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General Information
The prokaryotes are a groupoforganisms that lackacellnucleus (=karyon),oranyothermembrane-boundorganelles
Few prokaryotessuch asmyxobacteria havemulticellularstagesintheir
life cycles Prokaryotesare the earliestandmostprimitive formsoflife on earth
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General Information
Asorganizedinthe Three Domain
System,prokaryotesinclude bacteria
andarchaeans.
Able to live andthrive invarioustypesof
environmentsincluding extreme habitats
such as hydrothermal vents, hot
springs,swamps, wetlands,andthe
gutsofanimals
The prokaryotesare dividedintotwo
domains:the bacteria andthe archaea
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Archaea
Theyare a groupofsingle-celledmicroorganisms
A single individual orspeciesfromthisdomainiscalledanarchaeon
They have nocell nucleusoranyotherorganelles
Archaea have anindependentevolutionary
history andshow manydifferencesintheirbiochemistry
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Eubacteria
The bacteria are a large groupofunicellular,prokaryote,microorganisms.
Wide range ofshapes,rangingfromspheres torodsandspirals
Bacteriaare ubiquitous
There are approximatelytentimesasmanybacterial cellsinthe humanflora ofbacteriaasthere are humancellsinthebody
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Eubacteria
Large numbersofbacteriaonthe skin andasgutflora
The vastmajorityofthebacteriainthe bodyare
rendered harmlessbytheprotective effectsoftheimmune system(parasites),andafew are
beneficial
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Types ofEubacteria
Heterotrophs -theyfeedonorganiccompounds,producedbyotherorganisms
Saprophytes- obtainnutrientsfromdeadorganismsorbreakdownorganicmatter
Heterophic aerobes :oxygenrequiring / Heterophic-anaerobes:can live withoutoxygen
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Prokaryotic Cell Structure
Prokaryoticcellsare notascomplexas
eukaryoticcells
Have notrue nucleusasthe DNA isnot
contained withinamembrane or
separatedfromthe restofthe cell
DNA iscoiledupinaregionofthe
cytoplasmcalledthe nucleoid
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Prokaryotic Cell Structure
Capsule - Foundinsome
bacterial cells,thisadditional
outercovering protectsthe cell
Cell Wall - Outercovering ofmostcells
Cytoplasm - A gel-like
substance composedmainlyof
waterthatalsocontainsenzymes,salts,cell
components,andvarious
organicmolecules.
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Prokaryotic Cell Structure
Cell Membrane or Plasma Membrane - Surroundsthecell'scytoplasmandregulatesthe flow ofsubstancesinandoutofthe cell.
Pili - Hair-like structuresonthe surface ofthe cell thatattach tootherbacterial cells..
Flagella - Long, whip-like protrusionthataidsincellularlocomotion.
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Prokaryotic Cell Structure
Ribosomes - Cell structuresresponsible forproteinproduction.
Plasmids - Gene carrying,circularDNA structuresthatare notinvolvedinreproduction.
Nucleiod Region - Areaofthe cytoplasmthat
containsthe single bacterial DNA molecule.
Endospores it hasprotective function
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Binary Fission
Mostprokaryotesreproduce asexually through aprocesscalledbinaryfission
DNA molecule replicating andboth copiesattaching tothe cell membrane.
Cell membrane beginsto grow betweenthe two DNAmolecules.
A cell wall thenformsbetweenthe two DNA moleculesdividing the original cell intotwoidentical daughtercells.
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Cyanobacteria
Cyanobacteriaisaphylumofbacteria
thatobtaintheirenergythrough
photosynthesis.
Itisalsoknownasblue-greenalgae,
blue-greenbacteriaorcyanophyta. Thename "cyanobacteria" comesfromthe
colorofthe bacteria(Greek:
(kyans)=blue).
Theyare asignificantcomponentofthe
marine nitrogencycle. Theyare a
significantcomponentofthe marine
nitrogencycle; Theyare alsofoundin
habitatsotherthanthe marine
environment
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Cyanobacteria
y Veryclose instructure andfunctiontothe true bacteria.They have all the structurestypical forbacteria, exceptthe flagella.
y Have a lotofmembrane lamellae (thylakoids)situatedinthe cytoplasm.
y Contain greenpigmentchlorophyll which helpthemtoabsorb energy,photosynthesize andobtainorganicsubstances. Thisis whycyanobacteriaare calledautotrophs.
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Cyanobacteria
Classification:
The cyanobacteria were traditionally
classifiedbymorphologyintofive sections.
Firstthree are Chroococcales,
Pleurocapsales,Oscillatoriales.
Lattertwoare NostocalesandStigonematales
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Importance ofbacteria
Bacteriaplayanimportantrole innature. Theyare amajorfactorinthe processofdecay.
Some bacteriaare nitrogen-fixing theycapture nitrogenfromthe
airandinclude itinthe synthesisofproteins.
Bacteriainhabitthe digestive systemsofboth humansandanimals.Inmanycasestheyaidthe breakdownofcellulose,containedinfood.
Cyanobacteriaare most widelyspreadinsoil andinpolluted waterbasins. Theirpresence isanindicatorofthe level ofwaterpolution.
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Health Risk
Certaincyanobacteriaproduce cyanotoxins which are toxinsthat
canbe dangerousto humansandanimals.
Several casesofhumanpoisoning have beendocumented.
Recentstudiessaysthatsignificant exposure to high levelsof
cyanobacteriacauses ALS (Lou Gerhig's Disease)
Cyanobacteriacause variousinfectiousillnessesin humansand
animals like dysentery,tetanus,plague, lung inflammation,
tuberculosis, etc.
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