Final Activity Report Summary - BACBONE (Predicting DNA survival in forensic and archaeological bone. Identifying determinants of DNA preservation and characterising bacterial degradation of bone)
Skeletal remains are an important resource for forensic identification, not only for osteological characteristics that are used to create a biological profile, but also as a source of deoxyribonucleic acid (DNA). Unfortunately, post-mortem degradation processes affecting bone can be detrimental to DNA survival. A major pathway of degradation in human bone is the destruction of the bone structure by micro-organisms such as fungi and bacteria. This, presumably, has a significant effect on DNA preservation since bone porosity is increased and organic material is removed.
It was found, during a previous study on the preservation of archaeological bone, that intact human burials showed more bacterial alteration than fragmented and processed bones. Based on this and other work it was hypothesised that bacterial alteration started early post-mortem during putrefaction of the body. This type of degradation would in that case not occur in situations where putrefactive bacterial growth was inhibited, e.g. after exposure to extreme temperatures and bactericidal chemicals, or where putrefactive bacteria had had no opportunity to access the bone, e.g. in fragmentation, or in the case of animal caused bone defleshing or butchering.
The Joint POW/MIA accounting command-central identi?cation laboratory (JPAC CIL) recovered sand identifying the remains of American servicemen who died in past conflicts. As part of the identification process, skeletal remains were often tested for DNA at the Armed Forces DNA identification laboratory (AFDIL). Human bone material sampled for DNA at JPAC-CIL was analysed for degradation using histology and scanning electron microscopy (SEM). Histology was a useful technique to determine both the extent and type of microbial degradation in bone. The aim of the project was to characterise early degradation of bone, as well as to investigate the relationship between bone preservation and DNA results.
It became clear from the results that significant microbial alteration took place within the first 40 to 50 years post-mortem in bones from very different contexts and all sampled areas, including Europe, Asia, North America and Oceania. The type of incident, such as plane crash or ground loss, influenced significantly the realisation of bacterial alteration, which could be explained by the levels of fragmentation of the remains.
The bone preservation data was compared to DNA yield and DNA fragmentation to assess the influence of different types of degradation. Microbial alteration was on average less extreme in these samples in the middle of the transversal bone section. At first look there was a clear relation between the DNA fragment size and the preservation of bone microstructure. This effect was lessened somewhat by applying more efficient DNA extraction methods which led to better recovery. Still, more fragmented DNA was found in bones that were poorly preserved. It was possible therefore to use information from the bone microstructure as an aid to asses DNA fragmentation prior to analysis.
In conclusion, it was clear that degradation processes could alter or destroy biological information contained in skeletal remains. Signatures presented in bone, left there by post-mortem processes, could provide additional information about the taphonomic history of remains. Increased knowledge of taphonomy could inform about the early post-mortem history and time since death of the remains via the use of these signatures, forming a valuable and promising approach in forensic research.
It was found, during a previous study on the preservation of archaeological bone, that intact human burials showed more bacterial alteration than fragmented and processed bones. Based on this and other work it was hypothesised that bacterial alteration started early post-mortem during putrefaction of the body. This type of degradation would in that case not occur in situations where putrefactive bacterial growth was inhibited, e.g. after exposure to extreme temperatures and bactericidal chemicals, or where putrefactive bacteria had had no opportunity to access the bone, e.g. in fragmentation, or in the case of animal caused bone defleshing or butchering.
The Joint POW/MIA accounting command-central identi?cation laboratory (JPAC CIL) recovered sand identifying the remains of American servicemen who died in past conflicts. As part of the identification process, skeletal remains were often tested for DNA at the Armed Forces DNA identification laboratory (AFDIL). Human bone material sampled for DNA at JPAC-CIL was analysed for degradation using histology and scanning electron microscopy (SEM). Histology was a useful technique to determine both the extent and type of microbial degradation in bone. The aim of the project was to characterise early degradation of bone, as well as to investigate the relationship between bone preservation and DNA results.
It became clear from the results that significant microbial alteration took place within the first 40 to 50 years post-mortem in bones from very different contexts and all sampled areas, including Europe, Asia, North America and Oceania. The type of incident, such as plane crash or ground loss, influenced significantly the realisation of bacterial alteration, which could be explained by the levels of fragmentation of the remains.
The bone preservation data was compared to DNA yield and DNA fragmentation to assess the influence of different types of degradation. Microbial alteration was on average less extreme in these samples in the middle of the transversal bone section. At first look there was a clear relation between the DNA fragment size and the preservation of bone microstructure. This effect was lessened somewhat by applying more efficient DNA extraction methods which led to better recovery. Still, more fragmented DNA was found in bones that were poorly preserved. It was possible therefore to use information from the bone microstructure as an aid to asses DNA fragmentation prior to analysis.
In conclusion, it was clear that degradation processes could alter or destroy biological information contained in skeletal remains. Signatures presented in bone, left there by post-mortem processes, could provide additional information about the taphonomic history of remains. Increased knowledge of taphonomy could inform about the early post-mortem history and time since death of the remains via the use of these signatures, forming a valuable and promising approach in forensic research.