Browsing by Author "Juma, Kelvin"

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    Genetic Characterization of Rhizosphere Bacteria that Inhabit Common Bean Nodules in Western Kenya Soils
    (OMICS International, 2017) Wekesa, Clabe; Muoma, John; Ombori, Omwoyo; Maingi, John; Okun, Daniel; Juma, Kelvin; Okoth, Patrick; Wamalwa, Emily; Kollenberg, Mario; Mauti, Eliakim
    Background: With the increasing world population, there is increasing demand for food. This has led to overuse of agricultural farms causing reduced soil fertility and accumulation of phytopathogens. Inorganic fertilizers and pesticides have been extensively used in response to these challenges. Extensive integration of inorganic fertilizers and pesticides in the farming system has contributed to soil and water pollution worsening the eutrophication in rivers lake waters. Alternative farming methods are therefore necessary to address this problem. Recent studies have found that rhizobacteria that colonize nodules of leguminous plants are capable of increasing yield and health of the tested plants. Their plant growth promoting ability depends on the rhizobacteria type, soil properties, and climatic conditions. The aim of this study, therefore, was to genetically characterize rhizobacteria that closely associate with common bean nodules by analyzing the nucleotide sequence of 16SrRNA gene. Results: The 16SrRNA gene analysis revealed that common bean nodule associated bacteria in Western Kenya soils are genetically diverse as indicated by the evolutionary genetic distances. Not even organisms in the same species had zero genetic distance though they formed independent groups on the phylogenetic tree. The isolates belonged to the genus Pseudomonas, Providencia, Rhizobia, Klebsiella, Enterobacter, Delfitia and Acinetobacter as identified through nucleotide BLAST at the NCBI GenBank database. Conclusion: Rhizobacteria that colonize common bean nodules are genetically diverse. Those found in this study may be adaptable to Western Kenya soils and further tests are required to determine their plant growth promoting efficiency.
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    In Vitro Antioxidant Activity of Haloalkaliphilic Fungal Extracts from Lake Magadi, Kenya
    (Science Mundi, 2025) Kiboi, Nathan; Abonyo, Collins; Ouko, Nahashon; Kimani, James; Juma, Kelvin; Ngugi, Mathew Piero; Marera, Domnic; Were, Tom
    The wide-ranging saline-alkaline ecological setting is steadily acquiring appreciation as a rich source harbouring a repertoire of extremophilic fungal diversity exerting exclusive biological activities ranging from anti-inflammatory, antipyretic, analgesic among other varied medicinal capacities. However, studies characterizing biochemical functionalities from structurally unique haloalkaliphilic fungal biota remain scanty and undocumented. Importantly, saline emitting hot-springs situated in Rift valley soda lakes are gaining recognition as natural reservoirs with enormous fungal microbial community bearing potential for antioxidation capacity. Therefore, we conducted a cross-sectional laboratory based experimental study through random sampling aimed at characterizing in vitro antioxidant activity from haloalkaliphilic fungal strains of Lake Magadi in Kenya. Sample types comprising wet sediments, soils and surface water were cultured in sabouraud’s dextrose agar (SDA), potato dextrose agar (PDA) and malt extract agar (MEA) plates at temperatures of 250c and 410c respectively, for 1-3 weeks. Resulting pure isolates underwent molecular identification. PCR proceeded using ITS-1 & 4 universal primers followed by Sanger sequencing. NCBI’s nBLAST supported molecular identification with ≥90% identity cut-off values. Fermentation and extracts production progressed for 28 days at 250c accompanied by lyophilisation. Yielded freeze-dried extracts were profiled for antioxidant activity through hydroxyl, superoxide, DPPH, hydrogen peroxide, FRAP and lipid peroxidation inhibition assays. Extracts’ total phenolics and flavonoids content were also estimated. IC50 was tabulated based on dose-response curves against standards through linear regression. One-way ANOVA compared means across treatments and Tukey’s post hoc used for pairwise group comparisons. Statistical significance was considered at P≤0.05. Genera Cladosporium exhibited dominance (n=4) among sampled fungal biota. Samples P1, P6, P9 and P5 extracts exhibited maximal scavenging activity at higher concentrations against hydroxyl (76.53% ± 1.27), superoxide (78.90% ± 1.29), H202 (76.19% ± 0.40) and DPPH (80.19% ± 0.94) radicals, respectively. Ferric reductive (0.583 ± 0.005) and lipid peroxidation inhibitive (80.95% ± 1.07) activities for isolate P5 was statistically higher relative to other profiled extracts. Radical scavenging capacity of respective antioxidant standards was substantially higher against assayed extracts. Profound IC50 scavenging effect occurred at extract concentrations between 2.5 - 3.5 mg/ml. P7 extracts revealed peak total phenolic content of 3.61 ± 0.05 mg gallic acid equivalents/mg crude extract at 4mg/ml, while P6 expressed comparable total flavonoid content of 3.32 ± 0.04 mg quercetin equivalents/mg crude extract. Overally, fungi extracts showcased free radicals scavenging ability against reactive species in assorted antioxidant assays. Besides safety profile validation, our extracts demonstrate applicability for antioxidative potential that may further be discerned via comparative in vivo and ex vivo murine experimentation models.