bacteria & archaea
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BACTERIA & ARCHAEACAMPBELL & REECECHAPTER 27
PROKARYOTIC ADAPTATIONS
typical prokaryote: 0.5 -5 microns unicellular variety of shapes▪ cocci (spherical)▪ bacilli (rods)▪ spirochetes (corkscrews)
Cell-Surface Structures
nearly all have cell wall maintains shape protects cell plasmolyze in hypertonic solution▪ water loss inhibits cell division hence salt used as food preservative (ham)
Cell Wall Structure
PROKARYOTES bacterial cell
walls contain peptidoglycan: a polymer made of sugars cross-linked with short polypeptides
EUKARYOTES cell walls mostly
cellulose or chitin
ARCHAEA (-) peptidoglycan (+) variety
polysaccharides & proteins
Peptidoglycan
Gram Staining
used to classify many bacteria as gram + or gram –
+ or – staining due to differences in cell wall composition
GRAM + simpler cell
walls more
peptidoglycan
GRAM - more complex less
peptidoglycan + outer
membrane with lipopolysaccharides
GRAM + GRAM -
GRAM + RODS GRAM - RODS
Medical Implications of Gram Stain
GRAM + some strains
virulent some drug
resistance (staph)
GRAM - many strains
virulent: tends to be:
toxic (fever, shock more likely)
drug resistance
Penicillin
works by inhibiting peptidoglycan cross-linking makes cell nonfunctional
since none in eukaryotic cells does not harm them
Penicillin
Which infection would more likely respond to treatment with pcn?
Prokaryotic Capsules
dense, well-defined outermost layer (called slime layer if not well-defined)
Sticky stick to each other in a colony or to
infected individual’s cellsmake it more difficult for
immune system to get to bacterial cell
Capsules
Fimbriae
used to stick to host cellsshorter & more numerous than
pili
Pili
appendages that pull cells together prior to DNA transfer between cells
aka sex pili
Bacteria Motility
taxis: a directed movement toward or away from a stimulus
chemotaxis: movement toward a chemical (+ chemotaxis) or away from a toxic chemical (- chemotaxis)
Flagella
most common structure used for prokaryotic motility
Flagella
not covered by extension of plasma membrane as in eukaryotic cell flagellum
smaller (~ 1/10th width of eukaryotic flagella)
Bacteria & Archaea flagella similar in size & rotation mechanism but composed of different proteins
Flagella
all these differences suggest flagella arose independently in all 3 Domains
so are analogous structures not homologous structures
Flagella
ARCHAEA BACTERIA
Bacterial Flagella
3 main parts:1. motor2. hook3. filament
Bacterial Flagella
evidence indicates it started as a simpler structure that has been modified in steps over time
(like evolution of eye) each step would have had to have been useful
analysis shows only ~1/2 proteins in flagellum necessary for it to function
Bacterial Flagella
analysis shows only ~1/2 proteins in flagellum necessary for it to function
19 of 21 proteins in flagella are modified versions of proteins that perform other tasks in bacteria
this is example of exaption: process in which existing structures take on new functions through descent with modification
DNA in Prokaryotic Cells
most have less DNA than eukaryotic cell
circular chromosome with many fewer proteins
loop located in nucleoidmost also have a plasmid:
smaller ring(s) of independently replicating DNA
DNA in Prokaryotic Cells
Inner Membranes in Prokaryotic CellsSo how do some prokaryotic
cells undergo photosynthesis and cellular respiration if they do not have membrane-bound organelles?
Inner Membranes in Prokaryotic Cells
Reproduction of Prokaryotic Cells
1. BINARY FISSION
Bacterial Reproduction
many bacteria can divide in 1- 3 hrs. (some in 20 min)
factors that slow down reproduction:1. loss of nutrients2. toxic metabolic waste3. competition with other bacteria4. eaten by predators
Survivors in Extreme Environments
1. Halobacterium rod-shaped Archaea lives in 4M saline (or higher)
Endospores
developed by certain bacteria to withstand harsh conditions
resistant cells develop when essential nutrients lacking
Endospores
survive boiling water remain dormant & viable for
centuries
Prokaryotic Evolution
short generations (up to 20,000 in 8 yrs)
adapt rapidlypopulations have high genetic
diversityhave been around for 3.5 billion
yrs
Genetic Diversity
Factors that promote genetic diversity:
1. rapid reproduction2. mutation3. genetic recombination
Rapid Reproduction & Mutation
because generations are so short even 1 mutation will produce many offspring and so increase genetic diversity which contributes to evolution
Genetic Recombination
the combining of DNA from 2 sources
occurs 3 ways in prokaryotes 1. transformation2. transduction3. conjugation
Transformation in Prokaryotic Cellsuptake of foreign DNA from its
surroundingsmany bacteria have cell-surface
proteins that recognize DNA from closely related species & transport it into the cell
Transformation in Prokaryotic Cells
Transduction in Prokaryotic Cellsbacteriophages (phages) carry
prokaryotic genes from 1 host cell to another…..usually as result of “accidents” during replicative cycle
Transduction
Conjugation & Plasmids
DNA is transferred between 2 prokaryotic cells (usually same species) that are temporarily joined by a mating bridge (from pilus)
transfer in 1 direction onlymust have particular piece of
DNA: F factorDNA transferred either plasmid
or section of loop DNA
Conjugation
Conjugation
Plasmids & Antibiotic Resistance
Genetic Recombination in Prokaryotic Cells
Metabolic Adaptations in Prokaryotic Cellsphototrophs: obtain energy from
lightchemotrophs: obtain energy
from chemicalsautotrophs: need CO2 as carbon
sourceheterotrophs: require at least 1
organic nutrient to make other organic compounds
Oxygen
obligate aerobes: must use O2 for cellular respiration
obligate anaerobes: O2 is toxic to them (fermentation)
faculative anaerobes: use O2 when available but also carry out fermentation if have to
Oxygen & Prokaryotic Cells
Nitrogen Metabolism
N essential to make a.a. & nucleic acids
Nitrogen Fixation cyanobacterium & some
methanogens N2 from atmosphere NH3 used
by plants
Nitrogen Fixation
Metabolic Cooperation
1. heterocysts formation2. biofilms3. sulfate/methane consuming
bacteria
Metabolic Cooperation
Anabaena, a cyanobacterium carries genes for both photosynthesis and N fixation but any one cell can only do one or the other at same time
Anabaena forms filamentous chains, most carry out photosynthesis but a few, heterocysts only do N fixation
Anabaena Filaments
heterocysts surrounded by thickened cell wall to prevent O2 from getting in (O2 turns off enzymes for N fixation)
intercellular connections allow heterocyst to send fixed N to neighboring cells
Anabaena Filaments
Biofilms
surface-coating colonies of different prokaryotic species
channels in biofilm allow nutrients to reach cells in interior (& wastes to leave)
cells secrete1. signaling molecules recruit
nearby cells2. polysaccharides & proteins that
stick cells together
Biofilms
Sulfate/Methane Consumers
1 archaea species that is a methane consumer forms ball-shaoed aggreagate with 1 sulfate consuming bacteria on ocean floor:
1 uses wastes of other to obtain necessary nutrients
Prokaryotic Phylogeny
b/4 technology made molecular systematics available prokaryotic organisms grouped by: nutrition shape motility Gram stain
Molecular Systematics
began comparing prokaryotic genes in the 1970’s
concluded some prokaryotes more closely related to eukaryotes than to rest of bacteria…..Bacteria & Archaea Domains
Polymerase Chain Reaction(PCR)
http://www.sumanasinc.com/webcontent/animations/content/pcr.html
used in 1980’s to make multiple copies of genes from prokaryotes in soil & water:
handful of soil could have up to 10,000 species of prokaryotes (overall there are only 7,800 with scientific names)
Comparison of 3 Domains of Life
BACTERIA ARCHAEA EUKARYAPEPTIDOGLYCAN IN CELL WALL + - -MEMBRANE LIPIDS
unbranched
hydrocarbons
some branched
hydrocarbons
unbranched
hydrocarbons
RNApolymerase
1 kind severalkinds
severalkinds
Introns in genes
very rare in some genes
in many genes
initiator a.a. forprotein synthesis
formyl-methionine
methionine methionine
ARCHAEA
share some traits with Bacteria, some with Eukarya
some unique traits too
Extremophiles
1.extreme halophiles live in highly saline
environmentssome tolerate high salinitysome require high salinity
proteins function best in extremely salty environments (die if salinity <9%) (ocean is 3.5%)
Halobacterium
Extremophiles
2. extreme thermophiles thrive in hot environmentsSulfolobus live in sulfur-rich
volcanic springs up to 90ºCstrain-121 lives in deep-sea
hydrothermal vents up to 121ºC Most cells would die: DNA would
unfold, proteins would unwind; these cells have adaptations that avoid this.
strain-121
Extremophiles
3. methanogens live in moderate environments
swamps, marshes under ice in Greenland in bovine colon, in termites
use carbon dioxide to oxidize H2 gas produces energy & methane as a waste product
strict anaerobes
Methanogens
Archaea
new clades continue to be found
Bacteria
majority of prokaryotic specieshave diverse nutritional &
metabolic capabilities
Proteobacteria
a large & diverse cladeGram (-) (+) for photoautotrophs,
chemoautotrophs, & heterotrophs
some aerobic, some anaerobic
Proteobacteria
Chlamydias
all parasites IntracellularGram(-) but lack peptidoglycan
in cell wallChlamydia trachomatis: #1
cause of blindness in the world & causes most common STD in USA
Chlamydia trachomatis
Chlamydia trachomatis
Spirochetes
helical heterotrophs internal flagellum-like structures
that allows them to corkscrew through their environment
pathogenic strains: Treponema pallidum: syphilis Borrelia burgdorferi: Lyme disease
Spirochetes
SYPHILIS LYME DISEASE
Cyanobacteria
photoautotrophic likely have common ancestor
with chloroplastsolitary or filamentous (some
filaments have cells specialized for N fixation)
component of freshwater or marine phytoplankton
Cyanobacteria
Gram + Bacteria
ACTINOMYCES
fungus-like form branched
chains includes TB and
leprosy includes many
decomposers in soil (earthy odor in soil)
ACTINOMYCES ODONTOLYTICUS
Diversity of Gram + Bacteria
Diversity of Gram + Bacteria
Diversity of Gram + Bacteria
Diversity of Gram + Bacteria
Diversity of Gram + Bacteria
Mycoplasmas only bacteria known to lack cell walls
smallest known cells (diameters 0.1 micron)
some free-living soil bacteria, some pathogens
Mycoplasma pneumoniae
Prokaryotic Interactions in Biosphere
1. Decomposers recycle nutrients from dead organisms
& waste products
2. Autotrophic bacteria convert CO2
organic cpds; some releasing O2
others (kingdom Crenarchaeota) fix N2 gas organic cpds
3. Symbiotic Relationships Mutualism Commensalism Parasitism Pathogens
Flashlight FishMutualistic Relationship
Pathogenic Prokaryotes
usually cause illness by producing:1. exotoxin2. endotoxin
EXOTOXINS
released by pathogen
cause illness even if bacteria no longer present
example: Clostridium botulinum
ENDOTOXINS
lippolysaccharide from outer membrane of gram
(-) bacteria released when
bacteria die example:
Salmonella typhi
How Bacteria can become more Virulent
1. carry resistant genes2. horizontal gene transfer
harmless bacteria virulent strains
Horizontal Gene Transfer
Example of Horizontal Gene Transfer
E coli strain 0157:H7 has become a global threat: causes severe bloody diarrhea
1,387 genes in this strain not originally from E coli …many are phage genes 1 of those genes codes for an
adhesive fimbriae that allow bacteria to attach self to intestinal wall cells & extract nutrients
Prokaryotes in Research & Technology
long history: making cheese, wine, sewage treatment
new biotechnologies: transgenic grains, rice bacteria used in manufacture of
plastics biodegradableethanol- producing bacteriabioremediation:
bacteria that can degrade oil spills
Medical Uses of Prokaryotes
with genetic engineering bacteria can produce: Vitamins Antibiotics Hormones Enzymes
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