Pathogenic Microorganisms 222 PHARM Lecture Notes PDF

Pathogenic Microorganisms 222 PHARM Bacterial structures and function 1/3/2025 2  Objectives ❑Provide details microscopic bacterial structure: ❑Internal Structure (Intracytoplasmic structure) ❑Bacterial cell wall Structure ❑Surface Structure (Structures outs...

Pathogenic Microorganisms 222 PHARM Bacterial structures and function 1/3/2025 2  Objectives ❑Provide details microscopic bacterial structure: ❑Internal Structure (Intracytoplasmic structure) ❑Bacterial cell wall Structure ❑Surface Structure (Structures outside cell wall) ❑Differentiate between Gram-positive & Gram-negative cell wall ❑Describe the bacterial movement ❑Describe the spore formation 1/3/2025 3  BACTERIAL STRUCTURE image via www.pixgood.com 1/3/2025 4  STRUCTURE OF EUBACTERIA II. Additional (non-essential) I. Essential structures Capsule Cell wall Slime layer Cell membrane Flagella Cytoplasm Pili, Fimbriae Ribosome Inclusions Nuclear material Spores Plasmids 1/3/2025 5  STRUCTURE OF EUBACTERIA I. External structure III. Internal structure II. Cell envelop (Extracytoplasmic) (Intracytoplasmic) Glycocalyx 1. Outer membrane Cytoplasm Flagella 2. Cell wall Ribosome Pili 3. Cell membrane Nuclear material Fimbriae Inclusions Spores Plasmids 1/3/2025 6  I. External structures 1. Glycocalyx ❑NON-essential structure i.e. a. Capsule not preset in all bacteria b. Slime layer 2. Surface appendages ❑Extracytoplasmic a. Flagella/-um ❑Located outside of the cell b. Pili/-us c. Fimbria/ae wall (CW) 1/3/2025 7 1. Glycocalyx ❑Capsule or slime layer is used to describe glycocalyx ❑Surround the whole bacterial cell ❑Gelatinous, sticky, high molecular weight secretory substance ❑Polysaccharide (mainly) and/or polypeptide(unique)) ❑Capsule is thick, organized, rigid & firmly attached to CW ❑Slime layer is thin unorganized & loosely attached to CW ❑Bacteria that have Capsule: S. pneumoniae, H. influenzae, N. meningitidis ❑Bacteria that have Slime layer S. epidermidis, Pseudomonas aeruginosa ❑Colonies of bacteria that have glycocalyx are smooth & mucoid 1/3/2025 8 1. Glycocalyx: Function 1.Virulence factor 2.Prevents phagocytosis 3.Aids in the attachment 4.Resistance to drying 5.Immunogenic 6.Capsule is K antigen Used in Identification e.g. E. coli K1 7.Slim layer is important in biofilm formation ❑ Slime layer of Streptococcus mutans allows it to accumulate on tooth enamel 1/3/2025 9 1. Glycocalyx ❑Extracellular polymeric substances (EPS) is a Glycocalyx that is a component of a biofilm ❑Biofilm is complex aggregation of microbes ❑Microorganisms within biofilm are very resistant to antibiotics ❑The formation of biofilms make infections difficult to treat 1/3/2025 10  Surface (Filamentous) Appendage ❑Two types of surface appendage: Flagella & Pili ❑Pili means hairs while Flagellum means whip ❑Flagella occur on Gram-positive & Gram-negative bacteria ❑Flagella are found on many bacilli but rarely on cocci ❑Thin, long, slender, filamentous hair-like helical appendages ❑The protein subunits are assembled to form a cylindrical structure with a hollow core 1/3/2025 11 2. FLAGELLA (H antigen): Function 1. Motility: organ of locomotion ❑ Responsible for swimming motility to propel the cell by beating in a whip-like motion ❑ Movement of bacteria toward or away from a particular stimulus is called taxis ❑ Stimuli include chemicals (Chemotaxis) & light (Phototaxis) 2. Aid in pathogenesis 3. Flagellar H antigen is useful in identification ❑e.g. E. coli O157:H7 1/3/2025 12  FLAGELLA ARRANGEMENT ❑Location on the cell varies depending on the species ❑At polar region(s): At one or both ends of the bacterium ❑At lateral regions: Along the sides of the bacterium 1.Atrichous: Absence of flagella 2.Monotrichous: Presence of single flagellum at one end 3.Lophotrichous: Presence of tuft of flagella at one end 4.Amphitrichous: Presence of single flagellum at both ends 5.Amphitlophorichous: Presence of tuft of flagella at both ends 6.Peritrichous: Presence of flagella all over the entire cell surface ❑Monotrichous & Peritrichous are most frequently in pathogenic strains 1/3/2025 13 FLAGELLA ARRANGEMENT AND STRUCTURE 1/3/2025 14 FLAGELLA STRUCTURE 1.Long Filament that lies external to the cell surface ❑Composed of chains of flagellin protein ❑ 10 m length &  10-20 nm diameter 2.Hook (protein) ❑Hook is wider in diameter & Curved tubular structure ❑Connects the basal body to the filament 3.Basal body (motor) ❑Only structure that is present within cell membrane ❑Connected to the hook ❑Rod-shaped structure with rings of microtubules 1/3/2025 15  AXIAL FILAMENTS ❑Also called Endoflagella ❑In spirochetes ❑Move in a unique spinning fashion via 6 thin endoflagella ❑Flagella lie between outer membrane & PDG layer ❑Anchored at one end of a cell ❑Rotation causes cell to move 1/3/2025 16 3. PILI and FIMBRIAE ❑The terms pili and fimbriae are usually used interchangeably ❑Shorter, rigid, straighter (non-helical ) & thinner than flagella ❑Composed of protein called pilin ❑Not for motility: Found on non-motile & motile species ❑Two types of Pili 1. Ordinadry pili (Fimbriae): Involved in attachment (Colonization) ❑ Loss of them  avirulent 2. Sex pili (F pili) are used in conjugation 1/3/2025 17  Item Pili (sex pili) Fimbriae (short pili) Presence Gram negative Gram positive & negative Size Longer & thicker Shorter & thinner Number/cell 1-4/cell 200-400/cell Rigidity Very rigid structure Less rigid structure Encoded on Plasmid Chromosome Function Conjugation Attachment 1/3/2025 18 Thank You