1. Prokaryotes & Protists
Chapter 27 & 28
Prokaryotes & Protists

2. Ch. 27 ~ Prokaryotes Overview: They’re (Almost) Everywhere!
Most prokaryotes are microscopic
But what they lack in size they more than make up for in numbers
The number of prokaryotes in a single handful of fertile soil
Is greater than the number of people who have ever lived

3. Prokaryotes thrive almost everywhere
Including places too acidic, too salty, too cold, or too hot for most other organisms
Figure 27.1

4. 27.1 ~ Structural, functional, and genetic adaptations contribute to prokaryotic success
Most prokaryotes are unicellular
Although some species form colonies
Prokaryotic cells have a variety of shapes
The three most common of which are spheres (cocci), rods (bacilli), and spirals
1 m
2 m
5 m
(a) Spherical (cocci)
(b) Rod-shaped (bacilli)
(c) Spiral

5. Cell-Surface Structures
One of the most important features of nearly all prokaryotic cells
Is their cell wall, which maintains cell shape, provides physical protection, and prevents the cell from bursting in a hypotonic environment

6. Using a technique called the Gram stain
Scientists can classify many bacterial species into two groups based on cell wall composition, Gram-positive and Gram-negative
(a)
Gram-positive. Gram-positive bacteria have
a cell wall with a large amount of peptidoglycan
that traps the violet dye in the cytoplasm. The
alcohol rinse does not remove the violet dye,
which masks the added red dye.
(b)
Gram-negative. Gram-negative bacteria have less
peptidoglycan, and it is located in a layer between the
plasma membrane and an outer membrane. The
violet dye is easily rinsed from the cytoplasm, and the
cell appears pink or red after the red dye is added.
Figure 27.3a, b
Peptidoglycan
layer
Cell wall
Plasma membrane
Protein
Gram-
positive
bacteria
20 m
Outer
membrane
Lipopolysaccharide
negative

7. The cell wall of many prokaryotes
Is covered by a capsule, a sticky layer of polysaccharide or protein
200 nm
Capsule
Figure 27.4

8. Some prokaryotes have fimbriae and pili
Which allow them to stick to their substrate or other individuals in a colony
200 nm
Fimbriae
Figure 27.5

9. Motility Most motile bacteria propel themselves by flagella
Which are structurally and functionally different from eukaryotic flagella
Flagellum
Filament
Hook
Cell wall
Plasma
membrane
Basal apparatus
50 nm
Figure 27.6

10. Internal and Genomic Organization
Prokaryotic cells
Usually lack complex compartmentalization
Some prokaryotes
Do have specialized membranes that perform metabolic functions
(a) Aerobic prokaryote
(b) Photosynthetic prokaryote
0.2 m
1 m
Respiratory
membrane
Thylakoid
membranes
Figure 27.7a, b

11. The typical prokaryotic genome
Is a ring of DNA that is not surrounded by a membrane and that is located in a nucleoid region
Figure 27.8
1 m
Chromosome

12. Some species of bacteria
Also have smaller rings of DNA called plasmids
Draw a prokaryotic cell and label the DNA and plasmids
Prokaryotes reproduce quickly by binary fission
And can divide every 1–3 hours
Many prokaryotes form endospores
Which can remain viable in harsh conditions for centuries
Endospore
0.3 m
Figure 27.9

13. 27.2
A great diversity of nutritional and metabolic adaptations have evolved in prokaryotes
Examples of all four models of nutrition are found among prokaryotes:
List Energy source & Carbon source:
Photoautotrophy
Chemoautotrophy
Photoheterotrophy
Chemoheterotrophy

14. Major nutritional modes in prokaryotes
Table 27.1

15. 27.3 Molecular systematics is illuminating prokaryotic phylogeny
Until the late 20th century
Systematists based prokaryotic taxonomy on phenotypic criteria
Applying molecular systematics to the investigation of prokaryotic phylogeny
Has produced dramatic results

16. A tentative phylogeny of some of the major taxa of prokaryotes based on molecular systematics
Domain Bacteria
Domain
Archaea
Eukarya
Alpha
Beta
Gamma
Epsilon
Delta
Proteobacteria
Chlamydias
Spirochetes
Cyanobacteria
Gram-positive
bacteria
Korarchaeotes
Euryarchaeotes
Crenarchaeotes
Nanoarchaeotes
Eukaryotes
Universal ancestor
Figure 27.12

17. Bacteria Diverse nutritional types The two largest groups are
Are scattered among the major groups of bacteria
The two largest groups are
The proteobacteria and the Gram-positive bacteria

18. Chlamydias, spirochetes, Gram-positive bacteria, and cyanobacteria
Chlamydia (arrows) inside an
animal cell (colorized TEM)
5 m
Leptospira, a spirochete
(colorized TEM)
5 m
1 m
Hundreds of mycoplasmas
covering a human fibroblast cell
(colorized SEM)
Streptomyces, the source of
many antibiotics (colorized SEM)
50 m
Figure 27.13
Two species of Oscillatoria,
filamentous cyanobacteria (LM)

19. Archaea Archaea share certain traits with bacteria
Table 27.2
Archaea share certain traits with bacteria
And other traits with eukaryotes

20. Some archaea live in extreme environments
Extreme thermophiles thrive in very hot environments
Extreme halophiles live in high saline environments
Colorful “salt-loving” archae live in these ponds near San Fransisco. Used for commercial salt production.
Methanogens
Live in swamps and marshes and produce methane as a waste product

21. 27.4 Prokaryotes play crucial roles in the biosphere
Chemical Recycling
Prokaryotes play a major role in the continual recycling of chemical elements between the living and nonliving components of the environment in ecosystems
Chemoheterotrophic prokaryotes function as decomposers
Breaking down corpses, dead vegetation, and waste products
Nitrogen-fixing prokaryotes
Add usable nitrogen to the environment

22. Symbiotic Relationships
Many prokaryotes -
Live with other organisms in symbiotic relationships such as mutualism and commensalism
Figure 27.15

23. 27.5 Prokaryotes have both harmful and beneficial impacts on humans
Some prokaryotes are human pathogens
But many others have positive interactions with humans
Prokaryotes cause about half of all human diseases
Lyme disease is an example
5 µm
Figure 27.16

24. Prokaryotes in Research and Technology
Experiments using prokaryotes have led to important advances in DNA technology
Prokaryotes are the principal agents in bioremediation
The use of organisms to remove pollutants from the environment
Prokaryotes are also major tools in
Mining, the synthesis of vitamins, production of antibiotics, hormones, and other products

25. Ch. 28 ~ Protists
28.1: Protists are an extremely diverse assortment of eukaryotes
Protists are more diverse than all other eukaryotes
And are no longer classified in a single kingdom
Most protists are unicellular, colonial or multicellular

26. Protists, the most nutritionally diverse of all eukaryotes, include
Photoautotrophs, which contain chloroplasts
Heterotrophs, which absorb organic molecules or ingest larger food particles
Mixotrophs, which combine photosynthesis and heterotrophic nutrition

27. There is now considerable evidence that much of protist diversity has its origins in endosymbiosis

28. Cladogram of Protists:

29. 28.3: Euglenozoans have flagella with a unique internal structure
Euglenozoa is a diverse clade that includes
Predatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites

30. Ciliates, a large varied group of protists
Dinoflagellates
Are a diverse group of aquatic
photoautotrophs and heterotrophs
Are abundant components of both
marine and freshwater phytoplankton
Ciliates, a large varied group of protists
Are named for their use of cilia to move and feed
Have large macronuclei and small micronuclei
Conjugation – Two cells exchange haploid micronuclei (similar to prokaryotic conjugation).
**Produces genetic variation

32. 28. 5 Hairy and smooth flagella 1
28.5 Hairy and smooth flagella 1. Diatom – Surrounded by a two part glass like wall and are a major component of phytoplankton.
Phytoplankton account for half of the photosynthetic activity on earth – responsible for much of the oxygen in our atmosphere.

33. 2. Golden Algae – Have two flagella and their color results from carotenoids.

34. 3. Brown Algae – multicellular mostly marine protists, commercially used; seaweeds

35. 28.6 Threadlike pseudopodia
Pseudopodia extend and help to injest microorganisms.

36. 28.7 ~ Amoebozoans Lobed shaped pseudopodia
*Entamoebas – parasites of vertebrates and cause amebic dysentry in humans.
*Slime molds – extend their pseudopodia through decomposing material, engulfing food by phagocytosis.

37. 28.8 ~ Red & Green Algae are the closest relatives of land plants.