Bacterial Cells
Their Structure
Structure of a Bacterial Cell
Cell Wall
•Outside membrane- maintains cell
structure
•May have cell wall + capsule (second
wall)
•Protects the cell
•Eubacteria-composed of peptidoglycan,
a polymer of sugars and amino acids
Plasma Membrane
•Controls what enters and exits, selectively
permeable
•phospholipid bilayer surrounding cell
http://en.wikipedia.org/wki/Image:Average_prokaryote_cell-_en.svg
•contains proteins that play a role in
transport of ions, nutrients, and wastes
Flagella (not found in all bacteria)
•tail-like structure used for locomotion
Structure of a Bacterial Cell
Nucleoid
•region DNA is found in prokaryotes
•single double-stranded circular
chromosome
•Contains all genetic information
Plasmid (some bacteria)
•small circular chromosome carrying
special genes
•may carry an antibiotic resistance
gene
•Can be exchanged through
conjugation
http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg
Ribosomes
•site of protein synthesis
(translation)
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard
Bacterial Structure
• Ribisomes
– Bacteria have
ribosomes that make all
proteins for the cell
• Respiratory Enzymes
– Use enzymes in the
cytoplasm to undergo
respiration
• Cytoplasm
– Fluid filling cell
Two Kingdoms of Bacteria
• Kingdom Archaebacteria
- “Ancient”, most primitive
earliest known form of life
-
•Kingdom Eubacteria
- includes bacteria and
Fluorescent micrograph
of an archaeon
cyanobacteria (blue-green)
microbeworld.org
Eubacteria
EUBACTERIA
the “true” bacteria- more common
Cell Walls
• eubacterial cells have two different cell wall
structures. A technique called gram staining
can distinguish between:
– Gram-positive: cell wall containing mainly
peptidoglycan- stains purple
– Gram-negative: bacterial cell has a second, outer
layer of lipids and carbs- stains pink
Kingdom Eubacteria
Photosynthetic – 2 groups
1) cyanobacteria (aerobes)
–Have chlorophyll a
and phycocyanin (blue)
–Other colors, too
–Most live in fresh water
–Others live in salt water,
soil and lichens
Nostoc
Schraer, 637
Starr, 315
More photosynthetics
2) green-sulfur and purple bacteria
- anaerobic
- colors range from pink to black
- photosynthesize without water
- make no oxygen
- live in pond and sea mud
Cyanobacteria
This is a group of bacteria that
includes some that are single
cells and some that are chains
of cells. You may have seen
them as "green slime" in your
aquarium or in a pond.
Cyanobacteria can do "modern
photosynthesis", which is the
kind that makes oxygen from
water. All plants do this kind of
photosynthesis and inherited
the ability from the
cyanobacteria.
Cyanobacteria were the first organisms on Earth to do modern
photosynthesis and they made the first oxygen in the Earth's
atmosphere.
Biologic Importance of
Bacteria
1) Essential to nutrient cycling
2) Decomposers – in soil, inside animals
Enterobacteria – live inside us,
break down waste, make vitamins
3) Process foods – cheese, yogurt etc..
4) Some MAKE antibiotics (streptomyacin)
5) Aid in human digestion- make vitamins
• Many Bacteria live symbiotically in the guts of
animals or elsewhere in their bodies.
• For example, bacteria in your gut produce
vitamin K which is essential to blood clot
formation.
Bacterial uses cont.
6) Help with sewage treatment
– Break down wastes
7) Can be utilized in genetic engineering,
molecular research…
– Insert foreign genes into new organism
– Can be used to make specialized products like
insulin
8) Indicate pollution levels
– Provide visual clue to presence of pollution
9) Nitrogen Fixation
– Still other Bacteria live
on the roots of certain
plants, converting
nitrogen into a usable
form.
Some cause disease
We call these “pathogens”
Anthrax, as seen by Koch
microbeworld.org
But most are
beneficial
Bacteria ferment cheese
Schraer, 641
Archae are extremophiles
Live in habitats like early earth
Too harsh for most organisms
1) methanogens – decomposers,
live in intestines, swamps & bogs
sewage treatment
2)
Halophiles
– “love salt”
Great Salt Lake, Dead Sea
Thermophiles – hot springs, geysers
4) Acidophiles – acidic environments
3)
Starr,635
Kingdom Archaebacteria
Why a separate kingdom?
Archae differ chemically from other bacteria.
1) cell wall - different amino acids and sugars.
Eubacteria have peptidoglycan
Archaebacteria have varied polysaccharides
but not peptidoglycan.
2) membrane lipids
3) ribosomes
4) enzymes - - - - - - - - - - - - >
5) gene sequences . . . And MORE
RNA polymerase
Archaebacteria
• Lack important
carbohydrate found in
cell walls
• Have different lipids
in their cell
membrane
• Different types of
ribosomes
• Very different gene
sequences
• Archaebacteria can
live in extremely
harsh environments
• They do not require
oxygen and can live in
extremely salty
environments as well
as extremely hot
Archaea, the “extremophiles”
methanogens, thermophiles, halophiles
Eubacteria and Archaebacteria
Chemosynthetic
make glucose using energy
from chemical compounds
**Mostly archae
Tube worms at ocean vent
Fed by chemoautotrophs
Nitrogen-fixing
Starr, 745
Fix nitrogen in special
cells called heterocysts
Legume roots – nodules contain
nitrogen-fixing bacteria
Starr, 314