Download Mouth “animalcules” (bacteria) 1684

Mouth animalcules (bacteria) 1684
http://en.citizendium.org/images/thumb/9/94/Leeuwenhoek.jpg/300px-Leeuwenhoek.jpg
Prokaryotic Cell Shapes
Coccus - cocci
Bacillus - bacillus
Spirillum - spirilli
Vibrio - vibrios
Cell Associations
Coccus
Cells are attached to
each other by
intercellular glue or a
secreted sheath
made of mucilaginous
polysaccharides
Diplococcus
The sheath can provide
antibiotic resistance
too!
Streptococcus - filamentous
Staphylococcus - colonial
?
Streptobacillus
What shapes and associations are shown in these SEMs?
http://www.hhs.gov/asphep/presentation/images/bacteria.jpg
What are the shapes of these disease bacteria?
http://microbewiki.kenyon.edu/images/a/a8/V_cholerae.jpg
http://www.cab.unimelb.edu.au/images/helico.jpg
Vibrio cholerae
Helicobacter pylori
Are they motile?
If so, by what
mechanism?
Comparing Cell Sizes
Mycoplasma 0.3-0.8 µm
E. coli 1x2 µm
Cyanobacteria 10 µm diam
Plant Cell 30x75 µm
Obviously eukaryotic
Nucleus present
Mitochondrion ≈ Bacterium
Chloroplast ≈ Cyanobacterium
Endosymbiosis: Eukaryotes are Chimeras!
Cell Structure: Boundary
Mycoplasma
cytosol
cell membrane bilayer only…
glycolipid, sulfolipid
transport proteins
regulates input/output
ETS for PSN, Resp
Gram Positive
Gram Negative
cell wall-murein
peptidoglycan
muramic acid - peptide
prevents dye release
prevents bursting
turgor pressure
penicillin sensitive
additional
membrane bilayer
glyco- sulfo-lipids releases dye
Cell Structure: Cytosol
Water and enzymes for
fermentation, glycolysis,
Kreb s cycle, Calvin
cycle, naked circular DNA
for transcription, 70S
ribosomes for translation
Mycoplasma
cytosol
cell membrane bilayer
glycolipid, sulfolipid
transport proteins
regulates input/output
ETS for PSN, Resp
Gram Positive
Gram Negative
cell wall-murein
peptidoglycan
muramic acid - peptide
prevents dye release
prevents bursting
turgor pressure
penicillin sensitive
additional
membrane bilayer
glyco- sulfo-lipids releases dye
This cartoon is not
labeled, so it merely
acts as a key, to orient
the viewer to the
enlarged portion of the
TEM image.
Cytoplasm
Plasma
membrane
Cell wall
Figure 7-2 Page 121
Is this example Gram+ or Gram−?
The cytosol area
(labeled
cytoplasm)shows the
nucleoid (DNA) area at
the top.
The cell membrane
shows that it is a bilayer.
The cell wall shows that
it is multilayered.
Ribosomes
This is a cartoon
image created by an
artist to emphasize
certain structures.
Plasmids
Cytoplasm
Flagellum
Chromosome
Plasma
membrane
Cell wall
This is the
transmission electron
microscopy image
that inspired the
cartoon.
Light microscopy
would be even less
detailed!
Figure 7-1 Page 120
DNA
This diagram
shows you an
enlargement of a
TEM.
The DNA double
helix is further
twisted to form
the coils you are
seeing here.
Supercoiled DNA
in chromosome
Figure 7-3 Page 121
The functions of
the nucleoid are
transcription
(making mRNA),
and replication
(making a copy of
DNA prior to cell
division).
The area including the naked, circular DNA molecule (lacking
DNA-binding proteins) is called the nucleoid; it is not a nucleus!
The bacterium is prokaryotic (before-nucleus).
Ribosome
Large subunit
of ribosome
Small subunit
of ribosome
Figure 7-4 Page 121
Ribosomes are
70S in size in
prokaryotes,
mitochondria, and
plastids.
Those found in the
eukaryotic cytosol
are 80S in size.
The function of the
ribosome in both
kinds of cells is
translation; the
synthesis of protein
from the
information in
mRNA.
Cell Structure: Nucleoid
Nucleoid - genome
one circular DNA molecule
no histone protein association
attached to cell membrane
mRNA transcription by RNA polymerase
70S Ribosome
rRNA + protein + ribozymes
translation of mRNA into protein
Prokaryotic Growth
•  Cells are generally very small
•  Cells may double in volume, but only before
binary fission
•  Growth is mostly in terms of cell number or
colony size, etc.
•  The doubling time in cell numbers may be 20
minutes in ideal conditions
•  Bacteria could quickly take over the earth if
conditions could remain ideal
•  They are very competitive, but often shed byproducts that inhibit their own survival, so
ideal conditions are usually not sustainable.
•  They are ultimate survivors - 3.5 billion years!
Cell Structure: Nucleoid
Nucleoid - genome
one circular DNA molecule
no histone protein
association
attached to cell membrane
DNA replication by DNA polymerase
separation of chromosomes
cytokinesis by furrowing
Process called binary fission
NOT mitosis!
• Genome and copy are identical
• Genome is haploid
• There is no synapsis
• There is no recombination