campbell reece chapter 27
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CAMPBELL & REECE CHAPTER 27. BACTERIA & ARCHAEA. 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

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prokaryotic adaptations
  • typical prokaryote:
    • 0.5 -5 microns
    • unicellular
    • variety of shapes
      • cocci (spherical)
      • bacilli (rods)
      • spirochetes (corkscrews)
cell surface structures
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
Cell Wall Structure



cell walls mostly cellulose or chitin


(-) peptidoglycan

(+) variety polysaccharides & proteins

  • bacterial cell walls contain peptidoglycan: a polymer made of sugars cross-linked with short polypeptides
gram staining
Gram Staining
  • used to classify many bacteria as gram + or gram –
  • + or – staining due to differences in cell wall composition
Gram +

Gram -

more complex

less peptidoglycan

+ outer membrane with lipopolysaccharides

  • simpler cell walls
  • more peptidoglycan
Gram +

Gram -

Gram + Rods

Gram - Rods

medical implications of gram stain
Medical Implications of Gram Stain

Gram +

Gram -

many strains virulent:

tends to be:

toxic (fever, shock more likely)

drug resistance

  • some strains virulent
  • some drug resistance (staph)
  • works by inhibiting peptidoglycan cross-linking  makes cell nonfunctional
  • since none in eukaryotic cells  does not harm them
  • Which infection would more likely respond to treatment with pcn?
prokaryotic capsules
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 cells
  • make it more difficult for immune system to get to bacterial cell
  • used to stick to host cells
  • shorter & more numerous than pili
  • appendages that pull cells together prior to DNA transfer between cells
  • aka sex pili
bacteria motility
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)
  • most common structure used for prokaryotic motility
  • 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
  • all these differences suggest flagella arose independently in all 3 Domains
  • so are analogous structures not homologous structures



bacterial flagella
Bacterial Flagella
  • 3 main parts:
  • motor
  • hook
  • filament
bacterial flagella1
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 flagella2
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
DNA in Prokaryotic Cells
  • most have less DNA than eukaryotic cell
  • circular chromosome with many fewer proteins
  • loop located in nucleoid
  • most also have a plasmid: smaller ring(s) of independently replicating DNA
inner membranes in prokaryotic cells
Inner Membranes in Prokaryotic Cells
  • So how do some prokaryotic cells undergo photosynthesis and cellular respiration if they do not have membrane-bound organelles?
bacterial reproduction
Bacterial Reproduction
  • many bacteria can divide in 1- 3 hrs. (some in 20 min)
  • factors that slow down reproduction:
    • loss of nutrients
    • toxic metabolic waste
    • competition with other bacteria
    • eaten by predators
survivors in extreme environments
Survivors in Extreme Environments
  • Halobacterium
    • rod-shaped
    • Archaea
    • lives in 4M saline (or higher)
  • developed by certain bacteria to withstand harsh conditions
  • resistant cells develop when essential nutrients lacking
  • survive boiling water
  • remain dormant & viable for centuries
prokaryotic evolution
Prokaryotic Evolution
  • short generations (up to 20,000 in 8 yrs)
  • adapt rapidly
  • populations have high genetic diversity
  • have been around for 3.5 billion yrs
genetic diversity
Genetic Diversity
  • Factors that promote genetic diversity:
  • rapid reproduction
  • mutation
  • genetic recombination
rapid reproduction mutation
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
Genetic Recombination
  • the combining of DNA from 2 sources
  • occurs 3 ways in prokaryotes
    • transformation
    • transduction
    • conjugation
transformation in prokaryotic cells
Transformation in Prokaryotic Cells
  • uptake of foreign DNA from its surroundings
  • many bacteria have cell-surface proteins that recognize DNA from closely related species & transport it into the cell
transduction in prokaryotic cells
Transduction in Prokaryotic Cells
  • bacteriophages (phages) carry prokaryotic genes from 1 host cell to another…..usually as result of “accidents” during replicative cycle
conjugation plasmids
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 only
  • must have particular piece of DNA: F factor
  • DNA transferred either plasmid or section of loop DNA
metabolic adaptations in prokaryotic cells
Metabolic Adaptations in Prokaryotic Cells
  • phototrophs: obtain energy from light
  • chemotrophs: obtain energy from chemicals
  • autotrophs: need CO2 as carbon source
  • heterotrophs: require at least 1 organic nutrient to make other organic compounds
  • 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
nitrogen metabolism
Nitrogen Metabolism
  • N essential to make a.a. & nucleic acids
  • Nitrogen Fixation
    • cyanobacterium & some methanogens
    • N2 from atmosphere  NH3  used by plants
metabolic cooperation
Metabolic Cooperation
  • heterocysts formation
  • biofilms
  • sulfate/methane consuming bacteria
metabolic cooperation1
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
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
  • surface-coating colonies of different prokaryotic species
  • channels in biofilm allow nutrients to reach cells in interior (& wastes to leave)
  • cells secrete
  • signaling molecules  recruit nearby cells
  • polysaccharides & proteins that stick cells together
sulfate methane consumers
Sulfate/Methane Consumers
  • 1 archaea species that is a methane consumer forms ball-shaoedaggreagate with 1 sulfate consuming bacteria on ocean floor:
  • 1 uses wastes of other to obtain necessary nutrients
prokaryotic phylogeny
Prokaryotic Phylogeny
  • b/4 technology made molecular systematics available prokaryotic organisms grouped by:
    • nutrition
    • shape
    • motility
    • Gram stain
molecular systematics
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
Polymerase Chain Reaction(PCR)
  • 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)
  • share some traits with Bacteria, some with Eukarya
  • some unique traits too

1.extreme halophiles

  • live in highly saline environments
  • some tolerate high salinity
  • some require high salinity
    • proteins function best in extremely salty environments (die if salinity <9%) (ocean is 3.5%)

2. extreme thermophiles

  • thrive in hot environments
  • Sulfolobuslive in sulfur-rich volcanic springs up to 90ºC
  • strain-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.

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
  • new clades continue to be found
  • majority of prokaryotic species
  • have diverse nutritional & metabolic capabilities
  • a large & diverse clade
  • Gram (-)
  • (+) for photoautotrophs, chemoautotrophs, & heterotrophs
  • some aerobic, some anaerobic
  • all parasites
  • Intracellular
  • Gram(-) but lack peptidoglycan in cell wall
  • Chlamydia trachomatis: #1 cause of blindness in the world & causes most common STD in USA
  • helical heterotrophs
  • internal flagellum-like structures that allows them to corkscrew through their environment
  • pathogenic strains:
    • Treponemapallidum: syphilis
    • Borreliaburgdorferi: Lyme disease


Lyme disease

  • photoautotrophic
  • likely have common ancestor with chloroplast
  • solitary or filamentous (some filaments have cells specialized for N fixation)
  • component of freshwater or marine phytoplankton
gram bacteria
Gram + Bacteria



  • fungus-like
  • form branched chains
  • includes TB and leprosy
  • includes many decomposers in soil (earthy odor in soil)
diversity of gram bacteria4
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
  • Mycoplasmapneumoniae
prokaryotic interactions in biosphere
Prokaryotic Interactions in Biosphere
  • 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

Symbiotic Relationships
  • Mutualism
  • Commensalism
  • Parasitism
  • Pathogens
pathogenic prokaryotes
Pathogenic Prokaryotes
  • usually cause illness by producing:
    • exotoxin
    • endotoxin


lippolysaccharide from outer membrane of gram

(-) bacteria

released when bacteria die

example: Salmonella typhi

  • released by pathogen
  • cause illness even if bacteria no longer present
  • example: Clostridium botulinum
how bacteria can become more virulent
How Bacteria can become more Virulent
  • carry resistant genes
  • horizontal gene transfer
    • harmless bacteria  virulent strains
example of 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
Prokaryotes in Research & Technology

long history: making cheese, wine, sewage treatment

new biotechnologies:

  • transgenic grains, rice
  • bacteria used in manufacture of plastics  biodegradable
  • ethanol- producing bacteria
  • bioremediation:
    • bacteria that can degrade oil spills
medical uses of prokaryotes
Medical Uses of Prokaryotes
  • with genetic engineering bacteria can produce:
    • Vitamins
    • Antibiotics
    • Hormones
    • Enzymes