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TA: Will Spencer

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1 TA: Will Spencer

2 Functions of bacterial cell parts Lengeler et al. pp Cellular and subcellular organization of procaryotes

3 1. Protoplasm Nucleoid Ribosomes / polysomes Cytosol Storage granules

4 2. Bacterial cell envelopes Cytoplasmic (=inner membrane, plasma membrane), CM Outer membrane, OM Periplasm Cell wall Capsule

5 3. Bacterial appendages Pilus, pili Flagellum, flagella

6 4. Disruption of bacterial cells Boiling in SDS Sonic oscillation French pressure cell

7 1. Protoplasm Nucleoid: Function, Properties –Compact lobular body: skein –Loops, coils DNA –Genome –Center of cell; CM attached –1 copy / cell; > 1 copy / cell; rapidly growing

8 1. Protoplasm Nucleoid: Molecular composition –Circular 2 x double stranded DNA helix –4.7 x 10 6 bp –Supercoiled –Proteins: packing DNA –Proteins: remove supercoils

9 1. Protoplasm Ribosomes: Function, Properties –Sites of protein synthesis –mRNA  translation to protein –E. coli: 18,000 ribs / cell –Polysomes = > 1 ribosome on same mRNA

10 1. Protoplasm Ribosomes: Molecular composition –rRNA = 62% –Proteins = 38% –Large subunit = 50 S 2 rRNAs + 32 proteins –Small subunit = 30 S 1 rRNA + 21 proteins

11 1. Protoplasm Cytosol: Function and properties –enclosed by CM –1000s of proteins: metabolism –[protein] ~ 20% –Gel

12 1. Protoplasm Cytosol: Molecular composition –80% dry weight = protein –60 tRNA molecules –mRNA –Metabolites –Vitamins, cofactors, ATP, inorganic ions –H 2 O

13 1. Protoplasm Storage granules: Function and properties –Deposits –Short-term energy source Storage granules: Molecular composition –Polysaccharides: glycogen –Degradation  free sugars

14 2. Bacterial cell envelopes CM: Function and properties –Selectively permeable boundary –Passage of H2O, nutrients, ions –Transport systems –Nutrient E  ATP

15 2. Bacterial cell envelopes CM: Molecular composition –Bilayer of 7 different phospholipids –100s of proteins: > 2 x 105 / CM –30% lipid; 70% protein

16 2. Bacterial cell envelopes OM: Function and properties –Molecular sieve –Protection vs chemicals –Specific transport proteins: Scavenge rare nutrients

17 2. Bacterial cell envelopes OM: Molecular composition –Asymmetric bilayer: Inner leaflet: phospholipids Outer leaflet: lipopolysaccharide –50 proteins: 10 6 molecules / cell

18 2. Bacterial cell envelopes Periplasm: Function and properties –Between OM and CM –Aqueous gel –Proteins: nutrition, detoxification

19 2. Bacterial cell envelopes Periplasm: Molecular composition –Peptidoglycan = murein: rigidity Several layers Sacculus –Gram - = thin; Gram + = thick –Binding proteins: nutrients –Degradative enzymes

20 2. Bacterial cell envelopes Capsule: Function and Properties –Defense against host cell’s phagocytes –Colonization of environments –Growth conditions Capsule: Molecular composition –High mol weight complex polysaccharides –Amorphous slime

21 3. Bacterial appendages Pilus, -i : Function and properties –Type 1 pili; / cell Attaching to surfaces –F1 pili = sex pilus; 1 – 3 / cell Conjugation Conduit for transfer of DNA to recipient

22 3. Bacterial appendages Pilus, -i : Molecular composition –Pilin = single species protein –Minor protein at tip = adhesin –Carbohydrate binding –Attachment

23 3. Bacterial appendages Flagellum, -a: Function and properties –Cell swimming –Basal body complex: M, S, P, L rings –Central rod –Hook –Filament

24 3. Bacterial appendages Flagellum, -a: Molecular composition –Flagellin –Hook protein –Basal body complex: 10s of protein Rotary motor

25 4. Disruption of bacterial cells Boiling in 2% SDS –Cell lysate: all contents dissolved –Proteins: SDS-PAGE Sonic oscillation –Pop bacteria French pressure cell –16,000 psi


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