Mangroves leaves phyllosphere bacteria community and its ability to survive under pyrene stress during the acclimation process

Abstract

Plants in general and mangroves in particular can harbor hyper-diverse microorganisms in their different compartments including the phyllosphere area. This study used the leaves of three mangrove species; black mangrove (Avicenia germinans), red mangrove (Rhizophora mangle) and mangrove apple (Sonneratia alba) in order to evaluate the phyllosphere epiphytic bacterial community on their leaves surface and assess the ability of some epiphytic bacteria to tolerate and survive under pyrene stress. Through the 16S rRNA genes sequencing, 380203, 405203 and 344863 OTUs were identified respectively in the leaves of mangroves apple, black and red mangroves. The identified OTUs was positively correlated with leaves-wax (p < 0.05, r² = 0.904), nitrogen (r² = 0.72), phosphorus content (r² = 0.62) and the water factor (r² = 0.93). It was however highly and negatively correlated with the canopy cover (r² = 0.93). The pyrene degradation rate in the mineral salt medium (MSM) containing pyrene as external stress was different in each mangrove species and varied depending on various factors. Therefore, through the succession culture in MSM, several bacteria strain belonging to Rhizobiales and Enterobacteres were found to be abundant in red mangroves. Bacteria belonging to Bacilliales and Sphingobacteriales were more abundant in mangroves apples and bacteria from Xanthomonadales and Sphingomonadales were more presents in back mangroves. The important finding was to reveal that the black mangrove at the non-submerged substrate, recorded the highest number of OTU, coinciding with its highest leaf's nitrogen and phosphorus content and most importantly, its highest rate of pyrene degradation. The general result of this study join previous research results and get place in the mangrove agenda, as part of a better understanding insight into the role of plant identity in driving the phyllosphere epiphytic microbial community structures in mangrove ecosystems.

Keywords: Epiphytic bacterial community; Leaf-wax content; Mangroves leaves; Phyllosphere; Pyrene.