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Introduction
Carnivorous plants characterized by a cluster of morphological and physio-biochemical features commonly known as “carnivorous syndrome” have evolved independently during evolution and are distributed in five orders and ten families of angiosperms (1, 2). These unique features enable the photoautotrophic plants in attracting, capturing and digesting the prey for acquisition of nitrogen, phosphorus, potassium, magnesium and sulphur from the insects by secreting a plethora of hydrolytic enzymes. In many of them the digestion of prey is aided by the enzymes of bacteria and/or fungi (1, 3) while others are entirely dependent on the enzymes secreted by the plant-associated microbiota (4, 5).
Preliminary analysis by Lindquist (1975) for the first time documented the occurrence of proteolytic, chitinolytic and pectin hydrolyzing bacterial species in the pitcher fluid of Sarracenia purpurea. Bacterial and fungal communities present in the trap fluid of Byblis, Brocchinia, Darlingtonia and Heliamphora also played the key role in prey degradation in complete absence of plant enzymes (5, 7). In Utricularia foliosa, U. purpurea and U. vulgaris bacteria constituted nearly 58% of the trap microbial biomass and secreted extracellular phosphatases which benefit the rootless aquatic plant with acquisition of phosphate instead of nitrogen (8).
Bacterial diversity comprising firmicutes (46.8%), proteobacteria (33.9%), acidobacteria, actinobacteria, bacteriodetes, chloroflexi, cyanobacteria, chlamydiae, and tenericutes were observed in the traps of U. hydrocarpa and Genlesia filiformis (9). Recent whole-genome shotgun metagenomics approach (10) has unraveled the taxonomic and functional diversity of the trap microbiome in U. gibba and suggested that trap bacteria play a significant role both in nutrient scavenging and assimilation. While Glen and Bodri (6) have isolated bacterial and fungal endophytes from glandular and digestion/absorption zone of the pitcher in Sarracenia orephila, endophytes of stem and leaf tissues of Nepenthes spp. were predominated by Bacillus (59.4%) followed by beta- and gamma-proteobacteria (11).
The endophytic microcosm within carnivorous hosts has been speculated to produce a large number of bioactive metabolites which not only contribute to nutrient utilization of their host but also ensure protection and survival against pathogen infections (12, 13). Assemblage of diazotrophic endophytes showing the presence of nif H gene were recorded from root and leaf segments of Drosera villosa var. villosa growing on oligotrophic habitat (14). Likewise, root endophytic actinobacterial and pseudomonad populations from D. latifolia...