Phage metagenomics.

The vast majority of novel DNA sequences deposited in the databases now comes from environmental phage DNA sequences. Methods are presented for the cloning and sequencing of phage DNA that might otherwise be lethal to bacterial host vectors or contain modified DNA bases that prevent standard cloning of such sequences. In addition, methods are presented for the isolation of viral particles directly from soil and sediment environmental samples or from large volumes of environmental water samples. The viral particles are then purified by cesium-chloride density centrifugation followed by DNA extraction. This purified viral metagenomic DNA is then used for cloning and sequencing.