Hello Natasha, and all
I don't know if you are planning on DNA analysis being a part of your project? We are thinking at the moment about how best to preserve wet remains in the field, which can then be used for potential DNA studies, either for plant identification or for analysis of crop domestication and movements.
I very much like Angela Schlumbaum et al's review paper for general principles and good examples of the analyses people have done with plant ancient DNA. They recommend that samples for DNA analysis are identified in the field, and treated as DNA samples, rather than general archaeobotanical samples. Take some measures to minimise contamination of the ancient DNA by modern DNA, for instance from pollen in the air, other samples, other strata, etc.
DNA degradation is thought likely to be worse in wet remains than dry, due to the effect of hydrolysis on the molecules, but how best to handle the samples in the field to a) stop bacterial and fungal degradation and b) preserve as much as possible of the DNA in the sample?
Our thinking at the moment is that fomalin is likely to damage the DNA, based on a number of studies of DNA in museum samples. Alcohol is possibly not as bad, but definitely not ideal. If you want to store in liquid, sterile saline might be the best possibility. Ideally though, we think that drying the samples and getting them cold as quickly as possible seems the best way to go. In the field, desiccants (silica gel or rice) might be the most practical means of drying.
Does anyone else have any experiences or views to share on handling waterlogged samples in the field, for the purpose of DNA extraction later?
From: The archaeobotany mailing list on behalf of Natasha Lyons
Sent: Mon 3/24/2008 6:09 PM
To: [log in to unmask]
Subject: Re: Archaeobotany workshop at Worcester in May
I'm writing you from Vancouver, Canada - greetings. I am an archaeobotanist
who is entering a project with a local First Nation that has been excavating
a large and unprecedented plant processing site. There are both wet and dry
site components. I myself have worked only on dry sites and largely with
macroremains. My role in the project is to help figure out sampling and
processing for the wet site macroremains (and suggest where to sample and
arrange for microremain analysis, as appropriate) and to teach members of
the Nation to process and analyse these remains. It's a long term ongoing
type of project. My questions are very rudimentary with regards to doing
work in a wet site context. The matrix is very peaty and I am unsure how to
proceed with either sampling or processing (eg. what size of samples to aim
for, should we try water seiving before going to the microscope, are there
specific techniques for macroscopic analysis of wet plant materials?),
though I am gaining ideas from reading the British/European literature. Any
help with references or anecdotal experience would be very much appreciated.
I will be at the upcoming Society for American Archaeology meetings as well
as at the World Arky Congress in Dublin this summer - I'd be happy to buy
beers in exchange for knowledge! And of course I can be contacted at this
Very much appreciated.
Post-doctoral Fellow, Simon Fraser University
Burnaby, British Columbia, Canada
E: [log in to unmask]