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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Campbell reece chapter 27




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?

Reproduction of prokaryotic cells
Reproduction of Prokaryotic Cells


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

Anabaena filaments1
Anabaena Filaments


  • 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

Chlamydia trachomatis
Chlamydia trachomatis

Chlamydia trachomatis1
Chlamydia trachomatis


  • 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

Flashlight fish mutualistic relationship
Flashlight FishMutualistic Relationship

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