Parish,

The answer to your question depends upon the time line (hours - years) and which tissues (fat, muscle and bone). Then there is the issue of mass (dry weight or premortem weight). Are you considering entombed or soil covered, thereby introducing other organisms (beetles, etc.). 

Within hours of death, the gut bacteria are found through the soft tissues. 

A few thoughts,

Christopher

Morris, J. A., Harrison, L. M., & Partridge, S. M. (2006). Postmortem bacteriology: a re-evaluation. Journal of clinical pathology, 59(1), 1-9.

Aturaliya, S., & Lukasewycz, A. (1999). Experimental forensic and bioanthropological aspects of soft tissue taphonomy: 1. Factors influencing postmortem tissue desiccation rate. Journal of Forensic Science, 44(5), 893-896.

Ubelaker, D. H., & Zarenko, K. M. (2011). Adipocere: what is known after over two centuries of research. Forensic science international, 208(1), 167-172.

Hi Parish

Unfortunately as Christopher suggests there is no definitive answer here. Autolysis is facilitated by bacteria which naturally occur in the gut, but as the levels of bacteria and the strains present are not consistent across all species or even within a species we would certainly anticipate variations here. There is also consideration of externally introduced bacteria from surrounding soil/water or whatever the burial context and the rate at which they migrate towards and into the body could also vary based on clothing, fur or injuries.

I know that doesn't really help much to answer your question. Here are a few articles around the topic of Forensic Ecogenomics which you may find of interest:

Article The potential use of bacterial community succession in foren...

Article Vertebrate Decomposition Is Accelerated by Soil Microbes

Conference Paper Forensic Microbiology: Determining the Potential of Microbia...

Article Shifts in soil biodiversity—A forensic comparison between Su...

Great thank you both that helps a lot and for the references too.