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