Time Course Of Decomposition Research Articles

Inferring the Postmortem Interval of Rat Cadaver after Boiling Water Treatment Based on Microbial Community Succession

Abstract Background: In forensic investigations, accurate estimation of the postmortem interval (PMI) is an important task, but also an ongoing challenge. Especially in cases where the cadaver has been specially treated, for example, by boiling, the determination of PMI becomes extremely difficult. Previous studies have shown that the succession of the microbial community after decomposition of the cadaver can be used to infer PMI. However, the feasibility of determining the PMI of boiled cadavers has not yet been demonstrated. Aims and Objectives: The main objective of this study was to test whether we can infer PMI of boiled cadavers based on the succession of microbial communities. Materials and Methods: SD rats were killed by cervical dislocation. Subsequently, the rat cadavers were divided into the case (boiled cadavers) and control (unboiled cadavers) groups. Rectal samples were collected from the rats for 45 days and at nine time points. High-throughput sequencing of the 16S rRNA gene was performed to characterize the microbial community in the rectum. Results: The results showed that the composition and relative abundance of bacterial communities at the phylum level were significantly different between the case and control groups. The alpha diversity of the microbial community showed a decreasing trend with the decomposition process. Principal coordinate analysis showed that the case and control groups had obvious patterns along the succession of microbial communities. The rectal microbial communities showed a significant linear trend in the time course of decomposition. A random forest model was used to infer PMI. The goodness-of-fit (R2) of the model was 68.00% and 84.00%, and the mean absolute errors were 2.05 and 1.48 days within 45 days of decomposition for the case and control groups, respectively. Conclusions: Our results suggest that microbial community succession could be a potential method to infer PMI of boiled cadavers.

Effects of extracts of reed and cattail on the growth of a cyanobacterium, Microcystis aeruginosa

The effect of reed (Phragmites australis) and cattail (Typha angustifolia) extracts at different decomposition stages (fresh and dead) on the growth of a cyanobacterium, Microcystis aeruginosa, was investigated. Effective concentration 50 (EC50) of extracts were quantified based on dissolved organic carbon (C) concentration. The 100-day extract of fresh cattail showed the most inhibitory EC50 value of 19.3 mg C/L. We found that the fresh plant was more inhibitory than the dead plant for both species based on EC50 and the comparison of growth percentage in the maximum concentration of extracts, implying different compounds were produced during the time course of decomposition. The results of this study suggest that lake restoration efforts that include using emergent macrophytes to control nuisance algae should consider macrophyte life stage and decomposition time together with selecting macrophyte species, although further chemical identification is required to understand the allelochemical production in a variety of decomposition stages.

Function of bacterial community dynamics in the formation of cadaveric semiochemicals during in situ carcass decomposition.

The decomposition of dead mammalian tissue involves a complex temporal succession of epinecrotic bacteria. Microbial activity may release different cadaveric volatile organic compounds which in turn attract other key players of carcass decomposition such as scavenger insects. To elucidate the dynamics and potential functions of epinecrotic bacteria on carcasses, we monitored bacterial communities developing on still-born piglets incubated in different forest ecosystems by combining high-throughput Illumina 16S rRNA sequencing with gas chromatography-mass spectrometry of volatiles. Our results show that the community structure of epinecrotic bacteria and the types of cadaveric volatile compounds released over the time course of decomposition are driven by deterministic rather than stochastic processes. Individual cadaveric volatile organic compounds were correlated with specific taxa during the first stages of decomposition which are dominated by bacteria. Through best-fitting multiple linear regression models, the synthesis of acetic acid, indole and phenol could be linked to the activity of Enterobacteriaceae, Tissierellaceae and Xanthomonadaceae, respectively. These conclusions are also commensurate with the metabolism described for the dominant taxa identified for these families. The predictable nature of in situ synthesis of cadaveric volatile organic compounds by epinecrotic bacteria provides a new basis for future chemical ecology and forensic studies.

Synthesis and characterization of the most distorted 16π porphyrin: 16π octaisopropyltetraphenylporphyrin (OiPTPP)

Previously unreported octaisopropyltetraphenylporphyrin (OiPTPP) was prepared from 3,4-diisopropylpyrrole, an unstable previously unisolated heterocyclic compound. Purification of the free-base 18π porphyrin required conversion to its 18π zinc(II) complex, chromatographic separation, and acid mediated demetalation. Oxidation of the 18π porphyrin with SbCl5 furnished metal-free 16π octaisopropyltetraphenylporphyrin (OiPTPP). X-ray structural determination revealed that the novel species is the most distorted 16π porphyrin to date. The time course of decomposition of the oxidized species monitored by UV-vis spectra implied that the introduction of high steric repulsion was effective for enhancing stability of the 16π porphyrin. The reaction of metal-free 16π OiPTPP with LiBF4 followed by Pd2(dba)3 gave the corresponding 18π OiPTPP palladium(II) complex via reduction of the OiPTPP lithium(I) complex as previously reported for 16π octaisobutyltetraphenylporphyrin (OiBTPP). The new 18π porphyrin system could be characterized by the X-ray analysis of the 18π OiPTPP palladium(II) complex. The X-ray structure of the 18π metal complex also indicated that the distortion of the porphyrin ring had become larger than that of previously known 18π porphyrins

Association of the Genus Acinetobacter with the Decomposition of a Swine Carcass and the Isolation and Characterization of a Novel Strain of Acinetobacter sp. P4

Using fluorescence in situ hybridization (FISH) and a selective and differential medium, Acinetobacter numbers were enumerated over the time course of decomposition, from fresh to putrid/dry, of a swine carcass. In addition, Acinetobacter diversity and succession were also characterized. Acinetobacter bacterial counts were observed to be the lowest before exposure (undetectable) and increased to their highest during active decay then decreased and leveled during advanced decay through putrid/dry. FISH analysis revealed Acinetobacter cells were mostly clustered together, which is consistent with growth in a non-mixed environment, such as soil. The abundance of Acinetobacter cells decreased from active decomposition to putrid/dry. BLAST analysis using the 16S rRNA-gene sequence identified the isolates as one of the following Acinetobacter spp: A. baumannii, A. haemolyticus, A. junii, A. johnsonii, and A. gerneri. Phenotypic description of the identified isolates closely matched those of known genomic species. One isolate, P4, was observed to be unique in its phenotypic and phylogenetic characteristics and was more closely related to A. sp E10. The isolates from this study displayed multi-antibiotic resistance. The results from the study revealed the association of Acinetobacter spp. with that of carrion which adds to our knowledge of the ecology of this genus along with the potential implications of infection for this opportunistic pathogen.

Characterization of the soil microbial community associated with the decomposition of a swine carcass

Identification of bacterial species and their metabolic activity may be useful in differentiating soil samples associated with forensic analyses of large animal carcasses. In this preliminary study, lipolytic and proetolytic soil bacteria were enumerated over the time course of decomposition of a swine carcass. A 60-kg pig was used because it resembles a human body in its fat distribution and cover of hair. Soil core-samples (grave-soil) were taken underneath the carcass every three days until day 15, and then sampled on days 28, 43, 57, and 71 between September and December 2008. Results indicated that lipolytic bacterial counts were initially the lowest at day 0 (before exposure) and increased to their highest between days 9 and 12 (active decomposition); they then decreased and leveled at days 15 through 71. Conversely, the proteolytic bacterial counts initially were the highest at day 0, slowly decreased at days 3 (fresh) and 6 (bloat) with a rapid decline at day 9 (active) followed by a second major decline at day 28 (advanced); they then leveled through the remaining time period. Of the 33 isolates that could be identified, 18 were in the genus Acinetobacter. The qPCR results using Group I lipase-specific primers followed a similar pattern as the lipolytic CFU observed.

Evidence for an early onset of endogenous alcohol production in bodies recovered from the water: implications for studying alcohol and drowning

Endogenous alcohol production can increase the blood alcohol concentration (BAC) of drowning victims following submersion and confound epidemiological studies of the role of alcohol. This study seeks to determine how soon after a drowning death a victim’s BAC is influenced by post-mortem alcohol production. The drop in mean lung weight that occurs over time in the water was hypothesized to serve as a proxy for the time course of decomposition, and thus provide an empirical measure to determine how soon after death to first suspect endogenous alcohol. The autopsy lung weights of 562 previously healthy males who drowned were compared across six submersion time groups (0–11.9, 12–23.9, 24–47.9, 48–95.9, 96–167.9 and ≥168 h) and two times of year (winter and non-winter). The hypothesis that a drop in lung weight is sensitive to the time course of decomposition was supported by (1) a statistically significant drop in mean lung weight that occurred 12–23.9 h post-submersion in the non-winter months, but not until 96–167.9 h in the colder winter months; and (2) a significant drop in lung weight was not observed in the group of cases with zero BAC. With a parallel finding that an increase in the proportion of cases with a positive BAC first occurred at the 12–23.9 h submersion group during the warmer non-winter months, we concluded that production of alcohol can occur in bodies recovered from the water as early as 12 h after death. Because excluding drownings with submersion durations greater than 12 h would exclude almost half of our cases from epidemiological studies of alcohol and drowning, additional evidence from the forensic literature was used to develop an adjustment procedure to account for endogenous alcohol production for submersion times of up to 1 week.

Will rising atmospheric CO 2 affect leaf litter quality and in situ decomposition rates in native plant communities?

Though field data for naturally senesced leaf litter are rare, it is commonly assumed that rising atmospheric CO2 concentrations will reduce leaf litter quality and decomposition rates in terrestrial ecosystems and that this will lead to decreased rates of nutrient cycling and increased carbon sequestration in native ecosystems. We generally found that the quality of␣naturally senesced leaf litter (i.e. concentrations of C, N and lignin; C:N, lignin:N) of a variety of native plant species produced in alpine, temperate and tropical communities maintained at elevated CO2 (600-680 μl l-1) was not significantly different from that produced in similar communities maintained at current ambient CO2 concentrations (340-355 μl l-1). When this litter was allowed to decompose in situ in a humid tropical forest in Panama (Cecropia peltata, Elettaria cardamomum, and Ficus benjamina, 130 days exposure) and in a lowland temperate calcareous grassland in Switzerland (Carex flacca and a graminoid species mixture; 261 days exposure), decomposition rates of litter produced under ambient and elevated CO2 did not differ significantly. The one exception to this pattern occurred in the high alpine sedge, Carex curvula, growing in the Swiss Alps. Decomposition of litter produced in situ under elevated CO2 was significantly slower than that of litter produced under ambient CO2 (14% vs. 21% of the initial litter mass had decomposed over a 61-day exposure period, respectively). Overall, our results indicate that relatively little or no change in leaf litter quality can be expected in plant communities growing under soil fertilities common in many native ecosystems as atmospheric CO2 concentrations continue to rise. Even in situations where small reductions in litter quality do occur, these may not necessarily lead to significantly slower rates of decomposition. Hence in many native species in situ litter decomposition rates, and the time course of decomposition, may remain relatively unaffected by rising CO2.