Abstract:
Numerous tropical karst landscapes are found in the Philippines, with the largest being
located in Samar province. Despite the existence of these karst landscapes, research
focusing on the soil microbiome remains limited. This study focused on the determination
of the taxonomic and functional profile of the microbial community existing in karst forest
soils in Guiuan, Samar Province. Metagenomic analysis was used to generate a taxonomic
and functional profile of karst soil samples. To describe the taxonomic composition of the
microbial communities present, MetaPhlan2 and MG-RAST servers were used, while the
Level 1 subsystems from the SEED Subsystems database of MG-RAST were used to
describe the functional potential. The SEED database utilizes subsystems, which are a set
of functional roles that are related with each other, to provide functional annotation to the
metagenomic reads. Taxonomic profiling using MetaPhlan2 showed that all members of
the microbiome belonged to domain Bacteria, with dominance of the phylum
Actinobacteria, followed by Proteobacteria, Acidobacteria, and Firmicutes, while the use
of MG-RAST showed predominance of domain Bacteria, while members of domains
Archaea, Eukaryota, and Viruses were also detected. MG-RAST results showed
dominance of phylum Proteobacteria, Actinobacteria, Firmicutes, and Acidobacteria.
Phyla Chloroflexi and Planctomycetes were also abundant. Functional profiling using the
SEED Subsystems database revealed dominance of subsystems related to carbohydrates,
clustering-based subsystems, amino acids and derivatives. Possible reasons are due to
carbon-rich karst soils, presence of bacterial species involved in cycling of carbon and
metabolism of carbohydrates, as well as the involvement of the soil microbiome in the
different biogeochemical cycles. The results can be used as a basis for further studies that
can elaborate more on specific taxa or subsystems of interest, most especially since there
are phyla detected that have pathogenic members.
