scholarly journals Mycobacterial SigA and SigB Cotranscribe Essential Housekeeping Genes during Exponential Growth

mBio ◽  
2019 ◽  
Vol 10 (3) ◽  
Author(s):  
Kelley Hurst-Hess ◽  
Rajesh Biswas ◽  
Yong Yang ◽  
Paulami Rudra ◽  
Erica Lasek-Nesselquist ◽  
...  
Keyword(s):  
Stationary Phase ◽  
Exponential Growth ◽  
Sigma Factor ◽  
Housekeeping Genes ◽  
Sigma Factors ◽  
Rrna Gene ◽  
Content Type ◽  
Group I ◽  
Group Ii

ABSTRACTMycobacterial σBbelongs to the group II family of sigma factors, which are widely considered to transcribe genes required for stationary-phase survival and the response to stress. Here we explored the mechanism underlying the observed hypersensitivity of ΔsigBdeletion mutants ofMycobacteriumsmegmatis,M. abscessus, andM. tuberculosisto rifampin (RIF) and uncovered an additional constitutive role of σBduring exponential growth of mycobacteria that complements the function of the primary sigma factor, σA. Using chromatin immunoprecipitation sequencing (ChIP-Seq), we show that during exponential phase, σBbinds to over 200 promoter regions, including those driving expression of essential housekeeping genes, like the rRNA gene. ChIP-Seq of ectopically expressed σA-FLAG demonstrated that at least 61 promoter sites are recognized by both σAand σB. These results together suggest that RNA polymerase holoenzymes containing either σAor σBtranscribe housekeeping genes in exponentially growing mycobacteria. The RIF sensitivity of the ΔsigBmutant possibly reflects a decrease in the effective housekeeping holoenzyme pool, which results in susceptibility of the mutant to lower doses of RIF. Consistent with this model, overexpression of σArestores the RIF tolerance of the ΔsigBmutant to that of the wild type, concomitantly ruling out a specialized role of σBin RIF tolerance. Although the properties of mycobacterial σBparallel those ofEscherichiacoliσ38in its ability to transcribe a subset of housekeeping genes, σBpresents a clear departure from theE. coliparadigm, wherein the cellular levels of σ38are tightly controlled during exponential growth, such that the transcription of housekeeping genes is initiated exclusively by a holoenzyme containing σ70(E.σ70).IMPORTANCEAll mycobacteria encode a group II sigma factor, σB, closely related to the group I principal housekeeping sigma factor, σA. Group II sigma factors are widely believed to play specialized roles in the general stress response and stationary-phase transition in the bacteria that encode them. Contrary to this widely accepted view, we show an additional housekeeping function of σBthat complements the function of σAin logarithmically growing cells. These findings implicate a novel and dynamic partnership between σAand σBin maintaining the expression of housekeeping genes in mycobacteria and can perhaps be extended to other bacterial species that possess multiple group II sigma factors.

scholarly journals Alternative Sigma Factor SigK Has a Role in Stress Tolerance of Group I Clostridium botulinum Strain ATCC 3502

2013 ◽  
Vol 79 (12) ◽  
pp. 3867-3869 ◽  
Author(s):  
Elias Dahlsten ◽  
David Kirk ◽  
Miia Lindström ◽  
Hannu Korkeala
Keyword(s):  
Stress Tolerance ◽  
Sigma Factor ◽  
Clostridium Botulinum ◽  
Alternative Sigma Factor ◽  
Strain Atcc ◽  
Content Type ◽  
Osmotic Stress Tolerance ◽  
Group I ◽  
Temperature Downshift

ABSTRACTThe role of the alternative sigma factor SigK in cold and osmotic stress tolerance ofClostridium botulinumATCC 3502 was demonstrated by induction ofsigKafter temperature downshift and exposure to hyperosmotic conditions and by impaired growth of thesigKmutants under the respective conditions.

Role of estrogen deficiency in the formation and progression of cerebral aneurysms. Part I: experimental study of the effect of oophorectomy in rats

2005 ◽  
Vol 103 (6) ◽  
pp. 1046-1051 ◽  
Author(s):  
Mohammad A. Jamous ◽  
Shinji Nagahiro ◽  
Keiko T. Kitazato ◽  
Junichiro Satomi ◽  
Koichi Satoh
Keyword(s):  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
Bilateral Oophorectomy ◽  
Gelatinase Activity ◽  
Content Type ◽  
Group Iii ◽  
Group I ◽  
Group Ii ◽  
Fine Print

Object. Estrogen has been shown to play a central role in vascular biology. Although it may exert beneficial vascular effects, its role in the pathogenesis of cerebral aneurysms remains to be determined. To elucidate the role of hormones further, the authors examined the effects of bilateral oophorectomy on the formation and progression of cerebral aneurysms in rats. Methods. Forty-five female, 7-week-old Sprague—Dawley rats were divided into three equal groups. Group I consisted of intact rats (controls). To induce cerebral aneurysms, the animals in Groups II and III were subjected to ligation of the right common carotid and bilateral posterior renal arteries. One month later, the rats in Group II underwent bilateral oophorectomy. Three months after the experiment began all animals were killed and cerebral vascular corrosion casts were prepared and screened for cerebral aneurysms by using a scanning electron microscope. Plasma was used to determine the level of estradiol and the gelatinase activity. Hypertension developed in all rats except those in the control group. The estradiol level was significantly lower in Group II than in the other groups (p < 0.01). The incidence of cerebral aneurysm formation in Group II (60%) was three times higher than that in Group III (20%), and the mean size of aneurysms in Group II (76 ± 27 µm, mean ± standard deviation) was larger than that in Group III (28 ± 4.6 µm) (p < 0.05). No aneurysm developed in control animals (Group I), and there was no significant difference in plasma gelatinase activity among the three groups. Conclusions. The cerebral aneurysm model was highly reproducible in rats. Bilateral oophorectomy increased the susceptibility of rats to aneurysm formation, indicating that hormones play a role in the pathogenesis of cerebral aneurysms.

Genoprotective role of vitamin E and selenium in rabbits anaesthetized with sevoflurane

2004 ◽  
Vol 23 (8) ◽  
pp. 413-419 ◽  
Author(s):  
Cetin Kaymak ◽  
Ela Kadioglu ◽  
Hulya Basar ◽  
Semra Sardas
Keyword(s):  
Dna Damage ◽  
Vitamin E ◽  
Comet Assay ◽  
Antioxidant Supplementation ◽  
Group Iii ◽  
Sevoflurane Anaesthesia ◽  
Group I ◽  
The Mean ◽  
Group Ii

In this study, genotoxic effects of repeated sevoflurane anaesthesia were investigated in rabbits with or without antioxidant supplementation. Twenty-one New Zealand male rabbits were included in the study and randomized into three groups as: placebo treated (Group I), vitamin E supplemented (Group II) and selenium supplemented (Group III). Vitamin E and selenium were given intraperitoneally for 15 days before anaesthesia treatment. Anaesthesia was administered using 3% sevoflurane in 4 L/min oxygen for a 3-hour period and continued for 3 days. Blood samples were collected before anaesthesia (Sample 1), after the first, second and third days of sevoflurane administration (Sample 2, Sample 3 and Sample 4 respectively) and the last samples were taken 5 days after the last sevoflurane administration (Sample 5). Genotoxic damage was examined using the comet assay. The degree of damage is assessed by grading the cells into three categories of no migration (NM), low migration (LM) and high migration (HM) depending on the fraction of DNA pulled out into the tail under the influence of the electric field. The number of comets in each sample was calculated (1 × number of comets in category NM + 2 × number of comets in category LM + 3 ×number of comets in category HM) and expressed as the total comet score (TCS), which summarizes the damage frequencies. In Group I, a significant increase in the mean TCSs was observed for Samples 3 and 4 as compared with Sample 1. However, there were no significant differences between Samples 1, 2 and 5. The mean TCS of Sample 4 was significantly higher than Sample 1, 2 and 3 in Group II. Group III demonstrated no significant mean TCSs for any experimental conditions. Statistical differences were also observed between the groups with significant P values. This experimental study points out the presence of DNA damage with repeated sevoflurane anaesthesia and the genoprotective role of antioxidant supplementation on DNA damage in mononuclear leukocytes of rabbits by highly sensitive comet assay.

scholarly journals Effects of Combination of Different −10 Hexamers and Downstream Sequences on Stationary-Phase-Specific Sigma Factor ςS-Dependent Transcription in Pseudomonas putida

2000 ◽  
Vol 182 (23) ◽  
pp. 6707-6713 ◽  
Author(s):  
Eve-Ly Ojangu ◽  
Andres Tover ◽  
Riho Teras ◽  
Maia Kivisaar
Keyword(s):  
Stationary Phase ◽  
Pseudomonas Putida ◽  
Sigma Factor ◽  
Sigma Factors ◽  
Deficient Mutant ◽  
Wild Type ◽  
In Vivo Experiments ◽  
Silent Genes ◽  
Rna Polymerase Holoenzyme

ABSTRACT The main sigma factor activating gene expression, necessary in stationary phase and under stress conditions, is ςS. In contrast to other minor sigma factors, RNA polymerase holoenzyme containing ςS (EςS) recognizes a number of promoters which are also recognized by that containing ς70 (Eς70). We have previously shown that transposon Tn4652 can activate silent genes in starvingPseudomonas putida cells by creating fusion promoters during transposition. The sequence of the fusion promoters is similar to the ς70-specific promoter consensus. The −10 hexameric sequence and the sequence downstream from the −10 element differ among these promoters. We found that transcription from the fusion promoters is stationary phase specific. Based on in vivo experiments carried out with wild-type and rpoS-deficient mutant P. putida, the effect of ςS on transcription from the fusion promoters was established only in some of these promoters. The importance of the sequence of the −10 hexamer has been pointed out in several published papers, but there is no information about whether the sequences downstream from the −10 element can affect ςS-dependent transcription. Combination of the −10 hexameric sequences and downstream sequences of different fusion promoters revealed that ςS-specific transcription from these promoters is not determined by the −10 hexameric sequence only. The results obtained in this study indicate that the sequence of the −10 element influences ςS-specific transcription in concert with the sequence downstream from the −10 box.

Evaluation of Recurrent Pediatric Syncope: Role of Tilt Table Testing

PEDIATRICS ◽  
1994 ◽  
Vol 93 (4) ◽  
pp. 660-662
Author(s):  
Margaret J. Strieper ◽  
Debbie O. Auld ◽  
J. Edward Hulse ◽  
Robert M. Campbell
Keyword(s):  
Pediatric Patients ◽  
Neurocardiogenic Syncope ◽  
Tilt Table ◽  
Conversion Reaction ◽  
Cell Counts ◽  
Group I ◽  
Tilt Table Testing ◽  
Group Ii ◽  
Made In

Objective. To determine the current practice and effectiveness of evaluating recurrent syncope in pediatric patients, and to establish the role of tilt table testing in the evaluation. Design. Retrospective analysis of 54 pediatric patients with the history of syncope referred to cardiologists. Group I consisted of 27 patients examined without tilt table testing group II consisted of 27 patients whose examination included tilt table testing. Results. Group I had an average of 5.4 studies and group II, 6.6 studies performed per patient. Studies included chest radiograph (16 vs 13), electrocardiogram (24 vs 27), echocardiography (21 vs 27), 24-hour electrocardiogram (14 vs 16), transtelephonic monitor (7 vs 8), electrophysiology study (1 vs 3), complete blood cell counts (11 vs 12), chemistries (10 vs 11), thyroid function test (3 vs 3), neurology consult (12 vs 6), electroencephalogram (12 vs 5), and head computed tomographic scan (5 vs 3). Of the 298 non-tilt studies, the results of only 5 (1.6%) were abnormal. Diagnoses were made in 5 (18.5%) of 27 group I patients (Wolff-Parkinson-White syndrome, 1; conversion reaction, 2; hyperventilation, 1; migraines, 1), whereas diagnosis was made in 27 (100%) of 27 group II patients (neurocardiogenic syncope, 25; conversion reaction, 2). Conclusion. An extensive workup is not routinely indicated in syncopal patients with a history consistent with neurocardiogenic syncope. Tilt table testing performed early in the evaluation will increase the probability of a diagnosis, and will often prevent the need for further extensive, expensive anxiety-producing tests.

scholarly journals Effect of Aging on the Cornea of Male Albino Rat and Possible Therapeutic Role of Royal Jelly

QJM ◽  
2020 ◽  
Vol 113 (Supplement_1) ◽  
Author(s):  
H R Elareny ◽  
A I Ahmed ◽  
A F Alneklawy ◽  
M K Tawfik
Keyword(s):  
Royal Jelly ◽  
Male Rats ◽  
Distilled Water ◽  
Oral Gavage ◽  
Albino Rat ◽  
Therapeutic Role ◽  
Once Daily ◽  
Group I ◽  
Group Ii

Abstract Introduction Nowadays interest in aging has greatly increased, Aging is a complex natural process involving every molecule, cell, and organ in the body that is associated with tissue dysfunction in many organs. Aging of the cornea causes major eye effects and leads to substantial cost in medical and social terms. These effects include the highly prevalent dry eye disease (DED) that affects both visual function and quality of life in elderly. Symptoms of (DED) include, ocular pain, visual disturbances, and increase lacrimation. Functional foods such as Royal jelly (RJ) have a growing attention because of consumers increasing concerns about their health. Its importance not only for its nutritional properties but also for its functional and biological properties such as antioxidant, anti-inflammatory, antibacterial, antiviral, and anti-ulcerous activities. It is used as a cheap natural source in daily life and medicine. (RJ) is a complex substance composed of proteins, sugars, lipids, amino acids, vitamins, and minerals. Aim The present study aimed to investigate the histological effect of aging on the cornea of male albino rat and possible therapeutic role of (RJ) on senile group. Materials and Methods Twenty-four male albino rats were used in this study divided into Group I: consisted of 6 adult male rats aged 3- 6 months. Group II: consisted of 18 senile male rats aged 18-24 months, were further subdivided into three subgroups as follows: Group II A: (n = 6) negative control senile rats, not subjected to any procedure for 4 weeks. Group II B: (n = 6) control senile rats and were given distilled water by oral gavage once daily for 4 weeks. Group II C: (n = 6) senile rats were given (RJ) by oral gavage dissolved in distilled water once daily for 4 weeks. At the end of the experiment, rats were sacrificed after being deeply anesthetized with ether according to the protocol of the Committee of Animal Research Ethics (CARE). The cornea of each animal was carefully dissected out after death and immediately fixed in 10% formalin for preparation of paraffin blocks 5 micrometer thickness. Sections were stained with hematoxylin and eosin (I-I&E), Masson's trichrome and periodic acid-Schiff (PAS). Statistical analysis and quantitative morphometric study were done. Results Light microscopic examination of corneas of senile rats revealed different pathological changes included irregularity in the surface epithelium as well as surface erosions and cytoplasmic vacuolations. The stroma showed widely separated collagen fibers with decreased keratocyte density. It was concluded that (RJ) supplementation to senile rats obviously unproved all layers of the cornea histologically.

Synthesis of high viscosity index base stock and study on the lubricating properties

2016 ◽  
Vol 68 (1) ◽  
pp. 52-56 ◽  
Author(s):  
Weiwei Wang ◽  
Shan Jiang ◽  
Yan Shen ◽  
Shunba Xia ◽  
Jiujun Xu
Keyword(s):  
Ionic Liquid ◽  
Reaction Time ◽  
Viscosity Index ◽  
Content Type ◽  
Group I ◽  
Film Forming ◽  
Wide Range ◽  
Catalyst Dosage ◽  
Group Ii ◽  
Lubricating Properties

Purpose – This paper aims to address the polymerization of 1-decene by [Emim]Cl/AlCl3 ionic liquid and the film-forming properties of the product compared with commercially available base stocks. Design/methodology/approach – Experiments were carried out to investigate the influence of [Emim]Cl/AlCl3 mole ratio, catalyst dosage, reaction temperature, reaction time and water on the polyreaction. Poly alpha-olefin (PAO) is prepared under optimal reaction condition. Film-forming properties of PAO have been compared with those of Group I, Group II and Group III base stocks, which are selected with approximately the same viscosity. Findings – Experimental results show that after a 4-h reaction time, yield of PAO can be higher than 85 per cent and viscosity index can be up to 160 with [Emim] Cl/AlCl3 mole ratio of 2:1, catalyst dosage of 3 per cent wt. and water content of 20 ppm. A strong influence of water on reaction is observed. With approximately the same viscosity, PAO shows the superiority in film thickness at low-sliding speeds compared with Group I and Group II base stocks. At high temperature, PAO provides a thicker film than other base stocks. Originality/value – In recent years, there has been considerable interest in ionic liquids. As a novel catalyst, it has so many advantages including low corrosion, low toxicity, low cost and a potentially wide range of properties compared with traditional catalysts. This paper reports the polymerization of 1-decene by [Emim]Cl/AlCl3 ionic liquid and the study on lubricating properties of PAO compared with mineral base stocks.

scholarly journals Physiological Evidence for Isopotential Tunneling in the Electron Transport Chain of Methane-Producing Archaea

2017 ◽  
Vol 83 (18) ◽  
Author(s):  
Nikolas Duszenko ◽  
Nicole R. Buan
Keyword(s):  
Escherichia Coli ◽  
Electron Transport ◽  
Stationary Phase ◽  
Exponential Growth ◽  
Electron Transport Chain ◽  
Methanosarcina Barkeri ◽  
Metabolic Efficiency ◽  
Methanosarcina Acetivorans ◽  
Content Type ◽  
Transport Chain

ABSTRACT Many, but not all, organisms use quinones to conserve energy in their electron transport chains. Fermentative bacteria and methane-producing archaea (methanogens) do not produce quinones but have devised other ways to generate ATP. Methanophenazine (MPh) is a unique membrane electron carrier found in Methanosarcina species that plays the same role as quinones in the electron transport chain. To extend the analogy between quinones and MPh, we compared the MPh pool sizes between two well-studied Methanosarcina species, Methanosarcina acetivorans C2A and Methanosarcina barkeri Fusaro, to the quinone pool size in the bacterium Escherichia coli. We found the quantity of MPh per cell increases as cultures transition from exponential growth to stationary phase, and absolute quantities of MPh were 3-fold higher in M. acetivorans than in M. barkeri. The concentration of MPh suggests the cell membrane of M. acetivorans, but not of M. barkeri, is electrically quantized as if it were a single conductive metal sheet and near optimal for rate of electron transport. Similarly, stationary (but not exponentially growing) E. coli cells also have electrically quantized membranes on the basis of quinone content. Consistent with our hypothesis, we demonstrated that the exogenous addition of phenazine increases the growth rate of M. barkeri three times that of M. acetivorans. Our work suggests electron flux through MPh is naturally higher in M. acetivorans than in M. barkeri and that hydrogen cycling is less efficient at conserving energy than scalar proton translocation using MPh. IMPORTANCE Can we grow more from less? The ability to optimize and manipulate metabolic efficiency in cells is the difference between commercially viable and nonviable renewable technologies. Much can be learned from methane-producing archaea (methanogens) which evolved a successful metabolic lifestyle under extreme thermodynamic constraints. Methanogens use highly efficient electron transport systems and supramolecular complexes to optimize electron and carbon flow to control biomass synthesis and the production of methane. Worldwide, methanogens are used to generate renewable methane for heat, electricity, and transportation. Our observations suggest Methanosarcina acetivorans, but not Methanosarcina barkeri, has electrically quantized membranes. Escherichia coli, a model facultative anaerobe, has optimal electron transport at the stationary phase but not during exponential growth. This study also suggests the metabolic efficiency of bacteria and archaea can be improved using exogenously supplied lipophilic electron carriers. The enhancement of methanogen electron transport through methanophenazine has the potential to increase renewable methane production at an industrial scale.

Rhizobium paknamense sp. nov., isolated from lesser duckweeds (Lemna aequinoctialis)

2013 ◽  
Vol 63 (Pt_10) ◽  
pp. 3823-3828 ◽  
Author(s):  
Chokchai Kittiwongwattana ◽  
Chitti Thawai
Keyword(s):  
Dna Hybridization ◽  
Type Species ◽  
Sequence Similarity ◽  
Housekeeping Genes ◽  
Rrna Gene ◽  
Content Type ◽  
Link Type ◽  
Low Levels ◽  
Sequence Similarity Analysis ◽  
Ph Range

A Gram-stain-negative, rod-shaped bacterium was isolated and designated strain L6-8T during a study of endophytic bacterial communities in lesser duckweed (Lemna aequinoctialis). Cells of strain L6-8T were motile with peritrichous flagella. The analysis of the nearly complete 16S rRNA gene sequence indicated that strain L6-8T was phylogenetically related to species of the genus Rhizobium . Its closest relatives were Rhizobium borbori DN316T (97.6 %), Rhizobium oryzae Alt 505T (97.3 %) and Rhizobium pseudoryzae J3-A127T (97.0 %). The sequence similarity analysis of housekeeping genes recA, glnII, atpD and gyrB showed low levels of sequence similarity (<91.5 %) between strain L6-8T and other species of the genus Rhizobium with validly published names. The pH range for growth was 4.0–9.0 (optimum 6.0–7.0), and the temperature range for growth was 20–45 °C (optimum 30 °C). Strain L6-8T tolerated NaCl up to 2 % (w/v) (optimum 1 % NaCl). The predominant components of cellular fatty acids were C19 : 0 cyclo ω8c (31.32 %), summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c; 25.39 %) and C16 : 0 (12.03 %). The DNA G+C content of strain L6-8T was 60.4 mol% (T m). nodC and nifH were not amplified in strain L6-8T. DNA–DNA relatedness between strain L6-8T and R. borbori DN316T, R. oryzae Alt505T and R. pseudoryzae J3-A127T was between 11.2 and 18.3 %. Based on the sequence similarity analyses, phenotypic, biochemical and physiological characteristics and DNA–DNA hybridization, strain L6-8T could be readily distinguished from its closest relatives and represents a novel species of the genus Rhizobium , for which the name Rhizobium paknamense sp. nov. is proposed. The type strain is L6-8T ( = NBRC 109338T = BCC 55142T).

Endothelin effects in isolated, perfused lamb lungs: role of cyclooxygenase inhibition and vasomotor tone

1991 ◽  
Vol 261 (2) ◽  
pp. H443-H450 ◽  
Author(s):  
H. Toga ◽  
J. Usha Raj ◽  
R. Hillyard ◽  
B. Ku ◽  
J. Anderson
Keyword(s):  
Vasomotor Tone ◽  
Cyclooxygenase Inhibition ◽  
Group Iii ◽  
Group I ◽  
Before And After ◽  
Pulmonary Arterial ◽  
Group Ii ◽  
Sites Of Action ◽  
Arteries And Veins

We have determined the sites of action of endothelin-1 (ET) in the lamb pulmonary circulation. The influence of cyclooxygenase inhibition and baseline vasomotor tone on ET effects was also studied. Lungs of 14 lambs (6-9 wk of age, 12.1 +/- 0.6 kg body wt) were isolated and perfused with blood. Group I lungs (n = 5) were untreated, group II lungs (n = 5) were treated with indomethacin to inhibit cyclooxygenase, and group III lungs (n = 4) were treated with indomethacin and a thromboxane A2 analogue, U-46619, to elevate vasomotor tone. All lungs were perfused with constant flow in zone 3, with left atrial and airway pressures being 8 and 6 cmH2O, respectively. We measured pulmonary arterial pressure and, by the micropuncture servo-null method, pressures in 20- to 50-microns diameter subpleural venules, both before and after each dose of ET was infused (50, 100, 250, and 500 ng/kg). Group I lungs, with high baseline vasomotor tone, exhibited a biphasic response to ET; 50-100 ng/kg of ET dilated both arteries and veins, whereas 500 ng/kg of ET constricted both arteries and veins. In group II lungs with low vasomotor tone, all doses of ET caused constriction of arteries only. In group III lungs (indomethacin treated with elevated vasomotor tone), 50-100 ng/kg of ET caused dilation of arteries and veins, whereas 500 ng/kg of ET induced constriction, this time only in arteries. We conclude that ET has both dilator and constrictor effects in arteries and veins of isolated, perfused lamb lungs. ET-induced arterial and venous dilation is dependent on initial vasomotor tone but not on cyclooxygenase metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

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