Recent studies have identified cemeteries as potential environmental reservoirs of multi-drug resistant pathogenic bacteria that could contaminate groundwater sources posing public health threats. However, these findings were based on the identification of culturable bacteria and at times not below burial grounds. Investigation on the bacterial diversity and functional profiles of bacterial communities above and below burial grounds in human cemeteries are few. The current study used high-throughput sequencing techniques to determine the bacterial composition and their associated functional profiles in cemetery soil samples collected at the surface and below burial ground in two South African cemeteries (Maitland Cemetery in Cape Town and Fontein Street Cemetery in Middelburg) to evaluate the potential health threat to surrounding populations through contamination of groundwater. Significant differences were observed between sample depths with the clustering of the surface (0 m) and the 2 m samples into separate groups. Pseudomonas and Corynebacterium were the most abundant genera across all samples. Pseudomonas and Rhodococcus were the dominant genera in the 2 m samples while Prauserella and Staphylococcus were dominant in the surface samples. The 2 m samples showed a lower alpha diversity but recorded higher proportions of human diseases functional classes compared to the surface samples. Human disease functional profiles revealed involvement, in infectious (cholera), neurodegenerative (Alzheimer's disease) cardiovascular (hypertrophic cardiomyopathy) immune system (Systemic lupus erythematosus) metabolic (Type I & II diabetes) diseases and cancer. Antibiotic resistance and antibiotics synthesis signatures were also identified. Thus, cemeteries could be potential sources of microbial and antibiotic pollution in groundwater, especially in areas with shallow water tables such as Maitland. Selection of sites for use as cemeteries should, therefore, require a proper understanding of the hydrogeological characteristics of the selected site. However, further studies are required to trace the actual movement of these pollutants into groundwater resources.
Table S1. Total OTUs across all cemetery soil samples based on Greengene database.
Table S2. Similarities and differences of OTUs between soil samples obtained from different
Table S3. Comparison of samples based on Fisher exact test (P value<0.05) at genus level using
R companion package.
Table S4. Predicted functional classes of the bacterial populations extracted from soils of
different cemeteries located in South Africa. The functional classes were explored using Pi-based
on the KEGG database (Level 3).
Table S5. Predicted functional classes of the bacterial populations extracted from soils of
different cemeteries located in South Africa. The functional classes were predicted using
Piphillin based on the KEGG database.
Table S6. Predicted pathways based on Piphillin results using the KEGG pathway database.