Metabolic modelling of the entomopathogenic nematode Steinernema feltiae

                       Metabolic modelling of the entomopathogenic nematode Steinernema feltiae

                                              Sonal Dahale and Claudio Avignone Rossa

                          Systems Microbiology Lab, Department of Microbial Sciences FHMS

The entomopathogenic nematode Steinernema feltiae infects a number of insects and is used against many agricultural and horticultural pests. The life cycle of a nematode consists of four stages: egg stage, four larval / juvenile stages, and adult stage. Industrial production of the nematode requires complex media and tightly controlled culture conditions.

We studied gene expression data of Juvenile and Young Adult stage of Steinernema feltiae. The expressed genes belonging to metabolic pathways were annotated by identifying their orthologs and used to screen differentially expressed genes between the two stages. 

Gene expression data was used to reconstruct Genome-Scale Metabolic Networks (GEMs) of the Juvenile and Young Adult stages. GEMs are used for simulating and quantifying metabolic fluxes in organisms through optimization methods. Integrating transcriptomics data into the information described by GEMs allows accurate descriptions of metabolic states. Flux balance analysis simulations of the reconstructed models were performed to analyse the activity and connectivity of the different metabolic pathways. 

 The first draft of the model has 142 pathways with 2235 reactions catalysed by products of 1314 expressed genes. All the expressed genes were functionally annotated and categorized into 389 Pathways and 56 modules. The analysis showed that 2791 (out of 29063 expressed genes) were differentially expressed, including 1118 upregulated and 1673 downregulated genes. Flux Balance Analysis revealed auxotrophy for some amino acids and capacity for hypoxic growth.

The model provides details of nutritional limitations and activity of metabolic pathways at the different stages. This is essential for production of this environmentally-friendly pest control agent.

Acknowledgments. SD is funded by Doctoral College Studentship Award 3 (DCSA3) from the University of Surrey. We would like to thank BASF Agricultural Solutions UK for their support and advice.