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Evolution &Evolution & DiversityDiversity
Among theAmong the MicrobesMicrobes
BIOL BIOL 108 108 Intro to Bio Intro to Bio SciSci
Chapter Chapter 1313
Rob Rob SwatskiSwatski Assoc Prof Assoc Prof BiologyBiology
HACCHACC--YorkYork
Learning GoalsLearning Goals Learning GoalsLearning Goals
Know there are microbes
in all three domains
Know that bacteria may be
the most diverse of
all organisms
Describe how, in
humans, bacteria can have
harmful or beneficial
health effects
Discuss how
Archaea exploit
some of the most extreme habitats
Discuss how
viruses are at the
border between living and non-living
2
13.1–13.2 There are
microbes in all three domains.
13.1 Microbes are the simplest, 13.1 Microbes are the simplest, but most successful organisms on but most successful organisms on
earth.earth.
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How can a microbe function when How can a microbe function when its body is just a single cell?its body is just a single cell?
Amoeba as an example
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How would you decide whether How would you decide whether a group of organisms can be a group of organisms can be
considered successful? considered successful?
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Microbes Are Genetically DiverseMicrobes Are Genetically Diverse
>500,000 kinds
Millions more expected to be distinguished!
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Microbes Can Live Almost Anywhere Microbes Can Live Almost Anywhere and Eat Almost Anythingand Eat Almost Anything
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Microbes are
abundant!
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TakeTake--Home Message 13.1 Home Message 13.1
Microbes are simple, but they do everything
that multicellular organisms do.
Microbes are simple, but they do everything
that multicellular organisms do.
They can live anywhere, from
moderate to extreme environments.
They can live anywhere, from
moderate to extreme environments.
There are millions of different kinds of
microbes on earth, in enormous numbers.
There are millions of different kinds of
microbes on earth, in enormous numbers.
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13.2 Microbes are not all 13.2 Microbes are not all evolutionarily related.evolutionarily related.
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TakeTake--Home Message 13.2 Home Message 13.2
Microbes are organisms too small to see without
magnification and are grouped together only because they
are small, not because of evolutionary relatedness.
Microbes are organisms too small to see without
magnification and are grouped together only because they
are small, not because of evolutionary relatedness.
They occur in all three domains of life, and include viruses that are not in any of
the domains.
They occur in all three domains of life, and include viruses that are not in any of
the domains.
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13.3−13.5 Bacteria
may be the most
diverse of all
organisms.
13.3 What are bacteria?13.3 What are bacteria?
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TakeTake--Home Message 13.3 Home Message 13.3
Bacteria are efficient single-celled organisms, with an envelope surrounding the
cytoplasm, which contains the DNA (they have no nuclei and
no intracellular organelles).
Bacteria are efficient single-celled organisms, with an envelope surrounding the
cytoplasm, which contains the DNA (they have no nuclei and
no intracellular organelles).
Bacterial cells undergo binary fission, and a single cell can grow into a colony of cells.
Bacterial cells undergo binary fission, and a single cell can grow into a colony of cells.
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13.4 Bacterial growth and 13.4 Bacterial growth and reproduction is fast and reproduction is fast and
efficient.efficient.
20
Bacteria Carry Genetic Information in Bacteria Carry Genetic Information in Two StructuresTwo Structures
1) A circular DNA molecule called the chromosome (1 or more)
2) Circular DNA molecules called plasmids
• metabolic plasmids
• resistance plasmids
• virulence plasmids
21
Would it be useful to be able to Would it be useful to be able to transfer genetic information from transfer genetic information from
one adult human to another? one adult human to another?
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Bacterial ReproductionBacterial Reproduction
If bacteria can reproduce from one cell to thousands in a few hours, why don’t they totally
overrun life on earth?
27
Bacterial ReproductionBacterial Reproduction
A given bacterium has a generation time of one hour. This means that the number of bacteria present will double in one hour. Assume you start out with one
bacterial cell that reproduces by binary fission, which of course means that no other cell is needed for
reproduction to take place. How many cells will there
be after 24 hours?
28
TakeTake--Home Message 13.4 Home Message 13.4
Bacteria grow rapidly. Bacteria grow rapidly.
They have efficiently organized chromosomes—genes are organized in groups with
related functions and virtually all the DNA codes for proteins.
They have efficiently organized chromosomes—genes are organized in groups with
related functions and virtually all the DNA codes for proteins.
Bacteria sometimes carry the genes for specialized traits on small DNA molecules called
plasmids that can be transferred from one bacterial cell to another by conjugation.
Bacteria sometimes carry the genes for specialized traits on small DNA molecules called
plasmids that can be transferred from one bacterial cell to another by conjugation.
DNA can also be transferred laterally between bacterial
cells by transduction or transformation.
DNA can also be transferred laterally between bacterial
cells by transduction or transformation.
29
13.5 13.5 Metabolic diversity among the Metabolic diversity among the bacteria is extreme.bacteria is extreme.
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TakeTake--Home Message Home Message 13.5 13.5
Some bacteria eat organic molecules, some eat
minerals, and still other bacteria carry out photosynthesis.
Some bacteria eat organic molecules, some eat
minerals, and still other bacteria carry out photosynthesis.
About 2.6 billion years ago, the photosynthesizing
bacteria were responsible for the first appearance of free oxygen in the Earth's
atmosphere.
About 2.6 billion years ago, the photosynthesizing
bacteria were responsible for the first appearance of free oxygen in the Earth's
atmosphere. 34
13.6–13.9 In humans, bacteria can
have harmful or beneficial
health effects.
13.6 13.6 Many Many bacteria are bacteria are beneficial.beneficial.
36
You Owe Your Life to BacteriaYou Owe Your Life to Bacteria
Your normal flora
• benign bacteria that are your first line of defense against infection by harmful bacteria
Probiotic therapy
• a method of treating infections by deliberately introducing benign bacteria
37
TakeTake--Home Message Home Message 13.6 13.6
Your body fights bacteria with bacteria.
Your body fights bacteria with bacteria.
A disease-causing bacterium must colonize your body
before it can make you sick, and your body is already covered with harmless
bacteria.
A disease-causing bacterium must colonize your body
before it can make you sick, and your body is already covered with harmless
bacteria.
If the population of harmless bacteria is dense
enough, it will stop invading bacteria.
If the population of harmless bacteria is dense
enough, it will stop invading bacteria.
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13.7 Bacteria cause many 13.7 Bacteria cause many human diseases.human diseases.
Pathogenic Bacteria
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TakeTake--Home Message 13.7 Home Message 13.7
Some bacteria always cause disease and others do no harm
except under certain conditions.
Some bacteria always cause disease and others do no harm
except under certain conditions.
For example, Streptococcus pyogenes can be harmless, but
under some conditions it releases toxins that are responsible for strep throat, scarlet fever, and
necrotizing fasciitis (caused by the flesh-eating strains).
For example, Streptococcus pyogenes can be harmless, but
under some conditions it releases toxins that are responsible for strep throat, scarlet fever, and
necrotizing fasciitis (caused by the flesh-eating strains).
42
13.8 13.8 Bacteria’s resistance to Bacteria’s resistance to drugs can drugs can evolve evolve quicklyquickly..
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Where do antibiotics come Where do antibiotics come from, and why do they so from, and why do they so
quickly lose their effectiveness? quickly lose their effectiveness?
Chemicals that kill!
46
Bacteria and other microbes resist antibiotics in a variety of ways:
Pumping antibiotics out of their cell
Proteins that bind to the antibiotic molecule and block its lethal effect
Enzymes that break down the antibiotic
molecules that are then used as fuel to help the bacteria grow faster
47
Why is it essential to take every Why is it essential to take every dose of an antibiotic prescribed dose of an antibiotic prescribed
by a doctor?by a doctor?
48
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TakeTake--Home Message 13.8 Home Message 13.8
Microbes routinely evolve resistance to antibiotics.
Microbes routinely evolve resistance to antibiotics.
The genes that allow bacteria to combat antibiotics are located on
plasmids, and plasmid transfer allows an antibiotic-resistant
bacterium to pass that resistance to other bacteria.
The genes that allow bacteria to combat antibiotics are located on
plasmids, and plasmid transfer allows an antibiotic-resistant
bacterium to pass that resistance to other bacteria.
Excessive use of antibiotics in medicine and agriculture has
made several pathogenic bacteria resistant to every antibiotic, and
infections caused by these bacteria are nearly impossible to
treat.
Excessive use of antibiotics in medicine and agriculture has
made several pathogenic bacteria resistant to every antibiotic, and
infections caused by these bacteria are nearly impossible to
treat.
50
13.10–13.12 Archaea
exploit some of the most
extreme habitats.
13.10 13.10 ArchaeaArchaea are profoundly different are profoundly different from bacteria.from bacteria.
52
Additional Differences among Additional Differences among Bacteria, Bacteria, ArchaeaArchaea, and , and EukaryaEukarya
Chemical compositions of the plasma membranes, cell walls, and the flagellae
Eukarya have a distinct cell nucleus and a nuclear membrane; Bacteria and Archaea do not .
53
TakeTake--Home Message Home Message 13.10 13.10
Archaea show a set of characteristics that places them
between bacteria and eukaryotes on the tree of life.
Archaea show a set of characteristics that places them
between bacteria and eukaryotes on the tree of life.
Archaea and bacteria may look similar, but they have large and significant differences in their
DNA sequences, as well as differences in their plasma membranes, cell walls, and
flagella.
Archaea and bacteria may look similar, but they have large and significant differences in their
DNA sequences, as well as differences in their plasma membranes, cell walls, and
flagella.
Furthermore, neither archaea nor bacteria resemble eukarya in one key way: only eukarya have a distinct cell nucleus and nuclear
membrane.
Furthermore, neither archaea nor bacteria resemble eukarya in one key way: only eukarya have a distinct cell nucleus and nuclear
membrane.
54
13.11 13.11 ArchaeaArchaea thrive in habitats thrive in habitats too extreme for most other too extreme for most other
organisms.organisms.
55
ExtremophilesExtremophiles
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TakeTake--Home Message Home Message 13.11 13.11
Archaeans can tolerate extreme physical and chemical conditions
that are impossible for most other living organisms, but they also live in moderate conditions
and even in the human intestine.
Archaeans can tolerate extreme physical and chemical conditions
that are impossible for most other living organisms, but they also live in moderate conditions
and even in the human intestine.
58
13.12 13.12 Much Much ArchaeanArchaean diversity has diversity has yet to be discovered.yet to be discovered.
59
Important applications in Important applications in bioengineering and bioengineering and
environmental remediationenvironmental remediation
60
Enormous Potential for Industries: Enormous Potential for Industries: BioremediationBioremediation
Degrade hydrocarbon
Clearing mineral deposits from pipes in the cooling systems of power plants
61
TakeTake--Home Message Home Message 13.12 13.12
Archaea are hard to study because many require
extreme heat or pressure to grow, and these conditions are not easy to provide in a
laboratory.
Archaea are hard to study because many require
extreme heat or pressure to grow, and these conditions are not easy to provide in a
laboratory.
But the ability of archaea to grow in such extreme
conditions makes them potentially valuable for
industrial and environmental purposes.
But the ability of archaea to grow in such extreme
conditions makes them potentially valuable for
industrial and environmental purposes.
62
13.16–13.19 Viruses are
at the border
between living and non-living.
13.16 13.16 Viruses are not exactly living Viruses are not exactly living organisms.organisms.
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TakeTake--Home Message Home Message 13.16 13.16
A virus is not alive, but it can carry out some of the same functions as living
organisms, provided that it can get inside a cell.
A virus is not alive, but it can carry out some of the same functions as living
organisms, provided that it can get inside a cell.
A virus takes over the protein-making machinery of the host cell to produce more viral genetic material
(RNA or DNA) and more viral protein.
A virus takes over the protein-making machinery of the host cell to produce more viral genetic material
(RNA or DNA) and more viral protein.
The viral proteins and genetic material are
assembled into new virus particles and released from
the cell.
The viral proteins and genetic material are
assembled into new virus particles and released from
the cell.
66
13.17 13.17 Viruses are responsible for Viruses are responsible for many health problems.many health problems.
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Why do flu viruses change quickly?Why do flu viruses change quickly?
DNA vs. RNA viruses
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TakeTake--Home Message Home Message 13.17 13.17
Many diseases are caused by viruses.
Many diseases are caused by viruses.
DNA viruses are relatively stable because DNA
replication enzymes check for errors and correct
them during replication.
DNA viruses are relatively stable because DNA
replication enzymes check for errors and correct
them during replication.
RNA viruses change quickly because RNA
replication enzymes do not have error- checking
mechanisms.
RNA viruses change quickly because RNA
replication enzymes do not have error- checking
mechanisms.
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13.18 13.18 Viruses infect a wide Viruses infect a wide range of organisms.range of organisms.
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What role does a pig play in the What role does a pig play in the transmission of virus from a bird transmission of virus from a bird
to a human? to a human?
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Bird FluBird Flu
So far requires close contact with infected flocks of birds or by eating birds that had died of the virus.
WHO and national health agencies are preparing for a worldwide pandemic.
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Mixing RNAMixing RNA
Pig + bird flu virus + human virus = might produce a new form of the virus that carries the genes that make the bird flu lethal to humans AND the gene that codes for the host-entry glycoprotein.
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TakeTake--Home Message Home Message 13.18 13.18
Glycoproteins on the surfaces of viruses
determine what cells they can invade.
Glycoproteins on the surfaces of viruses
determine what cells they can invade.
Most viruses infect just one species, or only a few
closely related species, and enter only one kind of cell in that species.
Most viruses infect just one species, or only a few
closely related species, and enter only one kind of cell in that species.
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