The Rules of (chemo)Attraction

February is the month of love, and there is no greater depiction of pure and honest love than in the ABC reality show, the Bachelor. For those who have managed to avoid an episode of the bachelor or one of its many franchises for the past 15 years, the premise is simple: 20 women compete for the affection of one man, who reciprocates that affection by giving roses to his favorite women. Thus, every move each woman makes is with one goal in mind: to get a rose. Exactly what is so alluring about rose may be hard for viewers to understand. Is it true love? Is it fame? Although uncertain in the show, attractions in nature are much less mysterious.

image02

A rose. Image Credit: Flickr via Benson Kua.

Will you accept this rose?

In the Bachelor scenario, the rose serves as an attractant for the women who want to find love. In nature, certain chemicals serve as attractants for organisms who want to find food, energy or shelter. Organisms move toward these attractive chemicals, known as chemoattractants, in a process called chemotaxis. Researchers were able to exploit this phenomenon in an international chemotaxis competition that used chemical gradients to direct cells through a maze to the finish line. When the cells detected that there was more of the chemical around the corner than in their present  environment, they moved around the corner towards the chemical and closer to the finish line. The same concept applies to contestants on the Bachelor. The more validation they sense from the Bachelor in the form of attention or alone time, the harder they try cross finish line and win the ultimate validation: a rose! Chemotaxis is useful for more than just fun science games, however. It plays important roles in symbiosis, disease, and even conception.

image01

Chemotaxis of a cell in response to a gradient of chemical stimulus. Image Credit: Wikimedia Commons via Kohidai, L.

One-on-one date

Like the coveted alone time a woman gets on a one-on-one date with the bachelor, chemotaxis is the driving force behind some amazing relationships. One such relationship exists between certain plants called legumes and the bacteria that live in their roots. Legume roots secrete a molecule called a flavonoid that attracts the soil bacteria rhizobia to its roots. The bacteria enter through root hairs, where they form nodules and break down nitrogen into a form the plant uses to make molecules essential for survival. Another relationship formed as the result of chemotaxis is between the Hawaiian Bobtail squid and the bacterium Vibrio fischeri that lives in the squid’s special light organ. Sugar molecules found in mucus around the squid’s light organ attract the bacteria to the organ. Other sugars inside the organ entice the bacteria to stay, like the “one-on-one date” rose entices a woman to stay in the competition for the Bachelor’s heart. In high numbers, these bacteria are bioluminescent, and the squid uses their glow to ward off predators.  

image04

Hawaiian Bobtail Squid. Red arrow points to light organ. Image Credit: Adapted from Flickr via Macroscopic Solutions.

Fantasy Suite

If a contestant makes it far enough on the show, she’ll earn a  Fantasy Suite Date with uninterrupted and undocumented alone time with the Bachelor. Although no one knows exactly what goes on during these dates, there are certain implications. While no babies have resulted from these dates yet, the process of chemoattraction could aid in this possibility. Cells surrounding a mature egg send out the hormone progesterone. This hormone activates the sperm to swim towards the egg – the more progesterone, the harder the sperm will swim. Only fully developed sperm can respond to the chemoattractant gradient, ensuring that only the ones capable of fertilizing the egg are attracted.

Not here for the right reasons

In the same way as a Bachelor villain might follow the attraction of fame to wreak havoc on the show, pathogens and tumor cells can follow chemoattractants to wreak havoc on the body. Helicobacter pylori bacteria can cause stomach ulcers when they are attracted to minor injuries in the stomach’s lining, often caused by smoking, excessive salt intake, medications, or alcohol. Chem
oattractants direct the bacteria to the damaged tissue where they interfere with repair of the wound, leading to long term damage and the opportunity for other pathogens to join. Similarly,
Campylobacter jejuni, a species of bacteria responsible for food poisoning, is attracted towards nutrients in the gut of poultry, where they eventually end up in humans who consume the undercooked meat of the infected bird. Once in the human intestinal

image03

Sperm fertilizing egg. Image Credit: Flickr via AndreaLaurel

tract, the bacteria will attach to intestinal cells and and release toxins that cause diarrhea.Chemoattraction may also lure melanoma cells from the skin to the bloodstream to invade other parts of the body. According to researchers, the cells follow the scent of lysophosphatidic acid (LPA), a nutrient source found in human tissues. The melanoma cells move from the middle of tumors, where the LPA has been used up by the growing cancer cells, to the bloodstream in search for more. In the Bachelor universe, a villain might move from franchise to franchise, following the scent of fame in much the same way.

Happily Ever After

After making it through rose ceremonies, one-on-one dates, fantasy suites, and fame-seeking villains, a couple that has found love on The Bachelor may have a happy ending to their love story after all.  Patients with certain diseases may be able to find a similar happy ending using chemotaxis research to treat their illness. Inhibiting chemical signals such as LPA that cause melanoma cells to migrate throughout the body could make cancer easier to treat. It’s even possible that the same signals that encourage Vibrio Fischeri  to colonize the squid might be used against flesh eating bacteria from the same Vibrio family in humans. Chemotaxis research could also be the key to developing male contraceptives. The possibilities are endless.

image00

Outward Migration of Melanoma Cells. Video Source: Youtube via PLOS Media.

We may not understand what attracts people to a reality tv competition, but we are learning more and more about what attracts cells to certain chemical signals. With this knowledge, we can exploit these cellular preferences to cure diseases or even treat infertilitythe same way that ABC exploits human preferences for TV ratings.

About the Author

image01Megan Prescott is a Ph.D candidate in the Department of Microbiology at the University of Georgia. She dedicates her time outside the lab to serving as President of UGA’s Women in Science (WiSci) organization, volunteering with the Junior League of Athens, and continuously watching The Office on Netflix. She counts each day she leaves the lab without giving herself TB as a success. More from Megan Prescott.