Classification of microorganisms

What is the role of microorganisms in the living

world?

What are microorganisms?

• Organisms that generally can not be seen with naked eye

• First observed in 1674 by Van Leeuwenhoek

• Carry out 90% of the biochemical reactions produced on earth

• Most numerous type of organism on earth

Major types of microorganisms

• Bacteria

• Protozoa

• Fungi

• Viruses

• Algae

Bacteria

• Single-celled organisms• Prokaryotic• Have thick rigid cell wall containing

peptidoglycan• Incredibly diverse:

– Live almost EVERYWHERE on earth– Can be free-living or parasitic– Can be heterotrophs or autotrophs– Can require or not require oxygen

Bacteria cell structure

Classification of bacteria• Classified by SHAPE into 3 groups:

Spiral:spirilla

rod-shaped: bacilli, bacillus

Round:cocci

Bacterial reproduction

• Reproduce by:– Binary fission

• Asexual reproduction (only one parent)

– Conjugation• Sexual

reproduction (2 parents involved)

Importance of bacteria

• Decomposers– Decompose dead organisms and return raw materials

to environment• Producers

– Among most important producers on the planet• Nitrogen fixers

– Convert nitrogen from air into usable form• Human uses

– Food production– Digest petroleum and remove human waste and

poison– Make drugs and chemicals

Examples of bacteria

Salmonella bacteria

Nitrogen-fixing bacteria Oil eating bacteria from the Gulf Oil Spill

Viruses

• Non-living particle made of proteins, nucleic acids (DNA or RNA) and sometimes lipids

• Can only reproduce by infecting living cells

Structure of Viruses

• Very small- only seen with very powerful microscope

• Have protein coat- capsid

• Can have few genes to hundreds of genes

How a virus enters a cell

• Proteins on the surface membrane of the virus bind to receptor proteins on a host cell

• The proteins “trick” the cell to take in the virus or its genetic material

Host cell Virus

Types of cells viruses can infect

• Most viruses only infect specific kind of cell

• Plant viruses infect plant cells

• Most animal viruses only infect certain species of animals

• Bacteriophages= viruses that infect bacteria

Viral infections

• Viruses use their genetic information to make multiple copies of themselves

• Some viruses replicate immediately → lytic infection

• Some viruses wait to do it → lysogenic infection

Lytic infection

Lysogenic infection

Flu virus animation