microbiologia 1

Available online at www.sciencedirect.com

Phytoremediation: plant–endophyte partnerships take the
challenge
Nele Weyens1, Daniel van der Lelie2, Safiyh Taghavi2 and
Jaco Vangronsveld1
A promising field to exploit plant–endophyte partnerships is the
remediation of contaminated soils and (ground) water. Many
plant growth promoting endophytes can assist their host plant
to overcomecontaminant-induced stress responses, thus
providing improved plant growth. During phytoremediation of
organic contaminants, plants can further benefit from
endophytes possessing appropriate degradation pathways
and metabolic capabilities, leading to more efficient
contaminant degradation and reduction of both phytotoxicity
and evapotranspiration of volatile contaminants. For
phytoremediation of toxicmetals, endophytes possessing a
metal-resistance/sequestration system can lower metal
phytotoxicity and affect metal translocation to the aboveground plant parts. Furthermore, endophytes that can degrade
organic contaminants and deal with or, even better, improve
extraction of the metals offer promising ways to improve
phytoremediation of mixed pollution.
Addresses
1
Hasselt University,Department of Environmental Biology, CMK,
Universitaire Campus building D, B-3590 Diepenbeek, Belgium
2
Brookhaven National Laboratory (BNL), Biology Department, Building
463, Upton, NY 11973-5000, USA
Corresponding author: Weyens, Nele (nele.weyens@uhasselt.be), van
der Lelie, Daniel (vdlelied@bnl.gov), Taghavi, Safiyh (taghavis@bnl.gov)
and Vangronsveld, Jaco (jaco.vangronsveld@uhasselt.be)Current Opinion in Biotechnology 2009, 20:248–254
This review comes from a themed issue on
Plant biotechnology
Edited by Dave Dowling and Sharon Lofferty Doty
Available online 25th March 2009
0958-1669/$ – see front matter
# 2009 Elsevier Ltd. All rights reserved.
DOI 10.1016/j.copbio.2009.02.012

Introduction
Plants and their associated microorganisms are characterized by varied andcomplex interactions and have been
the subject of extensive research and diverse applications.
Endophytic bacteria can be defined as bacteria colonizing
the internal tissues of plants without causing symptoms of
infection or negative effects on their host [1]. With the
exception of seed endophytes, the primary site where
endophytes gain entry into plants is via the roots. Severalmicroscopic studies confirm this route of colonization
Current Opinion in Biotechnology 2009, 20:248–254

[2,3]. Once inside the plant, endophytes either reside
in specific plant tissues like the root cortex or the xylem
(Figure 1), or colonize the plant systematically by transport through the vascular system or the apoplast [4,5].
Endophytic bacteria have been isolated from a variety of
healthyplant species ranging from herbaceous crop plants
[6,7,8,9] and different grass species [10,11] to woody tree
species [12–14,15]. In general, Pseudomonaceae, Burkholderiaceae and Enterobacteriaceae are among the most common genera of cultivable endophytic species found [16].
In comparison with rhizosphere and phyllosphere bacteria, endophytic bacteria are likely to interact more
closely withtheir host. In these very close plant–endophyte interactions, plants provide nutrients and residency
for bacteria, which in exchange can directly or indirectly
improve plant growth and health (for review see [16]).
Direct plant growth promoting mechanisms may involve
production of plant growth regulators such as auxins,
cytokinins and gibberellins, suppression of stress ethylene production by1-aminocyclopropane-1-carboxylate
(ACC) deaminase activity, nitrogen fixation and the
mobilization of unavailable nutrients such as phosphorus
and other mineral nutrients. Endophytic bacteria can
indirectly benefit plant growth by preventing the growth
or activity of plant pathogens through competition for
space and nutrients, production of hydrolytic enzymes,
antibiosis, induction of plant...