Bacterial Cell Structure (continued). You are here. Peptidoglycan structure. Bacteria typically face hypotonic environments Peptidoglycan provides support, Limits expansion of cell membrane Bacteria need other protection from hypertonic situations. Gram negative cell wall. Outer membrane.
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extends from cell surface.
contains odd sugars
Gln-P and fatty acids
take the place of
“Sugar covering”: capsules are firmly
attached, slime layers are loose.
Multiple advantages to cells:
protection from predators, WBCs
protection from biocides (as part of biofilms)
attachment to surfaces and site of attachment by others.
S-layers are highly structured protein layers that function like
Both are appendages made of protein
Singular: fimbria, pilus
Both used for attachment
Fimbriae: to surfaces (incl. host cells) and other bacteria.
Pili: to other bacteria for exchanging DNA (“sex”).
www.ai.mit.edu/people/ tk/ce/flagella-s.gifwww.bmb.leeds.ac.uk/.../icu8/ introduction/bacteria.html
Bacteria change how they move in response to chemicals
Bacteria move toward attractants (e.g. nutrients).
Bacteria move away from repellants.
In this figure, bacteria use up nutrients in the agar, then move outward to where more nutrients are, producing rings of growth.
Some bacteria move without flagella
Movement on a solid surface.
No visible organelles of locomotion.
Cells produce, move in slime trails.
Unrelated organism glide:
cyanobacteria; appear to glide by
Cells glide in groups, singly, and
can reverse directions.
Cytoplasm may also contain inclusions, gas vacuoles,
extended membrane systems, or magnetosomes.
But generally NO membrane-bound organelles.
Membrane coated pieces of magnetite, assist bacteria in moving to microaerophilic environments. An organelle?
North is down.
Both prokaryotes and eukaryotes.
Small molecules like
gases can diffuse
through the bilayer.
Larger or more
Mitochondrion Plasmalemma (cell membrane)nucleus, ribosomeslysozomeendoplasmic reticulumgolgi body