I454 Life Science uses a chemistry that is completely different from Sanger DNA sequencing.  During DNA replication, when a nucleotide is added to extend the sequence, a pyrophosphate is released.  Pyrophosphate is then converted to ATP by sulfurylase.  With ATP and the existence of luciferase, luciferin will be oxidized and releases light, as shown below.

Here is the workflow based on this technology:

1. DNA samples are fractioned into small DNA fragments and separated into single strands.
2. Specific adapter sequences are added to both the ends of the DNA fragments.  This is the DNA library.
3. A single-stranded fragment is captured by a specifically designed DNA capture bead.  One bead captures only one fragment.
4. The beads are emulsified.  In this process, the amplification reagents in water are mixed with oil, which results  in a reaction cell with a lipid layer surrounding it.  In each cell, there is only one DNA capture bead, plus the amplification reagent.  The individual cell is also called a microreactor.
5. The microreactors go through emulsion PCR (emPCR). The fragments from the DNA library will be amplified, and for each bead, several million copies of the fragment are produced in the microreactor.
6. The emulsion is broken.  The beads with amplified fragments attached are enriched and loaded on a PicoTiterPlate for sequencing.  The plate has many reaction wells which can accommodate only one DNA capture bead in each well.  In addition, each reaction well is pre-loaded with the micro beads that have the attachment of the enzymes that are necessary for pyrophosphate detection.
7. The fluidic system of the instrument uses lamina flow to add individual nucleotides in a fixed order over the plate.  Because of the lamina flow, only one nucleotide can be added to the plate at one time.  If the nucleotide has its complementary nucleotide to bind in DNA extension, then light will be released and detected by the instrument.  Based on light and the nucleotide added to the plate, the sequence in each reaction well can be determined.

Instead of using emPCR, Illumina uses bridge a PCR and and anchor PCR product on a flow cell.  Here is the illustration of how bridge PCR works:

When the amplification of sheared DNA fragments is completed, the flow cell will be loaded into a sequencer for automated cycles of extension and imaging.