Photosynthesis is an organic process developed in the nascent stages of life on earth. It converts electromagnetic radiation into chemical energy. Photosynthesis has two pathways. The first pathway, the light dependent process, converts light into a quick source of energy, ATP. The second pathway, the light independent process called the Calvin cycle, converts ATP into sugars for long term energy storage. Colloquially photosynthesis is understood to be a process endemic only to plant cells; however, this process occurs in bacteria too. Instead of using chlorophyll, bacteria uses bacteriochlorophyll. In the context of absorbing light bacteriochlorophyll absorbs light at larger wavelengths than chlorophyll.

Our research investigates optical and quantum mechanical parameters attributed to photosynthetic bacteria. The subject for our experiments is a non-sulfur purple bacteria, Rhodobacter Sphaeroides. These metabolically versatile bacteria and their photosynthetic systems are well understood; thus, serving as a good subject for our research. The main picture shown above shows growth of 6 anaerobic growing R.sphaeroides. Grown in Sistroms Minimal Medium, the bacterium’s photosynthetic pigments express a brown color when grown anaerobically.

Our current experiments attempt to grow bacteria with laser sources. These lasers emit wavelengths that range from visible to near infrared (400nm -1000nm). As the laser sources are directed at the bacteria we test the efficacy of the bacteria’s growth rate.

Today, growth rate measurements through absorbance is still widely used. It works by sending a light source with initial intensity through some media. Light that does not get absorbed gets measured by a sensor in tandem to the media. This is based off of Beer Lambert’s Law:

Where A is the absorbance of light passing through a medium with units of Optical Density (OD), ε is the extenxtion coefficient at a particular wavelength, c is the concentration of the cultured medium, and L is the path length that the light travels through the medium. As the concentration, commonly referred to as turbidity or cloudiness, increases so does the absorbance of light. Instead of this method, our lab is measuring growth rate by analyzing each individual bacterium using machine learning software. The benefit of this method is generation of large data densities from multiple parameters, not excluded to just growth rate. Using this method with our photosynthetic bacterium, the QMO lab hopes to generate interesting and profound breakthroughs in understanding the underlying processes of photosynthesis.

Ubiquitous to human kind is their proclivity in using tools to overcome biological disadvantages. Many of these tools are bioorganic, for example, horse power. Inspiration from nature has been paragon in technological innovations. In the QMO lab our current inspiration is with photosynthetic bacteria. One day a new unit of power could be called bacteria or cell power. While this idea is contrived, it illustrates the idea and scope of a palpable future in which photosynthetic bacteria could be used or to inspire technological innovations that involve power generation.