See more from this Session: Symposium--Connections-the Role of Connectivity in Soil Processes
Tuesday, November 2, 2010: 10:30 AM
Long Beach Convention Center, Room 104B, First Floor
Oxygen atoms from water are incorporated into DNA when it is newly formed so that when soil is incubated with 18O-water the DNA of growing organisms becomes labeled with 18O atoms. In stable isotope probing (SIP), labeled DNA is separated from non-labeled DNA along a cesium chloride gradient formed in an ultracentrifuge. Because 18O-atoms are heavier than 16O-atoms and, consequently, the buoyant density of labeled DNA is greater than non-labeled DNA, water can be used as a labeled substrate in SIP experiments. The technique allows study of the impact of environmental parameters on growth and mortality of microbial populations in soil. For instance we have found that fungi grow faster than bacteria in a Ponderosa Pine forest soil when a dry soil is rewet. We were also able to use SIP with 18O-water to identify a bacterial strain, Rhodococcus sp. strain RHA1, that degraded toluene in a junkyard soil. Finally we used SIP to study the impact of ammonium availability on population dynamics of ammonia oxidizing bacteria and archaea in soil.