Lecture 10 Prokaryotes Flashcards
where can prokaryotes thrive?
almost anywhere
-includes very acidic places, high salinity, extreme temperatures
what are the two domains that are considered prokaryotes?
bacteria and archaea
what are seven characteristics of prokaryotes?
- no nucleus
- plasmids
- lack compartmentalization
- prok < euk in size
- cell wall – peptidoglycan
- 1/2 of prok are motile
- reproduction and gene transfer in several forms
how is genetic material arranged in prokaryotes?
and how much is there?
- diffused, circular ring of DNA not enclosed by a membrane
- located in nucleoid region
- prok genome has less DNA than euk genome
what are plasmids?
small rings of DNA containing ‘extra’ genes
what is peptidoglycan?
a network of sugar polymers cross-linked by polypeptides
what is the function of the cell wall in prokaryotes? (3)
- maintains cell shape
- protects the cell
- prevents bursting in hypertonic environments
what are the two types of bacterial cell wall?
- gram +
- gram -
what is a gram + wall?
- simpler bacterial cell wall with a lot of external facing peptidoglycan
what is a gram - wall?
a bacterial cell wall that has a lipopolysaccharide layer outside of the cell wall which doesn’t absorb the gram stain readily
why are bacteria with gram - cell walls usually more pathogenic than gram + bacteria? (2)
can contain toxins and can resist antibiotics
what are 3 cell-surface structures of bacteria?
- capsule
- fibrae
- pili / sex pili
what is a capsule?
a polysaccharide or protein layer that covers many prokaryotes
what is a fimbrae?
what does it allow bacteria to do (2) ?
adaptation that allows the bacteria to stick to substrates or other individuals in a colony
how do most bacteria move?
using flagella scattered about the surface of the bacteria or concentrated at one or both ends
how are the flagella of bacteria, archaea, and eukarya diffferent?
composed of different proteins and most likely evolved independently
what is taxes/taxis?
the ability to move toward or away from a stimulus
ex: phototaxis – movement towards light
what form does bacterial reproduction NOT take
mitosis/meiosis
how do bacteria reproduce quickly
using binary fission – depends on environment
what are 3 factors that contribute to bacterial genetic variation
- rapid reproduction
- mutation
- genetic recombination
how is mutation a factor for genetic variation (despite that mutation rates of binary fission is very low)
mutations occur rapidly in a population because of rapid reproduction
how is prokaryotic DNA from different individuals brought together? (3)
- transformation
- transduction
- conjugation
what is transformation?
the uptake of foreign DNA from surroundings
ex: naked DNA from dead bacteria
what is transduction?
movement of prokaryotic genes between bateria by bacteriophages – usually a mistake on phage’s part
what is a bacteriophage?
a virus that infects bacteria
what is conjugation? (3)
- a process where genetic material is transferred between an donor cell to a recipient cell via PILUS
- unidirectional
- plasmids are often transferred
by which process are plasmids often transferred?
conjugation
what is metabolism?
chemical pathways used by living organisms to build up molecules
compare anabolism vs catabolism
catabolism is the breakdown of molecules to release energy –think catastrophy
anabolism is the breakdown of molecules to release energy
what are the four ways to catagorize prokaryotes by how they obtain energy and carbon?
- phototrophs
- chemotrophs
- autotrophs
- heterotrophs
what are phototrophs?
organisms that obtain energy from light
what are chemotrophs?
organisms that obtain energy from chemicals (usually inorganic)
what are autotrophs?
organisms that use CO2 as a carbon source
what are heterotrophs?
organisms that use organic nutrients to make organic compounds – often have to consume things
what are the two types of prok autotrophs?
- chemoautotrophs
- photoautotrophs
what are the two types of prok hetertrophs?
- photoheterotrophs
- chemoheterotrophs
what do archaea lack in their cell wall?
peptidoglycan
what kind of philes are archaea?
extremophiles
how do archaea respond to antibiotice that inhibit eubacterial growth?
they DON’T
what are three types of archaea covered in this course?
- methanogens: live in O2 free environments
- halophiles: very salty environments
- thermophiles: very hot habitats
what are four characteristics of eubacteria?
diverse, numerous, live almost everywhere, can be pathogenic or have positive interactions w/ humans
what are the 5 major clades of bacteria?
- proteobacteria
- chlamydias
- spirochaetes
- cyanobacteria
- “Gram +” bacteria
what are proteobacteria?
- large and metabolically diverse group of gram neg. bacteria
- 5 sub linages
- two examples: Rhizobium spp & E. coli
what is the proteobacteria Rhizobium spp.?
what relationship does it have with plants?
- live in root nodules of leguminous roots
- mutualistic–fix atm. nigtogen to make it available for the host plant to use, plant gives carbohydrates in return
what is the proteobacteria E. coli? (5)
- resides in many mammal intestines
- not normally pathogenic
- aids in digestion
- synthesis of vitamins & other nutrients
- some are toxic
what are chlamydias?
what do the NOT have in their cell wall?
- parasites only living within animal cells
- no peptidoglycan in cell walls
- ex: chlamydia trachomatis - common human STD, blindness in newborns
what are spirochaetes?
- long helical heterotrophic bacteria that swim by spiralling
- many free-living
- NASTY parasitic bacteria
- ex: syphilis & Lyme disease (ticks)
what are cyanobacteria/blue-green algae?
- only prokaryotes that produce oxygen via photoautrophy
- often benignt, but some have toxins that impair liver fxns or act as neurotoxins
where are plant chloroplasts thought to evolve from?
cynanobacteria via endosymbiosis
what is the “Gram +” bacteria clade?
- ONLY group with GRAM + bacteria (but also includes gram - taxa …?…)
- very important decomposers in soil
- source of many antibiotics like streptomycin
- and mycoplasmas – smallest known cells
- and clostridium botulinum – botulism
- and bacillus anthracis – anthrax – that can enter resistant endospore state
what is the importance of prokaryotes?
- producers of O2 and fixers of N
- major roles in recycling of chemical elements between living and non-living
- ex: chemoheterotrophic prok that are decomposers can increase availability of N, P and K for plants
what is symbiosis?
ecological relationship between two species that live in close contact specifically a larger host + a smaller symbiont
what are 3 types of symbiotic relationships
- mutualism: both benefit, ex methanogens in cow stomach, Rhizobium
- commensalism: one benefits, other is neither harmed nor benefits
- parasitism: parasite harms but doesn’t kill host (maybe eventually it will…)
what are parasites that cause disease called?
pathogens
what is the economic importance of prok?
- food production
- sewage treatment & bioremediation (decomposers)
- production of vitamins, antibiotics, hormones, biofuels
- ex Thermus aquaticus “taq” – used in PCR
