META-ANALYSIS OF MICROPLASTICS AND ASSOCIATED MICROBIOMES IN WINAM GULF OF LAKE VICTORIA, KENYA

Abstract

In recent years, an imperative discussion has been built around microplastics across different landscapes pointing to the threat of microplastic toxicity, including complexes with their environmental interactions regarding it as a fundamental concern on a global scale. While studies have explored this burgeoning problem, there is a paucity of data regarding their interaction with the environment in resource-limited settings of Western Kenya. Winam Gulf of Lake Victoria is an outstanding and delicate ecosystem that supports a wide range of livelihood including humans to the microorganisms. The aim of the study was to meta-analyze microplastic profiles and microbiomes in Winam Gulf with the aim of determining polymers, microbial diversity, degrading microbes and functions and the gaps in knowledge regarding microplastic-microbe interactions and enzymatic activities to inform bioremediation strategies.The study used a random but purposive sampling strategy by picking a number of samples, 70 water and 40 sediments samples in total across the Winam Gulf region based on hotspots affected by industrial, domestic and agricultural activities. Fourier Transform Infrared Spectroscopy analyses of water, sediments and fish samples revealed microplastic pollution of diverse origin with polymer types including polyethylene (PE), polypropylene (PP), polyacrylamide (PAM), ethylene copolymer (EC), polybutene (PB), nylon, vinyl chloride (VC). Shotgun metagenomics was employed to characterize microbial communities in water and sediment samples. The quantified libraries were sequenced using the Illumina platform. Taxonomical abundance was determined by comparing metagenomic reads to a database of taxonomically informative gene families (MicroNR database). Species annotation was done using DIAMOND software (V0.9.9.110) extracted from NCBI's NR database. Functional annotation was inferred based on its similarity to the sequence in the databases (KEGG) while functional category was annotated using MG-RAST Subsystems.Shotgun metagenomics analyses of taxonomic phyla revealed Firmicutes at [88%] abundance. The bacilli were most abundant in the class taxonomy at [78%] and Bacillus was the most abundant in the genome taxonomy. The highest microplastic degrading bacteria were Paracoccus denitrificans with Streptomyces sp. ranking second with the enzymes present including 3HV dehydrogenase, proteases, PHB depolymerase, nylonases, PET-hydrolase as well as polyesterases among others. These results suggest the presence of important microplastics-microbiomes interactions and the possibility of leveraging the functional capabilities of the microbiomes through bioremediation. The paper offers important information regarding microplastic contamination in Winam Gulf, the microbial communities linked to degradation and their possible enzymatical pathways. Short-term goals could involve the use of specific pollution reduction strategies such as community education and enforcements of policy, but long-term should be aimed at studying the prospects of utilizing the microbial and enzymatic activities of the naturally occurring microbial communities in order to develop a bioremediation strategy to eliminate microplastics in Winam Gulf of Lake Victoria in Kenya. Hence, future studies should develop controlled models to validate microbial degradation, explore genetic modifications to enhance biodegradation of Microplastics pollution.