Understanding Bacterial Sensors – The Future of WSN nodes

Wireless sensor networks (WSN) may have become an attractive solution for low power implementations and embedded systems. In this magazine we have shown by examples how WSN applications and its usage can span from critical physical infrastructure to historical buildings, structural health monitoring, monitoring natural disastersbiomedical applications, earthquake, Glaciers and mines. There is also possibility that under certain frequency WSN can be used in the oil and gas industries to prevent case like the Gulf of Mexico Oil spillage in 2010, environmental monitoring and underwater communication.

This article and news will give us a tip of the future of WSN nodes. A sensor node that will be multitasking; an efficient mobile sensor node with bacterial-like mobility for mobile communication; a proactive prevention communication approach – changing the usual practice from transmit-to-receive  to  receive-to- transmit in applications like earthquake and glaciers.

It is interesting to note that the future of WSN nodes lies in the understanding of the motile bacteria because nearly all motile bacteria can sense and respond to their surroundings – finding food, avoiding poisons, and targeting cells to infect, for example, through a process called chemotaxis. This allows the bacteria to move towards chemicals that they are attracted to, and away from ones that repel them; because chemotaxis plays a critical role in the first steps of bacterial infection. Therefore, a better understanding of the process could pave the way for the development of new, more effective antibiotics. Also, tiny biosensors can also be implanted as intruders in the human body to neutralise the effects of this bacterial giving us medical breakthrough  to treating cases which include cancer.

Bacterial sensor 4Researchers at California Institute of Technology Caltech are helping to reveal just how chemotaxis works. According to the the document made available to us, the sensing process begins with chemoreceptors—proteins that extend, like tiny antennae, from the cell body to the exterior of the cell. Chemoreceptors bind to attractants, like sugars and amino acids, and to repellents, like metals; they then send signals to motors controlling the whiplike flagella that steer the swimming bacterium in a particular direction.

To better understand chemotaxis, Grant Jensen, a professor of biology at Caltech, and a research specialist Ariane Briegel are working to determine the exact arrangement of these sensitive receptors. They have used an advanced electron microscopy techniques and new crystallography results in collaboration with researchers from Cornell University, built the first model that depicts precisely how chemoreceptors and the proteins around them are structured at the sensing tip of bacteria. Their results appeared recently in the Proceedings of the National Academy of Science (PNAS).

Bacterial sensor 1According to the published results, the entire chemotaxis system functions with about 11 proteins, making it one of the simplest examples of a signal transduction pathway (a system in which the activation of a receptor leads to any number of chemical steps that produce a specific response—in this case, a bacterium swimming in a particular direction). In humans, signaling pathways control everything from development and tissue repair to immunity and aspects of brain function; defects in such pathways produce diseases such as diabetes and cancer.  In animal cells, a signal transduction pathway might include 500 proteins. The relatively simple pathway producing the chemotaxis system, therefore, “is the best starting point to understand a full signal transduction pathway,” Briegel says.

According to Professor Jensen “A huge step forward is to understand what the Biologists had long known of two additional proteins, called CheA and CheW, which are also found within groups of chemoreceptors. These proteins were thought to hold the receptors together and to activate a protein that then binds to the flagellar motors and causes a change in its spinning direction. But no one knew exactly how CheA, CheW, and the receptors were linked”.

Jensen’s group was able to get the first glimpse of the chemoreceptor architecture in 2009. In order to observe the cell samples they used a state-of-the-art electron microscope instead of using traditional electron microscopy, the microscope could capture many high-resolution images as the sample is rotated. The both researchers discovered that chemoreceptors are arranged in a regular, repeating lattice of hexagons that are 12 nanometers apart, center-to-center.

The group’s next step  is to determine what structural changes take place when an attractant binds to a chemoreceptor to send a signal to the flagella motors. Having a model for the whole receptor array, Jensen says, makes that task easier. “Seeing the arrays was one thing,” he says. “Now, seeing the receptors with all the helper molecules and how they’re arranged and linked together, we have a chance of understanding what happens when one of them gets activated.”

Along with Briegel, Jensen, and Crane, additional authors on the PNAS paper, “Bacterial chemoreceptor arrays are hexagonally packed trimers of receptor dimers networked by rings of kinase and coupling proteins,” are Xiaoxiao Li and Alexandrine Bilwes of Cornell, and Kelly Hughes of the University of Utah. Their work was supported by the Howard Hughes Medical Institute and the National Institutes of Health.

Will the future of WSN nodes dance to the music of bacterial-like sensing?


Caltech News