Are compunds used for SIP studies radioactive?

No.  For stable isotope probing (SIP), Bio-Traps are baited with specially synthesized compounds containing a stable carbon isotope (carbon-13) not the radioactive isotope (carbon-14) commonly used for radiocarbon dating in the fields of archeology and geology.

Can Microbial Insights receive international samples?

Yes.  Microbial Insights has an international soil permit and has received samples without problem from many different countries. Please see international shipment for additional information.

Can Microbial Insights receive samples on Saturday?

Microbial Insights is now open on Saturdays.  However, coolers should be shipped to a FedEx drop location and held where an MI representative will collect them.  It is important to ship to the Saturday delivery address and follow all procedures as indicated under the sample shipment section.  Please note that due to the short hold time associated with RNA and culture, it is recommended that these samples NOT be shipped for Saturday delivery.

How can SIP help determine if I should apply an amendment?

SIP Studies can be used to show the effect of amendments on biodegradation at a given site.  For example, Bio-Trap samplers baited with 13C-enriched benzene could be placed in a natural attenuation (unamended) well, and in a location which has undergone some amendment (i.e. nitrate, sulfate, oxygen, etc.). By comparing the % incorporation  from the different sampling locations, the degree of enhancement due to the treatment in terms of actual biodegradation can be determined.

How does Stable Isotope Probing (SIP) work?

Microbes require carbon sources to make new cells and grow. Biodegradation of contaminants occurs when resident microbes break down the contaminant to use as a carbon source. SIP allows you to see that carbon atoms from the contaminant have been metabolized and incorporated into bacterial cells.

Carbon exists in various isotope forms, with carbon-12 (12C) being by far the most abundant. It is possible to enrich specific compounds of interest (benzene, MTBE, etc ) with a stable isotope of carbon (13C). If the enriched compound is broken down and used as a carbon source by microbes, the 13C molecules will be seen in the microbial cells (biomass).

How is SIP performed?

SIP is performed using Bio-Trap samplers that have been “baited” with a known concentration of a 13C enriched contaminant (i.e. benzene, MTBE, etc.). These samplers are placed in selected monitoring wells and allowed to incubate for ~30 days in order to allow microbial growth. Incubation times can vary depending upon scope of the study. Following incubation, the Bio-Trap samplers are removed from the well and shipped to Microbial Insights for analysis.

Bio-Traps are a unique sampling system which offers many advantages for microbial analysis. The Bio-Sep beads within the Bio-Trap provide a large surface area for colonization of actively growing microbes, they also allow for easy application of amendments (in this case with the 13C-labeled compound of interest).

What analyses are included with SIP and what do they tell me?

Bio-Trap samplers used for SIP studies are analyzed using a modified version of our PLFA analysis as well as by GC/MS to assess changes in the concentration of the contaminant of interest. Results from these two approaches are used to tell us the following:

1) PLFA analysis: 

  • Concentration of biomass which utilized the 13C enriched compound (which proves biodegradation occurred).
  • Concentration of total microbial biomass which can be used to calculate the % of the community which utilized the 13C enriched compound.
  • Microbial community structure. (see our pages on PLFA analysis for further details).

2) Contaminant assessment: 

  • Concentration of the compound of interest (e.g benzene, MTBE) which remains in the beads.

What states have SIP Bio-Trap studies been performed in?

Currently SIP Bio-Trap studies have been performed in the following states:  Arkansas, California, Colorado, Florida, Georgia, New York, New Jersey, North Carolina, Maryland,  Massachusetts, Missouri, Minnesota, Nebraska, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, and Virginia.

Outside the US these studies have been performed in Canada, Israel, Thailand, and United Kingdom.

Will the use of a SIP Bio-Trap Samplers in a well effect CSIA results?

YES, there is potential for the use of these enriched 13C tracer compunds to effect the results obtained from CSIA analyis for the same compound.  MI advices that if you are interested in performing CSIA please collect these samples prior to the deployment of SIP Bio-Trap samplers.


In order to minimize the effect these samplers had on the monitoring well, MI recommends purging three well volumes from the test well during the retrevial of the SIP Bio-Trap samplers.