Biology subjects

Assefa, F.

Publications and source records attributed to Assefa, F..

3 recordsLinked to original sources

bioRxiv2024

Managed honey bee colony losses and causes during the active beekeeping season 2022/2023 in nine Sub-Saharan African countries

This study reports for the first-time managed honey bee colony loss rates and associated risk factors during the active beekeeping season 2022/2023 in nine Sub-Saharan African countries, namely Kenya, Ethiopia, Rwanda, Uganda, Benin, Liberia, Nigeria, Cameroon and Democratic Republic of the Congo. The sustainability of bee swarm catches as a main honey bee colony source tool for operation expansion by African beekeepers was also evaluated in Kenya and Ethiopia. In this survey, the 1,786 interviewed beekeepers across these countries collectively managing 41,761 colonies registered an overall loss rate of 21.3%, which varied significantly among countries (from 9.7 to 45.3%) and hive types (from 10.6% in hives with movable frames to 17.9% in frameless hives). The perceived causes of losses in order of significance were issues beyond the beekeepers control (mainly theft, drought, and bushfire), absconding and pests (mainly wax moth, small and large hive beetles, ants and Varroa destructor mite), but this pattern varied greatly across countries. Among the management practices and characteristics, migratory operations and professional beekeepers experienced lower losses than stationary operations and semi-professionals and hobby beekeepers. Insights into the number of bee swarms caught revealed significant decreases in swarm availability over the past three years in Kenya. The opposite situation was observed in some regions of Ethiopia. These trends require further investigation. Overall, this comprehensive survey sheds light on the complexities and challenges beekeepers faced in Sub-Saharan Africa, pointing to the need for targeted interventions and sustained research to support the resilience and growth of the apicultural sector.

zoology↗

bioRxiv2024

Plant Development Drives Dynamic Shifts in the Root Compartment Microbiomes of Wild and Domesticated Finger Millet Cultivars

BackgroundPlant-microbe interactions in two root compartments - the rhizosphere and endosphere - play vital roles in maintaining plant health and ecosystem dynamics. The microbial communities in these niches are shaped in complex ways by factors including the plants developmental stage and cultivar, and the compartment where the interactions occur. Different plant cultivars provide distinct nutritional and ecological niches and may selectively enrich specific microbial populations through the secretion of root exudates. This gives rise to complex and dynamic plant-microbe interactions; some cultivars promote the recruitment of beneficial symbionts while others may deter pathogens. To clarify these processes, this work investigated the structure of the endosphere and rhizosphere microbial communities of wild type finger millet and five domesticated cultivars across two plant developmental stages. ResultsOur results showed that the plant developmental stage, compartment, and cultivar have varying degrees of impact on root-associated microbiomes. The dominant bacterial phyla in all samples were Proteobacteria, Actinobacteria, and Bacteroidetes, while the dominant fungal phyla were Ascomycota and Basidiomycota. All of these phyla exhibited pronounced variations in abundance. In general, an increased abundance of Actinobacteria in the endosphere was accompanied by a reduced abundance of Proteobacteria. The most pronounced changes in microbial community structure were observed in the rhizosphere during the flowering stage. Changes in the microbiome patterns of the rhizosphere were driven predominantly by the genus Pseudomonas. Moreover, the host plants developmental stage strongly influenced the microbial communities, suggesting that plants can recruit specific taxa based on their need for particular soil consortia. ConclusionsOur results show that both host developmental stage and domestication strongly affect the assembly and structure of the plant microbiome. Moreover, plant root compartments can selectively recruit specific taxa from associated core microbial communities to fulfill their needs in a manner that depends on both the plants developmental stage and the specific root compartment that is involved. These findings show that deterministic selection pressures exerted by plants during their growth and development can significantly affect their microbial communities and have important implications for efforts to create tools for manipulating the microbiome to sustainably improve primary productivity.

microbiology↗

bioRxiv2020

Purification and Characterization of Aspartic Protease Produced from Aspergillus oryzae DRDFS13 under Solid-State Fermentation

Aspartic proteases (E.C.3.4.23.) are endopeptidases with molecular masses ranging between 30-45 kDa. They depend on aspartic acid residues for their catalytic activity and show maximal activity at low pH. Thus the main objective of the present study was to purify and characterize aspartic protease from locally identified fungi by solid-state fermentation. The aspartic protease in the current study was obtained from A. oryzae DRDFS13 under SSF. The crude enzyme extract was purified by size-exclusion (SEC) and ion-exchange (IEC) chromatography. The protein contents of crude enzyme and IEC fractions were determined by BCA methods while the presence of N-glycosylation was checked using Endo-H. Inhibition studies were conducted using protease inhibitors. The milk-clotting activity (MCA), protease activity (PA); molecular weight and enzyme kinetics were determined using standard methods. Optimum temperature and stability, optimum pH and stability, and the effect of cations on MCA were assessed using standard methods. The maximum MCA (477.11 U/mL) was recorded from IEC fraction A8. The highest specific activity (183.50 U/mg), purification fold (6.20) and yield (9.2%) were also obtained from the same fraction (IEC A8). The molecular weight of 40 kDa was assigned for the purified enzyme (IEC A8). However, its molecular weight was decreased to 30 KDa upon deglycosylation assay which infers that the protein is glycosylated. Incubation of the pure enzyme (IEC A8) with pepstatin A caused a 94 % inhibition on MCA. The dialyzed enzyme showed a Km and Vmax values of 17.50 mM and 1369 U, respectively. The enzyme showed maximum MCA at 60 {degrees}C and pH 5.0 with stability at pH 4.5-6.5 and temperature 35-45 {degrees}C. Most cat-ions stimulate the activity of the enzyme; moreover, the highest MCA was detected at 50 mM of MnSO4. Furthermore, the results obtained in the present study confirmed that the aspartic protease enzyme produced from A. oryzae DRDFS13 and purified in ion-exchange chromatography could be used as a substitute source of rennet enzyme for cheese production. ImportanceThe production of pure aspartic protease enzyme from local microbes which is useful to substitute shortage of calf rennet enzyme and valuable to diversify cheese production throughout the world.

microbiology↗