The type strain of Entomopathogenic nematode-symbiotic bacteria species Xenorhabdus szentirmaii (EMC) and X. budapestensis: a chronicle of a twenty-year-long story

To join the past with the future, we review two decades of international cooperation research started in Hungary, continued in “laboratories without walls” internationally on the entomopathogenic bacteria (EPB),  Xenorhabdus szentirmaii  DSM16338(T) (EMC), and  X. budapestensis  DSM16342(T) (EMA), symbiotic partners of entomopathogenic nematodes (EPN) species Steinernema rarum and S. Bicornutum,  before returning to Hungary. A mystery of EPN/EPB symbioses is the cessation of bacterial propagation in the gut of the IJs. We suppose that a similar mechanism of homeoviscous membrane adaptation is responsible for that. Our EMA/EMC project includes identifications and characterizations.  EMC releases a large quantity of iodinin (we identified as 1,6-dihydroxyphenazine 5,10-dioxide) in a water-soluble form into the media, which condenses to form spectacular insoluble crystals.  The first functional annotation of the draft genome of EMC revealed 71 genes encoding antimicrobial synthesizer (non-ribosomal peptide synthases and polyketide synthases) enzymes with plant protection and veterinary perspectives. We turned to the antimicrobial potential of EMA and EMC since multidrug resistance (MDR) is a global challenge not only in clinical, but veterinary and agricultural aspects as well. Replacing antibiotics with antimicrobial peptides (AMPs) produced by soil-born organisms for protecting (soil-born) plants seems a preferable alternative. The natural role of AMPs produced by EPBs is to sustain optimally balanced pathobiome conditions for the EPN/EPB symbiotic complexes in polyxenic conditions (the colonized insect cadaver and soil), and they serve as abundant sources of drug candidates. When drawing attention to EMA’s, and EMC’s outstanding antimicrobial potential, we probably initiated and/or facilitated the fabclavine project. Fabclavines were discovered in EMA, and their biosynthetic pathway was revealed in EMC in the Bode lab, Frankfurt, Germany. The “crown” of that project, (the easyPACId technique) was first discovered in Germany, in the Bode lab. Since then, we have also reconstructed and used it, (see Boros presentation).