Bacteria precisely tune nanomotors to colonize different environments

A single molecule microscope reveals a motor of approximately 50 nanometers of bacteria, shown here as a bright yellow spot. Credit: Dr. PushkarLele / Texas A & M Engineering

For nearly 3.5 billion years on Earth, bacteria have fine-tuned the technology to colonize all types of habitats, from the inner layers of the gastrointestinal tract to the blistering hot water of geysers. However, in search of world domination, bacteria face significant obstacles as they move through different environments and maintain their navigation equipment.

In a new study published in the journal Nature CommunicationsResearchers at the University of Texas A & M have found that the appendages that control the navigation of bacteria, called flagella, adapt very accurately to changes in the viscosity of the liquid. This adaptation allows bacteria to use flagella to search for nutrients, sense the surface, and establish colonies in a variety of habitats.

“There is a great deal of interest in the field of biomedicine to understand how individual bacterial cells transition from loneliness to community lifestyles,” said Artie McFerrin, associate professor of chemical engineering. Dr. Pushkar Lele said. “To answer this question, we are investigating the role of flagella as a response hub when bacteria encounter different types of environments.”

Bacteria employ chemotaxis, the process of sensing chemicals and swimming in the direction of increasing or decreasing their concentration in order to move towards nutrients. The role of flagella in navigation is known. Flagella reversibly switch between clockwise and counterclockwise rotation to promote chemotaxis. Flagellar rotation is driven by an internal stator unit. This is similar in concept to a stator that rotates a rotor in electricity. motor Of the ceiling fan.

A single flagella motor is mechanically disrupted by mounting it on a glass surface, causing the bacterial cell body to rotate counterclockwise. Credit: Dr. Pushkar Lele

However, more recent evidence suggests that flagella also play a role in sensing mechanical changes in cells. environment— A process called mechanosing. Therefore, if a bacterium encounters an increase in resistance to flagellar rotation, it is perceived as an increase in the viscosity of the environment.

Correspondingly, the flagellar motor employs an additional stator unit to compensate by developing more power. However, studies have shown that this increase in resistance can prevent the flagella from switching directions and the chemotactic mechanism to fail.

“This observation caused a difficult problem,” Lele said. “It is unlikely that chemotaxis will be limited to one viscous environment. Therefore, adaptation is occurring within the flagellar motor that restores directional switching, and thus chemotaxis in various viscous environments. I thought it might be. “

In their experiments, researchers selected an E. coli strain containing CheY-P, a fluorescently labeled chemotactic protein that binds to flagellar motors and initiates flagellar switching. Researchers added resistance to the motor and used a high-magnification microscope to observe the level of fluorescence. They found that the fluorescence was below baseline when the stator protein was removed using genetic technology.

By comparison, the fluorescence level remained at baseline when the stator continuously torqued to rotate the motor. This suggested that the presence of the stator unit facilitated the binding of CheY-P to the motor.

Based on these observations, the team theorized the increase in mechanical torque provided by the extras in a high viscosity environment. stator The unit increases the coupling of CheY-P to the motor, thereby maintaining the homeostasis of the flagellar switching function.

Lele pointed out that this phenomenon of fine-tuning the internal state to adapt to changing mechanical loads is broadly similar to proprioceptive adaptation. Nervous system A continuous and intuitive understanding of their position and velocity in order to make adaptive changes to achieve homeostasis or a stable physiological state. For example, the musculoskeletal system of insects internally adapts and adjusts to various loads on the limbs to maintain posture and grip when walking on the floor or ceiling.

“Flagellar switching homeostasis seems to help motile bacteria form swarms and colonize different environments,” says Lele. “Explaining the rationale for the observed association between mechanosensing and chemotaxis will be important in preventing future bacterial colonization, infection and antibiotic resistance.”

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For more information:
Jyot D. Antani et al, the mechanically sensitive mobilization of the stator unit, facilitates the coupling of the response regulator CheY-P to the flagella motor. Nature Communications (2021). DOI: 10.1038 / s41467-021-25774-2

Quote: Bacteria obtained from on September 14, 2021 to colonize different environments Accurately adjust the nanomotor (September 14, 2021)

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Bacteria precisely tune nanomotors to colonize different environments

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