Genome Survey and Characterization of Endophytic Bacteria Exhibiting a
Beneficial Effect on Growth and Development of Poplar Trees+
Safiyh Taghavi,1 Craig Garafola,1 Se´bastien Monchy,1 Lee Newman,2 Adam Hoffman,2 Nele Weyens,3
Tanja Barac,3 Jaco Vangronsveld,3 and Daniel van der Lelie1*
BNL, Biology Department,
Building 463, Upton, NY 11973-5000.
The association of endophytic bacteria with their plant hosts has a beneficial effect for many different plant
species. Our goal is to identify endophytic bacteria that improve the biomass production and the carbon
sequestration potential of poplar trees (Populus spp.) when grown in marginal soil and to gain an insight in the
mechanisms underlying plant growth promotion. Members of the Gammaproteobacteria dominated a collection
of 78 bacterial endophytes isolated from poplar and willow trees. As representatives for the dominant genera
of endophytic gammaproteobacteria, we selected Enterobacter sp. strain 638, Stenotrophomonas maltophilia R551-3, Pseudomonas putida W619, and Serratia proteamaculans 568 for genome sequencing and analysis of their
plant growth-promoting effects, including root development. Derivatives of these endophytes, labeled with gfp,
were also used to study the colonization of their poplar hosts. In greenhouse studies, poplar cuttings (Populus
deltoides x Populus nigra DN-34) inoculated with Enterobacter sp. strain 638 repeatedly showed the highest
increase in biomass production compared to cuttings of noninoculated control plants. Sequence data combined
with the analysis of their metabolic properties resulted in the identification of many putative mechanisms,
including carbon source utilization, that help these endophytes to thrive within a plant environment and to
potentially affect the growth and development of their plant hosts. Understanding the interactions between
endophytic bacteria and their host plants should ultimately result in the design of strategies for improved
poplar biomass production on marginal soils as a feedstock for biofuels.
Keywoards:Populus spp, Gammaproteobacteria,Stenotrophomonas maltophilia R551-3, Pseudomonas putida W619,plant growth.
Corresponding author: Tel (631) 344-5349, Fax (631) 344-3407.