Soybean Seedling Root Growth Promotion by 1-Aminocyclopropane-1-Carboxylate Deaminase-Producing Pseudomonads

Abstract

Pseudomonad producing 1-aminocyclopropane-1-carboxylate (ACC) deaminase (E.C.4.1.99.4) has been known to promote plant growth by lowering ethylene biosynthesis in higher plants, which can be induced by indole-3-acetic acid (IAA) production. The objective of this study was to examine the ability of IAAproducing Pseudomonas isolated from local soil environment (rhizosphere of soybean grown in Plumbon's agricultural area<br />in Cirebon, West Java, Indonesia) to promote soybean root growth in relation to their ACC deaminase activities. The experiments were conducted in growth room and Laboratory of Soil Biology Research, Indonesian Soil Research Institute, Bogor, from January to August 2008. Soybean seeds were inoculated by immersing the seeds for 1 hour in bacterial cell suspension containing approximately 108-109 cells ml-1. The seeds were then germinated<br />for 2 days before planting in growth pouches containing sterilized distilled water. All treated and untreated seeds were grown for 7 days in growth room at 24°C with 1300 lux of light intensity for 12-hour followed by a 12-hour dark period at 22°C. ACC deaminase activity of the isolates was assayed based on their ability to grow in Dworkin-Foster’s salt minimal medium containing ammonium sulfate or ACC as a source of nitrogen. Thirteen out of 81 isolates tested significantly increased soybean root length and weight, up to 50% from untreated plants. Of 13 isolates, 11 demonstrated ACC deaminase activities. Two isolates that did not show ACC deaminase activities had lower capacity to produce IAA. The results suggest that the effectiveness of IAA producing Pseudomonas in promoting the growth of the soybean seedlings is associated with their ACC deaminase activities or they produce IAA at low levels.

Isolation and characterization of antagonistic bacteria with the potential for biocontrol of soil-borne wheat diseases

“…Salkowski assays were used to analyze IAA production in liquid cultures supplemented with L-tryptophan (0.5mg ml −1 ) for 48 h (48). Qualitative detection of ACC deaminase produced by the isolates was performed using DF-ACC salts minimal medium (49)…”

Mutualism between Klebsiella SGM 81 and Dianthus caryophyllus in modulating root plasticity and rhizospheric bacterial density

“…High density inoculum (10 8 CFU.mL −1 ) exhibited negative effect on plant root development whether grown in soil or on MS Agar. A number of reasons could account for this, for example: (i) higher inoculation might lead to more IAA production, which would induce ethylene production and thus inhibit root growth and development (Husen et al 2009); (ii) high density inocula could produce plant growth harmful metabolites inhibiting root development as shown in Convolvulus arvensis L (Sarwar and Kremer 1995); or (iii) high microbial titres may elicit plant defence mechanisms such as microbial associated molecular patterns (MAMPS) with adverse plant growth effects (Doornbos et al 2012). However, because the high density Klebsiella SGM 81 inoculum resulted in poorer health of D. caryophyllus that correlated with a rapid decline in the rhizospheric bacterial population but not in a decline of endophytic bacteria, we propose that whatever the cause of poor plant health, the decline of rhizophere bacterial population is mainly attributable to a lack of positive effects of the plant towards bacteria, rather than a plant defence mechanism that would also target endophytic bacteria.…”

In Vitro Study of Biocontrol Potential of Rhizospheric Pseudomonas aeruginosa against Pathogenic Fungi of Saffron (Crocus sativus L.)

“…Atmospheric nitrogen fixation was qualitatively determined using Estrada-De Los Santos's methodology [49]. ACC deaminase enzyme production was qualitatively determined using Penrose and Glick's methodology [50]. IAA production was qualitatively determined using Dowarah's methodology [51].…”