Browsing School of Environmental Sciences by Subjects
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Arthropod-microbe interactions on vertebrate remains: Potential applications in the forensic sciences.Understanding the process of insect colonization of human remains is a core area of research by forensic entomologists, with several recent studies suggesting that microbial communities influence the process and timing of colonization. Such information is crucial for determining when colonization occurred as related to the postmortem interval (PMI). This chapter reviews the basic field of forensic entomology; the phases of insect behavior associated with their detection, location, and utilization of the remains as postulated by Matuszewski (Matuszewski, S. (2011) Estimating the pre-appearance interval from temperature in Necrodes littoralis L. (Coleoptera: Silphidae). Forensic Science International, 212, 180–188) and Tomberlin et al. (Tomberlin, J. K., R. Mohr, M. E. Benbow, et al. 2011. A roadmap for bridging basic and applied research in forensic entomology. Annual Review of Entomology, 56, 401–421.); and how microbes play a key role mediating this process. The chapter concludes with a discussion of potential future directions related to microbe–insect interactions in association with vertebrate remains decomposition, and this is potentially important to forensics.
Detecting macroecological patterns in bacterial communities across independent studies of global soils.The emergence of high-throughput DNA sequencing methods provides unprecedented opportunities to further unravel bacterial biodiversity and its worldwide role from human health to ecosystem functioning. However, despite the abundance of sequencing studies, combining data from multiple individual studies to address macroecological questions of bacterial diversity remains methodically challenging and plagued with biases. Here, using a machine-learning approach that accounts for differences among studies and complex interactions among taxa, we merge 30 independent bacterial data sets comprising 1,998 soil samples from 21 countries. Whereas previous meta-analysis efforts have focused on bacterial diversity measures or abundances of major taxa, we show that disparate amplicon sequence data can be combined at the taxonomy-based level to assess bacterial community structure. We find that rarer taxa are more important for structuring soil communities than abundant taxa, and that these rarer taxa are better predictors of community structure than environmental factors, which are often confounded across studies. We conclude that combining data from independent studies can be used to explore bacterial community dynamics, identify potential ‘indicator’ taxa with an important role in structuring communities, and propose hypotheses on the factors that shape bacterial biogeography that have been overlooked in the past.
Microbial effects on the development of forensically important blow fly speciesColonisation times and development rates of specific blow fly species are used to estimate the minimum Post Mortem Interval (mPMI). The presence or absence of bacteria on a corpse can potentially affect the development and survival of blow fly larvae. Therefore an understanding of microbial-insect interactions is important for improving the interpretation of mPMI estimations. In this study, the effect of two bacteria (Escherichia coli and Staphylococcus aureus) on the growth rate and survival of three forensically important blow fly species (Lucilia sericata, Calliphora vicina and Calliphora vomitoria) was investigated. Sterile larvae were raised in a controlled environment (16:8 h day: night light cycle, 23:21 °C day: night temperature cycle and a constant 35% relative humidity) on four artificial diets prepared with 100 μl of 105 CFU bacterial solutions as follows: (1) E. coli, (2) S. aureus, (3) a 50:50 E. coli:S. aureus mix and (4) a sterile bacteria-free control diet. Daily measurements (length, width and weight) were taken from first instar larvae through to the emergence of adult flies. Survival rates were also determined at pupation and adult emergence. Results indicate that bacteria were not essential for the development of any of the blow fly species. However, larval growth rates were affected by bacterial diet, with effects differing between blow fly species. Peak larval weights also varied according to species-diet combination; C. vomitoria had the largest weight on E. coli and mixed diets, C. vicina had the largest weight on S. aureus diets, and treatment had no significant effect on the peak larval weight of L. sericata. These results indicate the potential for the bacteria that larvae are exposed to during development on a corpse to alter both developmental rates and larval weight in some blow fly species.