Challenge #24 Challenge "Stumper" Question #1 Can you identify this organism? 1. It is a single-celled, living organism whose enduring, wild spores are dispersed through the air. It has been known (and made use of) by humans for millennia. 2. This organism was probably first used by humans in the preparation of a beverage. Later, perhaps about 5,000 years ago, it was used in the preparation of solid food. 3. Its scientific (Latin) name is Saccharomyces which identifies the genus to which it belongs. Answer: Yeast Yeasts are used by brewers and winemakers to cause fermentation and by bakers and cooks as a leavening (raising) agent. In other circumstances certain species can also be the cause of annoying infections. Correct answer received from: Matt Dent, al, Sam J., chemteach, Stephen, dani, dragonia, steve wise, bob, ted, John-Michael, Bunyip, Sally P., Karen (with Leo's help), Rekhmire, Avia Jammar, Wes, proffeser (thus), Heather, John F, Peter (youth), Audrey Q. (youth), Beth Bemis, Young Kate, Freya, Joshua Kuebler (youth), Jane Kuebler, Sean D., David & Glenn, Phil Y. (youth), Mike Schell Jr, John (youth), Melissa, Abdul M. (youth),

Challenge "Stumper" Question #2 Many things that we cannot normally see have beneficial affects in our lives. Take for example, bacteria. The metabolic processes and products of bacteria are important in many ways including the manufacture of vinegar and some cheeses, the curing of black tea, coffee, cocoa and vanilla beans, the tanning of leather, and the production of silage. And, bacterial flora inhabiting the intestines of animals often play a part in digestion. Certain soil bacteria are important because they help maintain soil fertility which affects crop growth. These include some free living bacteria and some that live in a symbiotic relationship in the roots of certain plants. Their contribution to the enrichment of soil occurs because they help convert a particular gas into a form that is usable by plants. During the process of their normal metabolism they combine the gas with hydrogen to form a simple compound that reacts with substances in the soil to form a different compound. This new compound is used by the plant in the manufacture of complex organic molecules essential to both plant and animal life. The complex organic molecules are amino acids and proteins. What is this element that is freely abundant as a gas, is an essential component of all living organisms, but is not normally available to plants or animals until after it has been used in the metabolic processes of soil bacteria? Answer: Nitrogen Nitrifying bacteria living in the soil and others living in nodules on the roots of certain plants combine nitrogen gas from the air with hydrogen to produce ammonia. The ammonia reacts with other substances in the soil to form various nitrates which are the form of nitrogen most readily usable by green plants. Soil nitrates are also produced by other bacteria that transform the protein compounds of dead plant and animal bodies into nitrates. Correct answer received from: Matt Dent, al, Sam J., chemteach, robin (youth), Stephen, steve wise, bob, ted, John-Michael, Bunyip, Sally P., Karen (with Leo's help), Rekhmire, Avia Jammar, Wes, proffeser (thus), Heather, John F., Audrey Q. (youth), Beth Bemis, Young Kate, Liz., Freya, Jane Kuebler, Sean D., David & Glenn, Phil Y., Mike Schell Jr, John (youth), Melissa, Shriram.