"Shields Up!" How Microvilli Act As A Barrier Against Attack

How microvilli act as a biological force field generator

Source DOIs: Left: 10.1371/journal.pone.0009406; Right: 10.1152/ajpcell.00167.2002

What would a science fiction universe be like without those shields? The use of electrostatic energy to protect a person or spacecraft is a necessity to fend off an enemy attack. Depending on the source, these barriers can neutralize, deflect and even repel whatever weapon might be used and give the combatants a chance to win the battle.

While on a large scale, this concept may continue to be limited to the creative minds of fiction writers, at the microbial level, the use of energy to ward off attacks has been well-known for both animal and prokaryotic cells. As far back as the 1950s, researchers were aware of the need for electrostatic forces to prevent bacteriophages from attacking their bacterial prey. By the 1960s, the electrostatic energy of bacteria was better understood. A shield around the cells existed and directed many cell to cell interactions. Any differences in the nature of the field could predict the health of the organism and manipulation through external forces could lead to the death of the cell itself.

The information, interesting as it was, offered little from a medical perspective. The knowledge of a bacterial force field was not particularly useful to help achieve better health. But that all changed in the 1970s when infection by the infamous bacterium _Neisseria gonorrhoeae _appeared to depend on electrostatic forces. The difference, however, was that infection was based on two different fields: its own and the one produced by human cells. The finding suggested there was more to the infection story and opened the door to new energy-based antimicrobial strategies.

Over the coming decades, researchers focused on the interaction of a number of bacteria to determine the effects of electrostatic forces on infection and disease. The results were dramatic and offered insight never before realized. In 2008, a Dutch group uncovered the means by which bacteria interacted with the barrier. The answer laid in the nature of the molecules themselves and the amount of water-loving and water-repelling atoms. A resultant electrostatic charge was developed and led to either positive attraction or repulsion. The concept also held true for viruses as in 2010, a Swedish group discovered differences in the electrostatic field between skin and mucous-producing cells attracted different forms of cancer-causing papillomaviruses. In the same year, a European group showed how microbes such as E. coli could disrupt the shield using enzymes and toxins and eventually cause disease.

While the influence of the electrostatic barrier in health was better appreciated, there was still a significant problem in that no one knew exactly how it was formed. Last week, that changed as an American group found the source of the shield in the gastrointestinal tract. They also learned how disruption could offer pathogens a distinct advantage in causing disease.

The team honed in on microvilli, a structural characteristic of cells lining mucosal tracts known to develop electromagnetic potential. These biological power stations consist of uniform, hexagonal shaped projections that extend out from the cell and interact with the ionic extravellular environment to produce an overall electrical charge. The researchers altered one particular type of gastrointestinal tissue such that it could no longer form these extrusions. Once the mutation had been stabilized, the cells were subjected to a number of tests, including infection from several different types of bacteria. During the infections, the electrostatic barrier was measured to determine if there were any changes due to the mutation and whether the electrostatic deficit associated with any differences in the ability to fight off the attackers.

When the results came back, there was little doubt microvilli were the source of the electrostatic barrier. The control cells had an effective force as expected while on the other hand, the altered cells lost the barrier. When the bacteria were introduced, the results were not surprising; the controls effectively repulsed the microbes while the mutated forms had no defense.

These results alone were incredibly enlightening yet the authors wanted to go further. They attempted to demonstrate how pathogens may evade the defense through a Trojan Horse strategy. Two of the worst villains, enteropathogenic and enterohemorrhagic E. coli, are known to insert proteins called bacterial effacement effectors into cells rendering them severely injured and vulnerable to other attacks. The researchers inserted the gene expressing one such factor into the control cells. Sure enough, when the gene was expressed, the microvilli disappeared and the bacteria could infect at will. The effectors were the perfect way to compromise the shields.

Overall, the outcomes of the study revealed not only how the body can establish its own force field against infection but also how bacteria can use their own weaponry to evade and destroy the protective layer. In the context of human health, the authors suggest this may lay the ground for future research for drug and vaccine delivery. By working with the shield, absorption can be improved and the effect enhanced. In addition, there may be the potential to develop better acting probiotic species; one such bacterium, _Lactobacillus _already possesses the ability to interact with the epithelium to benefit rather than cause harm. Whether the route is natural or medical, increasing the harmonization with our human shields can only mean a better future for us all.