PROKARYOTES AND THE ORIGIN

OF METABOLIC DIVERSITY

Chapter 27p. 534-540

PROKARYOTIC LIFE: AN OVERVIEW Most abundant organisms on Earth

Able to grow in hot, cold, salty, acidic, or basic (alkaline) conditions

2 Types:Archaea: “ancient” live in extreme

environments similar to early EarthBacteria: modern bacteria

PROKARYOTIC LIFE: AN OVERVIEW Most are beneficial or non-harmful

Provide vitamins to humansCycle elements through biosphere (C)Are decomposers (digest dead/decaying

organisms)Form symbiotic relationships w/ other prokaryotes

& eukaryotes

STRUCTURE

Mostly unicellularMay aggregate into

groups called colonies

Shapes:Cocci: sphereBacilli: rodHelices: spiral or

corkscrew Diameter = 1-5

μm

CELL WALLS Maintains shape, protects, prevents

burstingSusceptible to plasmolysis (shrinkage)

Bacteria (not archaea) contain peptidoglycanGram Stain: tests for peptido.

Gram + = ↑ peptido.; stains purpleAntibiotics will inhibit peptido. formation

Gram - = ↓ peptido.; stains pinkCells have outer membrane of

lipopolysaccharidesGenerally more toxic (outer membrane protects)

CELL WALLS (CON’T) Capsule: sticky

substance outside cell wallAids in cell adhesion

(colonies) & protectsPolysaccharide or protein

Fimbriae: numerous hair-like appendages used to attach to host cell

Pili: hold cells together Sex Pilus: used on

conjugation

MOTILITY Flagella: long cellular appendage Composed of:

Basal Apparatus (motor): uses chemiosmosis (H+ diffusion INTO cell) to turn the hook

Hook: anchors filament to basal apparatus & turns Filament: composed of long chain of flagellin protein Under outer layer of cell wall

Taxis: movement toward/away from stimulusi.e.: chemical, light, magnetic field, each other (colonies)

CELLULAR & GENOMIC ORGANIZATION Instead of organelles,

have infolds of plasma membrane for metabolism

Nucleoid Region: where DNA located1 ring of ss DNA

(“genophore”) Plasmids: smaller separate

rings of DNA Have smaller

ribosomes; susceptible to antibiotics

GROWTH & ADAPTATION Binary Fission: asexual

reproduction; can exchange DNA by:1) Transformation: intake

from environment2) Conjugation: exchange

between 2 cells3) Transduction: w/ help of

viruses Mutations are main

source of genetic variationVery fast reproduction →

spread rapidlyAccelerated natural

selection

GROWTH & ADAPTATION (CON’T)

Prokaryotic “growth” = multiplication1-3 hours Inhibited by medium

or accumulation of waste

Endospores: thick-coated resistant cells formed within bacterial cellRequires ↑↑ temps

to kill (120°C min.)May remain dormant

& re-emerge

NUTRITIONAL & METABOLIC DIVERSITY All species require energy & C source 1) Photoautotrophs: light + CO2

i.e.: cyanobacteria (also plants & algae) 2) Chemoautotrophs: chemical (H2S,

NH3, Fe2-) + CO2

i.e.: Sulfolobus 3) Photoheterotrophs: light + organic

nutrientsrare

4) Chemoheterotrophs: chemical + organic nutrients i.e.: saprobes & parasites