classification of microorganisms what is the role of microorganisms in the living world?
TRANSCRIPT
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
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