M. AshcraftThe origin of MicroorganismsAnthony van Leeuwenhoek’s  animalcules were discovered in 1674- Robert Hooke first to observe a microorganism  Using ground glass, observed bread mold  De-bunked by Francesco Redi Italian at the end of the 17th century- Worm and meat experiment- Covered one meat with cheese cloth, and found no maggots formed- Disproved spontaneous generation: the theory that suggested organisms can arise from non living material - Despite his (Redi’s) work, the microorganism s. generation was difficult to refute because various experiments yielded conflicting results- John Needham (1749)showed that various boiled broths gave rise to mirco-organisms  Because brief boiling was thought to kill all microbes, this supported s. generation- Spallanzani(1776)- boiled the infusions longer and with a sealed tube, killing all the microbes and proving that s. generation was impossible- When the neck cracked, the broth would become cloudy - Others argued that boiling destroyed the “vital force” necessary for spontaneous generation- Louis Pasteur (1861)French chemist who refuted s. generation debate- Discovered air is filled with mirco-organisms- Filtered air through a cotton plug, trapping organisms to be examined under a microscope- Looked identical to those in the infusions- When dropped the cotton plug into the broth, saw that the microbes multiplied- (2) Proved that sterile infusions would remain sterile unless tainted - Organisms from the air would settle in the bend of the swan neck flask and not escape and would never reach the sterile solution- John Tyndall finally explained the differences between Pasteur’s mixed results- Different infusions require different lengths of boiling time - Found that there was heat resistant microbes by studying hay - Found that there were 2 types of microbeso Those killed by boilingo Those that are heat resistant- Heat resistantendospores (Bacillus, Clostridium)o Also discovered by Cohn and Kocho Mostly from soil - Proved that every part of an experiment must be replicated in order to produce the sameresultMircobiology: a human perspective- Features of a Mircobial World Microbes: including living and non living agents of the microscopic world Microscopic Extreme biodiversity- Account for most of the world’s biodiversity - Diverse among each other  Most abundantlargest biomass Longest living form of life on earth - Vital Roles Bacteria convert nitrogen into usable forms (airusuable for plants) Aquatic organisms replenish oxygen Degrade cellulose, sewage, and waste water- Applications of Microbiology Food Production- Cheese, bread, yogurt, beer Bioremedition- Degrade environmental pollutants like TNT, PCD, DDTM. Ashcraft Useful Products- Ethanol, antibiotics, cellulose- Medical Micro Past Triumphs- Killed more than war- Small pox, plague Present and Future Challenges- Many emerging diseases: Lyme, etc- New opportunities for spreading in rapidly moving world- Changing lifestyles bring more chance of disease  Resurgence of Old Diseases- Travel is main concern- Vaccination is becoming more lax as the disease is dormant in pop- Pop is inc in number of elderly people- Microorganisms as Model Organisms 3 Distinct Domains:- Bacteriao Look identical to Achaeao Prokaryotic: DNA is in nucleiodo Cylindrical (rod), spherical, spiralo Rigid cell walls contain chemical peptidoglycano Binary fissiondivides into 2 indentical cellso Flagella- Archaeao Prokaryotic  1000x smaller than eukaryotico Same as Bacteria in shape, comp, flagella, binary fission, but no peptidoglycano Grow in extreme environments- Eucaryao Eukaryotic  Organelles enveloped in membranes inside the cell DNA inside nucleus Mitochondria, Golgi body, endo reticulum carried out by membrane in prokaryoticso Includes:  Algae - energy from sunlight- rigid cell wall- generally aquatic - move by means of flagella- single or multiple celled, mirco or macroscopic fungi- large microorganisms like mushrooms - mostly terrestrial - organic material- single or multi-celled, micro or macroscopic protozoa- Aquatic and terrestrial environments- No rigid cell wall- Single-celled- Organic material- microscopic helminth: round and tapeworms- unlike fungi and algae, rigid cell wall- organic compounds as food Viruses, Viroids, PrionsM. Ashcraft- Nonliving, acellular agents- Virus A piece of nucleic matter (DNA or RNA) surrounded by a protein coat  Only multiply inside of the host cell using the host’s process of reproduction- Obligate intracellular parasites Can make the host cell produce toxin Phage therapy treating infection with vrisus that infect bacteria Bacteriophageviruses that infect bacteria- Viroids Single, short piece of RNA without a protein coat  Mostly plant pathogens- Prions Protein without any nucleic acid and a form of abnormal protein Cause neurological disease  Can be denatured by pH, heat When denatured stick together and