Any Colony morphology difference in strains of Pseudomonas fluorescence and Pseudomonas fluorescence CHA0?
Aims: To assess the impact of the biocontrol strain Pseudomonas fluorescens CHA0 on a
collection of barley rhizosphere bacteria using an agar plate inhibition assay and a plant
microcosm, focusing on a CHA0-sensitive member of the Cytophaga-like bacteria (CLB).
Methods and Results: The effect of strain CHA0 on a collection of barley rhizosphere
bacteria, in particular CLB and fluorescent pseudomonads sampled during a growth season,
was assessed by a growth inhibition assay. On average, 85% of the bacteria were sensitive in the
May sample, while the effect was reduced to around 68% in the July and August samples. In
the May sample, around 95% of the CLB and around 45% of the fluorescent pseudomonads
were sensitive to strain CHA0. The proportion of CHA0-sensitive CLB and fluorescent
pseudomonad isolates decreased during the plant growth season, i.e. in the July and August
samples. A particularly sensitive CLB isolate, CLB23, was selected, exposed to strain CHA0
(wild type) and its genetically modified derivatives in the rhizosphere of barley grown in
gnotobiotic soil microcosms. Two dry-stress periods were imposed during the experiment.
Derivatives of strain CHA0 included antibiotic or exopolysaccharide (EPS) overproducing
strains and a dry-stress-sensitive mutant. Despite their inhibitory activity against CLB23
in vitro, neither wild-type strain CHA0, nor any of its derivatives, had a major effect on
culturable and total cell numbers of CLB23 during the 23-day microcosm experiment.
Populations of all inoculants declined during the two dry-stress periods, with soil water
contents below 5% and plants reaching the wilting point, but they recovered after re-wetting
the soil. Survival of the dry-stress-sensitive mutant of CHA0 was most affected by the dry
periods; however, this did not result in an increased population density of CLB23.
Conclusions: CLB comprise a large fraction of barley rhizosphere bacteria that are sensitive to
the biocontrol pseudomonad CHA0 in vitro. However, in plant microcosm experiments with
varying soil humidity conditions, CHA0 or its derivatives had no major impact on the survival
of the highly sensitive CLB strain, CLB23, during two dry-stress periods and a re-wetting
period; all co-existed well in the rhizosphere of barley plants.
89
Hi Manohar
You can find several references on attachment 1
https://e-collection.library.ethz.ch/eserv/eth:23413/eth-23413-02.pdf
5
https://researchprofiles.herts.ac.uk/portal/services/downloadRegister/122202/101609.pdf
12
https://onlinelibrary.wiley.com/doi/10.1111/j.1574-6941.1997.tb00396.x/pdf
14
http://mic.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.28545-0
15
https://www.apsnet.org/publications/mpmi/BackIssues/Documents/1996Articles/Microbe09-83.pdf
16
https://academic.oup.com/femsec/article-pdf/2/3/151/2478055/2-3-151.pdf
19
https://www.cell.com/cell-chemical-biology/pdf/S1074-5521(06)00168-2.pdf
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