Lecture 3
? 2.4 Physiological Diversity of Microorganisms
? 2.5 Prokaryotic Diversity
? 2.6 Eukaryotic Microorganisms
? 4.4,Cell Morphology and the Significance of Being
Small
? 4.5 Cytoplasmic Membrane,Structure
? 4.6 Cytoplasmic Membrane,Function
? 4.8 The Cell Wall of Prokaryotes,Peptidoglycan and
Related Molecules
? 4.9 The Outer Membrane of Gram-Negative Bacteria
Carbon fixation
? autotrophs,fix carbon from CO2
– include most phototrophs,photoautotrophic
? heterotrophs,get carbon from pre-existing
organic compounds
Domain Bacteria:
root (common ancestor)
Env-OP2
? not yet cultured; known only by 16S rRNA
? SAR11,another clade identified by 16S
Domain Archaea
methanogens
halophiles
acidophiles
hyperthermophiles
Archaea
? tend to be extremophiles
? two clades of Env-marine isolates,not
found in extreme cnditions
? can grow over at 113oC
? can grow in cow rumens (produce methane)
? can grow at pH < 0 (!)
Domain Eukarya
multi-celled
Endosymbiotic theory
? archaeal organism evolved a nuclear
membrane,before or after engulfing a
bacterium
? organisms developed a symbiosis which
became an obligate relationship
? considerable sharing of genetic material
? similar mechanisms let to engulfing of a
cyanobacterium to evolve chloroplasts
Different Shapes
Fig,4.11
Different Sizes
Figure 4.13
*SAR11,even smaller!
Giant Bacteria
Fig,4.12
Epulopiscium fishelsoni
gut of tropical
sugeon fish
16s,related to
Clostridium (food
pathogen)
not cultured; can
cultivate enough for
sequencing
depend on nutrient-
rich environment
?Size affects rate of nutrient
and waste transport across the
cell membrane
?Small size ? more efficient
exchange,support of higher
metabolic rate
Surface Area vs,Volume
Phospholipid Bilayer
Lipids in Bacteria and Archaea
have different chemical bonds
Ester - Bacteria
Ether - Archaea
Fig,4.19
Structure of Cytoplasmic
Membrane
Protein domain prediction
? based on amino acid sequence:
– hydrophobic amino acid domains are expected
to lie within the cytoplasmic membrane
– hydrophilic amino acid domains are expected to
lie either on the cytoplasmic or outer side
? prediction confirmed by experimental
studies
Table 4.1 Comparative
Permeability of Membranes to
Various Molecules
Substance Ra t e of P ermeability
Wa ter 100
Glyce r ol 0.1
Tryptoph an 0.001
Gluco se 0.001
Cl
-
0.000001
K
+
0.0000001
Functions of Cytoplasmic
Membrane
? Permeability Barrier
– small,uncharged
(hydrophobic)
molecules can pass
through by diffusion
? Protein Anchor
– transport,generation of
energy,chemotaxis
? Generation of proton
motive force
Transport proteins
? Transporters have substrate specificities
? generally,a given protein will transport
– one substrate
– a few similar substrates
– a class of substrates
? membranes possess multiple transporters
Cell Walls of Bacteria
?Peptidoglycan is found only in bacteria
?Keeps cells from lysing,due to turgor pressure
Gram staining
? cells are stained purple and then washed:
–,Gram positive” cells show purple
–,Gram negative” cells are colourless
? pink counter-stain,
–,Gram positive” remain purple
–,Gram negative” cells stain pink
? Reason,outer membrane of Gram negative
cells resists purple stain
Protoplast Formation
Lysozyme -- a protein that breaks 1,4-glycosidic
bonds in peptidoglycan
Peptidoglycan Structure
peptide chains vary among species
Teichoic Acids
Acidic polysaccharides found in gram positive cell walls
Gram Positive Cell Wall
Fig 4.32b
Archaeal Pseudopeptidoglycan
Lipopolysaccharide (LPS)
Only in gram negative bacteria
Part of the outer membrane
Help protect organism from environment
Often cause of host reactions and symptoms of infectious disease
Gram Negative Outer Membrane
Porins - proteins that allow small molecules to cross membrane
-- specific and non-specific
? 2.4 Physiological Diversity of Microorganisms
? 2.5 Prokaryotic Diversity
? 2.6 Eukaryotic Microorganisms
? 4.4,Cell Morphology and the Significance of Being
Small
? 4.5 Cytoplasmic Membrane,Structure
? 4.6 Cytoplasmic Membrane,Function
? 4.8 The Cell Wall of Prokaryotes,Peptidoglycan and
Related Molecules
? 4.9 The Outer Membrane of Gram-Negative Bacteria
Carbon fixation
? autotrophs,fix carbon from CO2
– include most phototrophs,photoautotrophic
? heterotrophs,get carbon from pre-existing
organic compounds
Domain Bacteria:
root (common ancestor)
Env-OP2
? not yet cultured; known only by 16S rRNA
? SAR11,another clade identified by 16S
Domain Archaea
methanogens
halophiles
acidophiles
hyperthermophiles
Archaea
? tend to be extremophiles
? two clades of Env-marine isolates,not
found in extreme cnditions
? can grow over at 113oC
? can grow in cow rumens (produce methane)
? can grow at pH < 0 (!)
Domain Eukarya
multi-celled
Endosymbiotic theory
? archaeal organism evolved a nuclear
membrane,before or after engulfing a
bacterium
? organisms developed a symbiosis which
became an obligate relationship
? considerable sharing of genetic material
? similar mechanisms let to engulfing of a
cyanobacterium to evolve chloroplasts
Different Shapes
Fig,4.11
Different Sizes
Figure 4.13
*SAR11,even smaller!
Giant Bacteria
Fig,4.12
Epulopiscium fishelsoni
gut of tropical
sugeon fish
16s,related to
Clostridium (food
pathogen)
not cultured; can
cultivate enough for
sequencing
depend on nutrient-
rich environment
?Size affects rate of nutrient
and waste transport across the
cell membrane
?Small size ? more efficient
exchange,support of higher
metabolic rate
Surface Area vs,Volume
Phospholipid Bilayer
Lipids in Bacteria and Archaea
have different chemical bonds
Ester - Bacteria
Ether - Archaea
Fig,4.19
Structure of Cytoplasmic
Membrane
Protein domain prediction
? based on amino acid sequence:
– hydrophobic amino acid domains are expected
to lie within the cytoplasmic membrane
– hydrophilic amino acid domains are expected to
lie either on the cytoplasmic or outer side
? prediction confirmed by experimental
studies
Table 4.1 Comparative
Permeability of Membranes to
Various Molecules
Substance Ra t e of P ermeability
Wa ter 100
Glyce r ol 0.1
Tryptoph an 0.001
Gluco se 0.001
Cl
-
0.000001
K
+
0.0000001
Functions of Cytoplasmic
Membrane
? Permeability Barrier
– small,uncharged
(hydrophobic)
molecules can pass
through by diffusion
? Protein Anchor
– transport,generation of
energy,chemotaxis
? Generation of proton
motive force
Transport proteins
? Transporters have substrate specificities
? generally,a given protein will transport
– one substrate
– a few similar substrates
– a class of substrates
? membranes possess multiple transporters
Cell Walls of Bacteria
?Peptidoglycan is found only in bacteria
?Keeps cells from lysing,due to turgor pressure
Gram staining
? cells are stained purple and then washed:
–,Gram positive” cells show purple
–,Gram negative” cells are colourless
? pink counter-stain,
–,Gram positive” remain purple
–,Gram negative” cells stain pink
? Reason,outer membrane of Gram negative
cells resists purple stain
Protoplast Formation
Lysozyme -- a protein that breaks 1,4-glycosidic
bonds in peptidoglycan
Peptidoglycan Structure
peptide chains vary among species
Teichoic Acids
Acidic polysaccharides found in gram positive cell walls
Gram Positive Cell Wall
Fig 4.32b
Archaeal Pseudopeptidoglycan
Lipopolysaccharide (LPS)
Only in gram negative bacteria
Part of the outer membrane
Help protect organism from environment
Often cause of host reactions and symptoms of infectious disease
Gram Negative Outer Membrane
Porins - proteins that allow small molecules to cross membrane
-- specific and non-specific
