Fecal Samples for DNA Extraction

 


Feces for genetic analysis should be collected into RNALater nucleic acid preservation buffer or, alternatively (and less desirably) desiccated with silica gel.  You need only collect samples that have a fair bit of fecal material in them; if a deposition is largely just seeds, there is not that much material to extract DNA from, so it is probably not worth collecting.  Over the course of the year, try to collect from all individually-recognized animals that you can, two to three samples from each if possible, though if you can get a good, large sample but have no idea who deposited it, collect it anyway!


PREPARATION

         Fill sterile 8 mL Saarstedt screw top tubes about half full (~4 mL) or slightly less with RNALater buffer using a sterile syringe (the volume does not have to be measured exactly). Label the tube with "RNAL" so that you know it does not contain ethanol, water, etc.

         Fill sterile 15 mL Falcon tubes with ~10 mL of silica gel from the jar labeled "For DNA Only". We should only use silica gel if there is no RNALater available


IN THE FIELD

         Carry with you pre-filled 8 mL Saarstedt screw top tubes or 15 mL Falcon tubes.

         Collect ~2 to 4 mL of feces, with a minimum of seeds, into these tubes without touching it with your bare hands (use latex gloves or a stick to transfer feces into the tube).  You should be using a ratio of ~1:1 of feces to RNALater and a ratio of ~1:8 of feces to silica gel for good preservation.

         For samples collected into RNALater, homogenize the sample into a feces-buffer slurry as thoroughly as possible, using a stick to break up and mix the feces into the buffer, if necessary.

         Label each sample with the following information:

o        Date of collection

o        Time of collection

o        Collector Name

o        Species

o        Group (if known)

o        Sex (if known)

o        Age Class (if known)

o        Individual ID (if known)


IN THE LAB

         Store the sample in a cool, dark place (e.g., on a dedicated shelf in one of the lab filing cabinets).

         For RNALater-preserved samples, shake the sample thoroughly every week or so to make sure it is homogenized thoroughly. Check it once monthly or when you store a new sample, have a look at the previous ones and shake them a little.

         For silica-preserved samples, check the sample every few days initially to make sure it is dessicating completely and not growing fungus; add more silica gel if necessary (you can discard some of the old silica and add new silica), but discard any samples on which fungus grows.

         Add the relevant information on each sample you collect to the 'biological samples' table in the Proyecto Primates Master Database under your Observer Sample record for the day of collection AND add the sample number to the label on your tube using a permanent marker.