Approccio metaproteomico per paragonare le comunità microbiche in due specie della pianta Nepenthes, una coprofaga e una insettivora.

Nepenthes is one of the richest genera of carnivorous plants, accounting for more than 100 species. It is a pitcher plant characterized by a cone-shaped trap filled with liquid, responsible for the prey digestion. Although the primary nitrogen source is insect chitin (an amino-sugar), some Nepenthes species have established a mutualism with mammals, allowing them to catch nutrients from their excrement—a pre-digested and ready-available nitrogen source. Due to this pre-digested source of nutrients, coprophagous plants may present fewer digestive enzymes, suggesting that coprophagous and insectivorous plants possess different digestive mechanisms. It is reasonable to hypothesize that commensal bacteria exist that help the plant in nutrient digestion, however, little is known about the digestion process, especially if plant microbiota is involved in the nutrient’s degradation. DNA and RNA-based techniques are generally used to identify the presence of microorganism in complex ecosystems, but they cannot provide information regarding the functions and consequently about organisms interaction. For this reason, an innovative protein-directed technique, which implies protein extraction, protein separation, LC-MS/MS analysis, and data analysis with several software, has become essential. The current study focused on the microbial communities in the pitcher fluid of two Nepenthes species: N. hemsleyana and N. rafflesiana, respectively coprophagous and insectivorous plants. Plants were fed with four different treatments (arthropods, bat feces, both and empty for control), and the digestive fluid was analyzed by a metaproteomic approach. Two main questions were open: I) Does the microbial communities change among different nutrients? We found for most of the samples a similar taxonomic composition in commensal bacteria, suggesting a plant role in the shaping of the taxonomic composition of the microbiota. II) Are there differences in the digestive enzymes in the two species, hypothesizing that the coprophagous plant lost some traits due to the pre-digested source of nutrients? We found that the coprophagous plant didn’t lost any traits, but the insectivorous plant hosts more bacteria involved in prey degradation, suggesting their important commensal role in the digestive process.