Adaptive strategies of Enterococcus mundtii to different living conditions in the microbiome of Spodoptera littoralis larvae

The symbiotic microbial consortium in the gut of Spodoptera littoralis shows dramatic, but reproducible changes in line with the development of the insect from the egg via six larval instars to the pupa. Since the food is kept constant during development, factors from the insect host and certain microbial symbionts are assumed to control the composition of the microbiome. A GFP-tagged Enterococcus mundtii, one of the major players of the consortium, easily integrates into the microbiome and can be monitored in all gut segments at all developmental stages. The reporter organism can be recovered from the gut using a preparative flow cytometry allowing subsequent RNA extraction for transcriptomic analyses. The transcriptomic profile from the fluorescent Enterococcus cells provides information on the adaptation of the reporter organism to the local gut conditions. The concept of using a fluorescent reporter organism that can be recovered at any time from any area of the intestinal tract will allow a holistic analysis of adaptation strategies used by the microbes to adapt to the insect gut. In combination with the analysis of transcript patterns from the gut membranes, a first insight into the molecular interaction between the insect host and the microbiome can be expected.