Version 1: Characterisation of Microbiome Diversity Unveils Substantial Microbial Variation in Mangrove Soils from Coastal Regions of Malaysia

The mangrove ecosystems are highly productive and of great ecological importance found in tropical and subtropical coasts, including Malaysia. The microbial communities in the mangrove sediments play an indispensable role in maintaining homeostasis and supporting biodiversity. However, mangroves are facing various threats due to increasing anthropogenic activities that trigger deterioration culminating in irreversible damage to the coastal ecosystem. Thus, it is important to monitor the microbial community to improve our understanding of the impact of anthropogenic pressure on reshaping these ecosystems. This study examines the microbial community diversity in mangrove sediments of southern peninsular Malaysia. High throughput MinION sequencing of the 16S rRNA gene was performed to compare the soil microbiome diversity in 34 samples from eight different mangroves representing Sungai Sedili Kecil and Sungai Sedili Besar that flows into the South China Sea on the east; Sungai Pulai, Sungai Melayu, Sungai Danga, Sungai Skudai and Sungai Johor that joins Straits of Johor in the south; as well as Pulau Kukup from Straits of Malacca on the west. The metagenomic classification performed with 16S rRNA showed 101 taxa comprising 18 phyla. Sequence mean prevalence and total abundance analysis showed Proteobacteria (27-66%), Firmicutes (11-25%), Planctomycetes (3-50%), and Bacteroidetes (5-9%) as the relatively common phyla in all regions. Alpha diversity indices revealed significantly higher richness in samples from mangroves in the estuaries of the South China Sea. Richness indices varied significantly across the straits of Johor, specifically Sungai Johor and Sungai Melayu. Further, Shannon index showed a significant difference in diversity between Sungai Melayu and Sungai Pulai. Higher abundance of Betaproteobacteria, Epsilonproteobacteria and Planctomycete suggest a shift in the microbial community structure. This study stands as the first comprehensive analysis of microbial communities in these mangroves, serving as a valuable reference for future monitoring and conservation endeavours to safeguard these vital ecosystems.