAM and NAG molecules .

15. Gram-negative cell wall Outer membrane : Phospholipid layer which lies outside the thin peptidoglycan layer. Serves as a protective barrier to the cell. Outer membrane proteins (OMP) or porin proteins

16. Lipopolysaccharide (LPS): consists of: Lipid A or the endotoxin Core polysaccharide O side chain (or O antigen) Periplasmic space : A space between the inner and outer membrane. It encompasses the peptidoglycan layer

17. Bacterial Cell Wall The cell wall serves several important functions:- Protects the cell from osmotic lysis Provides rigidity Determines the shape of the cell Plays a role in cell division Protects the cell from toxic substances and is the target for various antibiotics The bacterial cell wall contains specific virulence factors (e.g., endotoxin) contributing to pathogenicity.- Antibodies raised against certain cell wall antigens (e.g., antibodies to LPS) can provide immunity against some bacterial infections.

18. Demonstration of the Cell Wall Plasmolysis - When bacteria are placed in hypertonic saline, shrinkage of the cytoplasm occurs, while the cell wall retains its original shape and size.

19. 2. Microdissection : a technique that uses a microscope to isolate specific cells or small tissue fragments from a larger sample for molecular analysis

20. 3. Differential staining

21. 4. Reaction with specific antibody 5. Electron microscopy

22. Differences between gram-positive and gram-negative cell wall Characters Gram Positive cell wall Gram Negative cell wall Peptidoglycan layer Thicker (15-80nm) Thinner (2nm)   At 3 rd position of tetrapeptide side chain L- Lysine present Mesodiaminopimelic acid present   Pentaglycine bridge Present Absent Lipid content Nil or scanty (2-5%) Present (15-20%) Lipopolysaccharide Absent Present (endotoxin) Teichoic acid Present Absent Variety of amino acids Few Several Aromatic amino acids Absent Present

23. Cell Membrane The fluid-mosaic model is the most widely accepted current model

24. Functions of Bacterial Cell Membrane Semi-permeable membrane - osmotic barrier Transport system Site for metabolic processes Special receptor molecules located in the membrane help the bacteria to detect and respond to chemicals in their surroundings.

25. Questions 1. Which of the following is a spherical-shaped bacterium? a) Bacillus b) Vibrio c) Coccus d) Spirillum

26. 1. Which of the following is a spherical-shaped bacterium? a) Bacillus b) Vibrio c) Coccus d) Spirillum

27. 2. Which shape is characteristic of Vibrio cholerae ? a) Spiral b) Comma-shaped c) Rod d) Filamentous

28. 2. Which shape is characteristic of Vibrio cholerae ? a) Spiral b) Comma-shaped c) Rod d) Filamentous

29. 3. Cocci arranged in chains are known as: a) Staphylococci b) Streptococci c) Diplococci d) Sarcinae

30. 3. Cocci arranged in chains are known as: a) Staphylococci b) Streptococci c) Diplococci d) Sarcinae

31. 4. Tetrads (groups of four cocci) are typically seen in: a) Micrococcus b) Streptococcus c) Sarcina d) Staphylococcus

32. 4. Tetrads (groups of four cocci) are typically seen in: a) Micrococcus b) Streptococcus c) Sarcina d) Staphylococcus

33. 5. Bacteria arranged in palisades (V or L shapes) are characteristic of: a) Corynebacterium diphtheriae b) Clostridium c) Bacillus anthracis d) Mycobacterium

34. 5. Bacteria arranged in palisades (V or L shapes) are characteristic of: a) Corynebacterium diphtheriae b) Clostridium c) Bacillus anthracis d) Mycobacterium

35. 6. The rigid shape of bacteria is due to: a) Capsule b) Cell membrane c) Peptidoglycan layer d) Ribosomes

36. 6. The rigid shape of bacteria is due to: a) Capsule b) Cell membrane c) Peptidoglycan layer d) Ribosomes

37. 7. Gram-positive bacteria have: a) Thin peptidoglycan layer b) Outer membrane c) Thick peptidoglycan layer d) No teichoic acid

38. 7. Gram-positive bacteria have: a) Thin peptidoglycan layer b) Outer membrane c) Thick peptidoglycan layer d) No teichoic acid

39. 8. Which of the following is absent in Gram-negative cell walls? a) Peptidoglycan b) Teichoic acid c) Outer membrane d) Lipopolysaccharide

40. 8. Which of the following is absent in Gram-negative cell walls? a) Peptidoglycan b) Teichoic acid c) Outer membrane d) Lipopolysaccharide

41. 9.The peptidoglycan is made up of: a) N-acetylglucosamine & N-acetylmuramic acid b) Lipopolysaccharide & lipid A c) Mannose & glucose d) Teichoic acid & peptide

42. 9.The peptidoglycan is made up of: a) N-acetylglucosamine & N-acetylmuramic acid b) Lipopolysaccharide & lipid A c) Mannose & glucose d) Teichoic acid & peptide

43. 10. The periplasmic space is present in: a) Gram-positive bacteria only b) Gram-negative bacteria c) Both Gram-positive and negative d) Archaea

44. 10. The periplasmic space is present in: a) Gram-positive bacteria only b) Gram-negative bacteria c) Both Gram-positive and negative d) Archaea

45. 11. Lipopolysaccharide (LPS) is a major component of: a) Gram-positive wall b) Outer membrane of Gram-negative bacteria c) Inner membrane of Gram-positive bacteria d) Mycoplasma membrane

46. 11. Lipopolysaccharide (LPS) is a major component of: a) Gram-positive wall b) Outer membrane of Gram-negative bacteria c) Inner membrane of Gram-positive bacteria d) Mycoplasma membrane

47. 12. Cell wall-less bacteria are: a) Rickettsiae b) Mycoplasma c) Chlamydia d) Spirochetes

48. 12. Cell wall-less bacteria are: a) Rickettsiae b) Mycoplasma c) Chlamydia d) Spirochetes

49. 13. Which structure provides osmotic protection to bacterial cells? a) Capsule b) Peptidoglycan c) Cell membrane d) Cytoplasm

50. 13. Which structure provides osmotic protection to bacterial cells? a) Capsule b) Peptidoglycan c) Cell membrane d) Cytoplasm

51. 14. Functions of the bacterial cell membrane include all EXCEPT: a) Selective permeability b) Energy generation c) Protein synthesis d) Transport of solutes

52. 14. Functions of the bacterial cell membrane include all EXCEPT: a) Selective permeability b) Energy generation c) Protein synthesis d) Transport of solutes

53. 15. Bacterial cytoplasmic membrane is composed of: a) Proteins and lipids b) Lipopolysaccharides c) Peptidoglycan d) Cellulose

54. 15. Bacterial cytoplasmic membrane is composed of: a) Proteins and lipids b) Lipopolysaccharides c) Peptidoglycan d) Cellulose