Nitric oxide synthase activity of a plant-colonizing bacterium

Abstract

Bacteria colonize the exterior and interior habitat of leaves, or phyllosphere, nourished by sugars and other products of plant metabolism. To establish a population on a leaf, a bacterium must be able to overcome several abiotic and biotic stresses including plant-derived potentially toxic hydrogen peroxide (H₂O₂). Here we report that H₂O₂ tolerance of Rhodococcus sp. strain APG1, in relation to nitric oxide (NO) production by cells cultured on a variety of C sources. Relative to cells grown on other sources of C, sucrose-grown cells were found to reach lower growth yields and show higher tolerance to H₂O₂ that correlated with increased formation of NO. The results suggest that sucrose may enhance H₂O₂ tolerance of Rhodococcus APG1 by increasing cellular NO producing capacity. We propose a regulatory role for NOS in promoting tolerance of Rhodococcus APG1 to oxidative stress in the phyllosphere.