The Origin and Evolution of Microbial Life: Prokaryotes and Protists

1
Chapter 16
0

• The Origin and Evolution of Microbial Life
  Prokaryotes and Protists

2
0

• How Ancient Bacteria Changed the World
• Mounds of rock found near the Bahamas
• Contain photosynthetic prokaryotes

3

• Fossilized mats 2.5 billion years old mark a time
  when photosynthetic prokaryotes
• Were producing enough O2 to make the atmosphere
  aerobic

4
EARLY EARTH AND THE ORIGIN OF LIFE

• 16.1 Life began on a young Earth
• Planet Earth formed some 4.6 billion years ago

5

• The early atmosphere probably contained
• H2O, CO, CO2, N2, and some CH4
• Volcanic activity, lightning, and UV radiation
  were intense

Figure 16.1A
6

• Fossilized prokaryotes called stromatolites
• Date back 3.5 billion years

Figure 16.1B
7

• A clock analogy tracks the origin of the Earth to
  the present day
• And shows some major events in the history of
  Earth and its life

Figure 16.1C
8

• 16.2 How did life originate?
• Organic molecules
• May have been formed abiotically in the
  conditions on early Earth

9
TALKING ABOUT SCIENCE

• 16.3 Stanley Millers experiments showed that
  organic molecules could have arisen on a lifeless
  earth

Figure 16.3A
10

• Simulations of such conditions
• Have produced amino acids, sugars, lipids, and
  the nitrogenous bases found in DNA and RNA

Figure 16.3B
11

• 16.4 The first polymers may have formed on hot
  rocks or clay
• Organic polymers such as proteins and nucleic
  acids
• May have polymerized on hot rocks

12

• 16.5 The first genetic material and enzymes may
  both have been RNA
• The first genes may have been RNA molecules
• That catalyzed their own replication

Figure 16.5
13

• 16.6 Membrane-enclosed molecular cooperatives may
  have preceded the first cells
• RNA might have acted as templates for the
  formation of polypeptides
• Which in turn assisted in RNA replication

Figure 16.6A
14

• Membranes may have separated various aggregates
  of self-replicating molecules
• Which could be acted on by natural selection

Figure 16.6B, C
15
PROKARYOTES

• 16.7 Prokaryotes have inhabited Earth for
  billions of years
• Prokaryotes are the oldest life-forms
• And remain the most numerous and widespread
  organisms

Figure 16.7
16
More bacteria inhabit a handful of soil than the
total number of people who have ever lived!

• Bacteria grow in extreme conditions (unsuitable
  for eukaryotes)
• Too Cold
• Too Hot
• Too salty
• Too acidic
• Too alkaline
• Bacteria have high genetic diversity
• Most prokaryotic cells have diameters in the
  range of 1 5 µm

17
Infamous Bacteria

• Bubonic Plague
• Yesinia pestis
• Tuberculosis
• Mycobacterium tuberculosis
• Cholera
• Vibrio cholerae

18
Not all bacteria is bad

• Bacteria in our intestines provide us with
  important vitamins
• There are approximately 100 trillion bacteria
  living inside each human. Ideally, the body
  should have at least 85 good bacteria for
  optimal health.
• Proper digestion of foodAbsorption of
  nutrientsProduction of vitaminsElimination of
  toxins.Prevention from allergies, since good
  bacteria allow the body to distinguish between
  harmful substances and healthy ones.

19
Not all bacteria is bad cont.,

• Bacteria in our mouth protect us against some
  harmful fungi
• candida fungus - thrush
• Bacteria that decompose dead organism
  (detritovoures)

20

• 16.8 Bacteria and archaea are the two main
  branches of prokaryotic evolution
• Domains Bacteria and Archaea
• Are distinguished on the basis of nucleotide
  sequences and other molecular and cellular
  features

21

• Differences between Bacteria and Archaea

Archaea have characteristics that resemble
prokaryotes (bacteria) and eukaryotes. One
theory is that present day archaea and eukaryotes
evolved from a common ancestor.
Table 16.8
22
Other differences between bacteria and archaea

• Domain Bacteria
• Cell wall
• Provides shape and protection
• peptidoglycan
• Plasma membrane
• Archaea
• Do not contain peptidoglycan
• Lipid structure of the plasmid membrane is
  different.

23

• 16.9 Prokaryotes come in a variety of shapes
• Prokaryotes may be shaped as
• Spheres (cocci)
• Rods (bacilli)
• Most bacillus occur singly
• Some in pairs or diplobacilli or chains
  streptobacilli
• Curves or spirals
• Syphilis - spirochete

Figure 16.9AC
24
The arrangement of the bacteria lends to its name

• Staphylo
• Clusters
• staphylococcus
• Strepto
• Chains
• Streptococcus
• streptobacilli

25
16.10 Various structural features contribute to
the success of prokaryotes

• External Structures
• The cell wall
• Is one of the most important features of nearly
  all prokaryotes
• Is covered by a sticky capsule

Figure 16.10A
26

• Some prokaryotes
• Stick to their substrate with pili

Figure 16.10B
27
Motility

• Many bacteria and archaea
• Are equipped with flagella, which enable them to
  move

Figure 16.10C
28
Reproduction and Adaptation

• Prokaryotes
• Have the potential to reproduce quickly in
  favorable environments
• Binary fission
• Most produce a new generation in 1- 3 hours
• Some can reproduce every 20 minutes!

29

• Some prokaryotes can withstand harsh conditions
• By forming endospores
• Thick, protective coating
• Dehydrates and becomes dormant
• It has the capacity to survive harsh conditions
• Some endospores remain dormant for centuries

Figure 16.10D
30

• Internal Organization
• Some prokaryotic cells
• Have specialized membranes that perform metabolic
  functions
• Aerobic, photosynthesis anaerobic
• Aerobic cyanobacteria

Figure 16.10E
31
16.11 Prokaryotes obtain nourishment in a variety
of ways

• As a group
• Prokaryotes exhibit much more nutritional
  diversity than eukaryotes
• Autotrophs
• Photoautotrophs
• Chemoautotrophs
• Heterotrophs
• Photoheterotrophs
• Chemoheterotrophs

32
Types of Nutrition

• Autotrophs make their own organic compounds from
  inorganic sources
• Photoautotrophs harness sunlight for energy and
  use CO2 for carbon
• Chemoautotrophs obtain energy from inorganic
  chemicals instead of sunlight
• H2S S Fe containing compounds

33

• Most prokaryotes are Heterotrophs (other feeders)
  they obtain their carbon atoms from organic
  compounds
• Photoheterotrophs can obtain energy from sunlight
• Chemoheterotrophs are so diverse that almost any
  organic molecule can serve as food for some
  species

Figure 16.11A
34

• Nutritional classification of organisms

Table 16.11
35

• Metabolic Cooperation
• In some prokaryotes
• The cyanobacteria has genes for photosynthesis
  and for nitrogen fixation (N2 ? NH3), but the O2
  production inactivates the nitrogen fixing enzyme
• To combat this they form colonies in which most
  cells photosynthesize, while others fix nitrogen

Figure 16.11B
36
Metabolic cooperation occurs in surface-coating
colonies called biofilms
37
16.12 Archaea thrive in extreme environments and
in other habitats

• 16.12 Archaea thrive in extreme environmentsand
  in other habitats
• Archaea are common in
• Salt lakes, acidic hot springs, deep-sea
  hydrothermal vents

Figure 16.12A, B
38
Extreme Halophiles

• Thrive in very salty places
• Great Salt Lakes
• Dead Sea

39
Extreme Thermophiles

• Heat loving
• Some live neat deep ocean vents where
  temperatures reach up to 100C
• Some thrive in acid

40
Methanogens

• Aerobic environments and give off methane
• They can be found in digestive tracts of cows,
  human and swamps.

41
16.13 Bacteria include a diverse assemblage of
prokaryotes

• Domain Bacteria is currently divided into nine
  groups, five of which are considered subgroups.
• Proteobacteria
• Chlamydias
• Spirochetes

Figure 16.13A, B
42
Subgroups cont.,

• Gram-positive bacteria
• Cell walls have thick layer of peptidoglycan
  which stains purple.
• Cyanobacteria, which photosynthesize in a
  plantlike way

Figure 16.13C, D
43
CONNECTION

• 16.14 Some bacteria cause disease
• Pathogenic bacteria cause disease by producing
• exotoxins or endotoxins
• Gram negative species are generally more
  threatening than gram positive .
• The lipids on the outer membranes are often toxic.

Figure 16.14A, B
44
Pathogenic bacteria cause about half of all human
diseases

• 2 million die from TB each year
• 2 million dies from diarrheal causing pathogens
  such as
• cholera
• Samonella
• campylobacter.

45

• Exotoxins
• secreted by bacterial cells and include some of
  the most potent poisons known, such as
• Botulinum toxin
• Endotoxins
• are part of the outer membrane of the cell wall
  of Gram-negative bacteria.
• Properly refer to as
• lipopolysaccharide complex
• pathogens such as Escherichia coli, Salmonella,
  Shigella, Pseudomonas, Neisseria, Haemophilus
  influenzae, Bordetella pertussis and Vibrio
  cholerae.

46
Preventing Bacterial Disease

• Sanitation
• Water treatment systems
• Sewage systems
• Antibiotics
• Education
• Lyme Disease
• Transmitted by ticks that attach to dear and mice
• Disease leads to debilitating arthritis, heart
  disease and nervous disorders
• Classic signs are the red-bulls eye target rash
• Using insect repellent and wear light colored
  clothing may help reduce contact with tics

47
Compare and contrast Exotoxins and Endotoxins
48
CONNECTION

• 16.15 Bacteria can be used as biological weapons
• Bacteria, such as the species that causes anthrax
  
• Can be used as biological weapons

Figure 16.15
49
Use of Bacteria as a weapon

• Anthrax spores mailed to Congress in 2001
  resulted in the death of 5 people and illness to
  18 others.
• During the middle ages, armies hurled individuals
  killed by bubonic plague at the enemy.
• Early settlers in South and North America gave
  the native American people items that purposely
  were contaminated with infectious bacteria often
  wiping out whole tribes.

50
Why is Bacillus Anthracis an effective bioweapon?

• It is easy to obtain
• Spore forming bacterium that lives in the soil of
  agricultural regions
• Easy to grow in the lab
• Form deadly endospores that are resistant to
  extreme conditions and can be stored for long
  periods.
• Easy to disperse

51
CONNECTION

• 16.16 Prokaryotes help recycle chemicals and
  clean up the environment
• All of life depends on the cycling of chemical
  elements between organisms and the nonliving
  parts of our environment.
• Rhizobium live in the nodules of legumes
• Convert large amounts of nitrogen gas to nitrates
  in the soil.
• Cyanobacteria
• Contribute to aquatic environmnets
• Release oxygen to the atmosphere
• Convert nitrogen gas to ammonium

52
Bioremediation

• The use of organisms to clean up pollution
• Prokaryotes are decomposers in
• Sewage treatment and can clean up oil spills and
  toxic mine wastes

53
PROTISTS

• 16.17 The eukaryotic cell probably originated as
  a community of prokaryotes
• Eukaryotic cells
• Evolved from prokaryotic cells more than 2
  billion years ago

54

• The nucleus and endomembrane system
• Probably evolved from infoldings of the plasma
  membrane

55

• Mitochondria and chloroplasts
• Probably evolved from aerobic and photosynthetic
  endosymbionts, respectively

56

• A model of the origin of eukaryotes

Figure 16.17
57

• 16.18 Protists are an extremely diverse
  assortment of eukaryotes
• Protists
• Are mostly unicellular eukaryotes
• Molecular systematics
• Is exploring eukaryotic phylogeny

Figure 16.18
58

• 16.19 A tentative phylogeny of eukaryotes
  includes multiple clades of protists
• The taxonomy of protists
• Is a work in progress

Figure 16.19
59

• 16.20 Diplomonads and euglenozoans include some
  flagellated parasites
• The parasitic Giardia
• Is a diplomonad with highly reduced mitochondria

Figure 16.20A
60

• Euglenozoans
• Include trypanosomes and Euglena

Figure 16.20B, C
61

• 16.21 Alveolates have sacs beneath the plasma
  membrane and include dinoflagellates,
  apicomplexans, and ciliates
• Dinoflagellates
• Are unicellular algae

Figure 16.21A
62

• Apicomplexans are parasites
• Such as Plasmodium, which causes malaria

Figure 16.21B
63

• Cilliates
• Use cilia to move and feed

Figure 16.21C
64

• 16.22 Stramenopiles are named for their hairy
  flagella and include the water molds, diatoms,
  and brown algae
• This clade includes
• Fungus-like water molds

Figure 16.22A
65

• Photosynthetic, unicellular diatoms

Figure 16.22B
66

• Brown algae, large complex seaweeds

Figure 16.22C
67

• 16.23 Amoebozoans have pseudopodia and include
  amoebas and slime molds
• Amoebas
• Move and feed by means of pseudopodia

Figure 16.23A
68

• A plasmodial slime mold is a multinucleate
  plasmodium
• That forms reproductive structures under adverse
  conditions

Figure 16.23B
69

• Cellular slime molds
• Have unicellular and multicellular stages

Figure 16.23C
70

• 16.24 Red algae and green algae are the closest
  relatives of land plants
• Red algae
• Contribute to coral reefs

Figure 16.24A
71

• Green algae
• May be unicellular, colonial, or multicellular

Figure 16.24B
72

• The life cycles of many algae
• Involve the alternation of haploid gametophyte
  and diploid sporophyte generations

Figure 16.24C
73

• 16.25 Multicellularity evolved several times in
  eukaryotes
• Multicellularity evolved in several different
  lineages
• Probably by specialization of the cells of
  colonial protists

Figure 16.25
74

• Multicellular life arose over a billion years ago