Chapter 4 Part B Bacterial ultrastructure continued 3

Chapter 4 Part B Bacterial ultrastructure (continued)

3) Fimbriae or pili • Composed of tubular protein = pilin • Contributes to pathogenicity in some bacteria • 2 types of pili: both coded by genes on plasmids – Common pili/fimbriae – used for adhesion to surfaces – Conjugation/sex pilus – coded by F plasmid; aid in transfer of plasmid and chromosomal DNA

Common fimbriae or pili

4) Glycocalyx = general term for the substances that surround bacterial cells • 2 types distinguished by degree of adhesion to cell surface: • Capsule – firmly attached • Slime sheath – loosely attached • Functions: – – Aid in cell attachment Protect vs. phagocytosis Protect vs. dessication Block toxins, bacteriophage, etc.

Glycocalyx example

5) Periplasmic space • Space between plasma membrane and cell wall • Composed of gellike substance = periplasm – Contains enzymes – Variety of receptors Is this cell Gram + or Gram - ? – linked to primitive sensory system…

6) Plasma membrane • Composed of a sel. permeable phospholipid bilayer • Associated with intrinsic/integral proteins and extrinsic/ peripheral proteins • Adheres to fluidmosaic model

Plasma membrane

Plasma membrane regulates movement of materials across it Simple diffusion: Occurs with O 2, CO 2, and some small, non-polar organic molecules

Plasma membrane regulates movement of materials across it Facilitated diffusion: Movement of H 2 O occurs this way!!!

osmosis

Plasma membrane regulates movement of materials across it Active transport:

The plasma membrane in prokaryotes is MULTI-FUNCTIONAL

7) Cytoplasm and the cell’s interior structures • Cytoplasm is composed mostly of water • It contains: – Single chromosome – Free and attached 70 S ribosomes – Plasmid(s) – Inclusions • Inorganic • Organic

8) Bacterial chromosome and nuclear area • Nuclear area = “nucleoid” • Haploid, just 1 chromosome; circular in many bacteria

9) extra-chromosomal DNA plasmids • Circular DNA segments • Replicate indep of chromosome • Not req’d for host growth or reproduction • Some carry genes that provide selective advantage: – R factor plasmids – Virulence factor plasmids

10) Bacterial ribosomes (70 S) • Site of protein synthesis • Composed of 2 subunits, each containing protein and r. RNA – Small subunit (30 S) – Large subunit (50 S) • Certain antibiotics (streptomycin, neomycin, tetracycline) affect 70 S ribosome, not 80 S ribosomes

11) Inclusion bodies Inorganic inclusions Organic inclusions

12) Endospores