![]() Hfq may undergo a similar stress response, for example, when salmonella is under attack by a person's immune system.Spring Roster | Spring Depth Chart | Spring Preview NotesĮAST LANSING, Mich. Hfq responds by entering a type of "survival mode" in which it makes the cells more virulent.īy learning how salmonella responds to stress in space, scientists hope to learn how it might handle stressful situations on Earth. Microgravity imposes mechanical stresses on bacterial cells by changing the way liquids move over their surfaces. As for the changes in gene expression in salmonella, scientists think they may result from a stress response in a protein called Hfq, which plays a role in controlling gene expression. They may simply have more room to grow than they do on Earth, where they tend to clump together at the bottom of petri dishes. There are several hypotheses as to why bacteria thrive in weightlessness. Studies performed after the flight found that these genetic tweaks made the salmonella almost three times more likely to cause disease in mice than control bacteria grown on Earth. ![]() ![]() A controlled experiment in 2007 testing salmonella growth on the space shuttle Atlantis showed that the space environment changed the expression of 167 of the bacteria's genes. Furthermore, some bacteria grow deadlier. coli colonies, for example, grow almost twice as fast as their Earth-bound counterparts. Thirty years of experiments have shown that bacterial colonies grow much faster in space. When there's no gravity, though, the expanding hot air experiences equal resistance in all directions, and so it moves spherically outward from its source. Because there are more cold air molecules pushing against the hot molecules at the bottom of the flame then there are at its top, the flame experiences less resistance at the top. As the hot air molecules expand outward, cold air molecules push back against them. As the air around a flame heats up, it expands, becoming less dense than the cold air surrounding it. That pressure difference causes an effect called natural convection. The atmospheric pressure difference over a height of one inch, though slight, is enough to shape a candle flame. Conversely, the atmosphere gets thinner and thinner as you move vertically, causing a gradual decline in pressure. The closer you are to the Earth's surface, the more air molecules there are, thanks to the planet's gravity pulling them there. In space, they move outward from their source in all directions. ![]()
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