LAVA

Recently my biology class did a lava lamp lab! We used a water bottle, vegetable oil, tap water, food coloring, and Alka Seltzer tablets. So, it wasn't an actual lava lamp...but it was pretty fun and easy to make! After doing our lab, we were asked to research the science behind a real lava lamp.

Interestingly enough, a real lava lamp isn't much different from the ones we made. The theory behind how a lava lamp (also known as a "liquid motion lamp") is that there are two liquids involved that are very close in density, and insoluable to one another. When you pour water and oil into a container, the water will sink below the oil due to the water having a higher density than the oil. Water and oil do not mix because an oil molecule is hydrophobic, or water fearing, so its molecules do not bond to the hydrogen molecules of the water.

When we added the food coloring, it only adhered to the water because the food coloring is hydrophilic, or water loving. The food coloring is able to bond to the water molecules, and thus the oil remains colorless. This is the same as in a real lava lamp. When you see the globs of "lava" bubbling and floating, you are really just seeing colored water ---sorry if you thought there was actual lava in lava lamps and I just spoiled your fun!

To actually make our "lava", we added Alka Seltzer tablets which chemically reacts when dropped into water because it contains citric acid and sodium bicarbonate, which produces the "fizz". This fizz was the energy source that moved our colored water to the top of the oil, and then the water sank back to the bottom of the water bottle, below the oil.  In a real lava lamp, the energy source is the heat from a light bulb. When the water becomes heated, it becomes less dense and floats to the top of the oil. As it cools down, it returns to its original location below the oil. This process continues, and gives the lava lamp it's unique characteristic.

Quorum Sensing

Many people have never heard of the term, "quorum sensing", which is most likely because it is a relatively new concept. Princeton's Bonnie Bassler and her team of scientists (which consist of her students) have developed a theory of how bacteria communicate with eachother. PBS got an excellent interview with Bassler a few years ago.

 So how exactly does quorum sensing work? Well, as the bacteria grows, it releases a small amount of chemicals called "auto-inducers". The chemical is proportional to the amount of bacteria cells. At first there is just a small amount of the chemical floating around, but after the cells replicate there is more of this chemical. The bacteria can sense with antennae-like sensors on their membrane that there is a significant amount of auto-inducers, and they begin to grab it and take hold. Because of this sensing, they now know that there is enough bacteria cells to do some damage, so to speak. It's basically like the concept that there is "strength in numbers". If just a few little bacteria cells released toxins into the body, it would be very easy for our immune system to identify that there is a toxic foreign substance in our body and fight of the bacteria, but when there is an unfathomable amount of bacteria it is harder for our immune system to fight it off. Your body is covered with bacteria! Your gut alone contains 10¹⁰ bacterial cells. Don't freak out and go stock up on antibiotics--many of the bacteria found in your body are helpful. People used to believe that bacteria cells were asocial, meaning they do not communicate between eachother, for they are unicellulor organisms. They only have one piece of DNA inside of them, making them the simplist for of organism. Bassler questioned the bacteria's actions and the body's response once being attacked: why doesn't the body fight of the bacteria as soon as it releases toxin? It would be much easier to fight off bacteria before it starts asexually reproducing and replicating. After much research, her team discovered that the bacteria chemically communicates with eachother and waits to release toxins until there are roughly 10⁸ or 10⁹ acting against you simultaneously. Smart, huh? It makes it much harder for the body's immune system to fight off such an extravagent amount of bacteria cells, compared to just a few hundred.

There is a certain type of bacteria that is responsible for bioluminescence called Vibrio harveyi.  It produces light due to quorum sensing. Bassler's team discovered that single cells of Vibrio harveyi do not illuminate by themselves. They wait until they have more cells in their colony before they illuminate.

Bassler hopes to some day be able to control quorum sensing and be able to put it into a practical application, such as making insulin from good bacteria and pro-biotics to help us from getting sick in the first place.