Decomposition is a complex process involving the interaction of both biotic and abiotic factors. Microbes play a critical role in the process of carrion decomposition. In this study, we analysed bacterial communities from live rats and rat remains decomposed under natural conditions, or excluding sarcosaphagous insect interference, in China using Illumina MiSeq sequencing of 16S rRNA gene amplicons. A total of 1,394,842 high-quality sequences and 1,938 singleton operational taxonomic units were obtained. Bacterial communities showed notable variation in relative abundance and became more similar to each other across body sites during the decomposition process. As decomposition progressed, Proteobacteria (mostly Gammaproteobacteria) became the predominant phylum in both the buccal cavity and rectum, while Firmicutes and Bacteroidetes in the mouth and rectum, respectively, gradually decreased. In particular, the arrival and oviposition of sarcosaphagous insects had no obvious influence on bacterial taxa composition, but accelerated the loss of biomass. In contrast to the rectum, the microbial community structure in the buccal cavity of live rats differed considerably from that of rats immediately after death. Although this research indicates that bacterial communities can be used as a “microbial clock” for the estimation of post-mortem interval, further work is required to better understand this concept.

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Chrysomya pinguis (Ch. pinguis) belongs to blowfly species of great medical and forensic importance. In this study, we report the complete mitochondrial genome of the Ch. pinguis for species identification. The 38 genes presented in the 15,838 bp circular genome has been found in a typical Metazoan genome, of which there are 23 transfer RNA genes, 13 protein-coding genes and 2 ribosomal RNA genes. In addition, there is a non-coding A + T-rich region between one and another tRNA-Ile. The array of the genes is similar to that discovered in other insects. The overall base compositions of A, G, C and T are 38.72%, 9.86%, 14.07% and 37.35% respectively. This study contributes to the availability of dipteran mitochondrial genomes and provides the first complete mitochondrial genome of Ch. pinguis for entomologists to identify diagnostic regions for species identifications and phylogenetic analysis.

The complete mitochondrial genome of Parasarcophaga similis collected from China was determined using PCR reactions. The mitogenome was 15,158 bp in length with a total A + T content of 76.4%, consisting of 22 transfer RNA genes, 13 protein-coding genes, 2 ribosomal RNA genes and a control region. The gene contents of the mitogenome were identical to those observed in other insects. The overall base compositions of A, G, C and T were 39.54%, 9.43%, 14.20% and 36.83%, respectively. This paper aimed to improve and perfect dipteran mitochondrial genomes and provided the first complete mitochondrial genome of Parasarcophaga similis for entomologists as a potential tool for application of phylogenetic analysis and forensic entomology.

Nonbinary single-nucleotide polymorphisms (SNPs) are potential forensic genetic markers because their discrimination power is greater than that of normal binary SNPs, and that they can detect highly degraded samples. We previously developed a nonbinary SNP multiplex typing assay. In this study, we selected additional 20 nonbinary SNPs from the NCBI SNP database and verified them through pyrosequencing. These 20 nonbinary SNPs were analyzed using the fluorescent-labeled SNaPshot multiplex SNP typing method. The allele frequencies and genetic parameters of these 20 nonbinary SNPs were determined among 314 unrelated individuals from Han populations from China. The total power of discrimination was 0.9999999999994, and the cumulative probability of exclusion was 0.9986. Moreover, the result of the combination of this 20 nonbinary SNP assay with the 20 nonbinary SNP assay we previously developed demonstrated that the cumulative probability of exclusion of the 40 nonbinary SNPs was 0.999991 and that no significant linkage disequilibrium was observed in all 40 nonbinary SNPs. Thus, we concluded that this new system consisting of new 20 nonbinary SNPs could provide highly informative polymorphic data which would be further used in forensic application and would serve as a potentially valuable supplement to forensic DNA analysis.