Browsing by Author "Gatebe, E."

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    Antimycobacterial and Cytotoxic Activities of Extracts from Fungal Isolates of Lake Magadi
    (International Formulae Group, 2017) Kowanga, Keno D; Munissi, Joan J.E; Masalu, Rose; Nyandoro, Stephen S.; Masimba, Pax; Gatebe, E.
    Antimycobacterial and cytotoxic activities of extracts from fungal isolates of Lake Magadi Keno David Kowanga, Joan John Eliona Munissi, Rose Masalu, Stephen Samwel Nyandoro, Pax Masimba, Erastus Gatebe Abstract In this study, antimycobacterial and cytotoxic activities of ethyl acetate extracts of fungal isolates from Lake Magadi were evaluated. The extracts were tested against Mycobacterium madagascariense (MM) and M. indicus pranii (MIP), and cytotoxicity against brine shrimp (Artemia salina) larvae. Fungal strains were identified using sequence comparison of the Internal Transcribed Spacer (ITS) region. Potent antimycobacterial activities against MM were exhibited by extracts from Volutella colletotrichoides, Helicoon richonis, Penicillium limosum, P. sacculum, Aspergillus parasiticus and A. nomius strains that exhibited minimum inhibition concentration (MIC) in the range of 0.19 – 12.5 mg/mL. On the other hand, significant antimycobacterial effects against MIP was shown by extracts from V. colletotrichoides, H. richonis, A. parasiticus, Fusarium merismoides, A. silvaticus and A. fumigatus strains in the same MIC range. Notable cytotoxic activities of the extracts were from A. versicolor, A. nomius, P. janthinellum and H. richonis strains with LC50 values ranging from 46.60 – 98.12 μg/mL. These results indicate that fungi inhabiting Lake Magadi have the ability to produce bioactive metabolites that could be further explored for potential medicinal agents
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    Can Climate-Driven Change Influence Silicon Assimilation by Cereals and Hence the Distribution of Lepidopteran Stem Borers in East Africa?
    (Elsevier, 2016) Calatayud, P. A.; Njuguna, E.; Mwalusepo, Sizah; Gathara, Mary; Okuku, G.; Kibe, A.; Musyoka, B.; Williamson, David; Ong’amo, Georges; Gerald, Juma; Johansson, Tino; Subramanian, Sevgan; Gatebe, E.; Le Ru, Bruno P.
    In East Africa, lepidopteran stemborers such as Chilo partellus and Busseola fusca are major constraints to production of maize, which is the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Using altitudinal ranges in the East African highlands as ecological surrogates for inferring climate change, it was shown that Si concentrations in soil and maize decreased with altitude. This was attributed, in part, to low temperatures at high altitudes, which negatively affected Si assimilation by maize. Experiments showed that B. fusca was more susceptible to Si than C. partellus. Hence the predominance of B. fusca in the highlands and of C. partellus in the lowlands could be partly explained by altitudinal differences in Si concentrations in maize plants. Therefore, a rise in temperature due to climate change should enhance the plants’ Si assimilation and as a result C. partellus might move into the higher altitudes and increasingly displace B. fusca.
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    Variation of Soil Nutrients in Maize Growing Areas along the Altitudinal Gradient of Taita Hills Transect in Kenya
    (2015) Njuguna, Elijah; Le Ru, Bruno P.; Okuku, G.; Gathara, Mary; Mwalusepo, Sizah; Juma, Gerald; Sambai, K.; Johansson, Tino; Ong’amo, Georges; Gatebe, E.; Calatayud, P. A.
    Maize is the main staple food crop in Kenya but its yield is being affected by biotic and abiotic factors which reduce maize yield while soil nutrient elements increase the yield. Most plants grow by absorbing nutrients from the soil depending on the nature of the soil. Soil texture affects how well nutrients and water are retained in the soil. Clays and organic soils hold nutrients and water much better than sandy soils. As water drains from sandy soils, it often carries nutrients along with it through leaching. When nutrients leach into the soil, they are not available for plants to use thus affecting the plant health. This study evaluated several physical and chemical properties of soil along the altitudinal gradients of Taita hills which is characterized by graded changes in climatic conditions. Both nitrogen and carbon increased with increase in altitude while Potassium, phosphorus and pH deceased with increase in altitude. Moisture and temperature appear to be important drivers in soil parameter and therefore biological patterning along the transect.