Transcript No Slide Title

BACTERIA (Ch. 24)
AND
VIRUSES (Ch. 25)
BACTERIA:
Simplest & most
primitive
life forms
(fossils from 3.5 bya)
2 Kingdoms:
Archaebacteria
Eubacteria
Archaebacteria:
“ancient bacteria”
live in extreme
environments
Thermoacidophile:
thrives in hot,
acidic
environments
Halophile:
thrives in
salty
environments
Methanogen:
thrives in
methane-rich
environment
Eubacteria
“true bacteria”
live in “normal”
environments
Simple Structure:
PROKARYOTE
no nucleus or
membrane-bound
organelles
Chromosome
is in one loop,
not in pairs
Chromosome # 1
Have ribosomes;
needed to make
structural proteins
and enzymes
Cell Wall:
Some cell walls have
a thick layer of
peptidoglycan, a
carbohydrate
Gram Positive:
stains purple;
stain is held by
peptididoglygan
layer
Gram Positive
Gram Negative:
Stains pink; stain
resistant since
there is a layer
over the
peptididoglycan
layer
Gram Negative
Cell Parts:
Classified by
Shapes
1.Bacillus: ovals
2.Coccus: round
3.Spirillus: wavy
or bent
Configurations:
Diplo: in pairs
Diplococcus
Strepto: in
chains
Streptococcus
Streptobacillus
Staphylo:
in clusters
Reproduction:
Binary Fission
Rapid life
cycle since
there is no
mitosis
Some genetic
recombination
by three
different
methods:
1.Conjugation
Two bacteria join up at
the pili (conjugation
bridge) and exchange a
small loop of DNA that
has detached from the
main DNA (plasmid)
The plasmid is incorporated into the DNA
of the receiving cells
conjugation
bridge
Transformation:
•Substitutes new
DNA for a similar
fragment in its
original DNA
Transformation:
Transduction:
•A virus obtains a piece
of DNA from host
bacterium
•Virus transfers DNA
to new cell that it
infects
Transduction:
NUTRITION:
AUTOTROPHIC
by photosynthesis
or chemosynthesis
Heterotrophic:
many are
saprophytic-eat dead stuff
METABOLISM/
RESPIRATION:
Obligate Aerobe
Must have Oxygen
to survive
Obligate
Anaerobe:
Can only survive
in the absence
of oxygen
Facultative
Anaerobe:
Can live with or
without
oxygen
Effects on
Humans:
•Decomposers
•Food & Drug
industries
•Clean up toxic
waste naturally
•Natural
pesticides
Nitrogen
fixation
Extract nitrogen
from the
environment for
plants to use
•Cause diseases
by releasing
toxins
into host
organism
Exotoxins:
•Produced by Gram
positive cells
•Toxins constantly
produced and steadily
released by cell
•Protein-based toxins
Endotoxins:
•Produced by Gramnegative cells
•Toxins released when
bacterium dies
•Lipid or carbohydrate
based toxins
How can we
control bacteria?
Antibiotics!
Wash hands!
Good sanitation!
Pasteurization
Immunizations!
Safe sex!!!
Problem:
ANTIBIOTIC RESISTANCE
•From overuse (antibiotics only
work on gram-positive
bacteria; doctors have
prescribed for any bacteria
and also viruses
•Patients don’t take all
prescribed medication, as
directed
•Bacterial mutations occur
that also result in
resistance
Example: Tuberculosis
used to respond to
penicillin but now it
doesn’t