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ItemThe antibacterial activity of bitterleaf (gymnanthemum amygdalinum (delile) sch.bip.) And water hyacinth (pontederia crassipes, mart) and their effect on growth and survival of juvenile Nile tilapia (oreochromis niloticus, linnaeus 1758)(Makerere University, 2025)Aquaculture, particularly the cultivation of Nile tilapia Oreochromis niloticus, plays a crucial role in global food security. However, disease outbreaks and suboptimal growth rates present significant challenges. Natural plant-based additives offer promising alternatives to synthetic antibiotics and growth promoters. The study aimed to investigate the antibacterial activity of bitter leaf, Gymnanthemum amygdalinum (Syn: Vernonia amygdalina) and water hyacinth Pontederia crassipes Mart and the effects on the growth and survival of juvenile Nile tilapia. Dry powdered leaves of G. amygdalinum and P. crassipes were used for proximate and phytochemical analyses. Fish of average weight 1.4 ± 0.3g distributed into 9 rectangular glass tanks (3 treatments) were fed for 10 weeks to assess the influence of the treated diets on the fish performance. Further, 60 fish fed on plant-treated diet for 10 weeks and 60 new but healthy Oreochromis niloticus were injected intraperitoneally with an estimated 108 cells of Aeromonas hydrophila to evaluate the prophylactic and therapeutic potential of the ground leaves of G. amygdalinum and P. crassipes. Results revealed that G. amygdalinum contained significantly higher crude protein (25.47 ± 0.33%) and carbohydrate content (43.13 ± 0.14%) than P. crassipes, which had higher fibre (26.00 ± 0.05%) and lipid content (7.50 ± 0.10%). Additionally, G. amygdalinum contained four phytochemicals including flavonoids, alkaloids, saponins, and tannins, whereas P. crassipes contained flavonoids and tannins. Growth performance trials demonstrated that Nile tilapia fed on a diet supplemented with G. amygdalinum had a higher survival rate, grew faster, and gained more body mass compared to those fed on P. crassipes and the control group. However, the diets did not yield better condition factor, linked to possible adverse effects on the fish's health. In a challenge experiment with Aeromonas hydrophila, Nile tilapia fed on G. amygdalinum as prophylaxis showed a more enhanced survival rate of 85% than the P. crassipes and the control diet. However, there was a lower survival rate of 40% in fish fed on the two plants used as chemotherapy. The findings suggest that G. amygdalinum could be a valuable ingredient in fish feed formulation due to its high protein content and antibacterial properties, contributing to better growth performance and disease resistance in juvenile Nile tilapia. Further studies are recommended to optimize the inclusion levels of G. amygdalinum in fish diets, explore alternative extraction methods for bioactive compounds, and assess the long-term health impacts on Nile tilapia.
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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.