Role of RpoS in Stress Tolerance and Environmental Fitness of the Phyllosphere Bacterium Pseudomonas fluorescens Strain 122 (original) (raw)
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Phytopathology, 2009
Establishment of suppressive populations of bacterial biological control agents on aerial plant surfaces is a critical phase in biologically based management of floral diseases. Periodically, biocontrol agents encounter inhospitable conditions for growth on plants; consequently, tolerance of environmental stresses may contribute to their fitness. In many gramnegative bacteria, including strains of Pseudomonas spp., the capacity to survive environmental stresses is influenced by the stationary phase sigma factor RpoS. This study focused on the role of RpoS in stress response and epiphytic fitness of Pseudomonas fluorescens A506, a well
Microbiology, 2005
Many micro-organisms exist in natural habitats that are subject to severe or dramatically fluctuating environmental conditions. Such is the case for bacteria inhabiting plant surfaces, where they are exposed to UV irradiation, oxygen radicals, and large fluctuations in temperature and moisture. This study focuses on the role of RpoS, a central regulator of stationary-phase gene expression in bacterial cells, in stress response and environmental fitness of Pseudomonas fluorescens Pf-5. Strain Pf-5 is a rhizosphere-inhabiting bacterium that suppresses plant diseases caused by several plant-pathogenic fungi and oomycetes. Previous studies demonstrated that rpoS was required for osmotic and oxidative stress resistance of Pf-5. The results of this study demonstrate a role for rpoS in tolerance of Pf-5 to freezing, starvation, UV irradiation and desiccation stress. In field studies, an rpoS mutant was compromised in rhizosphere colonization of plants in dry soil, whereas similar rhizosphere populations were established by Pf-5 and an rpoS mutant in well-irrigated soils. RpoS is a key determinant in stress response and environmental fitness of the rhizosphere bacterium P. fluorescens Pf-5. Abbreviations: AUPC, area under the population curve; RAUPC, relative area under the population curve. 0002-8077 G 2005 SGM Printed in Great Britain 3001 Microbiology (2005), 151, 3001-3009
Phytopathology, 2009
Hagen, M. J., Stockwell, V. O., Whistler, C. A., Johnson, K. B., and Loper, J. E. 2009. Stress tolerance and environmental fitness of Pseudomonas fluorescens A506, which has a mutation in rpoS. Phytopathology 99:679-688.
Reactive oxygen and oxidative stress tolerance in plant pathogenic Pseudomonas
FEMS microbiology letters, 2012
Reactive oxygen species (ROS) are a key feature of plant (and animal) defences against invading pathogens. As a result, plant pathogens must be able to either prevent their production or tolerate high concentrations of these highly reactive chemicals. In this review, we focus on plant pathogenic bacteria of the genus Pseudomonas and the ways in which they overcome the challenges posed by ROS. We also explore the ways in which pseudomonads may exploit plant ROS generation for their own purposes and even produce ROS directly as part of their infection mechanisms.
Journal compilation, 1865
The alternative sigma factor RpoN is a key regulator in the acclimation of Pseudomonas to complex natural environments. In this study we show that RpoN is required for efficient colonization of sugar beet seedlings by the plant growth-promoting bacterium Pseudomonas fluorescens SBW25, and use phenotypic and bioinformatic approaches to profile the RpoN-dependent traits and genes of P. fluorescens SBW25. RpoN is required for flagellar biosynthesis and for assimilation of a wide variety of nutrient sources including inorganic nitrogen, amino acids, sugar alcohols and dicarboxylic acids. Chemosensitivity assays indicate that RpoN-regulated genes contribute to acid tolerance and resistance to some antibiotics, including tetracyclines and aminoglycosides. Gain of function changes associated with loss of RpoN included increased tolerance to hydroxyurea and Guanazole. Bioinformatic predictions of RpoN-regulated genes show a close correspondence with phenotypic analyses of RpoNregulated traits and suggest novel functions for RpoN in P. fluorescens, including regulation of poly(A) polymerase. The reduced plant colonization ability observed for an rpoN mutant of P. fluorescens is therefore likely to be due to defects in multiple traits including nutrient assimilation, protein secretion and stress tolerance.
Survival, Growth, and Localization of Epiphytic Fitness Mutants of Pseudomonas syringae on Leaves
Applied and Environmental Microbiology, 1994
Among 82 epiphytic fitness mutants of a Pseudomonas syringae pv. syringae strain that were characterized in a previous study, 4 mutants were particularly intolerant of the stresses associated with dry leaf surfaces. These four mutants each exhibited distinctive behaviors when inoculated onto and into plant leaves. For example, while none showed measurable growth on dry potato leaf surfaces, they grew to different population sizes in the intercellular spaces of bean leaves and on dry bean leaf surfaces, and one mutant appeared incapable of growth in both environments although it grew well on moist bean leaves. The presence of the parental strain did not influence the survival of the mutants immediately following exposure of leaves to dry, high-light incubation conditions, suggesting that the reduced survival of the mutants did not result from an inability to produce extracellular factors in planta. On moist bean leaves that were colonized by either a mutant or the wild type, the prop...
Journal of Biological Control, 2018
Water stress in one of the limiting factors which influences the plant growth. Microbes being as a partner are an integral part of the ecosystem which influences the plant growth under stress. In the present study, Pseudomonas fluorescens (NBAII-PFDWD) subjected to osmotic stress by altering osmotic potential (-10.28 MPa and-26.82 MPa) using Polyethylene Glycol (PEG) 6000 in its growth media revealed expression of proteins which modulates its cell processes. MALDI TOF studies of selected spots from 2D gel analysis of P. fluorescens (NBAII-PFDWD) grown under different osmotic stresses revealed that the stress kindled genes which were involved in production of osmoprotectants, genes encoding DNA damage repair and increased the translational accuracy. The studies also showed that P. fluorescens possesses unique mechanisms for survival under osmotic stress. The studies indicate the diverse expression of proteins in P. fluorescens (NBAII-PFDWD) under different osmotic potentials which helped them to mitigate impact of osmotic stress. The present method unravelled the mechanisms adopted by P. fluorescens (NBAII-PFDWD) to thrive under osmotic stress. The bacterium is potential stress tolerant isolate which can be exploited as a plant growth promoting rhizobacteria for agricultural crops grown in stressed soils.
International Journal of Bacteriology, 2014
Plant growth promoting rhizobacteria (PGPR) has been identified as a group of microbes that are used for plant growth enhancement and biocontrol for management of plant diseases. The inconsistency in performance of these bacteria from laboratory to field conditions is compounded due to the prevailing abiotic stresses in the field. Therefore, selection of bacterial strains with tolerance to abiotic stresses would benefit the end-user by successful establishment of the strain for showing desired effects. In this study we attempted to isolate and identify strains of Bacillus and Pseudomonas spp. with stress tolerance and proven ability to inhibit the growth of potential phytopathogenic fungi. Screening of bacterial strains for high temperature (50°C), salinity (7% NaCl), and drought (−1.2 MPa) showed that stress tolerance was pronounced less in Pseudomonas isolates than in Bacillus strains. The reason behind this could be the formation of endospores by Bacillus isolates. Tolerance to d...
Proceedings of the National Academy of Sciences, 2013
Significance Plant leaves are heavily colonized by microorganisms, but the extent to which the surface sites differ from interior sites in selecting for microbial colonization traits is poorly understood. Global gene-expression studies of the foliar pathogen Pseudomonas syringae reveal that leaf surface sites specifically favor active exploration using flagellar motility, chemosensing, and chemotaxis. In contrast, interior sites favor production of enzymes and secondary compounds that modulate bacterial interactions with the plant and its defense system. Water limitation is a dominating force in both surface and interior sites. These findings provide a rich understanding of the leaf habitats encountered by bacteria.