1950s. For example, 14CO2 allowed analysis of rates of photosynthesis in the ocean (ref). Another significant breakthrough came in the 1980s, when microelectrodes sensitive to chemical species like O2 were developed. These electrodes have a spatial resolution of 50–100 μm, and have allowed analysis of spatial and temporal biogeochemical dynamics in microbial mats and sediments. Although measuring biogeochemical process rates could analyze what processes were occurring, they were incomplete because they provided no information on which specific microbes were responsible. It was long known that ‘classical’ cultivation techniques recovered fewer than 1% of the microbes from a natural habitat. However, beginning in the 1990s, a set of cultivation-independent techniques have evolved to determine the relative abundance of microbes in a habitat. Carl Woese first demonstrated that the sequence of the 16S ribosomal RNA molecule could be used to analyze phylogenetic relationships. Norm Pace took this seminal idea and applied it to analyze ‘who’s there’ in natural environments. The procedure involves (a) isolation of nucleic acids directly from a natural environment, (b) PCR amplification of small subunit rRNA gene sequences, (c) sequencing the amplicons, and (d) comparison of the those sequences to a database of sequences from pure cultures and environmental DNA. This has provided tremendous insights into the diversity present within microbial habitats. However, it does not resolve how to link specific microbes to their biogeochemical role. Metagenomics, the sequencing of total DNA recovered from an environment, can provide insights into biogeochemical potential, whereas metatranscriptomics and metaproteomics can measure actual expression of genetic potential but remains more technically difficult. Roles Microorganisms are the backbone of all ecosystems, but even more so in the zones where photosynthesis is unable to take place because of the absence of light. In such zones, chemosynthetic microbes provide energy and carbon to the other organisms. These chemotrophic organisms can also function in environments lacking oxygen by using other electron acceptors for their respiration. Other microbes are decomposers, with the ability to recycle nutrients from other organisms' waste products. These microbes play a vital role in biogeochemical cycles. The nitrogen cycle, the phosphorus cycle, the sulphur cycle and the carbon cycle all depend on microorganisms in one way or another. For example, the nitrogen gas which makes up 78% of the earth's atmosphere is unavailable to most organisms, until it is converted to a biologically available form by the microbial process of nitrogen fixation. Due to