plant surface microbiology.pdf

26 Quantifying the Impact of ACC Deaminase-
Containing Bacteria on Plants
Donna M. Penrose and Bernard R. Glick
1 Introduction
In 1994, we reported that the bacterium, Pseudomonas putida GR12–2 (Lifshitz
et al. 1986), a well-known plant growth promoting strain, contained the
enzyme, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (Jacobson
et al. 1994). This enzyme hydrolyzes ACC, the immediate precursor of ethylene,
in plant tissues (Yang and Hoffman 1984). Ethylene is required for seed
germination by many plant species and the rate of ethylene production
increases during germination and seedling growth (Abeles et al. 1992).
Although low levels of ethylene appear to enhance root initiation and growth,
and promote root extension, high levels of ethylene produced by fast growing
roots can lead to inhibition of root elongation (Mattoo and Suttle 1991; Ma et
al. 1998). We have proposed a model that suggests that ACC deaminase-containing
plant growth promoting bacteria can lower ethylene levels and thus
stimulate plant growth (Glick et al. 1998). It is quite likely that much of the
ACC produced during ethylene biosynthesis is taken up by the bacterium and
subsequently hydrolyzed to a–ketobutyrate and ammonia by ACC deaminase.
The uptake and cleavage of ACC by ACC deaminase would decrease the
amount of ACC, as well as ethylene.
2 Selection of Bacterial Strains that Contain ACC Deaminase
We developed a rapid and novel procedure for the isolation of ACC deaminase-containing
bacteria and used this technique to identify and isolate seven
plant growth promoting strains based on their ability to utilize ACC as the
sole source of nitrogen (Glick et al. 1995). These bacterial strains were isolated
from soil samples collected during late summer in Waterloo, Ontario, Canada
and various locations in California, USA from the rhizosphere of seven different
plants (Table 1). Originally, these strains were designated as Pseudomonas
sp., but were re-classified following fatty acid analysis (Shah et al. 1997).
Plant Surface Microbiology
A.Varma, L. Abbott, D. Werner, R. Hampp (Eds.)
© Springer-Verlag Berlin Heidelberg 2004