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 cellVirus

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