Transcript Chapter 4 Part B

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 gellike substance =
periplasm
– Contains enzymes
– Variety of receptors
Is this cell Gram + or Gram - ?
– linked to primitive
sensory system…
6) Plasma membrane
Figure 4.14b
• Composed of a sel.
permeable phospholipid bilayer
• Associated with
intrinsic/integral
proteins and extrinsic/
peripheral proteins
• Adheres to fluidmosaic model
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:
Figure 4.6a
– Single chromosome
– Free and attached 70S
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 (70S)
• Site of protein synthesis
• Composed of 2 subunits,
each containing protein
and rRNA
– Small subunit (30S)
– Large subunit (50S)
Figure 4.19
• Certain antibiotics
(streptomycin, neomycin,
tetracycline) affect 70S
ribosome, not 80S
ribosomes
11) Inclusion bodies
Inorganic inclusions
Organic inclusions
12) Endospores
Figure 4.21 - Overview