It’s a common practice for bakers. They arrive early in the morning, spend hours slaving in the back, and eventually get all the freshly made breads, cakes, pastries and buns organized in displays. Then, when the time is right, they invite the world to enjoy the wares of their labour by…

bakery(Opening The Door…)

If you happen to be walking by at just the right time, the attraction can be almost irresistible. The aroma coming from the freshly baked goods can stop you in your tracks and lead to an unexpected diversion into the store.

Scientifically speaking, this attraction is caused by a phenomenon known as odorant perception. An aromatic molecule called a volatile organic compound enters the nose or the mouth and interacts with the cells resting inside. As this happens, olfactory nerves sense the molecule and send a signal…

aroma(To the brain…)

Here’s where it gets interesting. The scent first is interpreted as either pleasant or repulsive. After the decision is made, a neurological signal is transmitted to the rest of the body to move. Pleasant aromas tell our bodies to get closer to the smell while those considered to be foul force us to move away.

If we rely on instinct alone, our bodies heed the command and we head, if only slightly, in the appropriate direction. If the smell is strong enough, it may even overcome our current mental plans. This is most common in repulsion, when being overtaken by a horrific odour causes us to move away quickly.

But, those clever bakers use the opposite reaction to their advantage. If they can make those wonderful aromas as strong as possible, people will fall victim to instinct and…

bakery2(Pick Up A Few Things…)

Odorant perception isn’t only for humans. Researchers have found other species rely on this phenomenon. Mice have it, fruit flies have, even worms have it. The response to external odours appears to be conserved in evolution…at least in animals. Until recently, no one quite knew if the use of volatile scents could attract or repel bacteria.

A few weeks ago, that changed when a team of researchers from McMaster University discovered a bacterial species capable of using odours to signal other members of the same species. It’s known as Streptomyces and it is the source for many antibiotics – think streptomycin. But the bacterium also has a rather fascinating capability. It can change the way it looks and functions over time…

streptomyces(Here’s the life cycle…)

The bacterium also likes to explore its environment in search of nutrients. However, this is no easy task. Those cells designated with the burden of exploring may encounter a long and arduous trip. They may have to travel great distances (millimetres) from the colony. They may face unspeakable challenges including giant chasms (agar cracks), rushing rivers (condensation), and of course, great mountains…

rock2(…or as we call them, small stones)

Depending on where the new resources are eventually found, these brave bacteria may be isolated in a brand new world without any means to signal the colony.

But thanks to this paper, there really is no reason to fret. We now know Streptomyces can use the same method as bakers to let their colleagues know food has been found and that more cells should come.

Here’s how it works. Upon finding the nutrients, the bacteria create a volatile organic compound – an aroma – that can travel through the air back to the colony. This airborne chemical reaches home base and informs the other members about the new source of food. Other explorers are then sent off like pilgrims to join these brave scouts and ensure the population continues to thrive in this new, rural area of the world.

At the end of the day, the explorers are joined by their peers, the colony extends and much like those who found new food at the bakery…

rock3(Everybody wins!)

There is, however, one particular difference between the lure of the baker and the signal from the explorer cells. That happens to be the nature of the volatile organic compound causing the attraction.

Humans tend to love chemicals such as maltol and methianol, which give off that fresh bread aroma. We simply cannot resist. But the bacteria have no interest in these molecules. For them, nothing is more delightful than trimethylamine. It’s what drives them to explore and is the key to their movement in this paper. For those who are not familiar with this scent, it’s most commonly associated with…

deadfish(Rotting fish…)

Guess it’s true that there are different strokes for different folks…or in this case, bacteria.

If you want to read more on how Streptomyces uses volatiles to communicate, you can read the entire paper. It can be found here:
Streptomyces exploration is triggered by fungal interactions and volatile signals

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