Chapter 27~Chapter 27~Prokaryotes and the Prokaryotes and the Origins of Metabolic Origins of Metabolic DiversityDiversity

ClassificationClassification

Domain: BacteriaDomain: Bacteria– Found almost Found almost

everywhereeverywhere

Domain: ArchaeaDomain: Archaea– Usually found in Usually found in

extreme environmentsextreme environments

Structure of BacteriaStructure of BacteriaShape Shape – cocci (sphere)cocci (sphere)

Can be alone Can be alone or in colonies or in colonies

– bacilli (rod) bacilli (rod) Usually solitary Usually solitary but can be in but can be in chains chains

– helical (spiral)helical (spiral)Corkscrew Corkscrew shapeshape

Structural characteristicsStructural characteristicsAlmost all prokaryotes have a Cell wallAlmost all prokaryotes have a Cell wall– Made of peptidoglycan (sugars & proteins) Made of peptidoglycan (sugars & proteins)

Gram +Gram +: large amount of peptidoglycan : large amount of peptidoglycan outside of membraneoutside of membrane

Gram -Gram -: little peptidoglycan in between : little peptidoglycan in between two two membranes- outer one has membranes- outer one has lipopolysaccharideslipopolysaccharides

–Usually more harmful and resistant to Usually more harmful and resistant to drugs than gram +drugs than gram +

Capsule: adherence and additional protectionCapsule: adherence and additional protection

Pili: adherence and conjugationPili: adherence and conjugation

MotilityMotilityFlagellaFlagella

Helical shape Helical shape (spirochetes)(spirochetes)

SlimeSlime

Taxis Taxis

– movement movement away or away or toward a toward a stimulusstimulus

Form & FunctionForm & FunctionNucleoid region (Nucleoid region (genophoregenophore: non-eukaryotic : non-eukaryotic chromosome)chromosome)

PlasmidsPlasmids

Asexual reproduction: Asexual reproduction: binary fissionbinary fission (not mitosis) (not mitosis)

““Sexual” reproduction (not meiosis): Sexual” reproduction (not meiosis): – transformationtransformation~ uptake of genes from ~ uptake of genes from

surrounding environment surrounding environment – conjugationconjugation~ direct gene transfer from 1 ~ direct gene transfer from 1

prokaryote to another prokaryote to another – transductiontransduction~ gene transfer by viruses~ gene transfer by viruses

Endospore: makes cell resistant in harsh Endospore: makes cell resistant in harsh conditions (250 million years)conditions (250 million years)

Prokaryotic GrowthProkaryotic Growth

Conditions for growth vary with speciesConditions for growth vary with species– cold conditions ( refrigerator) slow growthcold conditions ( refrigerator) slow growth

Most have generations times of 1-3 hours Most have generations times of 1-3 hours but some can divide every 20 minutesbut some can divide every 20 minutes

StatisticStatistic– 1 cell could give rise to a colony weighing 1 1 cell could give rise to a colony weighing 1

million kg in 24 hrs if no limits on growth!!!!!million kg in 24 hrs if no limits on growth!!!!!Equals 2.2 million pounds in 24hrs!Equals 2.2 million pounds in 24hrs!

Nutrition & MetabolismNutrition & MetabolismPhotoautotrophsPhotoautotrophs: photosynthetic; harness light to : photosynthetic; harness light to drive the synthesis of organic compounds drive the synthesis of organic compounds (cyanobacteria)(cyanobacteria)

ChemoautotrophsChemoautotrophs: oxidation of inorganics for : oxidation of inorganics for energy; get carbon from CO2energy; get carbon from CO2

PhotoheterotrophsPhotoheterotrophs: use light to generate ATP but : use light to generate ATP but get carbon in an organic formget carbon in an organic form

ChemoheterotrophsChemoheterotrophs: consume organic molecules : consume organic molecules for both energy and carbonfor both energy and carbon– saprobes- saprobes- dead organic matter decomposersdead organic matter decomposers– parasites- parasites- absorb nutrients from living hostsabsorb nutrients from living hosts

Nutrition & MetabolismNutrition & Metabolism

Oxygen relationships: Oxygen relationships: – Obligate aerobesObligate aerobes

Use O2 for cell. resp. and cannot live with out Use O2 for cell. resp. and cannot live with out itit

– Facultative anaerobesFacultative anaerobesWill use O2 if present but can grow by Will use O2 if present but can grow by fermentation in anaerobic environmentsfermentation in anaerobic environments

– Obligate anaerobes Obligate anaerobes Poisoned by O2Poisoned by O2

Domain Archea BacteriaDomain Archea Bacteria

3 main groups3 main groups

– MethanogensMethanogens

Give off methane, anerobes, live in Give off methane, anerobes, live in swamps and marshes where O2 is low, swamps and marshes where O2 is low, give off methane gasgive off methane gas

– HalophilesHalophiles

Live in saline places like great salt lakeLive in saline places like great salt lake

– Extreme thermophilesExtreme thermophiles

Hot environments, deep sea ventsHot environments, deep sea vents

Domain BacteriaDomain Bacteria

5 Major groups ( see pg 514 of book)5 Major groups ( see pg 514 of book)

Prokaryotic ecologyProkaryotic ecologyDecomposers: Decomposers: unlock organics from unlock organics from corpses and waste productscorpses and waste products

Symbiosis:Symbiosis:

– Symbionts ( organisms involed in Symbionts ( organisms involed in relationship) / host relationship) / host

– mutualism (+, +) mutualism (+, +) RhizobiumRhizobium and legumes and legumes

– parasitism (+, -)parasitism (+, -)Bacteria that cause illnessBacteria that cause illness

– commensalism (+, 0)commensalism (+, 0)Bacteria in human bodyBacteria in human body

Prokaryotes and DiseaseProkaryotes and DiseaseOpportunisticOpportunistic: normal residents of host; : normal residents of host;

cause illness when defenses are weakenedcause illness when defenses are weakened

Ex. Ex. Streptococcues pneumoniae Streptococcues pneumoniae

Exotoxins: bacterial proteins that can Exotoxins: bacterial proteins that can produce disease w/o the prokaryote present produce disease w/o the prokaryote present (botulism) (botulism)

Endotoxins: components of gram - Endotoxins: components of gram - membranes (membranes (SalmonellaSalmonella))