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ItemCharacterisation of petrochemical degrading bacteria from oil contaminated soils in automechanic workshops in Arua city, Uganda(Makerere University, 2025)Unregulated, indiscriminate disposal and poor handling of used oil products from automotive mechanic workshops in Uganda contaminate vast areas of soil and groundwater. The use of bacteria to clean up contaminated sites is considered to be a desirable bioremediation strategy. Soils from automobile workshops that have had continuous exposure to oil spills provide a suitable environment for isolating adapted bacteria for bioremediation. This study aimed to isolate, characterize, and identify petroleum hydrocarbon-degrading bacteria in oil-contaminated soils collected from auto mechanic workshops in Arua City, Uganda. The isolation and identification of cultured bacteria were performed using standard microbiological methods, including morphology and biochemical tests. The effectiveness of the bacteria in degrading petroleum hydrocarbons was evaluated following the dichlorophenol-indophenol redox indicator method during the 5-day treatment, using diesel as the sole carbon source. Molecular identification of the isolated petroleum hydrocarbon-degrading bacteria was conducted by PCR amplification and sequencing of the 16S rRNA gene. MEGA 11 software was used to draw a phylogenetic tree showing the relationships between the bacterial isolates. Results showed that the fifteen morphologically and biochemically distinct bacterial colonies mostly had gram-negative-rod-shaped catalase-positive bacteria, capable of utilising diesel as their sole carbon source at varying degrees. Isolates, particularly from genera such as Acinetobacter and Bacillus, known for hydrocarbon degradation, exhibited higher petrochemical degradation potential up to 90%. Molecular characterization identified all the isolates as Shewanella xiamenensis, Jeotgalibacillus marinus, Bacillus thuringiensis, Pseudomonas putida, Peribacillus simplex, Stutzerimonas chloritidismutans, Pseudomonas fluorescens, Acinetobacter johnsonii, Psychrobacillus insolitus, Acinetobacter pittii, Raoultella ornithinolytica, Acinetobacter calcoaceticus, Rhodococcus erythropolis, Enterococcus gallinarum, and Comamonas jiangduensis. These findings therefore provide valuable insights into the potential application of these microbial isolates in the bioremediation of diesel-contaminated environments.
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ItemThe influence of borassus aethiopum mart. (arecaceae) on plant diversity in Murchison Falls National Park(Makerere University, 2025)Borassus aethiopum is a palm native to Murchison Falls National Park (MFNP) and over the last six decades its density has significantly increased, spreading across vast area in the northern section of the park. Despite palm savanna grasslands such as MFNP being classified as Endangered (EN) on a national level under criterion A1 of the International Union for Conservation of Nature, the ecological impact of the proliferation of B. aethiopum within MFNP remained unknown. Therefore, this study investigated the population structure of B. aethiopum, its influence on plant species diversity, and the role of soil physico-chemical properties in shaping plant distribution across four strata categorized by Borassus density: high Borassus density (HBD), moderate Borassus density (MBD), low Borassus density (LBD), and no Borassus (NB). A total of 800 plots were sampled for vegetation, and 80 for soil properties. Results revealed a curve approximating to a reverse J-shaped curve for population structure with a high density of seedlings (263.2 individuals/ha) but a sharp decline in juveniles (33.0 individuals/ha) and mature individuals (22.8 individuals/ha). Plant species richness varied significantly across strata, with NB exhibiting the highest richness (231 species, H = 4.31) and HBD the lowest (179 species, H = 3.83). However, a weak positive correlation was found between Borassus density and plant diversity (R² = 0.016, p = 0.0013), implying that B. aethiopum does not significantly suppress plant diversity. In contrast, soil physico-chemical parameters, notably pH, organic matter, sodium, sand, silt, and clay, significantly influenced species distribution (p < 0.05), as revealed by CCA and ANOVA. For example, sand had strong effects in HBD, while pH and potassium were key in MBD. Notably, B. aethiopum established across a wide range of soil types, indicating its ecological adaptability. These findings suggest that while Borassus has a weak effect on diversity, soil conditions play a more critical role in shaping plant communities. Therefore, conservation efforts should prioritize maintaining soil health alongside managing Borassus populations. The ability of B. aethiopum to persist in varied soil environments also presents opportunities for its continued establishment in the park. Based on these insights, it is recommended that park management maintain moderate Borassus density as they do not adversely affect species richness; establish permanent plots (at least 20% of sampled plots) for long-term monitoring of plant and Borassus population dynamics and investigate how Borassus populations influence mammals
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ItemThe Y-Chromosomal haplotype diversity of the Sabiny, Jopadhola and Samia of Eastern Uganda(Makerere University, 2025)The Y-Chromosome genetic relatedness among and between the Sabiny, Jopadhola, and Samia populations from Eastern Uganda was investigated in this study. Y-Chromosome haplogroups of 117 individuals (35 Sabiny, 40 Jopadhola, and 42 Samia) were genotyped. Prior to this research, genetic studies on these populations were limited, particularly for those in remote areas. Six bi-allelic haplogroups were identified: A3-M32, B-M181, F-M89, E3a-M2, E3b2-M81, and E3b3-M123. Haplogroups E3a-M2 and E3b3-M123 were most prevalent, while E3b2-M81 and A-M32 showed moderate frequencies. B-181 and F-M89 were observed at very low frequencies. A low mean pairwise FST value (0.13588) between the three populations suggested a relatively recent common ancestor. Phylogeographic analysis, including data from other African populations, revealed that the study groups were more closely related to East African Nilo-Saharan, Afro-Asiatic, and Khoisan populations than to Central African Niger-Congo groups. This finding may reflect geographical barriers to gene flow between East African non-Bantu and Central African Bantu speakers. The study demonstrated that Eastern Uganda is an important source of Y-Chromosome diversity, with potential implications for understanding population history and migration patterns in the African Great Lakes region. These Y-Chromosome data from Sabiny, Jopadhola, and Samia individuals have potential applications in forensics, population genetics, and serve as valuable references for assessing Y-Chromosome diversity in other Ugandan and East African populations.
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ItemBiochemical responses of Robusta coffee to water deficit conditions(Makerere University, 2025)Drought stress poses a major challenge to crop productivity by altering the biochemical composition, antioxidant defenses, and morphological development. This study investigated how the biochemical responses and the antioxidant system in Robusta coffee relate to the morphological traits under water deficit conditions. Rooted cuttings of seven CWD-r Robusta coffee varieties (KR1-KR7) were evaluated under four watering regimes (100%, 75%, 50%, and 25% field capacity, FC) in a split-split plot randomized complete block design over two temperature environments, low (LTS) and high (HTS). Morphological parameters (plant height, leaf blade length, leaf blade width, stem internode length, number of stem nodes, and number of stem internodes) were measured fortnightly for four months. Fourier transform infrared spectroscopy was used to quantify key biomolecules (carbohydrates, lipids, and proteins) from the leaves, while the 2,2-diphenyl-1-picrylhydrazyl assay was used to assess total antioxidant activity and capacity monthly for four months. Findings demonstrated significant interactive effects of temperature, moisture regime, and variety on the biochemical profile, of CWD-r Robusta coffee varieties. However, under severe drought stress, this coordination weakens as antioxidants become decoupled from biochemical maintenance, particularly under high temperatures. KR5 consistently maintained the highest biomolecule accumulation across most regimes, while KR2 and KR4 had lower biomolecule reserves under stress. TAA and TAC were stable across varieties but peaked for variety KR6 under mild (75% FC) and moderate (50% FC) moisture stress, highlighting the role of antioxidants in stress mitigation. Correlation analyses revealed robust positive associations among the spectral regions corresponding to the biomolecules, confirming a coordinated response to drought stress. Correlations between the biochemical markers and morphological parameters (such as plant height, stem node/internode counts, and leaf dimensions) were weak to moderate, suggesting that while metabolic adjustments are integral for stress mitigation, the morphological outcomes are governed by a more complex interplay of factors. A multi-trait genotype-ideotype distance index was applied to rank variety performance under distinct stress scenarios. Under well-watered (100% FC) and mild water stress (75% FC), KR1 emerged as the most promising genotype. Under moderate water deficit (50% FC), KR7 and KR3 were identified as the most suitable varieties in the HTS and LTS, respectively. Under 25% FC, KR1 and KR5 showed the strongest combination of biochemical accumulation and antioxidant defenses in the HTS and LTS respectively securing their ranking as the most water stress resilient varieties.
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ItemDevelopment of an Azolla-Vermiculite Composite fertilizer for enhancing nutrient use efficiency and soil productivity in Uganda( 2025-06-20)Utilization of slow-release fertilizers is a sustainable agricultural strategy which steadily and consistently supplies nutrients throughout a plant’s life, thereby reducing fertilizer application rates. Such fertilizers also promote effective nutrient utilization by crops minimizing nutrient leaching and runoff to non-targeted areas, thereby maintaining a healthy environment. This study developed a slow-release fertilizer named Azolla-Vermiculite Composite fertilizer, which is an innovation from a blend of Azolla cristata powder as the mineral nutrient source, and exfoliated vermiculite as the carrier material. Azolla is an aquatic fern symbiotically associated with the nitrogen fixing cyanobacteria (Anabaena azollae). The cyanobacteria absorb atmospheric nitrogen and avail it to Azolla in form of ammonium ions. This makes Azolla a rich source of nitrogen, a characteristic that was manipulated in this study for developing the Azolla-Vermiculite Composite fertilizer. In this study, four species of Azolla were identified in Uganda through molecular characterization. These species had sequence identities of 100, 93.36, 99.22 and 99.39% to the reference database sequences namely; Azolla mexicana, Azolla microphylla, Azolla filiculoides and Azolla cristata, respectively. The four species were found distributed in four out of the ten agro-ecological zones of Uganda situated in close vicinity to large water masses of L.Victoria, L. Albert, and L. Kyoga. Principal Component Analysis results revealed that maximum rainfall and altitude significantly accounted for the variations in the distribution of Azolla in Uganda with factor loadings of 0.921 and 0.922, respectively. Following experiments of domestication and cultivation of the four Azolla species in the small ponds under uniform conditions, Azolla cristata was observed to have a significantly higher nutrient bio-accumulation of nitrogen, phosphorus and potassium as the primary mineral nutrients for plant growth (p<0.0001) in comparison with the other three species. It was on the basis of this superiority that it was selected out for massive cultivation in a larger pond in preparation for development of the slow-release Azolla-Vermiculite Composite fertilizer. These experiments were conducted at Bukobero village, Masuliita sub-county Wakiso district. Vermiculite is laminar hydrated clay like mineral with capacity to expand on heating and treatment with some chemicals like hydrogen peroxide. It is non-reactive, has an alkaline pH and xii a high water holding capacity. In this innovation, exfoliated vermiculite was used because exfoliation enhances the above properties. Laboratory analysis of both raw and exfoliated vermiculite indicated a significant difference in water holding capacity, bulk density, and electro conductivity with p-values of 0.0002, 0.0033, and 0.0002 respectively. Furthermore, analysis of vermiculite microstructure under the Scanning Electron Microscope exhibited a pure and asbestos free form of vermiculite that was used in the experiment. X-ray Fluorescence exhibited the richness of vermiculite in various minerals including; silica which contributed (>40%) and phosphorus (<1%) among other minerals. Therefore, it was on the basis of these unique properties exhibited by vermiculite after exfoliation, that it was selected for use as a carrier of Azolla powder in developing the slow-release composite fertilizer. When the Azolla-Vermiculite Composite (AVC) fertilizer was tested for growth performance, yield and nutritional composition of Zea maize (maize), the change in height and yield varied significantly between the composite fertilizer treated and control plants, with p values of <0.003 and ≤0.001 respectively. Proximate nutrient analysis of starch, reducing sugars, total carbohydrates and pro-vitamin A carotenoids all varied significantly between AVC fertilizer treated and control plants with p-values of <0.002. This significant variation was attributed to the availability of sufficient concentrations of mineral nutrients in the fertilizer that enhanced these nutritional components. In addition, all the fertilizer treated plants benefited from the water retention property of exfoliated vermiculite in AVC fertilizer. Since yield is a factor of various components with water as one of the major requirements, the water retention of AVC supported effective progression of various physiological processes including photosynthesis, cell turgor, nutrient uptake, among others. The result was enhanced accumulation of photoasssimilates in the sink tissues resulting into a boost in yield and nutritional composition. Therefore, AVC fertilizer is a promising Climate Smart Agricultural fertilizer technology for enhancing soil productivity translating into better food production and improved environmental health. As a sustainability measure, there is a need to improve this product so as to achieve its maximum potential in agricultural production. This will serve as a contribution in support of the FAO strategic framework 2021-2030 in the context of Agenda 2030 for sustainable development and Uganda’s vision 2040.