Soil Fungi: Their Potential use as a Forensic Tool

Identification of fungi found on desiccated human remains in an arid outdoor environment

Three fungi not previously reported on desiccated human remains were identified on cadavers at the Forensic Investigation Research Station (FIRS) in Whitewater, Colorado. The location of the FIRS provides the unique opportunity to observe the stages of decomposition in a high desert environment. The two cadavers used in the study were in the late stages of decomposition (PMI of approximately 1520 and 1820 days) to the point of desiccation and had developed an extensive black crust on the skin that remained. Skin samples of the two cadavers were taken and plated onto potato dextrose agar to determine whether fungi were present on the desiccated tissues. Three different fungi consistently dominated cultures grown from numerous samples taken from each cadaver. Based on morphological observations, nuclear rDNA sequence data, and phylogenetic analyses, two fungi were identified to species (Aureobasidium melanogenum and Didymella glomerata) and one fungus was identified to the genus level (Alternaria). These results will contribute to the understanding of the role that fungi might play in late-stage decomposition and the extended postmortem period.

Taphonomy of experimental burials in Taphos-m: The role of fungi

BACKGROUND

The fungi present in the decaying remains enable a better understanding of the processes of decomposition after death. There are not many studies about fungi on decaying bodies and it is not known which fungal sampling methods are effective.

AIMS

The main objective of this study was to find the best method for sampling fungi in carcasses, prove the effectiveness of this method and identify the fungal colonies in animal carcasses from experimental burials.

METHODS

Samples from 13 carcasses of Sus scrofa domestica, from the experimental project Taphos-m, were taken with different materials: spatula, sterile swabs and RODAC contact plates.

RESULTS

RODAC contact plates with the RBA culture medium showed higher proliferation of fungal colonies. Thirty genera of fungi were isolated from different substrates (bone, tissue, lime). Most of the fungi genera or groups identified have been described before in the literature, but the substrates they came from were different in some cases.

CONCLUSIONS

Sampling with RODAC contact plates was found to be the most effective method, as it provides a nutritional culture medium that may allow growth since the moment of sampling. Fungi colonies grew better in RBA culture medium because bacterial growth is inhibited. Most of the observed fungi are related to the environment but some others have been found related to decomposing bodies for the first time.

Fungal succession during mammalian cadaver decomposition and potential forensic implications

The necrobiome is the postmortem community that includes bacteria, fungi, arthropods, and other cadaver-associated organisms. It has been suggested as biological evidence for forensic investigation. Fungi form distinctive mildew spots in colonizing decomposing bodies, converting them into moldy cadavers. However, the postmortem fungal community consists of more than these visible species. Characterizing the succession pattern of the fungal community during decomposition is valuable not only for understanding the ecosystem composition of the cadaver decomposition islands but also for contributing to forensic investigations. In the present study, the fungal composition of pig cadavers and succession patterns during decomposition were investigated with high-throughput sequencing. The succession patterns were easier to discern in outdoor cadavers, compared with those that were placed indoors. The metabarcoding approach revealed trends linking particular fungal taxa with specific postmortem intervals (PMIs). Dominant species increased notably in cadavers and soil. Furthermore, the succession of the soil community was driven by the cadaver decomposition. Significant mycoflora differences were observed between environmental and cadaveric soil. The results obtained suggested that postputrefaction mycoflora have considerable potential for PMI estimation, particularly in cases that involve heavily decomposed bodies. In addition, the diversity of fungal communities revealed by the metabarcoding approach allowed us to discriminate the sites of cadaver decomposition, implying that postputrefaction mycoflora may be helpful in identifying the environment in which a cadaver has been placed, or the original location from which a cadaver has been moved. Our results provide an important step towards developing fungal evidence for use in forensic science and add to the growing body of work on postmortem microbial communities.

Diverse Secondary Metabolites from the Marine-Derived Fungus Dichotomomyces cejpii F31-1

By adding l-tryptophan and l-phenylalanine to GPY medium, twenty-eight compounds, including amides, polyketides, a sesquiterpenoid, a diterpenoid, a meroterpenoid, diketopiperazines, β-carbolines, fumiquinazolines, and indole alkaloids, were discovered from the marine-derived fungus Dichotomomyces cejpii F31-1, demonstrating the tremendous biosynthetic potential of this fungal strain. Among these compounds, four amides dichotomocejs A–D (1–4), one polyketide dichocetide A (5), and two diketopiperazines dichocerazines A–B (15 and 16) are new. The structures of these new compounds were determined by interpreting detailed spectroscopic data as well as calculating optical rotation values and ECD spectra. Obviously, Dichotomomyces cejpii can effectively use an amino acid-directed strategy to enhance the production of nitrogen-containing compounds. Dichotomocej A (1) displayed moderate cytotoxicity against the human rhabdomyosarcoma cell line RD with an IC₅₀ value of 39.1 µM, and pityriacitrin (22) showed moderate cytotoxicity against the human colon carcinoma cell line HCT116 with an IC₅₀ value of 35.1 µM.

First record of Talaromyces udagawae in soil related to decomposing human remains in Argentina

The morphologic features of Talaromyces udagawae Stolk and Samson are here described and illustrated. This teleomorphic Ascomycota fungus was isolated from soil obtained in Buenos Aires province (Argentina) from beneath a human cadaver in an advanced state of decomposition. After washing and serial dilution of the soil along with moist-chamber techniques for fungal cultivation, T. udagawae formed very restricted colonies of bright yellow color on different growth media with 8-ascospored asci. The ascospores were ellipsoidal and ornamented. The anamorphic state was not observed. Molecular-genetic techniques identified the species. The present record is the first of the species in Argentina, pointing it as a tool to identify soils where cadaver decomposition occurs.