Affiliation:
1. Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
2. Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
Abstract
ABSTRACT
The leaf surfaces of the salt-excreting tree
Tamarix aphylla
harbor a wide diversity of halophilic microorganisms, including
Halomonas
sp., but little is known of the factors that shape community composition in this extreme habitat. We isolated a strain of
Halomonas variabilis
from the leaf surface of
T. aphylla
and used it to determine the heterogeneity of salt concentrations experienced by bacteria in this environment. This halophilic strain was transformed with a
proU
::
gfp
reporter gene fusion, the fluorescence of which was responsive to NaCl concentrations up to 200 g liter
−1
. These bioreporting cells were applied to
T. aphylla
leaves and were subsequently recovered from dew droplets adhering to the leaf surface. Although cells from within a given dew droplet exhibited similar green fluorescent protein fluorescence, the fluorescence intensity varied between droplets and was correlated with the salt concentration measured in each drop. Growth of
H. variabilis
was observed in all droplets, regardless of the salt concentration. However, cells found in desiccated microniches between dew drops were low in abundance and generally dead. Other bacteria recovered from
T. aphylla
displayed higher desiccation tolerance than
H. variabilis
, both in culture and on inoculated plants, despite having lower osmotic tolerance. Thus, the
Tamarix
leaf surface can be described as a salty desert with occasional oases where water droplets form under humid conditions. While halotolerant bacteria such as
Halomonas
grow in high concentrations of salt in such wet microniches, other organisms are better suited to survive desiccation in sites that are not wetted.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
15 articles.
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