Enterobacter cloacae, an Endophyte That Establishes a Nutrient-Transfer Symbiosis With Banana Plants and Protects Against the Black Sigatoka Pathogen

Abstract

Banana ( Musa spp.) is an important crop worldwide, but black Sigatoka disease caused by the fungus Pseudocercospora fijiensis threatens fruit production. In this work, we examined the potential of the endophytes of banana plants Enterobacter cloacae and Klebsiella pneumoniae , as antagonists of P. fijiensis and support plant growth in nutrient limited soils by N-transfer. The two bacterial isolates were identified by MALDI-TOF mass spectrometry and corroborated by 16S rRNA sequence analysis. Both bacteria were positive for beneficial traits such as N-fixation, indole acetic acid production, phosphate solubilization, negative for 1-aminocyclopropane 1-carboxylic acid deaminase and were antagonistic to P. fijiensis . To measure the effects on plant growth, the two plant bacteria and an E. coli strain (as non-endophyte), were inoculated weekly for 60 days as active cells (AC) and heat-killed cells (HKC) into plant microcosms without nutrients and compared to a water only treatment, and a mineral nutrients solution (MMN) treatment. Bacterial treatments increased growth parameters and prevented accelerated senescence, which was observed for water and mineral nutrients solution (MMN) treatments used as controls. Plants died after the first 20 days of being irrigated with water; irrigation with MMN enabled plants to develop some new leaves, but plants lost weight (−30%) during the same period. Plants treated with bacteria showed good growth, but E. cloacae AC treated plants had significantly greater biomass than the E. cloacae HKC. After 60 days, plants inoculated with E. cloacae AC showed intracellular bacteria within root cells, suggesting that a stable symbiosis was established. To evaluate the transference of organic N from bacteria into the plants, the 3 bacteria were grown with 15 NH 4 Cl or Na 15 NO 3 as the nitrogen source. The 15 N transferred from bacteria to plant tissues was measured by pheophytin isotopomer abundance. The relative abundance of the isotopomers m/z 872.57, 873.57, 874.57, 875.57, 876.57 unequivocally demonstrated that plants acquired 15 N atoms directly from bacterial cells, using them as a source of N, to support plant growth in restricted nutrient soils. E. cloacae might be a new alternative to promote growth and health of banana crops.

Culturable diversity of bacterial endophytes associated with medicinal plants of the Western Ghats, India

“… 2002 ; Macedo-Raygoza et al . 2019 ) and Enterobacter sp. J49, a biofertilizer for peanut and maize (Ludueña et al .…”

Complete Genome Sequence of Enterobacter roggenkampii ED5, a Nitrogen Fixing Plant Growth Promoting Endophytic Bacterium With Biocontrol and Stress Tolerance Properties, Isolated From Sugarcane Root

“…The Enterobacter strains are well-known nitrogen fixers, plant colonizers, and highly resistant to biotic and abiotic stresses ( English et al, 2010 ; Zhu et al, 2013 ; Sarkar et al, 2018 ; Macedo-Raygoza et al, 2019 ). All selected strains showed significant biocontrol activities against several pathogens used by dual culture method, and E. roggenkampii (ED5) showed highest antagonistic activity against F. moniliforme , F. cubense , B. cinerea , C. paradoxa , and S. scitamineum which indicates the potential application for management of diseases caused by various pathogens.…”

Effects of Enterobacter cloacae HG-1 on the Nitrogen-Fixing Community Structure of Wheat Rhizosphere Soil and on Salt Tolerance

“…PGPR can induce plant systemic tolerance (IST) by increasing the concentrations of dissolved phosphorus, ACC deaminase activity, volatile substances, iron carriers, and plant hormones ( Farag et al., 2013 ; Kumari S. et al., 2015 ). Some studies have shown the potential of E. cloacae to be a plant growth promoter and its characteristic of salt tolerant ( Bhise et al., 2016 ; Macedo-Raygoza et al., 2019 ). In the present study, ten strains were isolated from alkali-saline soil samples and screened to obtain E. cloacae HG-1 that had high salt tolerance.…”