Download I.What is a bacterium?

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Animal Plant
Heterotroph/
Autotroph/
Both
Mulitcellular/
Unicellular
Cell Wall?
If so, what
material?
Prokaryote/
Eukaryote
Fungi Protist Eubacteria
Archea
I.What is a bacterium?
A. Unicellular prokaryote.
DNA
bacterial
flagellum
capsule
pilus
plasma
membrane
cell
wall
ribosomes
in cytoplasm
cytoplasm
Fig. 22.3, p. 356
Slide 3
I.What is a bacterium?
B. Anatomy
1. Cell Wall – often made of peptidoglycan
2. DNA – usually in single, circular strand
3. Plasmids – extra DNA, codes for nonvital
traits
4. Ribosomes – assemble amino acids
5. Flagellum – movement
6. Plasma Membrane – under cell wall
7. Pilus – use for attachement
I.What is a bacterium?
C. Bacterial Shapes
coccus
bacillus
spirillum
in-text, p. 356
Slide 4
I.What is a bacterium?
D. Bacterial Classification
1. Gram Positive/Negative
Gram Positive
display
peptidoglycan
in cell wall.
I.What is a bacterium?
D. Bacterial Classification
2. Metabolism:
a. Photoautotroph: Use light as energy
source.
b. Chemoautotroph: Autotrophs that
use inorganic compounds as energy
source.
c. Heterotroph
II. Bacterial Growth and Reproduction
A. Asexual: Prokaryotic Fission
Circular DNA (lacking histones)
replicates, then is divided between two
new cells.
a Bacterium (cutaway view)
before DNA replication. The
bacterial chromosome is
attached to the plasma
membrane.
b DNA replication starts. It
proceeds in two directions
away from the same site in
the bacterial chromosome.
c The new copy of DNA is
attached at a membrane site
near the attachment site of
the parent DNA molecule.
d New membrane grows
between the two attachment
sites. As it increases, it moves
the two DNA molecules apart.
e At the cell midsection,
deposits of new membrane
and new wall material extend
down into the cytoplasm.
f The ongoing, organized
deposition of membrane and wall
material at the cell midsection
divides the cell in two.
Fig. 22.7, p. 358
II. Bacterial Growth and Reproduction
B. Sexual Recombination: Bacterial Conjugation
A plasmid (extrachromosomal DNA) can be
transferred from one bacterium to another
through the extension of a sex pilus.
nicked plasmid
conjugation tube
a A conjugation tube has already formed between
a donor and a recipient cell. An enzyme has nicked
the donor’s plasmid.
b DNA replication starts on the nicked plasmid.
The displaced DNA strand moves through the tube
and enters the recipient cell.
c In the recipient cell, replication starts on the
transferred DNA.
d The cells separate from each other; the plasmids
circularize.
Fig. 22.8, p. 359
II. Bacterial Growth and
Reproduction
C. Transduction: DNA transferred through
virus
When a virus infects a bacterium, it may
transfer bacterial DNA when it infects
other bacteria.
III. Bacterial Diversity
Prokaryotes are too diverse to fit into one
kingdom, ‘Monera’
A. Archea: Extremophiles, Live in extreme
environments.
1. Methanogens: Swamps, animals guts;
anaerobic.
2. Halophiles: Salt-loving
3. Thermophiles: Heat-loving
III. Viruses
A.
B.
C.
D.
Noncellular Infectious Agent
Contain either DNA or RNA (never both)
Have outer protein coat (capsid)
May have tail or other attachment
adaptation
E. Smaller than bacterium
III. Viral Infection
A. There are four stages to a viral infection:
• Attachment – the virus must be of the correct shape to ‘fool’ a
host cell into importing the genetic material (remember, large
and charged items can’t pass through a cell membrane, so the
virus can’t just pass through with no resistance).
• Penetration – the entire virus, or just the genetic material, is
injected into the host cell.
• Assembly – the viral DNA is read and transcribed by the host
cell. In some cases, restriction enzymes cut the host DNA and
the viral genes are inserted directly into the host genome (this
is how the first restriction enzymes were discovered).
• Release – once the viral genetic material has been translated,
the new viruses are released from the cell and are set to infect
other cells.
LYTIC PATHWAY
e Lysis of host cell is
induced; infections
particles escape.
d Tail fibers and other
parts are added to coats.
a Virus particles bind to
wall of suitable host cell.
Viral genetic material
enters cell cytoplasm.
c Viral protein molecules
are assembled into coats;
DNA is packaged inside.
Fig. 22.18a, p. 366
IV. Viral Infection
B. Lytic Virus: Cause host cell to lyse, or
burst.
C. Lysogenic Virus: Displays latent period,
during which virus DNA is inserted into
host DNA and ‘quietly’ replicates.
D. Retrovirus: Insert RNA, then use ‘reverse
transcriptase’ to copy back into DNA.