ABSTRACT

Bacterial communities play an indispensable role in the environment by providing essential ecosystem sei vices such as biogeochemical cycling, nutrient cycling, decomposition and degradation etc., that are yeiy ciitica in tie survival of all kinds of lives on earth. This study is aimed at determining the physicochemistry, distribution diversity, and ecosystem functions of bacterial assemblages in (the upstream- US, midstream- MS, and downstream-DS stations) sediments of humic freshwater of Eniong River, Itu, Akwa Ibom State, using standard analytical, microbiological, molecular and functional category techniques. Results revealed variable bacterial assemblages and specie richness of the ecosystem. Using culture-dependent techniques, thirty seven (37) bacterial and two (2) Actinomycetes species were isolated and identified with thirteen (13) bacteria isolates being heterotrophic with a mean count of 5.94±0.41 log10cfu/g. Amongst the heterotrophic groups, Staphylococcus sp., had the highest mean density of 5.90±1.16 logiocfu/g, while Actinomycetes with a mean count of 3. 9± . logiocfu/g was the least. Bacteria species identified include V. cholerae, V. parahaemolyticus, E. coll, Salmonella sp, Shigella sp, Enterobacter sp, S. aureus, Proteus vulgaris, B. subtilis, B. cereus, P. aeruginosa, Desulfovibt io vulgaris, Desulfuromonas sp, Desulfobacter sp, Burkholderia pseudomallei, Micrococcus sp, Lactobacillus casei, Sphingomomnas sp, Serratia mercescins, C. botulinum, C. perfringes, Mycobacterium sp, Flavobactei ium aquatile, Brevibacterium hydrophilus, Citrobacterfreundii, P. putida, Acetobacter aceti, Enterobacterfaecalis, Klebsiella pneumonia, Yersinia pestis, Streptococcus sp., and Aeromonas hydrophila, while Actinomycetes were Nocardia sp. and Streptomyces griseus. Bacteria were widely distributed in the ecosystem with the highest occurrence observed in DS station while the least was in the US station. Metagenomic analyses revealed that all bacteria isolates belonged to 7 phyla, 30 orders and 42 distinct families. The analysis further revealed a total of 43 genera and 57 sp. The phylogenetic tree shows evolutionary relationships among diverse bacterial sp. based on sequence data. The two Streptococcus sp. (PP939615 and PP939580) formed a cluster, indicating their close evolutionary relationship. Leuconostoc sp. is distantly related but closer to Streptococcus sp. than to other taxa. Broader divisions reveal distinct evolutionary paths among groups, such as Sphingomonas sp., Neisseria sp., and Propionibacterium sp., reflecting significant genetic divergence. The tree highlights evolutionary distinctions between Gram-positive and Gram-negative bacteria, with G. positive sp. like Streptococcus and Leuconostoc forming a shared lineage, whereas G. negative taxa, including Sphingomonas sp. and Stenotrophomonas sp., diverge along separate branches. Species, such as Propionibacterium sp., Herbiconix sp., and Agromyces sp., exhibit longer branch lengths, underscoring their unique evolutionary trajectories and functional adaptations. This analysis reveals patterns of genetic similarity, divergence, and shared ancestry among the species, offering insights into microbial evolution and taxonomy. Functional genomics ofthe sediments of Eniong River revealed a total of 15 categories and a total of 13 classes of proteins annotated. From the result, it is obvious that the humic freshwater Eniong River sediment provided a unique ecological niche to different bacteria that play diversely important roles in the ecosystem. These findings suggest that P. aeruginosa and Micrococcus sp. are more efficient at utilizing HS as a carbon and energy source compared to B. subtilis, with the latter showing reduced growth at higher concentrations of HS. Physiological results of growth and survival of bacteria in sterilized humic water medium after 30 hours incubation showed that B. subtilis with growth rate (Gr) of 3.32 exhibited the best growth. Isolate with the weakest ability to proliferate in humic acid was Shigella sp. with Gr of 0.90. Oil-degrading potentials of bacteria demonstrated variable capabilities to utilize crude oil, with B. subtilis, Micrococcus sp., B. cereus and P. aeruginosa showing a very strong (+++) crude-oil degrading potentials. Water and sediment samples were analyzed tor a range of parameters, including pH, temperature, dissolved oxygen (DO), total dissolved solids (TDS), total suspended solids (TSS), electrical conductivity, organic carbon, nitrogen compounds, and heavy metals. The results indicated that the pH ofthe water and sediment was within the acceptable range (6.42-6.48), with temperature values averaging around 27°C. Key water quality indicators, such as DO (7.67 mg/ml), TDS (19.0 mg/ml), and TSS (12.5 mg/ml), were within tolerable limits for freshwater ecosystems. Total organic carbon content was significantly higher in the sediment (11.17%) compared to the water (4.79%), highlighting the role of sediment in nutrient cycling. Additionally, the river water exhibited relatively low concentrations of chloride, fluoride, and sulphate, while the sediment contained higher levels of total iron, chromium, copper, lead, and zinc. The particle size distribution in the sediment revealed a predominance of sand (71%) with moderate amounts ofsilt (17%) and clay (11%). Heavy metal concentrations, particularly lead (Pb). and iron (Fe), exceeded recommended levels in the sediment, indicating potential anthropogenic contamination. Overall, the study provides a comprehensive baseline of the physicochemical characteristics of the Eniong River and underscores the need for regular monitoring to ensure the health of this humic freshwater ecosystem.