Recent research from Arizona State University has unveiled groundbreaking mechanisms that allow bacteria to move without the traditional flagella, the slender, whip-like structures typically responsible for propulsion. This innovative movement, which enables bacteria to form communities, disperse, and evade threats, could have significant implications for developing strategies to combat infections.
In a study led by Navish Wadhwa and his team, they demonstrated that bacteria such as Salmonella and E. coli can traverse moist surfaces even when their flagella are rendered nonfunctional. By fermenting sugars, these bacteria create tiny outward currents that essentially carry them forward, a process the researchers have dubbed “swashing.” This newfound method of movement may help explain how pathogenic microbes manage to colonize medical devices, wounds, or food-processing surfaces effectively.
Wadhwa expressed surprise at the bacteria’s ability to migrate without functional flagella, noting, “Our collaborators originally designed this experiment as a ‘negative control,’ expecting the cells to remain stationary. Instead, the bacteria migrated with abandon, prompting a long-term investigation into their movement mechanisms.” The findings were published in the Journal of Bacteriology and have been recognized as an Editor’s Pick, underscoring the significance of the research.
Understanding Sugar-Fueled Movement
The study reveals that when bacteria metabolize sugars like glucose, maltose, or xylose, they produce acidic by-products such as acetate and formate. These by-products pull water from the surface, generating currents that facilitate movement. The researchers emphasized that the presence of fermentable sugars is crucial; without them, the bacteria cannot execute swashing. In environments abundant with sugars, such as mucus in the human body, harmful bacteria may find it easier to spread and cause infections.
Notably, the introduction of surfactants disrupted the swashing movement but did not affect the coordinated, flagella-driven swarming behavior of bacteria. This distinction indicates that swashing and swarming utilize different physical mechanisms, suggesting that surfactants could be employed strategically to selectively inhibit one form of movement while allowing the other.
The implications of these findings extend beyond laboratory settings. Understanding that bacteria can colonize surfaces despite impaired flagella raises concerns about infection control in medical environments. For instance, E. coli and Salmonella are notorious for causing foodborne illnesses, and knowing they can spread via passive fluid flows may inform better cleaning protocols in food processing facilities.
Revolutionizing Bacterial Navigation
In a separate study spearheaded by Abhishek Shrivastava and his colleagues, researchers explored a different group of bacteria known as flavobacteria. Unlike E. coli, these bacteria do not swim but instead navigate surfaces using a unique mechanism called the type 9 secretion system (T9SS). This system operates like a conveyor belt, enabling the bacteria to glide along surfaces by moving an adhesive-coated belt around their cell body.
The researchers identified a specific protein within the T9SS, known as GldJ, which functions akin to a gear-shifter, directing the rotation of the motor that propels the bacteria. A small alteration to the GldJ protein can switch the motor’s spin direction, profoundly impacting bacterial movement. The study, published in the journal mBio, highlights the evolutionary advantage this molecular gear provides bacteria, enabling them to adeptly navigate complex environments.
The T9SS not only plays a role in bacterial movement but also has significant health implications. In the human oral microbiome, bacteria utilizing T9SS are associated with gum disease, contributing to inflammation and potentially leading to conditions like heart disease and Alzheimer’s. Conversely, in the gut microbiome, T9SS proteins can enhance immune responses, emphasizing the dual nature of these bacterial mechanisms.
Shrivastava expressed enthusiasm about the discovery, stating, “We are very excited to have discovered an extraordinary dual-role nanogear system that integrates a feedback mechanism.” This research opens avenues for developing targeted therapies that could disrupt harmful bacterial movement and biofilm formation while harnessing beneficial properties for health applications.
The two studies collectively illustrate a broader theme: bacteria have evolved multiple and often surprising methods of movement. These findings challenge traditional approaches to infection control, which have typically focused on targeting flagella. Instead, researchers are beginning to realize that factors such as environmental conditions—including sugar levels, pH, and surface chemistry—are equally crucial in managing bacterial behavior.
As scientists continue to unravel the complexities of bacterial movement, these insights could lead to innovative strategies for combating bacterial infections and improving public health outcomes.