Comparison of metabolites produced in vitro and in vivo by Photorhabdus luminescens, a bacterial symbiont of the entomopathogenic nematode Heterorhabditis megidis

Abstract

The types of metabolites produced by Photorhabdus luminescens C9 when it is introduced by Heterorhabditis megidis 90 into Galleria mellonella larvae are different from those produced in tryptic soy broth. Only 3,5-dihydroxy-4-isopropylstilbene 1 was identified from the organic extracts of P. luminescens culture broth, but both 3,5-dihydroxy-4-isopropylstilbene 1 and 3,5-dihydroxy-4-ethylstilbene 3 were isolated from the organic extracts of nematode-bacterium infected G. mellonella larvae. In addition to two pigments, both of which had been previously reported from P. luminescens C9 culture broth, three pigments, 1,8-dihydroxy-3-methoxy-9,10-anthraquinone 2, 1-hydroxy-2,6,8-trimethoxy-9,10-anthraquinone 6, and 1,4-dihydroxy-2,5-dimethoxy-9,10-anthraquinone 7 were isolated from the organic extracts of G. mellonella larvae infected by the nematode-bacterium complex. Among these, compounds 6 and 7 are novel and isolated from a natural source for the first time.Key words: Photorhabdus luminescens, Heterorhabditis megidis, 1-hydroxy-2,6,8-trimethoxy-9,10-anthraquinone, 1,4-dihydroxy-2,5-dimethoxy-9,10-anthraquinone, pigment.