Researchers demonstrated that biofilm growth may be regulated using laser light in the form of optical traps. The discoveries could help scientists use biofilms for a variety of bioengineering applications.
Biofilms – sticky coatings generated when bacteria adhere to a surface – enable germs to protect themselves from harsh environments and even resist antibiotics. In a recent study, researchers demonstrated that laser light in the form of optical traps can be utilized to control biofilm growth. The discovery could enable scientists to use these microbial layers for a variety of bioengineering applications.
“Producing microscopic components usually requires a highly technical fabrication process, but we found that optical tweezers can be used to precisely control the position of individual bacteria or clusters of bacteria,” said research team leader Anna Bezryadina from California State University Northridge. “This allows us to influence the growth patterns of bacterial structures on a microscopic level with high precision.”
In the Optica Publishing Group journal Biomedical Optics Express, the researchers describe their trials with optical traps to control bacterial aggregation and biofilm formation. They discovered that different lasers may be used to stimulate and inhibit biofilm formation.
“We can even create a sort of bacterial Lego block that can be moved around, stuck together and destroyed as needed,” Bezryadina, the researcher, added. “This work could lead to new types of biodegradable materials or a new generation of biofilm-based biosensors, for example.”
Producing microscopic components usually requires a highly technical fabrication process, but we found that optical tweezers can be used to precisely control the position of individual bacteria or clusters of bacteria.
Anna Bezryadina
Using light to control bacterial growth
Most biofilm research has focused on mechanical, chemical and biological approaches to suppress and control biofilms. Although scientists have shown that synthetic and chemical approaches can be used to activate and control biofilms and engineer biofilms into specific spatial structures, Bezryadina and her team wanted to find out if optical methods could be used to control biofilm dynamics. Accomplishing this required an interdisciplinary team with expertise in advanced optical technology and microbiology.
The researchers used Bacillus subtilis, a non-pathogenic bacteria that naturally produces biofilms. They employed a low-nutrient environment that is toxic to B. subtilis to induce the bacteria to build a biofilm. After producing tiny biofilm clusters, they performed optical trapping studies with either a 473 nm blue laser or a near infrared Ti:sapphire laser that could be modulated between 700 and 1000 nm.
They discovered that utilizing a laser illuminating at wavelengths ranging from 820 nm to 830 nm allowed for longer optical entrapment of biofilm clusters while limiting photodamage. However, applying a laser at 473 nm, which is strongly absorbed by bacteria, led the cells to burst and biofilm clusters to disintegrate. They also observed that the ideal bacterial clusters for optical manipulation consisted of three to 15 cells.
Making patterns
When the researchers studied bacteria dynamics and biofilm formation using optical tweezers at 820 nm wavelength for an hour, they discovered that bacterial clusters aggregated near optically trapped clusters, adhered to the surface and started to form a microcolony. They could also move optically trapped bacterial clusters throughout the sample to a specific position, which could be useful for building structures out of bacteria. The NIR laser did not seem to disrupt biofilm formation for bacterial clusters exposed to the highly focused NIR laser, which implies that NIR wavelengths in the 800 nm to 850 nm range could be used for extended periods of time for optical trapping, manipulation and pattern formation of bacterial clusters.
“Despite the apparent uncontrolled bacterial biofilm formation in nature, our work showed that bacterial biofilm formation can be influenced by light,” Bezryadina, the study’s lead author, remarked “This research marks the first stage in a long-term project to develop microscopic building materials from easily available resources such as bacteria. In future research, we intend to leverage what we discovered to create a process for building structures out of bacterial Lego blocks.”
Overall, the tests indicated some flexibility in the specific growth circumstances, cluster sizes, and wavelengths required to manipulate the biofilms. According to the researchers, their technology may also be applicable to other types of biofilm-forming microbes.
