Download The Endosymbiotic Theory

The Endosymbiotic Theory
Possible Origins of Eukaryotes
The Plant Cell
Endosymbiotic Theory
Lab 4. The Prokaryote and the
Plant Cell
Today in Lab...
• Looking at exceptions to the prokaryotes-arewithout-organelles rule
• Gram-staining bacterial and environmental
samples
• Examining a green algae
• Looking at moss cells and making protoplasts
• Revisiting the chromoplast (hopefully better
samples) and pigment distribution in various
plant species
• Looking at cell types in Tobacco plants
(Nicotiana tabacum and N. benthamiana)
• Finally, we will examine plant cells in context
using Brassiceae and a polychromatic stain
Some bacteria DO
have organelles(!)
e.g. the
acidocalcisomes in
Agrobacterium
Electron microscopy and x-ray microanalysis of
wholeA. tumefaciens. D–H, electron micrographs
of intact bacteria (D–F) and volutin granule
fractions (Gand H). Arrows show vacuoles, some
containing an electrondense material in the
periphery (D and E), some completely occupied by
electron-dense material (E, arrowhead), and some
apparently empty (F, arrowhead). Fractions show
almost empty vacuoles containing an electrondense material in their periphery (G and H). A
membrane is clearly seen enclosing the vacuoles
(arrow in E; arrowheads in F, G, andH). Bars, 0.1
μm.
Seufferheld M, et al. (2003) JBC, 278, 29971-29978.
Magnetospirillummagnetic bacteria!
Figure 1. Features of magnetosomes. (a) A
transmission electron microscopy (TEM)
image of sectionedMagnetospirillum
magneticum AMB-1 reveals the presence of a
chain of electron-dense magnetite crystals
[Image courtesy of T. Beveridge, reprinted
with permission from Komeili et al. (2004)]. (b)
Sections from an electron cryotomographic
image of AMB-1 show that magnetosomes are
invaginations of the inner cell membrane at
various stages of biomineralization. (c) The
same study shows the presence of filaments
parallel to the magnetosome chain [Images in
b and c courtesy of Z. Li and G. Jensen
reprinted with permission from Komeili et al.
(2006)].
Magnetospirillum (cont.)
• Magnetosomes aligned by
“microbial tubulin” filaments
Figure 4. Magnetosome chain formation. (a)
Image of an AMB-1 wild-type cell generated by
segmentation of an electron cryotomogram.
Numerous filaments (green) can be seen
flanking the magnetosome chain (yellow). (b)
Similar analysis of an AMB-1 strain deleted
formamK. In contrast to wild type,
magnetosomes are disorganized and not
flanked by filaments. [Images in a and b
courtesy of Z. Li and G. Jensen reprinted with
permission from Komeili et al. (2006)]. (c) TEM
images of wild-type (left panel)
and mamJ deletion mutant (right panel)
of Magnetospirillum gryphiswaldense MSR-1.
Note that the magnetosome chain has collapsed
into a ball in the absence of mamJ [reprinted
with permission from Scheffel et al. (2006)].
Photosynthetic purple bacteria:
Rhodobacter
• Use phycobilins instead of
chlorophyll
• Do not evolve oxygen
• Function in anaerobic
conditions
• Photosynthetic membranes
organized in chromatophores
• Contain PSII complexes
http://www.bbsrc.ac.uk/news/archive/2009/090617-f-bacteria-make-light-work-of-hydrogen-production.aspx
Cyanobacteria: Synechocystis sp
The blue-green “algae”
• The ancestor of the modern day
chloroplast
• Possesses both PSI and PSII
• Has chlorosome compartments
that contain thylakoid
membranes
1000x
Though we’ve been looking at
“exceptional” bacteria, all
prokaryotes can be classified
according to a basic cellular
determinant: Their cell wall.
Classifying bacteria
The Gram stain
Moving onto the Eukaryotes...
Eukaryotes: The Algae
Chlamydomonas reinhardtii
http://www.uni-jena.de/en/DFG_Research__Group_1261.html
Physcomitrella patens: a Moss
Protoplast
Carrot chromoplasts
Tobacco Cells
Cell Wall Lecture Supplements
Scanning Electron Micrograph of Plasma
Membrane with clusters of Rosettes
Giddings TH Jr, Brower DL, Staehelin LA. J. Cell Biol. 1980 Feb;84(2):327-39.
Close up of Rosettes occurring in PM
Cellulose
synthesis in
Context
What happens when things go
wrong? Cellulose Mutants:
Arabidopsis
thaliana
Left to right:
Columbia wild
type, low lignin
mutant, low
cellulose mutant
Talbot JM, KK Treseder. In press. Lignin, cellulose, and N interactions are major drivers of litter chemistry-decay relationships. Ecology. DOI: 10.1890/110843.1.
Cellulose Mutants Up Close
Chapter 3:
The Plant Cell and
the Cell Cycle
A colourised scanning electron micrograph showing how cell shapes go astray when the mechanical properties are wrong. The main image is a mutant that
makes less cellulose. The inset is the wild type with normal cellulose levels. Reprinted with permission from Arioli et al 1998, Science 279, 717-720.
Complexity of the Cell Wall
Secondary Cell Walls
Layers of Secondary Cell Wall
Orientation of Cellulose Microfibrils
Determines Cell Shape and Expansion
Bay Area Biofuel Companies