Transcript Bacteria - science4warriors

Bacteria
Chapter 23
Prokaryotes
 Are the most numerous organisms on earth.
 The earliest fossils are about 3.5 billion years old.
 Single celled organisms that do NOT have a
membrane bound nucleus
 Major source of food for many organisms
 Help to digest food
 Important as decomposers of dead organic matter
in the environment
Prokaryotes
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Domain Archaea
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 More closely related to
eukaryotes than bacteria
 Differ from bacteria in
their cell walls, membrane
lipids, their genetics, and
their metabolism.
 Archaea cell walls do
NOT have peptidoglycan
Domain Archaea continued
 First found in extreme environments like swamps,
salt lakes, and hot springs
 3 groups:
 Methanogens- produce methane
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 Halophiles-live in areas of high salt concentrations
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 Thermoacidophiles- lives in areas of high heat
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Domain Bacteria
 Most known prokaryotes
 Most are one of three basic shapes – bacilli
(rods), cocci (spheres), and spirilla (spiral
shaped).
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Domain Bacteria continued
 Streptococci – chains
of cocci
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 Staphylococci –
clusters of cocci
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Domain Bacteria continued
 Gram-negative
bacteria
 small amounts of
peptidoglycan – appear
reddish pink in color
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 Gram-positive bacteria
 larger amounts of
peptidoglycan – appear
purple
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Important Bacterial Groups
 1.
 2.
 3.
 4.
 5.
Proteobacteria (p.464)
Gram-Positive Bacteria (p.465)
Cyanobacteria (p.466)
Spirochetes (p.466)
Chlamydia (p.466)
Biology of Prokaryotes
Section 23.2
Structure and Function of
Prokaryotes
 Cell Wall – protects the cell and gives the cell its shape
 Cell Membrane – regulates the types of molecules that
move into and out of the cell.
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Structure and Function of
Prokaryotes continued
 Cytoplasm – contains
DNA, ribosomes, and
organic compounds
that are needed for
life.
 Chromosome –
carries genetic info.
From one generation
to the next
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Structure and Function of
Prokaryotes continued
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 Pilus – helps the
cell attach to
surfaces and other
cells during
conjugation
 Flagellum –
propels the cell by
rotating in a
whiplike motion
Structure and Function of
Prokaryotes continued
 Outer membrane – protects the cell against some
antibiotics (present only in gram-negative bacteria)
 Capsule – protects the cell and helps the cell attach to
other cells and surfaces
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Structure and Function of
Prokaryotes continued
 Plasmids – carries genes that are transferred
through genetic recombination – is a small
circular DNA loop
 Endospore – contains DNA, is a thickcoated, resistant structure
Nutrition and Metabolism
 *Heterotrophs
 Photoheterotrophs –
uses light energy but
gets its carbon from
other organisms
 Chemoheterotroph –
obtains both energy
and carbon from
other organisms
 *Autotrophs
 Photoautotroph – uses
light energy and gets
carbon from carbon
dioxide
 Chemoautotroph –
extracts energy from
inorganic compounds
and uses carbon
dioxide as a carbon
source
Prokaryotic Habitats
1. Obligate anaerobes – Cannot live where
oxygen is present
2. Facultative anaerobes – can live with or
without oxygen
3. Obligate aerobes – cannot live without
oxygen
Reproduction and Recombination
 Prokaryotes usually reproduce by binary fission
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 Can exchange pieces of DNA that can be added to
the cells DNA without reproduction –>
Recombination
Recombination
 Can happen three different ways
1) Transformation – prokaryote takes in DNA from
its environment
2) Conjugation – two prokaryotes bind together and
one cell transfers DNA to the other
3) Transduction – a virus obtains a small part of
DNA from a host prokaryote and then transfers it
to the next prokaryote
Bacteria and Humans
Section 23.3
Pathology
 the scientific study of disease. Bacteria and
other organisms that cause disease are
called pathogens.
a re
Qu ic kTi me ™ a n d a
d e c o mp re s so r
ne e d e d to s e e t hi s
p ic tu r e.
 Exotoxins
 toxic substances
that bacteria secrete
into the
environment
 Endotoxins
 toxic substances
that bacteria keep
inside the cell until
they die.
 Antibiotics –
chemicals that inhibit
the growth or kill
other microorganisms
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 Antibiotic resistance
– the evolution of
populations of
pathogenic bacteria
that antibiotics are
unable to kill
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Zoonosis
 a disease that can pass from animals to
humans.
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Bioremediation
 Process that bacteria recycle compounds.
Bacteria break down pollutants.
Ex: oil spills
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