Team:SF Bay Area DIYBio/Description
Project Description
Bio Sun Block (Evolved Bacterial Sunscreen)
Introduction
No, not sunscreen for bacteria - sunscreen made by bacteria. We are going to make e.coli bacteria create shinorine, a UV absorbing compound that is currently being extracted from algae as an eco-friendly susnscreen.
Genetic Engineering is arguably the greatest leap forward in human understanding and manipulation of nature in the whole history of mankind, above and greater than the invention of fire and the wheel combined. This project makes use of Genetic Engineering to force a bacteria to create a compound that it would never make and then use the tools of evolution to enhance that ability.
E.coli can easily be killed by UV light. By equipping it with the genes to produce UV absorbing compounds, we expect that the E. coli will become somewhat UV resistant as well. After designing the process, we want to make it better, so we will employ “directed evolution” to make the process better. We think that if we stress the bacteria with UV that they will start to evolve better and more efficient mechanisms to protect themselves from UV.
So that is our project: start some bacteria making sunscreen then subject them to a lot of sunshine and they will evolve to make more and better sunscreen.
What is sunscreen
Sunscreens are chemical compounds that absorb or reflect UV thus preventing the UV from damaging cells. We tend to put sunscreen on our skin to protect the underlying skin cells from sunlight mostly UV. Sunscreen will absorb specific UV spectrum, the more (wider) the UV spectrum the better the effect of the sunscreen. Each chemical compound will absorb a part of the spectrum therefore it is best to have several different UV absorbing chemicals.
Mycosporine
Mycosporine-like amino acids (MAAs) are small secondary metabolites produced by organisms that live in environments with high volumes of sunlight, usually marine environments. So far there are up to 20 known MAAs identified. They are commonly described as “microbial sunscreen” but their function is not limited to sun protection.
Though most MAA research is done on their photo-protective capabilities, they are also multifunctional secondary metabolites that have many cellular functions. MAAs are effective antioxidant molecules and are able to stabilize free radicals within their ring structure. In addition to protecting cells from mutation via UV radiation and free radicals, MAAs are able to boost cellular tolerance to desiccation, salt stress, and heat stress.
Physics of sunscreen
The Sun Protection Factor (SPF) rating of sunscreen essentially measure how much longer it allows someone to stay in the sun before getting a sunburn caused by UV-B light (290-320 nanometers). This is an imperfect measure of skin damage because invisible damage and skin aging are also caused by ultraviolet type A (UV-A, wavelengths 320–400 nm), increasing the risk of malignant melanomas.
UV rays carry high energy and are suspected of causing cancer through damage to the skin's DNA. High energy in sunlight comes in two forms:
UV-A (320-400 nanometers)
UV-B (290-320 nanometers)
The UVB waves tend to receive more criticism than the less energetic UVA waves.
But, in actual fact, both UVB and UVA can damage the skin. Unfortunately, the chemistry of sunscreen, in most cases, does not enable the blocking of UVA as effectively, if at all, as they do UVB.
Note that the germicidal UV lights we use in the laboratory (e.g. built into the biosafety cabinet) emit the even short wavelength and even higher energy UV-C light (wavelengths 100–280nm). These wavelengths do not actually occur in natural sunlight, because they are absorbed by the Earth's atmosphere.
Mycosporine
Mycosporine–like amino acids are rather small molecules (<400Da). The structures of over 30 Mycosporine-like amino acids have been resolved and all contain a central cyclohexenone or cyclohexenimine ring and a wide variety of substitutions. The ring structure is thought to absorb UV light and accommodate free radicals. All MAAs absorb ultraviolet light, typically between 310 and 340 nm. It is this light absorbing property that allows MAAs to protect cells from harmful UV radiation. Biosynthetic pathways of specific MAAs depend on the specific MAA and the organism that is producing it. These biosynthetic pathways often share common enzymes and intermediates with other major biosynthetic pathways. An example of this is the shikimate pathway that is classically used to create phenylalanine; many intermediates and enzymes from this pathway are utilized in MAA synthesis.
Directed Evolution
