The global regulator GacS of a biocontrol bacterium Pseudomonas chlororaphis O6 regulates transcription from the rpoS gene encoding a stationary-phase sigma factor and affects survival in oxidative stress

Kang, Beom Ryong; Cho, Baik Ho; Anderson, Anne J.; Kim, Young Cheol

doi:10.1016/j.gene.2003.10.004

Cited by 31 publications

(42 citation statements)

References 26 publications

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“…Therefore, increasing the ability to withstand and/or repair oxidative damage leads to a decrease in the inactivation rate. Several authors have observed that stationary-phase cells are more resistant to oxidative chemicals after the entry into the stationary phase (19,48), which is in agreement with our observations. Furthermore, Aldsworth et al (3) suggested that the intrinsic suicide mechanism that they proposed could also explain in part the higher resistance to inimical processes of stationary-phase cells than exponentialphase cells by assuming that this oxidative burst is more prominent, and thus destructive, in actively respiring cells (2).…”

Section: Vol 76 2010 Hhp Inactivation Of S Aureus 6987supporting

confidence: 93%

Biological Approach to Modeling of Staphylococcus aureus High-Hydrostatic-Pressure Inactivation Kinetics

Cebrián

Michiels

Mañas

et al. 2010

Appl Environ Microbiol

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Graphs for survival under high hydrostatic pressure (450 MPa; 25°C; citrate-phosphate buffer, pH 7.0) of stationary-growth-phase cells of eight Staphylococcus aureus strains were found to be nonlinear. The strains could be classified into two groups on the basis of the shoulder length. Some of them showed long shoulders of up to 20 min at 450 MPa, while others had shoulders of <3.5 min. All strains showed tails. No significant differences in the inactivation rate were found during the log-linear death phase among the eight strains. The entry into stationary growth phase resulted both in an increase in shoulder length and in a decrease in the inactivation rate. However, whereas shoulder length proved to depend on sigma B factor activity, the inactivation rate did not. Recovery in anaerobiosis decreased the inactivation rate but did not affect the shoulder length. Addition of the minimum noninhibitory concentration of sodium chloride to the recovery medium resulted in a decrease in shoulder length and in an increase in the inactivation rate for stationary-growthphase cells. In the tail region, up to 90% of the population remained sensitive to sodium chloride.The development of nonthermal methods for food preservation has been a matter of extensive study in the last 25 years. High hydrostatic pressure (HHP) is one of these proposed alternative processes that are being used commercially for the nonthermal pasteurization of different food products (17,22). This technology consists of the application of pressures in the range of from 100 to 1,000 MPa in order to inactivate pathogenic and spoilage microorganisms without affecting the quality of foods (40).A prerequisite for the definitive implementation of a new technology is reasonably detailed knowledge of its inactivation kinetics, which will allow calculation and adjustment of the intensity of the treatments (process criterion) and a certain number of log 10 cycles of bacterial inactivation to be secured (performance criterion). In addition, to define the performance criteria, it is also necessary to determine the microbial species that represents the main risk in a particular food because of its frequent appearance, its concentration, its low infectious dose, and/or its high level of resistance.The data accumulated over the last 25 years indicate that microbial inactivation by HHP typically does not follow exponential kinetics. Most of the published survival graphs show pronounced tails (14,23,28,35,41) and sometimes also shoulders (21, 25). Occasionally, both phenomena occur simultaneously, giving rise to graphs with sigmoid profiles (11,20,43). The occurrence of shoulders and tails complicates the comparison of the resistance of different bacteria and also makes it difficult to determine process criteria reliably. In order to solve both problems, diverse mathematical models, initially developed for other aims, have been applied to fit experimental survival data. The most widely used are the models based on the Weibull distribution, the log-logistic model, the mo...

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Section: Vol 76 2010 Hhp Inactivation Of S Aureus 6987supporting

confidence: 93%

Biological Approach to Modeling of Staphylococcus aureus High-Hydrostatic-Pressure Inactivation Kinetics

Cebrián

Michiels

Mañas

et al. 2010

Appl Environ Microbiol

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“…In contrast to most bacteria described to date, which either supplement a constitutively expressed catalase with additional catalase species (19,26) or up-regulate the housekeeping catalase during stationary phase (5), A. vinelandii appears to undergo complete catalase switching from Kat2 in exponential phase to Kat1 in stationary phase. We also did not observe expression of a phase-specific catalase during or after the transition to nitrogen-fixing conditions.…”

Section: Discussionmentioning

confidence: 96%

“…Mounting evidence suggests that catalases are produced primarily to deal with exogenous peroxide threats, while endogenously created peroxides are removed mainly by peroxidases (31). Many pathogenic and strongly rhizosphere-associated pseudomonads produce large quantities and, in some cases, several types of catalases (19,20) for protection from host defenses and interspecies competition. As a free-living organism, A. vinelandii may not have developed this degree of ROI defense since it is less likely to encounter high levels of exogenous hydrogen peroxide.…”

Section: Discussionmentioning

confidence: 99%

RpoS Expression and the General Stress Response in Azotobacter vinelandii during Carbon and Nitrogen Diauxic Shifts

Sandercock

Page

2008

J Bacteriol

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The general stress response mediated by the sigma factor RpoS is important for survival of bacteria in adverse environments. A mutant unable to produce RpoS was constructed using the diazotrophic bacterium Azotobacter vinelandii strain UW. Under nondesiccating, solid-medium growth conditions the wild type was culturable for 16.5 years, while the rpoS mutant remained viable for only 10 months. The rpoS mutant exhibited reduced survival compared to the wild type following hydrogen peroxide stress, and stationary phase cells were killed rapidly by 15 mM H 2 O 2 . Three catalases (Kat1, Kat2, and Kat3) were expressed in the wild type under the conditions used. Kat2 was expressed in exponential phase during shake flask growth and could be induced under highly aerated conditions in all growth phases, suggesting that there was induction by reactive oxygen intermediates. Kat3 was possibly an isoform of Kat2. In contrast, Kat1 was expressed in an RpoS-dependent manner during the mid-exponential to late stationary phases. RpoS expression did not occur exclusively in stationary phase but was influenced by changes in carbon and nitrogen source availability. There was 26-to 28-fold induction of the RpoS protein during acetate-to-glucose and ammonium-to-N 2 diauxic shifts. Following recovery of growth on the alternative carbon or nitrogen source, RpoS protein concentrations declined rapidly to a basal level. However, rpoS mRNA levels did not correlate directly to RpoS levels, suggesting that there was posttranscriptional regulation. Evidence obtained using the RpoS-dependent reporter Kat1 suggested that there is regulation of the RNAP:RpoS holoenzyme at the level of complex formation or activity.The stress and starvation response is primarily regulated by the alternative sigma factor, variably designated 38 , S , or RpoS, in many gram-negative organisms. Expression of this factor during stationary phase has been shown to regulate (positively or negatively) nearly 360 genes or 10% of the annotated genome of Escherichia coli (32), while the homologue in Pseudomonas aeruginosa regulates 772 genes or 14% of the genome (38). RpoS has been shown to regulate the production of secondary metabolites and various pathogenicity determinants in pseudomonads (14,43). In addition to stationaryphase expression, RpoS induction is also observed when E. coli exhausts specific nutrients during growth in minimal medium (35). The magnitude of RpoS induction is the same (ϳ4-fold) whether the stress is a terminal starvation event, such as glucose exhaustion (35), or a transitional starvation event during a diauxic shift from glucose to lactose (10). Following the stress event, the concentration of RpoS decreases to a basal level, whether starvation is alleviated or not (10, 35). Although equivalent studies have been done during nitrogen exhaustion, no RpoS studies have been done during nitrogen diauxie in a diazotroph.Catalase, peroxidase, and superoxide dismutase are used by aerobes in all kingdoms to degrade reactive oxygen intermediates (ROIs), s...

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“…AY586457) encoding a protein of 335 amino acids, which showed an identity of 99 % with rpoS of P. chlororaphis strain 06 (Kang et al, 2004), 97 % with rpoS of P. fluorescens PfO1 (accession no. ZP_00266495.1), 93 % with rpoS of P. putida (Kojic et al, 1999), and 93 % with rpoS of P. syringae pv.…”

Section: Identification Of Rpos In P Chlororaphis Pcl1391mentioning

confidence: 99%

“…The ORF upstream of PCL1391 rpoS is homologous (98 % identity) to the lipoprotein gene nlpD of P. chlororaphis 06 (Kang et al, 2004). The ORF sequence identified downstream of rpoS shows homology (50 % identity) to a transposase gene of Ralstonia solanacearum (accession no.…”

Section: Identification Of Rpos In P Chlororaphis Pcl1391mentioning

confidence: 99%

Regulatory roles of psrA and rpoS in phenazine-1-carboxamide synthesis by Pseudomonas chlororaphis PCL1391

et al. 2006

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Production of the secondary metabolite phenazine-1-carboxamide (PCN) by Pseudomonas chlororaphis PCL1391 is crucial for biocontrol activity against the phytopathogen Fusarium oxysporum f. sp. radicis lycopersici on tomato. Regulation of PCN production involves the two-component signalling system GacS/GacA, the quorum-sensing system PhzI/PhzR and the regulator PsrA. This paper reports that a functional rpoS is required for optimal PCN and N-hexanoyl-l-homoserine lactone (C6-HSL) production. Constitutive expression of rpoS is able to complement partially the defect of a psrA mutant for PCN and N-acylhomoserine lactone production. Western blotting shows that rpoS is regulated by gacS. Altogether, these results suggest the existence of a cascade consisting of gacS/gacA upstream of psrA and rpoS, which influence expression of phzI/phzR. Overproduction of phzR complements the effects on PCN and C6-HSL production of all mutations tested in the regulatory cascade, which shows that a functional quorum-sensing system is essential and sufficient for PCN synthesis. In addition, the relative amounts of PCN, phenazine-1-carboxylic acid and C6-HSL produced by rpoS and psrA mutants harbouring a constitutively expressed phzR indicate an even more complex network of interactions, probably involving other genes. Preliminary microarray analyses of the transcriptomics of the rpoS and psrA mutants support the model of regulation described in this study and allow identification of new genes that might be involved in secondary metabolism.

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The global regulator GacS of a biocontrol bacterium Pseudomonas chlororaphis O6 regulates transcription from the rpoS gene encoding a stationary-phase sigma factor and affects survival in oxidative stress

Cited by 31 publications

References 26 publications

Biological Approach to Modeling of Staphylococcus aureus High-Hydrostatic-Pressure Inactivation Kinetics

Biological Approach to Modeling of Staphylococcus aureus High-Hydrostatic-Pressure Inactivation Kinetics

RpoS Expression and the General Stress Response in Azotobacter vinelandii during Carbon and Nitrogen Diauxic Shifts

Regulatory roles of psrA and rpoS in phenazine-1-carboxamide synthesis by Pseudomonas chlororaphis PCL1391

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