chapter 4 part b bacterial ultrastructure (continued)

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

Figure 4.11

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 gel-like substance = periplasm– Contains enzymes

– Variety of receptors

– linked to primitive sensory system…Is this cell Gram + or Gram - ?

6) Plasma membrane• Composed of a sel.

permeable phospho-lipid bilayer

• Associated with intrinsic/integral proteins and extrinsic/ peripheral proteins

• Adheres to fluid-mosaic modelFigure 4.14b

Plasma membrane

Figure 4.14 - Overview

Plasma membrane regulates movement of materials across it

Simple diffusion:

Occurs with O2, CO2, and some small, non-polar organic molecules

Plasma membrane regulates movement of materials across it

Facilitated diffusion:

Movement of H2O occurs this way!!!

osmosis

Figure 4.18 - Overview

Plasma membrane regulates movement of materials across it

Active transport:

The plasma membrane in prokaryotes is MULTI-FUNCTIONAL

Figure 4.15

7) Cytoplasm and the cell’s interior structures

• Cytoplasm is composed mostly of water

• It contains:– Single chromosome

– Free and attached 70S ribosomes

– Plasmid(s)

– Inclusions• Inorganic

• Organic

Figure 4.6a

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 (70S)

• Site of protein synthesis• Composed of 2 subunits,

each containing protein and rRNA– Small subunit (30S)– Large subunit (50S)

• Certain antibiotics (streptomycin, neomycin, tetracycline) affect 70S ribosome, not 80S ribosomes

Figure 4.19

11) Inclusion bodies

Organic inclusionsInorganic inclusions

12) Endospores

Figure 4.21 - Overview