If a culture starts with 50 cells, how many cells will be present after five generations with no cell death?ħ. What is the function of the Z ring in binary fission?ī) It forms a contractile ring at the septum.Ĭ) It separates the newly synthesized DNA molecules.ĭ) It mediates the addition of new peptidoglycan subunits.Ħ. Which of the following is the best definition of generation time in a bacterium?Ī) the length of time it takes to reach the log phaseī) the length of time it takes for a population of cells to doubleĬ) the time it takes to reach stationary phaseĭ) the length of time of the exponential phaseĥ. During which phase would penicillin, an antibiotic that inhibits cell-wall synthesis, be most effective?Ĥ. In which phase would you expect to observe the most endospores in a Bacillus cell culture?ĭ) log, lag, and death phases would all have roughly the same number of endospores.ģ. Which of the following methods would be used to measure the concentration of bacterial contamination in processed peanut butter?ĭ) direct counting of bacteria on a calibrated slide under the microscopeĢ.
Lake Natron in Tanzania, for example, owes its blood-red waters and high pH value of 10.5 to sodium carbonate, which is deposited by mineral-rich hot springs in the Southern Ewaso Ng’iro River.1. While Harpur Hill’s toxicity is the result of human activities, there are many naturally occurring caustic lakes around the world. Water in public swimming pools is kept at a pH level between a neutral 7 and a slightly alkaline 8. On the pH scale, a solution with the lowest value of 0 has the highest possible concentration of hydrogen ions, while pH 14 means that a solution has a lower concentration and is highly alkaline. The pH scale measures the concentration of hydrogen ions in a solution – the higher the concentration of hydrogen ions, the more acidic the solution. By dying the water black, the pool’s picturesque beauty was deliberately spoiled, in the hope that, by making the risks more visually obvious, many injuries, illnesses and even deaths will be prevented. Despite numerous warnings explaining the dangers of coming into contact with such a toxic solution, people continued to visit the quarry during warm summer weather, spurring the local government into action. Over years, the quarry stone and various chemicals pollutants reacted with the water to produce a beautiful but caustic alkaline solution, with a pH value of 11.4 – just two places below bleach. The pool’s original colour was a result of the site’s former life as a limestone quarry. Now the local council has taken a bold step to further dissuade people from taking a dip: they’ve dyed the ‘blue lagoon’ black! As well as being treacherously deep and strewn with debris, dead animals and other hazards, the quarry’s waters are highly toxic, with an alkalinity comparable to that of ammonia. But as the warning signs around its edge made clear, they did so at great risk to their health. With its vibrant blue hue, the pool looked more like a Mediterranean idyll than a disused quarry in Derbyshire, United Kingdom – which perhaps explains why swimmers could often be seen paddling across its surface on hot summer days.
For years, the turquoise waters of Harpur Hill have hidden dangerous secrets.
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