Nehemiah Ongeso

Dr. Nehemiah Ongeso

Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
orcid

Research Focus & Metrics

Academic Career Length

4Years (2023-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
2 March 2023 in BMC Microbiology
Verified
Journal Article
Open access
PDF file
FMFelix Matheri
Felix Matheri
AKAnne Kelly Kambura
Anne Kelly Kambura
MMMaina Mwangi
Maina Mwangi
NONehemiah Ongeso
Nehemiah Ongeso
EKEdward Karanja
Edward Karanja
SRSteven Runo
Steven Runo
Background: Thermophilic composting is a promising method of sanitizing pathogens in manure and a source of agriculturally important thermostable enzymes and microorganisms from organic wastes. Despite the extensive studies on compost prokaryotes, shifts in microbial profiles under the influence of various green materials and composting days are still not well understood, considering the complexity of the green material sources. Here, the effect of regimens of green composting material on the diversity, abundance, and metabolic capacity of prokaryotic communities in a thermophilic compost environment was examined. Methods: Total community 16S rRNA was recovered from triplicate compost samples of Lantana-based, Tithonia-based, Grass-based, and mixed (Lantana + Tithonia + Grass)- based at 21, 42, 63, and 84 days of composting. The 16S rRNA was sequenced using the Illumina Miseq platform. Bioinformatics analysis was done using Divisive Amplicon Denoising Algorithm version 2 (DADA2) R version 4.1 and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States version 2 (PICRUSt2) pipelines for community structure and metabolic profiles, respectively. In DADA2, prokaryotic classification was done using the Refseq-ribosomal database project (RDP) and SILVA version 138 databases. Results: Our results showed apparent differences in prokaryotic community structure for total diversity and abundance within the four compost regimens and composting days. The study showed that the most prevalent phyla during composting included Acidobacteriota, Actinobacteriota, Bacteroidota, Chloroflexi, and Proteobacteria. Additionally, there were differences in the overall diversity of metabolic pathways but no significant differences among the various compost treatments on major metabolic pathways like carbohydrate biosynthesis, carbohydrate degradation, and nitrogen biosynthesis. Conclusion: Various sources of green material affect the succession of compost nutrients and prokaryotic communities. The similarity of amounts of nutrients, such as total Nitrogen, at the end of the composting process, despite differences in feedstock material, indicates a significant influence of composting days on the stability of nutrients during composting.

3 June 2024 in Microbial Ecology
Verified
Journal Article
Open access
PDF file
RGRehemah Gwokyalya
Rehemah Gwokyalya
JHJeremy K. Herren
Jeremy K. Herren
CWChristopher W. Weldon
Christopher W. Weldon
SNShepard Ndlela
Shepard Ndlela
JGJoseph Gichuhi
Joseph Gichuhi
SMSamira Abuelgasim Mohamed
Samira Abuelgasim Mohamed
Koinobiont endoparasitoids regulate the physiology of their hosts through altering host immuno-metabolic responses, processes which function in tandem to shape the composition of the microbiota of these hosts. Here, we employed 16S rRNA and ITS amplicon sequencing to investigate whether parasitization by the parasitoid wasps, Diachasmimorpha longicaudata (Ashmaed) (Hymenoptera: Braconidae) and Psyttalia cosyrae (Wilkinson) (Hymenoptera: Braconidae), induces gut dysbiosis and differentially alter the gut microbial (bacteria and fungi) communities of an important horticultural pest, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). We further investigated the composition of bacterial communities of adult D. longicaudata and P. cosyrae to ascertain whether the adult parasitoids and parasitized host larvae share microbial taxa through transmission. We demonstrated that parasitism by D. longicaudata induced significant gut perturbations, resulting in the colonization and increased relative abundance of pathogenic gut bacteria. Some pathogenic bacteria like Stenotrophomonas and Morganella were detected in both the guts of D. longicaudata-parasitized B. dorsalis larvae and adult D. longicaudata wasps, suggesting a horizontal transfer of microbes from the parasitoid to the host. The bacterial community of P. cosyrae adult wasps was dominated by Arsenophonus nasoniae, whereas that of D. longicaudata adults was dominated by Paucibater spp. and Pseudomonas spp. Parasitization by either parasitoid wasp was associated with an overall reduction in fungal diversity and evenness. These findings indicate that unlike P. cosyrae which is avirulent to B. dorsalis, parasitization by D. longicaudata induces shifts in the gut bacteriome of B. dorsalis larvae to a pathobiont-dominated community. This mechanism possibly enhances its virulence against the pest, further supporting its candidacy as an effective biocontrol agent of this frugivorous tephritid fruit fly pest.

5 May 2025 in Environmental DNA
Verified
Journal Article
Open access
Cornelius OkelloCornelius Okello
Cornelius Okello
NWNina Wambiji
Nina Wambiji
SKSusana W. Kihia
Susana W. Kihia
NONehemiah Ongeso
Nehemiah Ongeso
SMSamuel Mwakisha Mwamburi
Samuel Mwakisha Mwamburi
MOMargaret Awuor Owuor
Margaret Awuor Owuor
Restoration of degraded arid and semi‐arid lands (ASALs) dryland ecosystems gained traction globally with the enactment of the Bonn Challenge and UN Decade of Restoration. This has been domesticated in Kenya's context by The Forest and Landscape Restoration Implementation Plan (FOLAREP). However, effectively monitoring restored ecosystems is crucial but challenging because of data gaps and technical hurdles, highlighting the need for innovative approaches to assess and restore biodiversity. This study aimed to pilot soil environmental DNA (eDNA) metabarcoding to detect species compositions rapidly, evaluate population structures and abundances, and characterize taxonomic groups. The results from this study serve as a foundational step toward monitoring the impact of water bunds, a restoration approach on biodiversity conservation, in Lower Naibunga Community Conservancy in Laikipia County, Kenya. This study used 16S rDNA and rbCL metabarcoding to assess prokaryotic and plant diversity. Plant growth‐promoting rhizobacteria species attributed to enhancing nutrient availability and improving plant resilience to abiotic stress were prevalent across all six sites: Lorubai (Site 1), Burtany (Site 2), Nkirashi (Site 3), Losopukia (Site 4), Munushoi (Site 5), and Loika (Site 6). Plant species attributed to drought tolerance and rangeland rehabilitation were also identified. The study demonstrates the potential of eDNA metabarcoding as an effective tool for monitoring nature‐based solutions (NbS) interventions to enhance biodiversity and ecosystem restoration in ASALs.

13 July 2023 in Heliyon
Verified
Journal Article
Open access
JGJohn K. Gitau
John K. Gitau
RMRosaline W. Macharia
Rosaline W. Macharia
KMKennedy Mwangi
Kennedy Mwangi
NONehemiah Ongeso
Nehemiah Ongeso
EMEdwin Murungi
Edwin Murungi
Rift Valley Fever (RVF) is a mosquito-borne viral disease caused by the Rift Valley Fever Virus. The disease is a zoonosis that largely affects domestic animals, including sheep, goats, and cattle, resulting in severe morbidity and mortality marked by massive storm abortions. To halt human and livestock deaths due to RVF, the development of efficacious vaccines and therapeutics is a compelling and urgent priority. We sought to identify potential key modules (gene clusters), hub genes, and regulatory motifs involved in the pathogenesis of RVF in Bos taurus that are amenable to inhibition. We analyzed 39 Bos taurus RNA-Seq samples using the weighted gene co-expression network analysis (WGCNA) R package and uncovered significantly enriched modules containing genes with potential pivotal roles in RVF progression. Moreover, regulatory motif analysis conducted using the Multiple Expectation Maximization for Motif Elicitation (MEME) suite identified motifs that probably modulate vital biological processes. Gene ontology terms associated with identified motifs were inferred using the GoMo human database. The gene co-expression network constructed in WGCNA using 5000 genes contained seven (7) modules, out of which four were significantly enriched for terms associated with response to viruses, response to interferon-alpha, innate immune response, and viral defense. Additionally, several biological pathways implicated in developmental processes, anatomical structure development, and multicellular organism development were identified. Regulatory motifs analysis identified short, repeated motifs whose function(s) may be amenable to disruption by novel therapeutics. Predicted functions of identified motifs include tissue development, embryonic organ development, and organ morphogenesis. We have identified several hub genes in enriched co-expressed gene modules and regulatory motifs potentially involved in the pathogenesis of RVF in B. taurus that are likely viable targets for disruption by novel therapeutics.

30 July 2024 in Sustainability
Verified
Journal Article
Open access
PDF file
FMFelix Matheri
Felix Matheri
NONehemiah Ongeso
Nehemiah Ongeso
DBDavid Bautze
David Bautze
SRSteven Runo
Steven Runo
MMMaina Mwangi
Maina Mwangi
MKMilka Kiboi
Milka Kiboi
Compost fauna act by releasing various enzymes that break down organic matter into a stable, agriculturally useful products. Mesofauna are the least studied compared to micro- and macrofauna, with the existing studies relying on classical methods such as morphological identification, essentially leaving out cryptic taxa. We sought to evaluate the ecological response of the mesofauna community to different composting materials and durations. Total mesofauna community 18S rRNA was purified in triplicate from lantana-based, tithonia-based, grass-based, and mixed (lantana + tithonia + grass)-based compost heaps after 21, 42, 63, and 84 days of composting and sequenced using the Illumina Miseq platform. Before performing statistical data analysis, we used the Divisive Amplicon Denoising Algorithm version 2 workflow for bioinformatic analyses. The composting duration, but not the composting materials, significantly influenced the total population and composition of the mesofauna communities. The composting materials and duration significantly affected the dispersion and uniqueness of the compost mesofauna communities. Canonical correspondence analysis of the compost’s physical–chemical and biological states showed a significant influence of the materials on the mesofauna community colonization capacity. The mesofauna communities had a significant response to the composting duration. This, therefore, presents them as valuable tools for understanding the temporal evolution of compost.

19 December 2023 in Research Square
Verified
Preprint
Open access
PDF file
RGRehemah Gwokyalya
Rehemah Gwokyalya
JHJeremy K. Herren
Jeremy K. Herren
CWChristopher W. Weldon
Christopher W. Weldon
SNShepard Ndlela
Shepard Ndlela
JGJoseph Gichuhi
Joseph Gichuhi
SMSamira A. Mohamed
Samira A. Mohamed
Background Koinobiont endoparasitoids regulate the physiological functioning of their hosts through altering metabolism and immune responses, processes which function in tandem to shape the structure and composition of the microbial communities of these hosts. Here we investigated the hypothesis that parasitisation by the virulent Diachasmimorpha longicaudata and the avirulent Pystallia cosyrae induce gut dysbiosis and differentially alter the gut microbial communities of an important horticultural pest, the oriental fruit fly, Bactrocera dorsalis. Consequently, we employed 16S rRNA and ITS amplicon sequencing to investigate the effect of parasitisation on the bacterial and fungal communities of B. dorsalis, respectively. We further investigated the bacterial communities of D. longicaudata and P. cosyrae using 16S rRNA sequencing. Results Exposure to both parasitoids induced perturbations in the microbial communities of B. dorsalis. The gut bacteriome of B. dorsalis larvae shifted from an Anoxybacillus, Acetobacter and Acinetobacter dominated community to one dominated by the generaMorganella, Stenotrophomonas, Weissella and Pantoea. These effects were especially more pronounced in the D. longicaudata-parasitised larvae compared to those parasitized by P. cosyrae. The diversity and abundance of the fungal community was negatively influenced by parasitisation with an overall reduction in fungi diversity, richness, and evenness. We found an increase in the abundance of Sacchromyces species in larvae parasitized by both wasps compared to the unparasitised controls. On the other hand, the bacterial communities of both parasitoids were less diverse. Arsenophonus nasoniaewas the dominant bacterium in P. cosyrae whereas Paucibacter and Pseudomonas species dominated the bacteriome of D. longicaudata. Conclusion This study presents the first report of the microbial communities of D. longicaudata and P. cosyrae as well as parasitism-induced gut perturbations in B. dorsalis, revealing host gut homeostasis as a possible driver of parasitoid virulence in this invasive pest.