Identical Bacteria But Different Behavior

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Researchers have discovered that genetically identical bacteria can act radically different, depending on how the cells divide. Scientists are hypothesizing the same is true for all cells, including human cells. This phenomenon has serious implications for the development of antibiotics and other drugs.

Daughter Cells

In a recent study published in the journal eLife, researchers from the University of Washington showed that when a bacterial cell divides into two daughter cells, there could be an uneven distribution of cellular organelles. How these organelles get divided up during mitosis determines their future behavior. And although the cells are genetically identical, the fact that they were divided differently allows them to act individually when they respond to obstacles such as scarce resources or antibiotics.

Dr. Samuel Miller, UW professor of microbiology, genome sciences, and medicine was the paper’s senior author and Bridget Kulasekara, who has a PhD in the UW Molecular and Cellular Biology Program was the lead author. They built their research on results from 2010 that showed that when bacteria divided, the concentration of an important regulatory molecule called cyclic diguanosine monophosphate (c-di-GMP) was unevenly distributed between the two daughter cells.

Identical Bacteria

Second Messenger Molecules

C-di-GMP is a second messenger molecule that transmits signals from sensors on the cell’s external membrane to targets within the cell, where they can quickly change a variety of cellular functions, such as metabolism and mobility toward food or away from danger. Because some cells have more c-di-GMP than others, some cells are uniquely prepared to gather resources or avoid toxins. “The effect of second messengers is almost immediate,” said Miller, “They allow bacteria to change their behavior within seconds.”

Cells With an Advantage?

Detecting the difference in c-di-GMP concentrations between cells required complex microbiology supplies. The researchers used a technique called FRET microscopy, which allowed them to measure changes of the concentration of c-di-GMP within individual bacteria as the changes occurred, second by second. They found that the cells behaved much differently depending on how much c-di-GMP they received in the cellular split.

When these cells divide, they pinch in half to create two daughter cells. Although genetically identical, only one daughter cell inherits the bacterium’s single propeller and the enzyme that lowers the concentration of c-di-GMP and allows for more controlled movements. The cells that receive the higher concentration of c-di-GMP are slower and don’t immediately have the propeller used to actively swim around, although they will eventually synthesize their own. According to Miller, “What we have shown is that the uneven inheritance of organelles is another way cells have to create diversity and increase the chances of the survival of its species.”

Antibiotic Resistance

Miller believes the team’s findings may help explain how bacteria resist antibiotic treatments by always having some cells in their populations that are in a slow-growing, resting state, such as the cells with the higher concentration of c-di-GMP. Since antibiotics target fast-growing cells, these resting cells are more likely to be unaffected by the treatment. These findings might also help explain how some bacteria settle and grow upon surfaces such as catheters, intravenous lines, and heart valves.

Ultimately, Miller and his team are hoping their ongoing research will bring them better understanding of the signals that can change second messenger concentrations quickly, and they are searching for compounds that might interrupt or alter those signals. It’s a critical time as instances of antibiotic resistance are on the rise, and finding compounds that might combat this drug resistance is imperative.

Bob Davidson is the Managing Partner at BVA Scientific, the leader in scientific laboratory supplies and equipment since 1989. With over 100 years of knowledge and experience, BVA Scientific has the expertise in the lab supply industry to help you keep your lab running efficiently.