CAMPBELL REECE CHAPTER 27 BACTERIA ARCHAEA PROKARYOTIC ADAPTATIONS

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 plasmolyze in hypertonic solution ▪ water loss inhibits cell division hence salt used as food preservative (ham)

Cell Wall Structure PROKARYOTES EUKARYOTES � bacterial � cell walls contain peptidoglycan: a polymer made of sugars cross-linked with short polypeptides 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 + GRAM - � some � many strains � tends to be: strains virulent drug resistance (staph) virulent: toxic (fever, shock more likely) drug resistance

Penicillin �works by inhibiting peptidoglycan crosslinking 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 cells �make it more difficult for immune system to get to bacterial cell

Capsules

Fimbriae �used to stick to host cells �shorter & 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 (~ 1/10 th 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. motor 2. hook 3. 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 nucleoid �most also have a plasmid: smaller ring(s) of independently replicating DNA

DNA 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?

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 nutrients 2. toxic metabolic waste 3. competition with other bacteria 4. eaten by predators

Survivors in Extreme Environments Halobacterium 1. rod-shaped Archaea lives in 4 M 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 rapidly �populations have high genetic diversity �have been around for 3. 5 billion yrs

Genetic Diversity �Factors that promote genetic 1. rapid reproduction 2. mutation 3. genetic recombination diversity:

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 �occurs 3 ways in prokaryotes 1. transformation 2. transduction 3. conjugation sources

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

Transformation 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

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 only �must have particular piece of DNA: F factor �DNA transferred either plasmid or section of loop DNA

Conjugation

Plasmids & Antibiotic Resistance

Genetic Recombination in Prokaryotic Cells

Metabolic Adaptations in Prokaryotic Cells �phototrophs: obtain energy from light �chemotrophs: obtain energy from chemicals �autotrophs: need CO 2 as carbon source �heterotrophs: require at least 1 organic nutrient to make other organic compounds

Oxygen �obligate aerobes: must use O 2 for cellular respiration �obligate anaerobes: O 2 is toxic to them (fermentation) �faculative anaerobes: use O 2 when available but also carry out fermentation if have to

Oxygen & Prokaryotic Cells

Nitrogen Metabolism �N essential to make �Nitrogen Fixation a. a. & nucleic acids cyanobacterium & some methanogens N 2 from atmosphere NH 3 used by plants

Nitrogen Fixation

Metabolic Cooperation 1. 2. 3. heterocysts formation biofilms 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 O 2 from getting in (O 2 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 secrete 1. signaling molecules recruit nearby cells 2. 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/ani mations/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 EUKARYA PEPTIDOGLYCAN IN CELL WALL + - - MEMBRANE LIPIDS unbranched hydrocarbons 1 kind RNA polymerase Introns in genes initiator a. a. for protein synthesis very rare formylmethionine some branched unbranched hydrocarbons several kinds in some genes methionine in many genes methionine

ARCHAEA �share some traits with Bacteria, some with Eukarya �some unique traits too

Extremophiles 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%)

Halobacterium

Extremophiles 2. extreme thermophiles �thrive in hot environments �Sulfolobus live 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.

strain-121

Extremophiles 3. methanogens �live in moderate environments swamps, marshes under ice in Greenland in bovine colon, in termites carbon dioxide to oxidize H 2 gas produces energy & methane as a waste product �strict anaerobes �use

Methanogens

Archaea �new clades continue to be found

Bacteria �majority of prokaryotic species �have diverse nutritional & metabolic capabilities

Proteobacteria �a large & diverse clade �Gram (-) �(+) for photoautotrophs, chemoautotrophs, & heterotrophs �some aerobic, some anaerobic

Proteobacteria

Chlamydias �all parasites �Intracellular �Gram(-) but lack peptidoglycan in cell �Chlamydia trachomatis: #1 cause of blindness in the world & causes most common STD in USA wall

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 chloroplast �solitary 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 � 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 Decomposers 1. recycle nutrients from dead organisms & waste products

2. Autotrophic bacteria convert CO 2 organic cpds; some releasing O 2 others (kingdom Crenarchaeota) fix N 2 gas organic cpds

3. � � Symbiotic Relationships Mutualism Commensalism Parasitism Pathogens

Flashlight Fish Mutualistic Relationship

Pathogenic Prokaryotes �usually cause illness by producing: 1. exotoxin 2. endotoxin

EXOTOXINS ENDOTOXINS � released by pathogen � cause illness even if � lippolysaccharide bacteria no longer present � example: Clostridium botulinum from outer membrane of gram (-) bacteria � released when bacteria die � example: Salmonella typhi

How Bacteria can become more Virulent carry resistant genes horizontal gene transfer 1. 2. harmless bacteria virulent strains

Horizontal Gene Transfer

Example of Horizontal Gene Transfer �E coli strain 0157: H 7 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 biodegradable �ethanol- producing bacteria �bioremediation: bacteria that can degrade oil spills

Medical Uses of Prokaryotes �with genetic engineering bacteria can produce: Vitamins Antibiotics Hormones Enzymes