Right now, bacteria distributed throughout your gut use quorum sensing during a never-ending war against harmful bacteria. Good or bad, the impact of bacteria on our daily lives is undeniable.
Humans have become effective communicators during our short time on Earth. However, our communication pales in comparison to bacteria. Bacteria communicate in a process known as Quorum Sensing.
Like languages between humans, these signals vary between species. With our many different languages, cultures, and nuances, humans have a long way to go before our communication structure rivals bacteria.
Quorum Sensing is like the social network of bacteria.
Bacteria are everywhere. They’re sitting at the tables you sit at, burrowing in the clothes you wear and unfortunately, also crawling around on your skin. For a long time, they’ve had a pretty bad reputation, and for good reason! They have caused plagues that have wiped out masses across the globe, driven up breath mint sales by thriving in your mouth, and mutated into every biologist’s Boogeyman when you try to kill them with antibiotics – superbugs!
Autoinducers are little chemical signaling molecules that each bacterium sends out into its immediate environment. These molecules allow for quorum sensing, or cell-to-cell communication, to take place among bacteria.
Quorum-sensing allows individual bacteria within colonies to coordinate and carry out colony-wide functions such as sporulation, bioluminescence, virulence, conjugation, competence, and biofilm formation.
Bacterial cells in biofilms are embedded into a complex extracellular matrix containing, among other components, charged helical nanofibrils from amyloid-forming peptides. Based on the current knowledge about the nanoscale structure and dynamics of the amyloids, the mechanical vibration of these nanofibrils allows the cells to transmit EM signals to their neighboring cells and the surrounding environment.
Biofilms Protect Bacteria from Attack
By some estimates, bacterial strains resistant to antibiotics—so-called superbugs - will cause more deaths than cancer by 2050. Bacteria use quorum sensing to build biofilms to help transport nutrients between colonies while simultaneously protecting them. This process essentially increases the infectious process. Microbial relationships with all life forms can be as free-living, symbiotic, or pathogenic. Human beings harbor 10 times more microbial cells than their own. Bacteria are found on the skin surface, in the gut, and in other body parts. Bacteria-causing diseases are the most worrisome. Most infectious diseases are caused by bacterial pathogens with the ability to form biofilm. Bacteria within the biofilm are up to 1000 times more resistant to antibiotics. This has taken a more serious turn with the evolution of multiple drug-resistant bacteria. Health Departments are making efforts to reduce high mortality and morbidity in man caused by them. Bacterial Quorum sensing (QS), a cell density-dependent phenomenon is responsible for a wide range of expressions such as pathogenesis, biofilm formation, competence, sporulation, nitrogen fixation, etc.
In one study, researchers found that E. coli aggregation and impaired cell division occurred after terahertz irradiation. THz radiation was shown to have adverse effects on bacterial populations.
Aggregation of E. coli cells after treatment with THz radiation. (a) Stand-alone bacteria in the unirradiated sample. (b) Agglomeration of aggregated bacteria after the irradiation. (c,d) Magnified parts of panel (b). (b–f) Examples of aggregation of short and elongated (filamentous) bacteria. (b–d) Bacteria aggregate via side surfaces. (e,f) Bacteria aggregate through apical regions.
Bacteria are sensitive to sound and also emit sound and, in an extension of the Frohlich hypothesis, Norris and Hyland have shown that these results can be explained in terms of intercellular integration mediated by THz modes.
They suggest that enzymes can emit radiation in this range and that the chromosomes that receive these waves alter gene activity. They identify a particular subunit of RNA polymerase as a candidate for the emitter of electromagnetic waves in the sender bacterial population.
Besides natural THz emission by biological organs, the THz frequency band has also been examined extensively for intra-body communication networks and sensing applications.
The self-assembly process of the amyloid nanofibers of bacteria biofilms involves backbone hydrogen bonding, to which the THz frequency has been shown extensively to have the ability to modulate.
The charged nanofibrils can vibrate due to thermal motions, variable stresses, and potentially due to some metabolic processes, and consequently, they radiate detectable EM waves. Thus, amyloid nanofibrils potentially play a role as nanoscale antennas capable of emitting and receiving the EM signals replicating some of the metallic and semiconducting assemblies.
These charged amyloid nanofibrils may play the role of mechanical antennas within biofilms to which the THz frequency wave may alter. As a result of this, EM signals will be created at the frequency and harmonics of the cell’s resonant vibration frequencies. The intensity of the induced electric field is proportional to the vibration amplitude of the nanonanofibril.
The Party is Over for Biofilms
Using optogenetics—a technique that couples light-sensing to gene expression—an interdisciplinary NTU team of engineers and biofilm experts engineered a quorum-quenching enzyme-producing bacterial biofilm whose growth and dispersal can be modulated by near-infrared and blue light.
External mechanical vibrations affect the antibiotic resistance of the bacteria, the growth of the bacteria, and the formation of biofilm. Nanocylinders on the surface can vibrate
resonantly at terahertz frequencies.
Light Waves
Terahertz frequency occupies a middle ground where the ranges of microwaves and infrared light waves overlap, known as the “terahertz gap”.
The optimal word here is “light” waves, as the THz frequency has been shown to vibrate at. Time to "shed some light" on harmful bacteria!
In conclusion, Terahertz frequency waves may have the ability to hijack bacterial Quorum Sensing enhancing the good bacteria while being detrimental to the bad.
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