Bacteria functional anatomy.docx

Capsule ‘Slime layer’ Not always present and it provides protection. Allows attachment to surface. Masks markers on cell wall that triggers immune response. Cell wall Complex, semi-rigid structure. Prevents osmotic rupture. Peptidoglycan Carbohydrate backbone (made of N-acetylglucosamine and N-acety...

Capsule ‘Slime layer’ Not always present and it provides protection. Allows attachment to surface. Masks markers on cell wall that triggers immune response. Cell wall Complex, semi-rigid structure. Prevents osmotic rupture. Peptidoglycan Carbohydrate backbone (made of N-acetylglucosamine and N-acetylmuramic acid) Has peptide cross-bridges. Tetrapeptide side chains Gram-negative cell wall has a thin layer of peptidoglycan. Has a outer membrane made up of lipopolysaccharide. Has a distinctive rough appearance under microscope. Gram-positive cell wall has a thick layer of peptidoglycan. Smoother appearance under microscope. Function of cytoplasmic membrane Permeability barrier. Site of proteins Site of generation of energy Cell membrane Made up phospholipids. Protein channels through membrane Encloses cytoplasm. Function of cytoplasmic membrane Permeability barrier- prevent leakage and allows things to move in and out. Protein anchor- site of many proteins for transport, communication etc Energy conservation- protein motive force. Flagella Important for motility. 4 arrangements relating to poles. Monotrichous- single polar flagellum Lophotrichous- two or more at one/both ends Amphitrichous- single polar flagellum at each end Peritrichous- distributed all over entire cell. Flagellum structure in Gram-negative bacteria. L ring P ring MS ring C ring Gram positive doesn’t have L ring but has a larger P ring. The energy required for movement of the flagella is from electrochemical gradient between inside and outside of the cytoplasm. Bacterial mobility Movement of flagella that drives the bacteria forward due to high in gradient is called run. (Counter clockwise). Movement of flagella that drives the bacteria backwards due to low in gradient is called tumble. (Clockwise) Same for mono and Peritrichous. Chemotaxis In response to chemical stimulus, can also be phototaxis, osmotaxis etc. Bacteria moves towards the nutrients that beneficial to them= chemoreceptors No real stimulus. Fimbriae and pili Fimbriae Allow adherence. Pili Exchange genetic information- horizontal gene transfer Bacterial genome Chromosome Single long circular molecule No envelope Plasmid Replicates interpedently Not critical for bacterial survival Transferable Conjugation Another method for horizontal gene transfer is called transformation. The cell wall is altered/disturbed using electricity or chemicals to allow it to accept plasmids and take it up. Ribosomes Eukaryotic= 80S Prokaryotic= 70S (2 subunits, 30S and 50S) Inclusion bodies Reserve bodies for storage. E.g. glycogen, carbohydrates, and lipids etc. Bacterial endospores //////// Exotoxins Mostly produced by Gram-positive bacteria. Produced inside the bacteria as part of growth. Proteins made of 2 subunits= active (A) and binding (B) Highly soluble in blood therefore rapid transmission. e.g. clostridium botulinum (Botox)- inhibits release of acetylcholine. Endotoxin Constituent of cell wall of gram-negative microbes Symptoms include= fever, weakness etc. Released upon cell lysis. Surface antigens Used to categorise bacteria based on features.