Ch.27 - Bacteria and Archaea Flashcards
Goals of Ch.27
- Identify components of prok cells and diff fr euk cells
- Know classifications based on cell shape/wall
- Explain, in detail, the three ways genetic recombination occurs in proks
Goals of Ch.27
- Identify components of prok cells and diff fr euk cells
- Know classifications based on cell shape/wall
- Explain, in detail, the three ways genetic recombination occurs in proks
Lifes earliest division involved what?
Proks diverged v early into two lineages:
- Archaea: some bac traits/ some euk traits/ many unique traits
- Bacteria: extremely diverse, every mode of nutrition and metabolism
Collective mass of proks is _____ (more or less) than ten times mass of all euks
Collective mass of proks is MORE than ten times mass of all euks, i.e. proks are “dominant” orgs.
of proks in handful of soil is greater than # of people who have ever lived
Describe the general struc, size, and shape of proks
Most unicellular; some form colonies
Most 0.5 μm - 5 μm (1μm=1/1000 of a mm)
Shapes:
- Cocci (spheres)
- Bacilli (rods)
- Spirals
Arrangement:
- Di- = two cocci side-by-side
- Strepto- = string of cocci
- Staphylo- = bowling pins
- Sarcina = cube
- Tetrad = square
Effect of hyper- vs hypotonic environ on cell
Bac cell walls contain ____________, a network of modified sugar polymers crosslinked by other short polymers
Bac cell walls contain peptidoglycan, a network of modified sugar polymers crosslinked by other short polymers
T/F: like bac, archael cell walls also contain peptidoglycans
FALSE
Archaeal cell walls contain a variety of polysacchs and proteins but lack peptidoglycan
Identify gram-positive vs -negative bac in attached imaged, and describe characteristics of assoc cell wall
Gram positive = dark blue/purple
- Simple walls
- Relativey high amnt of peptidoglycan
Gram negative = pink/red
- Complex walls
- Less peptidoglycan
- Outer layer contains lipopolysacchs
- Lipid layer
Gram-pos/neg and infection/treatment
Gram positive:
- Some antibiotics (ex. penicillin) inhibit crosslinking of peptidoglycans
- Can also evolve antibiotic resistance
Gram negative:
- Complex outer layer is often resistant to body’s defenses and entry of antibiotics
What is a capsule?
Capsule: sticky layer of polysacchs or proteins that forms a covering over a cell wall
- Enables bac to adhere to colony or substrate
- May also protect against dehydration or attacks by host’s immune system
Compare fimbriae and sex pili
Fimbriae (singular: fimbria): hairlike protein appendages; allow proks to stick to substrate or one/an
- Aka attachment pili
Sex pili: longer than fimbrae, allow proks to exchange DNA
~___% of proks are capable of directional movement
~50% of proks are capable of directional movement
Taxis vs flagella
Taxis: movement toward/away fr stimulus
Flagella (singular flagellum):
- 1/10 as wide as euk flagella
- not covered by pmem
Proks lack mem-bound organelles like mito. How is metabolism performed?
Specialized mems
Describe genome of proks
Typ genome: circular chromo, less DNA, and fewer proteins
- Plasmids: smaller rings of separately replicating DNA
Where are prok chromos located w/i cell?
Nucleoid region
What are plasmids?
Plasmids are smaller rings of separately replicating DNA
Proks have characteristically adapted to some extreme environs. Describe possible adaptations
Endospore forms when nutrients are limited
Tough wall around chromo copy
Metabolism halts when water lost
Cell disintegrates
Endospore survives in soil for years
Halophiles and thermophiles are two types of ________
Halophiles and thermophiles are two types of archaea (extremophiles)
Halophiles: high-salt environments
Thermophiles: extreme heat, adaptations keep DNA from denaturing
How do proks reproduce?
Binary fission: single prok cell divides into two cells
- Under ideal conditions will divide once every 1-3 hours
- Limits on reprod: exhaust nutrition supply, buildup of waste, competition, predation
Why are proks so genetically variable?
- Rapid reprod
- Mutation
- Genetic recombination (transformation, transduction, conjugation)
For sexually reproducing species (i.e. NOT proks), most GV comes fr reshuffling allele combinations.
For sexually reproducing species (i.e. NOT proks), most GV comes fr reshuffling allele combinations.
How, then, does genetic recomb contrib to prok GV?
Transformation - foreign DNA incorporated into genome.
Transduction - phage infiltrates → DNA recombines
Conjugation - GM xfrd b/w bac cells temporarily joined
Describe genetic transformation in proks
Foreign DNA fr environ taken in (recog by cell surface proteins)
DNA incorporated into genome
Harmless strains can become harmful if alleles from pathogen strains brought in
Describe genetic transduction in bac
Bacteriophages: viruses that infect bac; carry bac DNA b/w hosts.
- Phage infects bac
- Some new phages have bac DNA
- Recipient cell infected
- Host cell DNA recombines w recipient DNA
Results in a recombinant cell
Describe genetic conjugation in proks
GM xfrd b/w two bac cells that are temporarily joined
One-way xfr: donor cell uses sex pili to attach to recipient cell
F factor (f=fertility): piece of DNA w ~25 genes (most produce sex pili)
- Can exist as plasmid or segment of chromo
An F factor is a piece of DNA w ~25 genes, most of wh prod sex pili.
Describe F factor in plasmids
F+ cells: donors, have F factor as plasmid
F- cells: receivers, DO NOT have F factor
Sex pili forms mating bridge → F plasmid may be xfr’d; recipient cell becomes F+
An F factor is a piece of DNA w ~25 genes, most of wh prod sex pili.
Describe F factor in chromos
Hfr cell (High Freq of Recomb)
F factor in chromo – functions as donor
Homologous DNA segments align w donor cell DNA → recipient cells unlikely to become F+
What are R plasmids, and how are they typ xfrd?
R plasmids (r=resistance): carry genes that ↓ antibiotics’ effectiveness
Typ xfrd cell-to-cell by conjugation
Exposure to antibiotics provides selection for cells w resistance
T/F: All known pathogenic proks are bacteria
TRUE
All known pathogenic proks are bacteria, i.e. no archaea
- Bac orgs cause ~50% of all human disease
- Illness typ caused by poisons produced
Exo vs endotoxins
Exotoxins: proteins secreted by bac
- Signals body cells to carry out harmful actions, e.g. cholera → diarrhea
Endotoxins: lipopolysacchs of outer mem of gram-neg bac.
- Released only when bac die → cell walls break down, e.g. Salmonella
____________ is a form of antibiotic resistance in wh virulent genes are spread to normally harmless bac.
Horizontal gene transfer is a form of antibiotic resistance in wh virulent genes are spread to normally harmless bac.
- E.g. pathogenic E. coli strains
Why do we place plants, fungi, and proks in diff taxa?
We place plants, fungi, and prokaryotes in difftaxa due to their cell walls are composed of v diff biochemicals
T/F: some, but not all, deuterostomes have a pseudo coelom
FALSE
ALL deuterostomes have a pseudo coelom
T/F: Similar to most amoebozoans in the Unikonton group, some radiolarians have pseudopodia
TRUE
Similar to most amoebozoans in the Unikonton group, some radiolarians have pseudopodia
T/F: Most cells retain full range of function in simple multicellularity
TRUE
Most cells retain full range of function in simple multicellularity
T/F: Cell walls prevent cells from burning in hypotonic environment
FALSE
Cell walls prevent cells from burning in hypertonic environment
T/F: Sponges have no true tissue
True
Sponges have no true tissue
T/F: The animal kingdom in monophyletic
TRUE
The animal kingdom in monophyletic
Peptidoglycan is a common compound found in gram-___ (pos/neg) bacteria
Peptidoglycan is a common compound found in gram-positive bacteria
T/F: Sex pili are required for bacteria to carry genetic recombination through transformation
FALSE
Sex pili ARE NOT req’d for bac to carry genetic recomb thru transformation
- Sex pili are involved in conjugation
