Prokaryotic life

Characteristics, Classification, Evolution

• E. coli, a Typical Eubacterium

Peptidoglycan

Cell Membrane

Ribosomes

PiliDNAFlagellum

Cell Wall

Characteristics• Small

– few micrometers in length• Unicellular• No nucleus• May have flagella for

movement

Characteristics

• Have a cell wall– May contain peptidoglycan

(a sugar & protein polymer)• Found Everywhere• Many Cause Disease• Many are Useful• Very diverse

•Prokayotes can be autotrophs or heterotrophs

-Autotrophs: -Self producers, by sunlight or organic chemicals

-Heterotrophs:

- Consumes energy from other organisms

•Energy can be released by:•cellular respiration if there is oxygen available •fermentation if there is no oxygen.

Characteristics

Classification

• Divided into 2 Domains: – Archaea– Bacteria

Hot Spring Pool @ Yellowstone

Deep Ocean Vent

Compost

Food

Cavities

Archaebacteria vs. EubacteriaArchaebacteria • Are ancient. • Lack peptidoglycan.• Live mostly in harsh

environments – Salty lakes– Thick mud– Deep ocean vents– Guts of animals

Eubacteria• Considered “true bacteria”• Have peptidoglycan.• Live almost everywhere.

Classification

• Can be classified by shape:– Cocci- round– Bacilli- rod shaped– Spirilla- spiral

3 Possible Shapes of Bacteria

Bacilli

Cocci

Spirilla

Prefixes Used to Describe & Identify Bacteria:

•Diplo = 2– Neisseria meningitidis (aka diplococcus meningitidis)

•Strepto =chain– Streptococcus pneumonia

•Staphylo =clumps –Ex: Staphylococcus aureus

• Gram Staining - used to identify bacteria with extra membranes– Extra membrane helps them to better resist damage and

means they are usually more pathogenic (disease causing).

– Gram + stain purple (have peptidoglycan)– Gram – (extra membrane) stain red

Classification

• Their success depends on the selective pressures that are applied.

• If they can survive their environment they will survive to reproduce and spread.

• Obstacles that bacteria have to overcome:

– Temperature

– Food

– Chemical balance

– Antibiotics

– Antimicrobials

Evolution

Why so successful in evolving?

• Recall: All living organisms have evolved from a common ancestor.

• Short, rapid reproduction time

• Diversity of bacteria: Bacteria can be found virtually everywhere. They are in the air, soil, water, and in and on plants and animals, including us.

Examples of bacterial evolution:

• Bacterial resistance to anti-biotics

• Bacterial resistance to anti-microbials (hand sanitizer/soap)

Bacteria can share genetic content. This is why bacteria are so successful: the sharing of advantageous traits may enable evolving species to become even more successful.

Evolution of antibiotic resistant bacteria

Prokaryotic Reproduction

Binary fission and Conjugation

Bacterial Reproduction

• They can reproduce in 2 main ways:– Binary Fission (asexual): splitting in half– Conjugation (sexual): sharing genetic info

Binary Fission Video

-Conjugation (sexual) : swapping genes over a bridge between two bacteria

Successful Evolution

• Bacteria can reproduce very rapidly! – E.coli can reproduce in just 20 minutes!

• Environments exert natural selection on populations causing them to change.