BioProject

Arboreal ant species have high population densities and low genetic variability among workers, which should favour a high probability of disease spreading in a colony. More...

Arboreal ant species have high population densities and low genetic variability among workers, which should favour a high probability of disease spreading in a colony. However, rarely ant colonies are described to die out from infection events. This apparent paradox happens due to an extremely efficient social immunity mechanisms, with a severe control of the microorganisms inside the colony. On the other hand, little is known about how do the ant workers patrolling on tree leaves affect the phyllosphere microbiota. We investigated the interactions between Azteca chartifex ant (Formicidae: Dolichoderinae), their mutualistic bacteria, and bacteria on the phyllosphere of the tropical tree Byrsonima sericea DC (Malpighiaceae). The hypothesis is that bacteria associated to the worker’s exoskeleton may outcompete the leaf microbiota. Samples were taken from an Atlantic rainforest in Rio Doce State Park, Brazil. Bacteria were isolated from ant workers´ tarsi, sampled from the main nest and from satellite nests. Then, bacteria were isolated from leaf surfaces of B. sericeae, taken from 10 trees that had A. chartifex nests and workers frequent patrolling, and from 10 trees without nests or workers patrolling. Further, the obtained isolates were grouped by Gram guilds and identified at genus level. We tested the inhibition effect of Gram-negative bacteria associated to the ant´s tarsi by growing them over the leaf bacteria isolates. There was a higher percentage of isolates Gram-negative than positive in both ant tarsi and leaves, but higher in the ants and on the leaves patrolled by A. chartifex. There was a higher growth rate of ant bacteria from the main colony compared to those found in ants from the satellite nests. The most representative genus among ant isolates was Enterobacter sp. (Proteobacteria), which was also found in the phyllosphere of leaves patrolled by ants. Azteca. chartifex Gram-negative bacteria inhibited leaf bacteria by overgrowth, and a greater inhibition effect was found on the Gram-positive bacteria from leaves with no previous interaction with ants in the field. We demonstrated that ants carry bacteria capable of inhibiting exogenous microorganisms associated to their outside territory. Hence, the whole leaf microbiota of a patrolled tree could be shaped by the ant microbiota. suggesting that large ant colonies may have a key role in structuring canopy plant-microbes interactions. Less...