BIOL 1407 - Prokaryotes

Prokaryotes

Single-celled organisms without a nucleus, oldest and most abundant

Enrichment Cultures

used to isolate bacteria favoring particular conditions, used to study nutrition of prokaryotes, mostly culture disease causing bacteria - <1% current prokaryotes have been cultured

Koch's Postulates

a sequence of experimental steps for directly relating a specific microbe to a specific disease

metagenomics

environmental sequencing, document presence of species that wont grow in culture, quickly discover what species grow in particular habitats, ex: sutdy of human microbiome

Direct sequencing

focus on a particular gene

Early classification characterisistics

relied on staining and observable phenotypes

-photosynthetic or not, motile or nonmotile, unicellular, colony-forming, filamentous, formation of spores or division by transverse binary fission, importance as human pathogen or not

prokaryote classification

mainly use phylogenetic species concept, often based on small subunit rRNA sequences

Two domains of prokaryotes

bacteria (eubacteria), and archaea (many extremophiles)

Prokaryotic genetics

divide by binary fission, do not reproduce sexually, three types of horizontal gene transfer

-all three true for archaea

Morphological diversity

size, shape, motility

Cocci

spherical bacteria

bacilli

rod-shaped bacteria

spirilli

spiral-shaped

Main differences between bacteria and archaea

plasma membrane, cell walls, DNA replication, gene expression

Bacterial membrane

unbranched lipids, ester linkages

archaean membranes

glycerol skeleton, ether linkages, hydrocarbons with branches or rings, some have monolayer

Bacteria cell wall

contain peptidoglycan, gram positive and gram negative differ in amount and location of peptidoglycan

archaea cell wall

no peptidoglycan, pseudopeptidoglycan

Gram positive bacteria

Bacteria that have a thick peptidoglycan cell wall, and no outer membrane

Gram negative bacteria

Bacteria that have complex cell walls with less peptidoglycan but with lipopolysaccharides. Very toxic and hard to treat.

DNA and gene expression

single origin of replication in both bacteria and archaea, gene expression in archaea more similar to eukaryotes

phototrophs

energy source from sun

chemoorganotrophs

obtain energy from organic compounds

chemolithotrophs

obtain energy from inorganic molecules

autotrophs

Organisms that are able to make their own food

heterotrophs

Must acquire energy from other organisms- by ingesting them one way or another

cyanobacteria

early prokaryotes capable of photosynthesis (oxygenated the atmosphere of early Earth)

pseudopeptidoglycan

component of archaea cell walls that is similar to peptidoglycan in morphology but contains different sugars

gram stain

A staining method that distinguishes between two different kinds of bacterial cell walls

oxygenic photosynthesis

photosynthesis that produces oxygen ex: cyanobacteria

anoxygenic photosynthesis

photosynthesis that does not produce oxygen ex: heliobacteria

carbon cycle

The organic circulation of carbon from the atmosphere into organisms and back again

nitrogen cycle

The transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere

extremophiles

archaea that live in extreme environments, uninhabitable for most organisms (hot or cold, high salt)

halophiles

"salt-loving" archaea that live in environments that have very high salt concentrations (halobacteria)

Beneficial prokaryotes

fermentation, bioremediation, mutualism, carbon fixing and nitrogen fixing

mutualism

both parties benefit, nitrogen-fixing bacteria on plant roots

commensalism

one organism benefits, the other is unaffected

parasitism

A relationship between two organisms of different species where one benefits and the other is harmed

bioremediation

The use of living organisms to detoxify and restore polluted and degraded ecosystems, bacteria can be used to remove pollutants from the water, air, and soil