Thomas Onchuru


Dr. Thomas Ogao Onchuru

Evolutionary Ecology
Institute of Organismic and Molecular Evolution
Hanns-Dieter-Hüsch-Weg 15
55128 Mainz, Germany

phone: +49 - (0) 6131 - 39 25200
fax: +49 - (0) 6131 - 39 23731


Research Interests

Research interests

  • Defensive symbiosis
  • Host-mutualist-pathogen interactions
  • Microbial and Vector ecology

Methodological experience

  • Molecular techniques
  • Fluorescence in situ hybridization
  • Cell culture

Multi-partite interactions in complex host-mutualist-parasite systems

Guts of multicellular organisms are nutritionally rich making them conducive environments for microbial colonization especially by those ingested with food as well as microbes beneficial to hosts. Whereas mutualist bacteria help in food digestion, nutrient supplementation or protection against pathogens, non-beneficial microbes and parasites can be detrimental to hosts, hence a need for a well coordinated regulation by the host. Knowledge on how this regulation takes place and on the general interaction of all partners in complex systems is lagging way behind the already known and emerging benefits mutualists offer to hosts. My main areas of interest are;

  • How do hosts select and maintain beneficial microbes while at the same time fighting off pathogenic microbes?
  • What are the consequences of mutualistic relationships?
  • Multipartite interactions in Meta-organisms
  • Do mutualistic partnerships strengthen the ability of hosts to fight off intruders?

The African cotton stainer (D.fasciatus) presents a simple but perfect model system for gaining insights into these questions. D.fasciatus has simple but well conserved gut bacteria and trypanosomatid parasite, Leptomonas pyrrhocoris. Two of its gut bacteria, Coriobacterium glomerans and Gordonibacter sp. (Actinobacteria) are essential in B-vitamin supplementation. These essential symbionts are transmitted vertically to the host offspring by egg surface smearing from where they are probed by newly hatched nymphs. Although this mode of symbiont transmission is integral to the symbiotic relationship, we have demonstrated that it can also be costly. Leptomonas pyrrhocoris parasites exploit it to infect offsprings and persist in host populations with high frequencies. However, despite the higher infection rates, effects of parasitism to the host are rare. Taking advantage of vertical transmission mode, we are able to generate symbiont and parasite free individuals by egg surface sterilization, which can be re-infected with symbiont or parasite only. Applying transcriptomic and qPCR analyses on these treatments we are able to identify candidate host genes involved in regulation of symbiont and parasite as well as study the role of symbiont as an additional immune phenotype to the host. Using RNA interference for these genes combined with bioassays will help us to precisely identify their specific functions.
Fig.1 African cotton stainer (Dystercus fasciatus), a model system Fig.2 Fluoreszenz in situ Hybridisierung hybridization on a cross-section of D.fasciatus gut showing associated symbionts (pink) and parasites (green)