Bacterial Morphology and Structure
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This document discusses the morphology and structures of bacterial cells. It begins by outlining the learning objectives which are to describe different bacterial shapes and arrangements, basic bacterial cell structures and their functions, staining characteristics based on structures, and how structure relates to laboratory identification. It then details the various bacterial cell components such as the cell wall, plasma membrane, ribosomes, and other internal structures. It explains how these structures determine staining properties and relates morphology to identification. The document uses diagrams to illustrate the different bacterial forms, components, and arrangements.
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Bacterial Morphology and Structure
- 1. BACTERIAL MORPHOLOGY I Dr. Tarek Mahbub Khan MBBS, M.Phil (virology) Senior lecturer Faculty of Medicine Basic Medical Microbiology Semester 3, Year 2 Date: December 30, 2014 Time: 0930-1030 7/1/2015 1Dr.Tarek/KUIN
- 2. TLO (students will be able to) • describe different morphological form of bacteria and their arrangements. • describe basic structures and functions of a bacterial cell. • explain staining characteristics on the basis of structural components • explain the role of bacterial structure in laboratory identification. 7/1/2015 2Dr.Tarek/KUIN
- 3. SHAPE AND ARRANGEMENT OF BACTERIA 7/1/2015 3Dr.Tarek/KUIN
- 4. STRUCTURES ESSENTIAL COMPONENTS NONESSENTIAL COMPONENTS Cell Wall Capsule Plasma membrane Pilus or Fimbria Ribosome Flagellum Mesosome Spore Nucleoid Plasmid Periplasm Granules Glycocalyx 7/1/2015 4Dr.Tarek/KUIN
- 6. CELL WALL • Multilayered structure outside the cytoplasmic membrane • COMPOSED OF: – Peptidoglycans – Teichoic acid/ lipoteichoic acid – Lipopolysaccharide • Function provides: – cell shape, osmotic stability, transportation of molecules, antigenicity 7/1/2015 6Dr.Tarek/KUIN
- 8. A: E.coli B: Staphylococcus Penicillin acts Transpeptidase 7/1/2015 8Dr.Tarek/KUIN
- 9. Gram positive and Gram negative cell wall 7/1/2015 9Dr.Tarek/KUIN
- 11. CELL WALL OF ACID FAST BACTERIA 7/1/2015 11Dr.Tarek/KUIN
- 12. TEICHOIC ACID • Present on gram positive bacteria • Chemically glycerol phosphate or ribitol phosphate • Glycerol teichoic acid are lipoteichoic acid • Ribitol teichoic acid attached to NAM acid of CHO • Functions/effects: – Septic shock – Attachment to mucosa (e.g., Staphylococcus) 7/1/2015 12Dr.Tarek/KUIN
- 13. BACTERIAL RIBOSOME (70S) Antibiotic binds selectively Selective toxicity 7/1/2015 13Dr.Tarek/KUIN
- 14. CYTOPLASM AND GRANULES • Cytoplasm has two distinct regions: – Amorphous (e.g, Nutrient granules, ribosome etc.) – Nucleoid • Granules often contains high energy phosphates Red stained metachromatic granule Corynebacterium diphtheriae 7/1/2015 14Dr.Tarek/KUIN
- 15. NUCLEOID Not a true nucleus No nuclear membrane No nucleolus No mitotic spindle No histones No introns Bacterial genes are arranged in ‘Operons’ 7/1/2015 15Dr.Tarek/KUIN
- 16. PLASMID Extra chromosomal Double stranded Circular DNA molecules Self replicable Transmissible Non transmissible Contains Antibiotic R genes Genes for sex pilus Genes for exotoxins 7/1/2015 16Dr.Tarek/KUIN
- 17. BACTERIAL CAPSULE A gelatinous layer Polysaccharide in nature Antiphagocytic Antigenic Helps bacterial adherence Aids lab diagnosis Negative staining shows unstained capsule 7/1/2015 17Dr.Tarek/KUIN
- 18. FLAGELLA: Organ of motility 7/1/2015 18Dr.Tarek/KUIN
- 19. ARRENGEMENT OF FLAGELLA 7/1/2015 19Dr.Tarek/KUIN
- 20. PILI (Fimbria) Hair like filaments Composed of pilin proteins Short and straight than flagella FUNCTIONS Attachment (Ordinary pili) Conjugation (Sex pili) 7/1/2015 20Dr.Tarek/KUIN
- 21. GLYCOCALYX Often known as ‘Slime layer’ Covers surface as film Polysaccharides Components of biofilm Helps bacterial adherence Thick glycocalyx forms capsule 7/1/2015 21Dr.Tarek/KUIN
- 22. BACTERIAL SPORE Highly resistance form Forms in adverse condition RESISTANT FACTORS: Dipicolinic acid (Ca+ Chelator) Keratin like Spore coat Less water Less cytoplasm Resistant to boiling Killed by autoclaving 7/1/2015 22Dr.Tarek/KUIN
- 23. BACTERIA AND LOCATION OF SPORE 7/1/2015 23Dr.Tarek/KUIN
- 24. DIRECT OBSERVATION OF A BACTERIUM • Can not be observed in naked eye • Microscopy: • Direct evidence – Shape – Arrangement – Staining characteristics • Indirect evidence – Motility 7/1/2015 24Dr.Tarek/KUIN
- 25. HOW BACTERIAL STRUCTURE INFLUENCES STAINING METHOD • GRAM STAIN – Primary stain (crystal violet) is retained in gram positive bacteria due to thick cell wall. Hence bacteria stained purple or blue – Gram negative bacteria loss the primary stain easily due to thin cell wall and take the counter stain color (red carbol fuchsin) • ACID FAST STAIN – Due to mycolic acid in the cell wall of acid fast bacteria primary stained (red carbol fuchsin) is applied in hot state. Hence the bacteria is red 7/1/2015 25Dr.Tarek/KUIN
- 28. ACID FAST BACTERIA 7/1/2015 28Dr.Tarek/KUIN
- 29. EXAMPLES OF BACTERIA WITH MORPHOLOGICAL AND BIOCHEMICHEL PROPERTIES PROPERTIES EXAMPLES Capsulated Streptococcus pneumoniae, Neisseria meningitidis, Klebsiella pneumoniae Flagellated Escherichia coli, Salmonella, Vibrio, Proteus Piliated Neisseria gonorrhoeae, E.coli, Strict aerobe Mycobacterium tuberculosis, Pseudomonas Anaerobe Clostridium, Bacteriodes Facultative anaerobe E.coli, Salmonella, Shigella other enteric bacteria Spore forming Clostridium, Bacillus 7/1/2015 29Dr.Tarek/KUIN
- 30. REFERENCE • Warren Levinson. Review of Medical Microbiology and Immunology, 11th edition (2010). Appleton and Lange. • Geo. F. Brooks, Karen C. Carroll, Janet S. Butel, Stephen A. Morse, Timothy A. Mietzner. Medical Microbiology, 25th edition (2010). Appleton & Lange. Dr.Tarek/KUIN7/1/2015 30