Chapter 27: Bacteria & Archaea Flashcards
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Cell-Surface Structures
- eukaryote cell wall is made out of cellulose/chitin
- prokaryotic cell wall contains peptidoglycan (sugar polymers)
- archaea caintain polysaccharides and lack peptidoglycan
- Gram stain is used to classify bacteria by cell wall composition
- Gram (+): large amount of peptidoglycan & gram (-): less peptidoglycan
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Gram positive bacteria
- include colony forming groups to decompose matter
- include solitary species
- mycoplasms lack cell walls
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What is the capsule?
- sticky outer layer of polysaccharide/protein present in some prokaryotes
- allows adherence to substrate or other individuas
- can shield pathogenic bacteria from the host immune system
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What is an endospore?
- they are metabolically inactive formed by many prokaryotes
- can remain viable in harsh conditions for centuries
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What is the difference between fimbriae and pili?
- fimbriae: hairlike appendages that allow prokaryotes to stick to their substrate/individuals in a colony
- Pili (sex pili): longer than fimbriae; allow prokaryotes to exchange DNA
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Mobility
- Taxis: The ability to move toward or away from a stimulus
- Flagella are the most common strutures used by prokaryotes for movement
- flagella of prokaryotes & eukaryotes differ in structure, etc…
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Internal organization and DNA
- prokaryotic cells lack complex compartmentalization
- infoldings of the plasma membrane in these prokaryotic cells perform metabolic functions
- most of the genome consists of a circular chromosome
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Nucleoid
- where chromosome is located
- has no surrounding membrane
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Plasmids
- independtly replicating DNA found in typical prokaryotes
- have smaller rings
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Reproduction
- prokaryotes reproduce by binary fission and can divide every 1-3 hrs
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what are the key featires of prokaryote biology?
- they are small
- reproduce by binary fisiion
- have short generation times
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What three things contribute to prokaryotes’ genetic variation?
- rapid reproduction
- mutation
- genetic recombination
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Rapid reproduction and mutation
- prokaryotes reproduce asexually
- mutation rates are low but they accumulate rapidly (b/c generation times are short & populations are large)
- their cells have rapid adaptation to environmental change meaning that are highly evolved
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Genetic recombination
- def: combining of DNA from 2 sources that contributes to diveristy
- transformation, transduction, 7 conjugation facilitate this
- horizontal gene transfer: movement of genes among individuals from different species
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Transformation
when a prokaryotic cell takes up & incorporate foreign DNA from surrounding environment
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transduction
movement of genes between bacteria by phages (bacteriophages - viruses that infect bacteria)
1. phage infects bacterial donor cell that carries A+ & B+ alleles
2. phage dna is replicated & phage proteins are made
3. fragment of dna w/ A+ allele is packages within a phage capsid
4. phage w/ A+ allele infects bacterial recipient cell
5. incorporation of phage DNA creates recombinant cell with A+ & B-
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conjugation & plasmids
- conjugation: process where genetic material is transferred between prokaryotic cells
- the transferred DNA is often in the form of a plasmid
- F factor (piece of DNA) required for production of pili
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F factor as a plasmid
- F plasmid: DNA donors during conjugations
- Cells w/out f factor function as the recipient
- f factor is transferable during conjugation
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F factor in the chromosome
- cell with f factor in chromosome will be donot during conjugation
- ^^^ called Hfr cells (high frequenct of recombination)
- recipient becomes a recombinant bacterium with DNA from two different cells
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R plasmids and antibiotic resistance
- r plasmids carry genes for antibiotic resistance
- antibiotics dont kill bacteria with specific r plasmids
- some r plasmids carry genes for resistance to multiple antibiotics
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how are prokaryotes categorized by how they obtain energy/carbon?
- phototrophs obtain energy from light
- chemotrophs obtain energy from chemicals
- autotrophs require carbon dioxide as a carbon source
- heterotrophs require organic nutrient to make organic compounds
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Photoautotroph
- energy source: light
- carbon source: CO2, HCO3, etc…
- types of organisms: photosynthetic prokaryotes
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Chemoautotroph
- energy source: inorganic chemicals
- carbon source: CO2, HCO3, etc…
- types of organisms: unique to certain prokaryotes
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Photoheterotroph
- energy source: light
- carbon source: organic compounds
- types of organisms: unique to certain aquatic & salt-loving prokaryotes