Lecture 21 - Prokaryotes 1 Flashcards
Where do prokaryotes thrive?
- almost everywhere
- even too acidic, salty, cold , or hot for other organisms
Are prokaryotes macroscopic or microscopic?
microscopic
What are the two domains of prokaryotes?
- bacteria
2. archaea
What are the 3 elements of the tree of life?
- bacteria
- archaea
- eukaryotes
Archaea are more closely related to ______ than to ________
Eukaryotes, Bacteria
What were earth’s first organisms?
prokaryotes
Are prokaryotes uni or multicellular?
unicellular, but some species form colonies
How small are most prokaryotic cells?
0.5-5 micron
What are the 3 most common shapes of prokaryote cells?
- spheres (cocci
- rods (bacilli)
- spirals
What is trichodesmium?
colonial marine nitrogen-fixing cyanobacterium
What is the important feature of nearly all prokaryotic cells?
cell wall
What do cell walls do?
- maintains cell shape
- protects cell
- prevents it from bursting in a hypotonic environment
What are eukaryote cell walls made of?
- cellulose
- chitin
What are bacterial cell walls made of?
peptidoglycan
What is peptidoglycan?
- network of sugar polymers
- cross-linked by polypeptides
What doe archaea contain? lack?
- polysaccharides + proteins
- lack peptidoglycan
What is a gram stain used for?
to classify bacteria by cell wall composition
What will a gram-positive bacteria have?
-simpler walls with a large amount of peptidoglycan
What do gram-neg bacteria have?
- less peptidoglycan
- outer membrane that can be toxic
What do many antibiotics target? What do they do?
- peptidoglycan
- damage bacterial cell walls
Which type are more likely to be antibiotic resistant?
gram-negative
What also covers many prokaryotes?
capsule (slime layer)
What is an endospore?
- seed that forms inside cell (with DNA)
- inactive, can remain viable in harsh conditions for centuries
What do fimbriae do?
-allow prokaryotes to stick to their substrate or other individuals in a colony
What are pili?
- longer than fimbriae
- allow prokaryotes to exchange DNA
What are taxis?
ability to move toward or way from a stimulus
What is chemotaxis?
-movement toward or away from chemical stimulus
How do motile bacteria propel themselves?
-flagella scattered about the surface or concentrated at one or both ends
What are flagella composed of?
- different proteins
- likely evolved independently
What is phototaxis?
-movement toward or away from light
What are the 3 parts of a flagella?
- motor
- hook
- filament
What is exaptation?
existing structures take on new functions through descent with modification
prokaryotic cells usually lack
- complex compartmentalization
- organelles
what do some prokaryotes have? specialized _____
membranes that perform metabolic functions
the _____ genome has less DNA than the _____ genome
prokaryotic, eukaryotic
what does most of the genome consist?
circular chromosome
where is the chromosome located?
in the nucleoid region
What are plasmids?
smaller rings of DNA
What is the benefit of having differences between prokaryote and eukaryotic DNA replication, transcription, translatioN/
-allow people to use some antibiotics without harming themselves
How do prokaryotes reproduce?
binary fission
What are 3 key features of prokaryotic reproduction?
- they are small
- they reproduce by binary fission
- short generation times
What is an example of an extremophile bacteria?
-endoliths
What are endoliths?
live inside rocks + between mineral grains
What are 3 qualities of endoliths?
- found as deep as 2 miles below surface
- most are chemoautogtorphs
- reproduce maybe once per century
What is characteristic of prokaryotic offspring?
generally identic
Mutation rates are ____ during binary fission
low
What is a result of rapid reproduction?
mutations can accumulate rapidly in a population
Are prokaryotes primitive?
highly evolved
What is the Lenski long-term evolution experiment?
- ongoing study in experimental evolution
- tracking genetic changes in 12 initially identical populations
How can prokaryotic DNA be brought together?
-transformation, transduction, conjugation
what is horiziontal gene transfer
-move through completely unrelated bacteria species
what happens in transformation?
-prokaryotic cell take up and incorporate DNA from surrounding environment
What is transduction?
movement of genes between bacteria by bacteriophages
What are the 5 steps of a virus infecting bacteria?
1. 2. 3. 4. 5.
What is conjugation?
process where genetic material is transferred between prokaryotic cells
What happens when a donor cell attaches to a recipient?
pulls it closer, transfers DNA
what is the F factor?
piece of DNA required for the production of the pili
What are 4 steps of conjugation?
1.
2.
3.
4.
What does a cell with the F factor built into its chromosomes function as?
donor during conjugation
What does the recipient become?
recombinant bacterium (DNA from 2 different cells)
What are R plasmids?
carry genes from antibiotic resistance
How do R plasmids work with antibiotics?
resistant to antibiotics
What are phototrophs?
obtain energy from light
What are chemotrophs?
obtain energy from chemicals
What are autotrophs?
require CO2 as carbon source
What are heterotrophs?
require organic nutrient to make organic compounds
What are 4 major modes of nutrition?
- photoautotorphy
- chemoautotrophy
- photoheterotrophy
- chemoheterotropy
What are obligate aerobes?
require O2 for cellular respiration
What are obligate anaerobes?
- poisoned by O2
- use fermentation or anaerobic respiration
What are facultative anaerobes?
can survive with or without O2
What is nitrogen essential for?
production of amino acids, nucleic acids
What is nitrogen fixation?
some prokaryotes convert N2 to NH3
what are heterocysts?
nitrogen fixing cells
what happens in cyanobacterium Anabaena?
-photosynthetic cells + heterocysts exchange metabolic products
