2Gen Bacteriology 2 structure of bacter

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Structure of bacterial cell Dr Shamim Mumtaz Prof of Microbiology

PRACTICAL CONSIDERATION OF CELL WALL Cell wall or its parts can interact with human tissues & contribute to disease : 

PRACTICAL CONSIDERATION OF CELL WALL Cell wall or its parts can interact with human tissues & contribute to disease Outer Memb. In G-ive bacteria ;-- Extra barrier making it more impervious. require more aggressive therapy . Lps (endotoxin), complicating factor. Alcohol based compound can dissolve lipids, basis for gram- staining 5. Outer proteins of G+ive cell wall has toxic properties. 6. Stimulate Abs production. 7. Lipids in Mycobacterial cell wall are harmful to human cells.

EXCEPTION TO THE CELL WALL : 

EXCEPTION TO THE CELL WALL Mycobacteria and Nocardia Bulk of cell wall is composed of unique types of lipids, MYCOLIC ACID or Cord factor Resistance to certain chemicals and dyes Such resistance is the basis of Acid Fast stain ; TB, Leprosy.

EXCEPTIONS IN THE CELL WALL : 

EXCEPTIONS IN THE CELL WALL Several bacterial gps lack cell wall structure of G+ive and G-ive bacteria. Some bacteria have NO cell wall at all (Mycoplasma). Some bacteria can lose their cell wall during part of their life cycle, referred to as L forms.

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CONVERSION OF WALLED BACTERIAL CELLS TO L-FORM. can be induced artificially by treatment with elements like lysozymes and penicillin.

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Bound more tightly to the cell, has thicker , gummy consistency gives prominently sticky (mucoid) character to the colonies of encapsulated bacteria

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Surface like a film. Adhere, skin, heart vales & catheters. Enhances pathogenicity by protecting against pagocytosis. S. pneumomiae, H. influenzae, B. anthracis enhances colonization

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APPENDAGES FOR ATTACHMENT AND MATINING Pilus or Fimbria (e) Pathogens infect host tissue and colonize b/c of tight adhesions e.g. Gonococci, E. coli

THE SEX PILUS : 

THE SEX PILUS An elongated , rigid tubular structure, made of a special protein, PILIN Found only on Gram negative bacteria

TYPE OF FLAGELLAR ARRANGEMENTS : 

TYPE OF FLAGELLAR ARRANGEMENTS Monotrichous LOPHOTRICHOUS AMPHITRICHOUS flagella at both Poles of cell. PERITRICHOUS

Spores : 

Spores Under unfavorable conditions ( nutritional depletion, esp. C&N), bacteria like bacillus & clostridia are able to survive by forming spores. unable to multiply in unfavorable conditions. exhibit no measurable metabolic activity Under favorable conditions , multiply producing bacterial cells capable of reproduction. Antibiotics are ineffective against spores . Resistant to heat , cold and disinfectants. Destroyed by autoclaving (1210c ) ,not by boiling

spores : 

spores peptidoglycan keratin like protein

Plasmids : 

Plasmids Extra-chromosomal,double-stranded circular DNA molecule. Replicate independent of the bacterial chromosome. Can be integrated into the bacterial chromosome. Carry genes for antibiotic resistance, which is mediated by enzymes. Exotoxins, enterotoxins. Pili, adherence of bacteria to epithelial cells.

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Thankyou