Chapter 4 Part B Bacterial ultrastructure (continued)
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Transcript of 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