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
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Chemoheterotroph
- enerygy souce: light
- carboon osurce: organic compounds
- types of organisms: many prokaryotes
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role of oxygen in metabolism
- obligate aerobes: require O2 for cellular respiration
- obligate anaerobes: poisoned by O2 and live by fermentation
- facultative anaerobes: can/cant use O2 depending on presence of O2
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nitrogen metabolism
- prokaryotes can metabolize nitrogen via nitrogen fixation
- converting atmospheric nitrogen to ammonia
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metabolic cooperation
- allows prokaryotes to use environmental resources they could not use as individual cells
- heterocysts: nitrogen-fixing cells
- biofilms: surface coaitng colonies where metabolic cooperation between different proakryotes take place
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bacteria
diverse nutrional types are represented among bacteria
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proeobacteria
- gram negative
- include photoautotrophs, chemoautotrophs, & heterotrophs
- some anaerobic & others aerobic
- 5 subgroups
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Alpha proteobacteria
- closely associated w/ eukaryotic hosts
- hypothesize that mitochondria evolved from aerobic alpha via endosymbiosis
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Beta proteobacteria
- nutritionally diverse
- other members include aquatic species & pathogens
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Gamma proteobacteria
- include sulfur bacteria
- some are pathogenic
- some can reside in the intestines of many mammals
*ex: salmonella, escherichia coil
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Delta proteobacteria
- ex: myxobacteria prodouces drought-resistant myxospores
- ex: bdellovibrios: mount high speed attacks on other bacteria
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Epsilon proteobacteria
- most are pathogenic
- ex: campylobacter which causes blood poisoning & helopcobacter pylori which causes stomach ulcers
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Chlamydias
- parasites that live within animal cells
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Spirochetes
- helical gram-negative heterotrops
- some are parasites which cause syphilis and lyme disease
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Cyanobacteria
- gram negative photoautotrophs that make oxygen
- plant chloroplasts via endosymbiois prob evolved from this
- abundant components of freshwater & marine phytoplankton
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Archaea
- share certain traits w/ bacteri & other traits w/ eukaryotes
- have many unique characteristics
- extreme halophiles: live in highly saline environments
- extreme thermophiles: trhive in very hot environments
- mthanogens: live in swamps & marshes and produce methan as waste
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Chemical recycling
- prokaryotes recycle chemical elements between components of the environment
- decomposers: some chemoheterotrophic; break down dead organisms & waste products
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Ecological interactions
- symbiosis: two species live in close contact: a larger host & smaller symbiont
- prokaryotes often do this with larger organisms
- parasites that cause disease are called pathogens
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Mutalistic bacteria
they break down food that is undigested by human intestine
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pathogenic bacteria
bacteria cause about half of all human diseases
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exotoxins vs endotoxins
- exotoxin: secreted and cause disease; cell purposely release this to harm/protect cell
- endotoxin: released only when bacteria die and cell wall breaks down
