Inefficient Secretion of Anti-Sigma Factor FlgM Inhibits Bacterial Motility at High Temperature

2019 ◽  
Author(s):  
Iaroslav Rudenko ◽  
Timo Glatter ◽  
Victor Sourjik
Keyword(s):  
High Temperature ◽  
Sigma Factor ◽  
Bacterial Motility

scholarly journals Inefficient Secretion of Anti-sigma Factor FlgM Inhibits Bacterial Motility at High Temperature

iScience ◽  
2019 ◽  
Vol 16 ◽  
pp. 145-154 ◽  
Author(s):  
Iaroslav Rudenko ◽  
Bin Ni ◽  
Timo Glatter ◽  
Victor Sourjik
Keyword(s):  
High Temperature ◽  
Sigma Factor ◽  
Bacterial Motility

scholarly journals σ28-dependent small RNAs regulate timing of flagella biosynthesis

2021 ◽  
Author(s):  
Sahar Melamed ◽  
Aixia Zhang ◽  
Michal Jarnik ◽  
Joshua Mills ◽  
Hongen Zhang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Transcriptional Regulation ◽  
Cell Motility ◽  
Sigma Factor ◽  
Small Rnas ◽  
Posttranscriptional Regulation ◽  
Bacterial Motility ◽  
Coding Sequences ◽  
Protein Levels ◽  
Opposing Effects

Flagella are important for bacterial motility as well as for pathogenesis. Synthesis of these structures is energy intensive and, while extensive transcriptional regulation has been described, little is known about the posttranscriptional regulation. Small RNAs (sRNAs) are widespread posttranscriptional regulators, most base pairing with mRNAs to affect their stability and/or translation. Here we describe four UTR-derived sRNAs (UhpU, MotR, FliX and FlgO) whose expression is controlled by the flagella sigma factor σ28 (fliA) in Escherichia coli. Interestingly, MotR and FliX have opposing effects on flagellin protein levels, flagella number and cell motility, with MotR accelerating flagella synthesis and FliX decelerating flagella synthesis. Unlike most sRNAs, MotR and FliX base pair within the coding sequences of target mRNAs. They also uniquely act on ribosomal protein mRNAs thus coordinating flagella synthesis with ribosome production. The study shows how sRNA-mediated regulation can overlay a complex network enabling nuanced control of flagella synthesis.

scholarly journals Multiple groESL Operons Are Not Key Targets of RpoH1 and RpoH2 in Sinorhizobium meliloti

2006 ◽  
Vol 188 (10) ◽  
pp. 3507-3515 ◽  
Author(s):  
Alycia N. Bittner ◽  
Valerie Oke
Keyword(s):  
Escherichia Coli ◽  
Nitrogen Fixation ◽  
High Temperature ◽  
Sigma Factor ◽  
Host Plants ◽  
Sinorhizobium Meliloti ◽  
Free Living ◽  
Genes Encoding ◽  
Multiple Copies ◽  
Free Living Conditions

ABSTRACT Among the rhizobia that establish nitrogen-fixing nodules on the roots of host plants, many contain multiple copies of genes encoding the sigma factor RpoH and the chaperone GroEL/GroES. In Sinorhizobium meliloti there are two rpoH genes, four groESL operons, and one groEL gene. rpoH1 mutants are defective for growth at high temperature and form ineffective nodules, rpoH1 rpoH2 double mutants are unable to form nodules, and groESL1 mutants form ineffective nodules. To explore the roles of RpoH1 and RpoH2, we identified mutants that suppress both the growth and nodulation defects. These mutants do not suppress the nitrogen fixation defect. This implies that the functions of RpoH1 during growth and RpoH1/RpoH2 during the initiation of symbiosis are similar but that there is a different function of RpoH1 needed later during symbiosis. We showed that, unlike in Escherichia coli, overexpression of groESL is not sufficient to bypass any of the RpoH defects. Under free-living conditions, we determined that RpoH2 does not control expression of the groE genes, and RpoH1 only controls expression of groESL5. Finally, we completed the series of groE mutants by constructing groESL3 and groEL4 mutants and demonstrated that they do not display symbiotic defects. Therefore, the only groESL operon required by itself for symbiosis is groESL1. Taken together, these results suggest that GroEL/GroES production alone cannot explain the requirements for RpoH1 and RpoH2 in S. meliloti and that there must be other crucial targets.

scholarly journals Expression of botulinum neurotoxins A and E, and associated non-toxin genes, during the transition phase and stability at high temperature: analysis by quantitative reverse transcription-PCR

Microbiology ◽  
2006 ◽  
Vol 152 (3) ◽  
pp. 759-770 ◽  
Author(s):  
Aurélie Couesnon ◽  
Stéphanie Raffestin ◽  
Michel R. Popoff
Keyword(s):  
High Temperature ◽  
Reverse Transcription ◽  
Sigma Factor ◽  
Transition Phase ◽  
Pcr Analysis ◽  
Alternative Sigma Factor ◽  
Calcium Dependent ◽  
Reverse Transcription Pcr ◽  
Botulinum Neurotoxins ◽  
Protease Activation

Production of botulinum neurotoxin A (BoNT/A) and associated non-toxic proteins (ANTPs), which include a non-toxic non-haemagglutinin (NTNH/A) as well as haemagglutinins (HAs), was found previously to be dependent upon an RNA polymerase alternative sigma factor (BotR/A). Expression of the botR/A, bont/A and antp genes, monitored by reverse transcription and real-time PCR analysis, occurred concomitantly at the transition between the exponential and stationary growth phases of Clostridium botulinum A. The botR/A expression level was about 100-fold less than those of the bont/A and antp genes. Therefore, BotR/A is an alternative sigma factor controlling the botulinum A locus genes during the transition phase. The highest toxin concentration was released into the culture supernatant 12 h after maximum expression of the botR/A, bont/A and antp genes, without any apparent bacterial lysis. Toxin levels were then stable over 5 days in cultures at 37 °C, whereas a dramatic decrease in lethal activity was observed between 24 and 48 h in cultures at 44 °C. High temperature did inhibit transcription, since expression levels of the botR/A, bont/A and antp genes were similar in cultures at 37 and 44 °C. However, incubation at 44 °C triggered a calcium-dependent protease that degraded BoNT/A and NTNH/A, but not HAs. In C. botulinum E, which contains no gene related to botR, the bont/E and p47 genes were also expressed during the transition phase, and no protease activation at 44 °C was evident.

scholarly journals Alternative Sigma Factor RpoX Is a Part of the RpoE Regulon and Plays Distinct Roles in Stress Responses, Motility, Biofilm Formation, and Hemolytic Activities in the Marine Pathogen Vibrio alginolyticus

2019 ◽  
Vol 85 (14) ◽  
Author(s):  
Dan Gu ◽  
Jun Zhang ◽  
Yuan Hao ◽  
Rongjing Xu ◽  
Yuanxing Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
Osmotic Stress ◽  
Stress Responses ◽  
Sigma Factor ◽  
Biofilm Formation ◽  
Vibrio Alginolyticus ◽  
Alternative Sigma Factor ◽  
Rna Seq ◽  
Content Type ◽  
Regulatory Cascades

ABSTRACT Vibrio alginolyticus is one of the most abundant microorganisms in marine environments and is also an opportunistic pathogen mediating high-mortality vibriosis in marine animals. Alternative sigma factors play essential roles in bacterial pathogens in the adaptation to environmental changes during infection and the adaptation to various niches, but little is known about them for V. alginolyticus. Our previous investigation indicated that the transcript level of the gene rpoX significantly decreased in an RpoE mutant. Here, we found that rpoX was highly expressed in response to high temperature and low osmotic stress and was under the direct control of the alternative sigma factor RpoE and its own product RpoX. Moreover, transcriptome sequencing (RNA-seq) results showed that RpoE and RpoX had different regulons, although they coregulated 105 genes at high temperature (42°C), including genes associated with biofilm formation, motility, virulence, regulatory factors, and the stress response. RNA-seq and chromatin immunoprecipitation sequencing (ChIP-seq) analyses as well as electrophoretic mobility shift assays (EMSAs) revealed the distinct binding motifs of RpoE and RpoX proteins. Furthermore, quantitative real-time reverse transcription-PCR (qRT-PCR) analysis also confirmed that RpoX can upregulate genes associated with flagella, biofilm formation, and hemolytic activities at higher temperatures. rpoX abrogation does not appear to attenuate virulence toward model fish at normal temperature. Collectively, data from this study demonstrated the regulatory cascades of RpoE and an alternative sigma factor, RpoX, in response to heat and osmotic stresses and their distinct and overlapping roles in pathogenesis and stress responses in the marine bacterium V. alginolyticus. IMPORTANCE The alternative sigma factor RpoE is essential for the virulence of Vibrio alginolyticus toward marine fish, coral, and other animals in response to sea surface temperature increases. In this study, we characterized another alternative sigma factor, RpoX, which is induced at high temperatures and under low-osmotic-stress conditions. The expression of rpoX is under the tight control of RpoE and RpoX. Although RpoE and RpoX coregulate 105 genes, they are programming different regulatory functions in stress responses and virulence in V. alginolyticus. These findings illuminated the RpoE-RpoX-centered regulatory cascades and their distinct and overlapping regulatory roles in V. alginolyticus, which facilitates unraveling of the mechanisms by which the bacterium causes diseases in various sea animals in response to temperature fluctuations as well as the development of appropriate strategies to tackle infections by this bacterium.

Effect of High Temperature on Pseudomonas putida NBRI0987 Biofilm Formation and Expression of Stress Sigma Factor RpoS

2008 ◽  
Vol 56 (5) ◽  
pp. 453-457 ◽  
Author(s):  
S. Srivastava ◽  
A. Yadav ◽  
K. Seem ◽  
S. Mishra ◽  
V. Chaudhary ◽  
...  
Keyword(s):  
High Temperature ◽  
Pseudomonas Putida ◽  
Sigma Factor ◽  
Biofilm Formation ◽  
Sigma Factor Rpos

scholarly journals SigC sigma factor is involved in acclimation to low inorganic carbon at high temperature in Synechocystis sp. PCC 6803

Microbiology ◽  
2010 ◽  
Vol 156 (1) ◽  
pp. 220-229 ◽  
Author(s):  
Liisa Gunnelius ◽  
Ilona Tuominen ◽  
Susanne Rantamäki ◽  
Maija Pollari ◽  
Virpi Ruotsalainen ◽  
...  
Keyword(s):  
High Temperature ◽  
Growth Medium ◽  
Sigma Factor ◽  
Inorganic Carbon ◽  
Ph Dependence ◽  
Control Strain ◽  
Prolonged Incubation ◽  
Alkaline Conditions ◽  
Group 2 ◽  
Pcc 6803

Inactivation of the sigC gene (sll0184), encoding the group 2 sigma factor SigC, leads to a heat-sensitive phenotype of Synechocystis sp. PCC 6803. Cells of the ΔsigC strain grew poorly at 43 °C at pH 7.5 under ambient CO2 conditions. Addition of inorganic carbon in the form of 3 % CO2 or use of an alkaline growth medium (pH 8.3) restored the growth of the ΔsigC strain at 43 °C. These treatments compensate for the low concentration of inorganic carbon at high temperature. However, addition of organic carbon as glucose, pyruvate, succinate or 2-oxoglutarate did not restore growth of the ΔsigC strain at 43 °C. In the control strain, the amount of the SigC factor diminished after prolonged incubation at 43 °C if the pH of the growth medium was 7.5 or 6.7. Under alkaline conditions, the amount of the SigC factor remained constant at 43 °C and cells of the control strain grew better than at pH 7.5 or pH 6.7. The pH dependence of high-temperature growth was associated with changes in photosynthetic activity, indicating that the SigC factor is involved in adjustment of photosynthesis according to the amount of available inorganic carbon. Our results indicate that acclimation to low inorganic carbon is a part of acclimation to prolonged high temperature and that the SigC factor has a central role in this acclimation.

Influence of Thermo-Mechanical Processing on the Microstructure of Beryllia Dispersed Nickel Alloys

1973 ◽  
Vol 31 ◽  
pp. 184-185
Author(s):  
M.S. Grewal ◽  
S.A. Sastri ◽  
N.J. Grant
Keyword(s):  
High Temperature ◽  
Nickel Alloys ◽  
Thermomechanical Processing ◽  
Cold Work ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Mechanical Processing ◽  
Uniform Dispersion ◽  
Oxide Particles ◽  
Nickel Base

Currently there is a great interest in developing nickel base alloys with fine and uniform dispersion of stable oxide particles, for high temperature applications. It is well known that the high temperature strength and stability of an oxide dispersed alloy can be greatly improved by appropriate thermomechanical processing, but the mechanism of this strengthening effect is not well understood. This investigation was undertaken to study the dislocation substructures formed in beryllia dispersed nickel alloys as a function of cold work both with and without intermediate anneals. Two alloys, one Ni-lv/oBeo and other Ni-4.5Mo-30Co-2v/oBeo were investigated. The influence of the substructures produced by Thermo-Mechanical Processing (TMP) on the high temperature creep properties of these alloys was also evaluated.

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