Microbes are the simplest but most successful organisms on Earth. They exist in all three domains of life and can live in nearly any environment. Bacteria may be the most diverse group of organisms and exist in many forms, including pathogens. In humans, bacteria can have both harmful and beneficial health effects. Archaea inhabit some of the most extreme environments and their diversity remains largely undiscovered. Viruses exist at the boundary between living and non-living, replicating only inside host cells and causing many diseases in organisms.

1. Evolution &Evolution &
DiversityDiversity
Among theAmong the
MicrobesMicrobes
BIOLBIOL 108108
Intro to BioIntro to Bio SciSci
ChapterChapter 1313
RobRob SwatskiSwatski
Assoc ProfAssoc Prof BiologyBiology
HACCHACC--YorkYork

2. Learning GoalsLearning GoalsLearning 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

3. 13.1–13.2
There are
microbes in
all three
domains.

4. 13.1 Microbes are the simplest,13.1 Microbes are the simplest,
but most successful organisms onbut most successful organisms on
earth.earth.
4

5. How can a microbe function whenHow can a microbe function when
its body is just a single cell?its body is just a single cell?
Amoeba as an example
5

6. 6

7. How would you decide whetherHow would you decide whether
a group of organisms can bea group of organisms can be
considered successful?considered successful?
7

8. Microbes Are Genetically DiverseMicrobes Are Genetically Diverse
 >500,000 kinds
 Millions more expected to be distinguished!
8

9. Microbes Can Live Almost AnywhereMicrobes Can Live Almost Anywhere
and Eat Almost Anythingand Eat Almost Anything
9

10. Microbes
are
abundant!
10

11. TakeTake--Home Message 13.1Home 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.
11

12. 13.2 Microbes are not all13.2 Microbes are not all
evolutionarily related.evolutionarily related.
12

13. 13

14. TakeTake--Home Message 13.2Home 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.
14

15. 13.3−13.5
Bacteria
may be the
most
diverse of
all
organisms.

16. 13.3 What are bacteria?13.3 What are bacteria?
16

17. 17

18. 18

19. TakeTake--Home Message 13.3Home 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.
19

20. 13.4 Bacterial growth and13.4 Bacterial growth and
reproduction is fast andreproduction is fast and
efficient.efficient.
20

21. Bacteria Carry Genetic Information inBacteria 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

22. Would it be useful to be able toWould it be useful to be able to
transfer genetic information fromtransfer genetic information from
one adult human to another?one adult human to another?
22

23. 23

24. 24

25. 25

26. 26

27. 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

28. 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

29. TakeTake--Home Message 13.4Home 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

30. 13.513.5 Metabolic diversity among theMetabolic diversity among the
bacteria is extreme.bacteria is extreme.
30

31. 31

32. 32

33. 33

34. TakeTake--Home MessageHome Message 13.513.5
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

35. 13.6–13.9
In humans,
bacteria can
have
harmful or
beneficial
health effects.

36. 13.613.6 ManyMany
bacteria arebacteria are
beneficial.beneficial.
36

37. 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

38. TakeTake--Home MessageHome Message 13.613.6
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.
38

39. 13.7 Bacteria cause many13.7 Bacteria cause many
human diseases.human diseases.
Pathogenic Bacteria
39

40. 40

41. 41

42. TakeTake--Home Message 13.7Home 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

43. 13.813.8 Bacteria’s resistance toBacteria’s resistance to
drugs candrugs can evolveevolve quicklyquickly..
43

44. 44

45. 45

46. Where do antibiotics comeWhere do antibiotics come
from, and why do they sofrom, and why do they so
quickly lose their effectiveness?quickly lose their effectiveness?
Chemicals that kill!
46

47. 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

48. Why is it essential to take everyWhy is it essential to take every
dose of an antibiotic prescribeddose of an antibiotic prescribed
by a doctor?by a doctor?
48

49. 49

50. TakeTake--Home Message 13.8Home 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

51. 13.10–13.12
Archaea
exploit some
of the most
extreme
habitats.

52. 13.1013.10 ArchaeaArchaea are profoundly differentare profoundly different
from bacteria.from bacteria.
52

53. Additional Differences amongAdditional 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

54. TakeTake--Home MessageHome Message 13.1013.10
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

55. 13.1113.11 ArchaeaArchaea thrive in habitatsthrive in habitats
too extreme for most othertoo extreme for most other
organisms.organisms.
55

56. ExtremophilesExtremophiles
56

57. 57

58. TakeTake--Home MessageHome Message 13.1113.11
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

59. 13.1213.12 MuchMuch ArchaeanArchaean diversity hasdiversity has
yet to be discovered.yet to be discovered.
59

60. Important applications inImportant applications in
bioengineering andbioengineering and
environmental remediationenvironmental remediation
60

61. Enormous Potential for Industries:Enormous Potential for Industries:
BioremediationBioremediation
 Degrade hydrocarbon
 Clearing mineral deposits from pipes in the
cooling systems of power plants
61

62. TakeTake--Home MessageHome Message 13.1213.12
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

63. 13.16–13.19
Viruses are
at the
border
between
living and
non-living.

64. 13.1613.16 Viruses are not exactly livingViruses are not exactly living
organisms.organisms.
64

65. 65

66. TakeTake--Home MessageHome Message 13.1613.16
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

67. 13.1713.17 Viruses are responsible forViruses are responsible for
many health problems.many health problems.
67

68. Why do flu viruses change quickly?Why do flu viruses change quickly?
DNA vs. RNA viruses
68

71. TakeTake--Home MessageHome Message 13.1713.17
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.
71

72. 13.1813.18 Viruses infect a wideViruses infect a wide
range of organisms.range of organisms.
72

73. 73

74. What role does a pig play in theWhat role does a pig play in the
transmission of virus from a birdtransmission of virus from a bird
to a human?to a human?
74

75. 75

76. 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.
76

77. 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.
77

78. TakeTake--Home MessageHome Message 13.1813.18
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.
78