Lectures: Prokaryotes Flashcards
Prokaryotes
single-celled organism that lacks organelles and does not have nuclei surrounded by a nuclear membrane
e.g. bacteria & archaea
Do Prokaryotes comprise a monophyletic group?
No, Prokaryotes are not a great term for understanding the evolution of biodiversity
Are Archaea and Bacteria sister taxa?
No, Archaea is sister taxa with Eukarya
Anoxic
no molecular oxygen
Phototrophs
able to make its own food by converting solar energy to chemical energy
Early prokaryotes were ______.
phototrophs
What is another name for blue-green algae?
Cyanobacteria
- have oxygenic photosynthesis metabolism
- created oxygen as byproduct
- led to “oxygenation” of atmosphere
- allowed evolution of more efficient aerobic metabolism
How is prokaryotes diversity studied and classified?
- Cultures:
- Collect samples and try to grow cultures in different mediums and temperatures
- But, many can not be cultured - Metagenomics:
- Collect massive amounts of DNA or RNA sequences soils or water
– Detect species (genomic) or functional (expressed genes) diversity
What has Metagenomics revealed?
uncharacterized diversity
5 characteristics of a Prokaryote cell:
- Unicellular and lack membrane-bound organelles
- Circular chromosomes located in nucleoid
- Protective cell wall
- Some have capsule around cell wall
- Some have flagella used for locomotion
What are the 3 main shapes of the Prokaryotic cell?
- cocci (spherical)
- bacilli (rod-shaped)
- spirilli (spiral-shaped)
*archaea also have triangular and square shapes
Cell Wall
Protective layer that gives cell shape and rigidity
Bacterial cell walls contain _________, which is not in Archaea
Peptidoglycan
Peptidoglycan
material composed of polysaccharide chains cross-linked to unusual peptides
Bacteria can be split into 2 groups based on their reaction to what?
Gram Staining:
- Gram positive: contains mainly peptidoglycan in cell wall
- Gram negative: cell walls contain little peptidoglycan and an outer membrane
How are Bacteria and Archaea reproduce?
Binary Fission (asexual):
- DNA uncoils and duplicates
- Cell grows in size
- DNA copies move towards opposite poles
- New cell wall spilts into two
True or False. Binary Fission does not provide the opportunity for Recombination.
True, Recombination is seen in Eukarya and is an important source of genetic variation during sexual reproduction
Horizontal Gene Transfer
- gene transfer between already existing organisms (donor & recipient)
- an important way for asexually reproducing organisms like prokaryotes to acquire new traits
What are the 3 subtypes of HGT?
- Transformation: uptake of DNA from the environment
- Transduction: bacteriophage (virus) transfer DNA between cells
- Conjugation: direct transfer by cell-to-cell contact
How does HGT differ from sexual reproduction??
- one-way transfer
- Transfer is limited to a small number of genes
What has higher mutation rates? Prokaryotes or Eukaryotes? Why?
Prokaryotes, due to how common HGT = high genetic diversity (e.g. “superbugs”)
What are the dominant forms of life on Earth which are able to live in a wide variety or environments?
Bacteria and Archaea, due to wide diversity of metabolism (e.g. heterotroph, phototroph, etc)
Photoautotroph:
- Energy from light
- Carbon from inorganic CO2
e.g. plants. algae, cyanobacteria
Photoheterotrophs:
- Energy from light
- Carbon from organic molecule
e.g. only Bacteria and Archaea
