© 2014 Pearson Education, Inc. Prokayrotes & prokaryotic diversity Common characteristics Bacteria v Archaea Structure Genetics Metabolism

© 2014 Pearson Education, Inc.

Prokayrotes & prokaryotic diversity

Common characteristics

Bacteria v Archaea

Structure

Genetics

Metabolism

Role in env.


Prokaryotic history

Oldest form of life—3.5 bil yrs

First forms anaerobic

Development of aerobic forms oxygenated the atmosphere

3.5 b.y. of divergence incredible diversity

Most abundant organism on earth

Two groups: Bacteria & Archaea


Common Traits of Prokaryotes (Bacteria & Archaea)

Unicellular

..but….

Cell wall — not of cellulose or chitin

No membrane bound organelles

….but…..

No nucleus

Single circular chromosome

Small

0.5 micrometers – 5 micrometers


Bacteria v. Archaea

Bacteria Archaea

Cell wall Peptidoglycan Polysaccarides+protein (no peptidoglycan)

RNA Polymerase 1 kind Several kinds

Introns in DNA No Yes

Histone w/ DNA No yes

Extremophilic No yes


Table 27.2


Figure 27.UN04

Fimbriae

Cell wall

Capsule

Internalorganization

Flagella

Circularchromosome

Sex pilus


Structure & Diversity

Shape

Cell wall

Internal structure

DNA

motility

3 µ

m

1 µ

m

1 µ

m


Structure & Diversity

Many shapes

Cocci (spheres)

Bacilli (rods)

Spirilla (spirals/helixs)

Spherical Rod-shaped Spiral

3 µ

m

1 µ

m

1 µ

m


(a) Gram-positive bacteria Gram-negative bacteria

(b)

Cellwall

Peptido-glycanlayer

Plasmamembrane

Carbohydrate portionof lipopolysaccharide

violet

Cellwall

Outermembrane

Peptido-glycan layer

Plasma membrane

pink

Cell Wall and Capsule Cell wall of peptidoglycan

Gram –

Gram +

Capsule of polysaccharide or proteins


Endospores

Endospores are encapsulated DNA packets

Coat

Endospore


Motility

Flagella (different from Eukaryotic flagella)

Pili

Taxis = movement toward (+) or away from (-) stimuli


DNA Organization

Single circular chromosome

In nucleoid region

Plasmids: independently replicating loops of DNA


Reproduction Binary fission=chromosome replicated, then cell divides

ASEXUAL = clones (except for mutations)


Genetic Diversity

Short generations + mutation

Genetic Recombination/horizontal gene transfer

Conjugation: DNA transfer (plasmids)

Transformation:

Transduction


Figure 27.13

BacterialchromosomeF plasmid

F+ cell

F+ cell

F+ cell(donor)

Matingbridge

Bacterialchromosome

(a)

Conjugation and transfer of an F plasmid

F− cell(recipient)

Sex pilus

CONJUGATION


Figure 27.11-5

Phage infects bacterialdonor cell with A+ and B+alleles.

Phage DNA is replicatedand proteins synthesized.

Fragment of DNA with A+ allele is packaged withina phage capsid.

Phage with A+ alleleinfects bacterial recipientcell.

Incorporation of phageDNA creates recombinantcell with genotype A+ B−.

A+

Donor cell

Phage DNA

A+ B+

A+ B+

A+

B−A−

Crossingover

Recombinantcell

Recipient cell

B−A+

1

2

5

4

3

TRANSDUCTION


Transformation:Update of DNA in the environment by bacteria


Nutritional modes

SOURCE OF ENERGY

NUTRITIONAL MODES

Light as energy source

Chemicals as energy source

SOURCE OF CARBON

CO2 (or related inorganic)

Photoautotroph Chemoautotroph

Organic compounds Photoheterotrophs chemoheterotrophs

Photoautotrophs = photosynthetic

CO2 + H20 C6H12O6 + O2


Aerobic v. Anaerobic

Obligate Aerobes = require O2

Obligate Anaerobes = O2 is toxic

fermentation or anaerobic respiration in which substances other than O2 accept electron

Facultative Anaerobes:

Prefer to use O2, but don’t need it


Nitrogen Metabolism

some cyanobacteria and some archaea can fix nitrogen

N-fixing = N2 NH3

NH3 can be used as nitrogen source by other organism

Part of nitrogen cycle

All other organisms on earth depend on this in order to get N for proteins


Prokaryotic Cooperation

Filaments & colonies

Biofilms

Deep sea aggregates


Bacterial Diversity

Bacteria are currently organized into 5 non-monophyletic groups

Proteobacteria

Chlamydias

Spirochetes

Cyanobacteria

Gram-positivebacteria


Figure 27.15

UNIVERSALANCESTOR

Eukaryotes

Korarchaeotes

Euryarchaeotes

Crenarchaeotes

Nanoarchaeotes

Proteobacteria

Chlamydias

Spirochetes

Cyanobacteria


Do

main

Eu

karyaD

om

ain A

rchaea

Do

main

Bacteria


Proteobacteria (5 major subunits) Gram-

Aerobic & An_

All nut. Modes but photochem (which is archaean)

Incl nitrogen fixers (N cycle) & others involve w/ N-cycle

Sulfur metabolizers

Human pathogens: H pylori (ulcers), salmonella (food poisoning), Leginella (legionnaires disease), vibrio cholerae (cholera)


Chlamydias Gram –

Can only survive w/in animal cells and depend on host cells for ATP

Cell walls lack peptidoglycan (have a liposaccharide instead which inhibits it from being phogocytized by host)

Includes human pathogens (Chlamidia STD, most common STD world wide)

Can’t be cultured and was once thought to be a virus


Spirochetes

Spiral, move by rotating w/ internalized flagella like structure

Free living and pathogenic forms (syphilis and lyme disease)


Gram+ v. Gram-

Gram-positive bacteria have simpler walls with a large amount of peptidoglycanGram-negative bacteria have less peptidoglycan and an outer membrane that can be toxic


Figure 27.3c


Gram-negativebacteria

10 µm


Figure 27.1


Table 27.1


Cyanobacteria These are photoautotrophs that generate O2

Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis

CyanobacteriaOscillatoria, a filamentouscyanobacterium

40 µ

m

Photosyntheticcells

Heterocyst

20 µm

Anabaena


Gram-Positive Bacteria

Gram-positive bacteria include

Actinomycetes, which decompose soil

Bacillus anthracis, the cause of anthrax

Clostridium botulinum, the cause of botulism

Some Staphylococcus and Streptococcus, which can be pathogenic

Mycoplasms, the smallest known cells

Gram-positive bacteriaStreptomyces, the sourceof many antibiotics (SEM)

5 µ

m


Archaea Archaea share certain traits with bacteria and other traits with

eukaryotes

Some archaea live in extreme environments and are called extremophiles

Extreme halophiles live in highly saline environments

Extreme thermophiles thrive in very hot environments

Methanogens live in swamps and marshes and produce methane as a waste product

Methanogens are strict anaerobes and are poisoned by O2

In recent years, genetic prospecting has revealed many new groups of archaea


Figure 27.17


Ecological Interactions Symbiosis is an ecological relationship in which two species live in

close contact: a larger host and smaller symbiont

Prokaryotes often form symbiotic relationships with larger organisms

In mutualism, both symbiotic organisms benefit

In commensalism, one organism benefits while neither harming nor helping the other in any significant way

In parasitism, an organism called a parasite harms but does not kill its host

Parasites that cause disease are called pathogens


Humans & Mutualistic Bacteria

Human intestines are home to about 500–1,000 species of bacteria

Many of these are mutualists and break down food that is undigested by our intestines

Pathogenic Bacteria Bacteria cause about half of all human diseases

Some bacterial diseases are transmitted by other species

Exotoxins are secreted and cause disease even if the prokaryotes that produce them are not present

Endotoxins are released only when bacteria die and their cell walls break down


Prokaryotes are the principal agents in bioremediation, the use of organisms to remove pollutants from the environment

Bacteria can be engineered to produce vitamins, antibiotics, and hormones

Bacteria are also being engineered to produce ethanol from agricultural and municipal waste biomass, switchgrass, and corn

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© 2014 Pearson Education, Inc. Prokayrotes & prokaryotic diversity Common characteristics Bacteria v Archaea Structure Genetics Metabolism