Custom enzyme incorporates silicon into hydrocarbons

Science : All known life is carbon-based. But in theory, other elements, such as silicon, could serve as the chemical basis for life. In an attempt to show that silicon life-forms are possible, Frances Arnold of Caltech and her colleagues have evolved what might be the first step in demonstrating the viability of silicon biochemistry. Arnold’s team focused on a common enzyme called cytochrome c, which is present in many organisms’ cells and normally functions to transport electrons between proteins. The researchers found that cytochrome c has an additional role in a species of bacteria common in hot springs: In rare cases, the enzyme adds silicon atoms to hydrocarbon molecules. Arnold’s team selectively isolated the organisms that produced the most silicon-rich hydrocarbon molecules. In just three rounds of selection, the organisms were including silicon in hydrocarbons 2000 times as frequently as the original strain. The resulting compounds, called organosilicates, aren’t particularly useful because they are much shorter than the organosilicates used to produce adhesives and sealants. However, showing that a biological process can produce silicon-based chemicals is a step forward in proving that silicon-based life is more than a theoretical possibility.