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Survival and ice nucleation activity of Pseudomonas syringae strains exposed to simulated high-altitude atmospheric conditions.

ABSTRACT: Pseudomonas syringae produces highly efficient biological ice nuclei (IN) that were proposed to influence precipitation by freezing water in clouds. This bacterium may be capable of dispersing through the atmosphere, having been reported in rain, snow, and cloud water samples. This study assesses its survival and maintenance of IN activity under stressing conditions present at high altitudes, such as UV radiation within clouds. Strains of the pathovars syringae and garcae were compared to Escherichia coli. While UV-C effectively inactivated these cells, the Pseudomonas were much more tolerant to UV-B. The P. syringae strains were also more resistant to radiation from a solar simulator, composed of UV-A and UV-B, while only one of them suffered a decline in IN activity at -5?°C after long exposures. Desiccation at different relative humidity values also affected the IN, but some activity at -5?°C was always maintained. The pathovar garcae tended to be more resistant than the pathovar syringae, particularly to desiccation, though its IN were found to be generally more sensitive. Compared to E. coli, the P. syringae strains appear to be better adapted to survival under conditions present at high altitudes and in clouds.

SUBMITTER: de Araujo GG

PROVIDER: S-EPMC6533367 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Survival and ice nucleation activity of Pseudomonas syringae strains exposed to simulated high-altitude atmospheric conditions.

de Araujo Gabriel Guarany GG Rodrigues Fabio F Gonçalves Fabio Luiz Teixeira FLT Galante Douglas D

Scientific reports 20190523 1

Pseudomonas syringae produces highly efficient biological ice nuclei (IN) that were proposed to influence precipitation by freezing water in clouds. This bacterium may be capable of dispersing through the atmosphere, having been reported in rain, snow, and cloud water samples. This study assesses its survival and maintenance of IN activity under stressing conditions present at high altitudes, such as UV radiation within clouds. Strains of the pathovars syringae and garcae were compared to Escher ...[more]

PMID: 31123327

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Project description:The ice nucleation protein (INP) of Pseudomonas syringae has gained scientific interest not only because of its pathogenicity of foliar necroses but also for its wide range of potential applications, such as in snow making, frozen food preparation, and surface-display system development. However, studies on the transport activity of INP remain lacking. In the present study, a newly identified INP-gene variant, inaQ, from a P. syringae MB03 strain was cloned. Its structural domains, signal sequences, and the hydrophilicity or hydrophobicity of each domain, were then characterized. The deduced amino acid sequence of InaQ shares similar protein domains with three P. syringae INPs, namely, InaK, InaZ, and InaV, which were identified as an N-terminal domain, a central repeating domain, and a C-terminal domain. The expression of the full-length InaQ and of various truncated variants was induced in Escherichia coli to analyze their transmembrane transport and surface-binding activities, while using the green fluorescence protein (GFP) as the fusion partner. With two transmembrane segments and a weak secretion signal, the N-terminal domain (InaQ-N) alone was found to be responsible for the transport process as well as for the binding to the outer membrane, whereas the C-terminal region was nonfunctional in protein transport. Increased membrane transport and surface-binding capacities were induced by a low isopropyl-?-D-thiogalactoside concentration (0.1 mmol/l) but not by culture temperatures (15 ºC to 37 ºC). Furthermore, by constructing the GFP-fused proteins with a single InaQ-N, as well as two and three tandemly aligned InaQ-N molecules, the transport and membrane-binding activities of these proteins were compared using Western blot analysis, immmunofluorescence microscopy, and assays of the GFP specific fluorescence intensity of subcellular fractions and flow cytometry, which showed that the increase of InaQ-N repeats resulted in a coordinated increase of the surface-immobilization efficiency. Therefore, the results of this study can serve as a molecular basis for improving the performance of INP-based cell surface-display systems.

Project description:Interactions between epiphytic bacteria and herbivorous insects are ubiquitous on plants, but little is known about their ecological implications. Aphids are devastating crop pests worldwide, so understanding how epiphytic bacteria impact aphid populations is critically important. Recent evidence demonstrates that plant-associated bacteria, such as Pseudomonas syringae, can be highly virulent to one species of aphid, the pea aphid (Acyrthosiphon pisum). Currently, we have no knowledge on how broad this phenomenon is across diverse aphid species that are of high agricultural concern. In controlled experiments using oral exposure in an artificial diet, we challenged five aphid species of agricultural importance with three strains of P. syringae that vary in virulence to the pea aphid. These strains also vary in epiphytic ability and comprise two phytopathogens and one non-plant-pathogenic strain. In general, differences in virulence to aphids remained relatively constant across strains regardless of the aphid species, except for the bird cherry-oat aphid (Rhopalosiphum padi), which is significantly less susceptible to two P. syringae strains. We demonstrate that lower infection incidence likely plays a role in the reduced susceptibility. Importantly, these data support previous results showing that interactions with epiphytic bacteria are important for aphids and may play a large, but underappreciated, role in insect population dynamics. Our study illustrates a potential role of epiphytic bacteria in the biological control of aphid pests broadly but suggests the need for more research encompassing a greater diversity of pest species.IMPORTANCE Sap-sucking aphids are insects of huge agricultural concern, not only because of direct damage caused by feeding but also because of their ability to transmit various plant pathogens. Some bacteria that grow on leaf surfaces, such as Pseudomonas syringae, can infect and kill aphids, making them potentially useful in the biological control of pest aphids. However, only one aphid species, the pea aphid (Acyrthosiphon pisum), has been tested for infection by P. syringae Here, we challenged five aphid species of agricultural importance with three strains of P. syringae that vary in virulence to the pea aphid. We found that four of these aphid species were susceptible to infection and death, suggesting that these bacteria are broadly useful for biological control. However, one aphid species was much more resistant to infection, indicating that more testing on diverse aphid species is needed.

Project description:Background and aimsSelected beneficial Pseudomonas spp. strains have the ability to influence root architecture in Arabidopsis thaliana by inhibiting primary root elongation and promoting lateral root and root hair formation. A crucial role for auxin in this long-term (1week), long-distance plant-microbe interaction has been demonstrated.MethodsArabidopsis seedlings were cultivated in vitro on vertical plates and inoculated with pathogenic strains Pseudomonas syringae pv. maculicola (Psm) and P. syringae pv. tomato DC3000 (Pst), as well as Agrobacterium tumefaciens (Atu) and Escherichia coli (Eco). Root hair lengths were measured after 24 and 48h of direct exposure to each bacterial strain. Several Arabidopsis mutants with impaired responses to pathogens, impaired ethylene perception and defects in the exocyst vesicle tethering complex that is involved in secretion were also analysed.Key resultsArabidopsis seedling roots infected with Psm or Pst responded similarly to when infected with plant growth-promoting rhizobacteria; root hair growth was stimulated and primary root growth was inhibited. Other plant- and soil-adapted bacteria induced similar root hair responses. The most compromised root hair growth stimulation response was found for the knockout mutants exo70A1 and ein2. The single immune pathways dependent on salicylic acid, jasmonic acid and PAD4 are not directly involved in root hair growth stimulation; however, in the mutual cross-talk with ethylene, they indirectly modify the extent of the stimulation of root hair growth. The Flg22 peptide does not initiate root hair stimulation as intact bacteria do, but pretreatment with Flg22 prior to Psm inoculation abolished root hair growth stimulation in an FLS2 receptor kinase-dependent manner. These early response phenomena are not associated with changes in auxin levels, as monitored with the pDR5::GUS auxin reporter.ConclusionsEarly stimulation of root hair growth is an effect of an unidentified component of living plant pathogenic bacteria. The root hair growth response is triggered in the range of hours after bacterial contact with roots and can be modulated by FLS2 signalling. Bacterial stimulation of root hair growth requires functional ethylene signalling and an efficient exocyst-dependent secretory machinery.

Project description:Introduction: Technological advances have made high-altitude ski slopes easily accessible to skiers of all ages. However, research on the effects of hypoxia experienced during excursions to such altitudes on physiological systems, including the ocular system, in children is scarce. Retinal vessels are embryologically of the same origin as vessels in the brain, and have similar anatomical and physiological characteristics. Thus, any hypoxia-related changes in the morphology of the former may reflect the status of the latter. Objective: To compare the effect of one-day hypoxic exposure, equivalent to the elevation of high-altitude ski resorts in North America and Europe (∼3,000 m), on retinal vessel diameter between adults and children. Methods: 11 adults (age: 40.1 ± 4.1 years) and 8 children (age: 9.3 ± 1.3 years) took part in the study. They spent 3 days at the Olympic Sports Centre Planica (Slovenia; altitude: 940 m). During days 1 and 2 they were exposed to normoxia (FiO2 = 0.209), and day 3 to normobaric hypoxia (FiO2 = 0.162 ± 0.03). Digital high-resolution retinal fundus photographs were obtained in normoxia (Day 2) and hypoxia (Day 3). Central retinal arteriolar equivalent (CRAE) and venular equivalents (CRVE) were determined using an Automated Retinal Image Analyser. Results: Central retinal arteriolar and venular equivalents increased with hypoxia in children (central retinal arteriolar equivalent: 105.32 ± 7.72 µm, hypoxia: 110.13 ± 7.16 µm, central retinal venular equivalent: normoxia: 123.39 ± 8.34 µm, hypoxia: 130.11 ± 8.54 µm) and adults (central retinal arteriolar equivalent: normoxia: 105.35 ± 10.67 µm, hypoxia: 110.77 ± 8.36 µm; central retinal venular equivalent: normoxia: 126.89 ± 7.24 µm, hypoxia: 132.03 ± 9.72 µm), with no main effect of group or group*condition interaction. A main effect of condition on central retinal arteriolar and venular equivalents was observed (central retinal arteriolar equivalent:normoxia: 105.34 ± 9.30 µm, hypoxia: 110.50 ± 7.67 µm, p < 0.001; central retinal venular equivalent: normoxia: 125.41 ± 7.70 µm, hypoxia: 131.22 ± 9.05 µm, p < 0.001). Conclusion: A 20-hour hypoxic exposure significantly increased central retinal arteriolar and venular equivalents in adults and children. These hypoxia-induced increases were not significantly different between the age groups, confirming that vasomotor sensitivity of the retinal vessels to acute hypoxia is comparable between adults and prepubertal children.

Dataset Information

Survival and ice nucleation activity of Pseudomonas syringae strains exposed to simulated high-altitude atmospheric conditions.

Publications

Survival and ice nucleation activity of Pseudomonas syringae strains exposed to simulated high-altitude atmospheric conditions.

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