Food preservation Religion and mythology Microscopes Medicine Function in the biosphere

Transcription

1 History of microbiology : Food preservation Religion and mythology Microscopes Medicine Function in the biosphere Pay attention to the history but also to the ideas Prehistory? EARLY HISTORY (food preservation): Babylonians / yeast (a fungus) beer over 8000 years ago. Instructions for making beer in 6000 year-old hieroglyphics in Egypt. Wine making dates to about 5000 years ago in Persia (Iran) Also very ancient evidence in Egypt (see overheads) Beer and wine were ways to preserve food...ethanol in the wine acts as a preservative Religion and Mythology: Roman God of Mildew - holiday April 25th - sacrifice a red dog Medicine: ancient peoples realized that diseases could be transmitted via contaminated clothing and that humans could develop immunity to some diseases. Varro (Roman) proposed that diseases were caused by tiny animals. Dark Ages = big zero for science 1600's microscopes Robert Hooke ( ) Anton von Leeuwenhoek ( ) Dutch draper Used magnifying glasses to inspect cloth. Started grinding lenses as a past-time 30x magnification cork cells (L. cellulae, meaning small rooms) (see overhead) first to observe microscopic fungi. Fashioned a simple microscope by grinding grains of sand. Items could be magnified 300 times or more.

2 Looked at water in his microscope and saw: Where did the animacules come from??? Took clean dish, caught some rain - no critters! Not until the fourth day did he observe things swimming in the water. Tiny animacules Looked in other places Saw lots and lots of critters The plaque between his teeth! Louis Pasteur ( ) French - chemist Asked to help out at a winery - some vats were sick - not making any alcohol. Pasteur took samples from the sick vats and from some healthy vats. Found a guy who had never cleaned his teeth in his whole life - he had tons! In the healthy ones, he saw globules --> and realized they were yeast. In the liquid from the sick wine, he did not see any yeast, just small rod-shaped things swimming about. He also noticed the smell of sour milk from these vats. Pasteur reasoned that the yeasts must ferment the juice into alcohol, but that the bacteria fermented the juice into lactic acid instead. He put on a show. He said to the winemakers, Bring me a half dozen bottles of wine that has gone bad with different sicknesses. Do not tell me what is wrong with them, and I ll tell you what ails them without tasting them. The winemakers tried to fool him and slipped in a bottle of perfectly good wine

3 But, Pasteur got them all right. Where were these microbes coming from? Now the issue was how to keep these microbes out of the wine. They found that it simply took heating the wine gently - below the point of boiling - to keep the microbes out. At this point in time, people still believed in the theory of SPONTANEOUS GENERATION. This process is of course now known as Pasteurization. For example, at the time, this was a recipe for mice: Place a dirty shirt or some rags in an open pot or barrel containing a few grains of wheat or some wheat bran, and in 21 days, mice will appear. There will be adult males and females present, and they will be capable of mating and reproducing more mice. Microbes were thought to be the result of disease and not the cause... Theologians also had big problems with spontaneous generation Francesco Redi (Italian, ) meat experiment...good example of an experiment... Even with evidence like that, many still thought microbes were so simple that they didn't have to arise from other microbes. How to prove that simple microbes don t arise via spontaneous generation? hermetically sealed vessels didn t allow in the "vital force" = oxygen Pasteur s friend, Professor Balard, came in and gave him the idea for this: Also filtered air through sterile cotton = caught lots of microbes

4 Thus, Pasteur put an end to the idea that there was some "vital force" in air, and he was the first to show that some bacteria don't even need oxygen. anaerobes (literally (G), without air) aerobes can use O 2 in their metabolism. More Pasteur accomplishments: saved the vinegar industry saved the silkworm industry the first vaccine for rabies tried to improve the quality of French beer (but he really didn t like beer..) Back to Pasteurization for a minute Some things were hard to sterilize especially if they had touched soil Tyndall ( ) Cohn ( ) -endospore containing cells... Bacillus (aerobes) Clostridium (anaerobes). autoclave and pressure cooker (ca. 1880) Robert Koch ( ) Koch was a German physician in the late 1800 s. In his spare time, he began to study anthrax a disease of cattle and sheep and sometimes people. He noticed long threads in the blood of cattle that had died from the disease - they were the bacilli that other people had announced were the cause of the disease - but no one had proven it. Koch then went and got tons of blood from healthy cattle and sheep. Still, he wasn t satisfied. He wanted to be able to prove that the rods, the bacteria, grew inside the mouse. None of them had the bacilli in their blood. He thought and thought He began to experiment with mice, injecting blood from sick cows into them. Sure enough the mice got sick and when he looked at their blood under the microscope, he found the bacilli. He finally put some blood from a sick mouse into the aqueous humor from an ox s eye onto a slide. Lo and behold - the bacilli began to multiply!!

5 Koch continued to keep this culture of bacilli growing, every day repeating his experiment by adding a tiny bit of the infected drop into a new clean one. After eight days, he took a drop of this culture - one that had not been inside a mouse, and injected it into a fresh, healthy mouse. The next day. The mouse was dead! He looked at the mouse s spleen under the microscope and guess what he saw! the same bacilli. Koch and his postulates: 1) The disease organism must be present in sick animals and not present in healthy ones. 2) The organism must be cultivated in pure culture away from the patient s body. 3) This culture, when inoculated into a healthy animal should produce the characteristic symptoms of the disease. 4) The organism can be re-isolated from these animals. Fannie Hesse discovered that agar could be used as a solidifying agent for bacteriological media in This greatly accelerated the development of Microbiology. Paul Ehrlich and chemotherapy. Noticed bacteria picked up certain stains more readily than did mammalian tissue. Success was with Salvarsan that killed Trypanosomes and Treponema pallidum. Early chemo-therapeutic agents often had nasty side effects. It wasn't until the mid-1900s that very specific antibiotics were developed (more about that later). MICROBES IN NATURE Non-medical Micro. Martinus Beijerinck ( ) Enrichment culture technique... use media that is designed to isolate specific metabolic groups from nature e.g. N 2 -fixing bacteria and many other discoveries. Sergi Winogradsky ( ) Winogradsky was the first to describe sulfur oxidizing bacteria such as Beggiatoa. These organisms are chemoautotrophs (fix CO 2 without photosynthesis) Kluyver replaced Beijerinck at the University of Delft and ushered in the modern era of comparative biochemistry. Kluyver and van Niel proposed that all respiratory reactions (aerobic and anaerobic) could be summarized using the simple formula: AH 2 + B -----> A + BH 2 For Beggiatoa SH 2 + O > S o + H 2 O They also summarized all photosynthetic reactions with: CO H 2 A ----> CH 2 O (cell material) + H 2 O + 2 A We will come back to these reactions in a few weeks.