Microbes are ideally suited for biochemical and genetics studies and have made huge contributions to these fields of science such as the demonstration that DNA is the genetic material, that the gene has a simple linear structure, that the genetic code is a triplet code, and that gene expression is regulated by specific genetic processes. Jacques Monod and François Jacob used "Escherichia coli", a type of bacteria, in order to develop the operon model of gene expression, which lay down the basis of gene expression and regulation. Furthermore, the hereditary processes of single-celled eukaryotic microorganisms are similar to those in multi-cellular organisms allowing researchers to gather information on this process as well. Another bacterium which has greatly contributed to the field of genetics is "Thermus aquaticus", which is a bacterium that tolerates high temperatures. From this microbe scientists isolated the enzyme Taq polymerase, which is now used in the powerful experimental technique, Polymerase chain reaction(PCR). Additionally the development of recombinant DNA technology through the use of bacteria has led to the birth of modern genetic engineering and biotechnology.