scholarly journals Temperature-dependence of open-complex formation at two Escherichia coli promoters with extended −10 sequences

1996 ◽  
Vol 317 (1) ◽  
pp. 305-311 ◽  
Author(s):  
Helen D. BURNS ◽  
Tamara A. BELYAEVA ◽  
Stephen J. W. BUSBY ◽  
Stephen D. MINCHIN
Keyword(s):  
Escherichia Coli ◽  
Low Temperature ◽  
Complex Formation ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Dna Fragments ◽  
Promoter Sequences ◽  
E Coli ◽  
Base Sequences ◽  
Open Complex Formation

We have studied the formation of open complexes between purified RNA polymerase from Escherichia coli and DNA fragments carrying the galP1 promoter, a promoter with an extended -10 region. Unusually, these complexes are formed readily at low temperatures. This low-temperature opening is unaffected by deletions of either upstream or downstream promoter sequences. We conclude that low-temperature open-complex formation is due to specific base sequences in and just upstream of the extended -10 region. In contrast, open complexes are not formed at low temperatures with DNA fragments carrying the E. coli cysG promoter, which also has an extended -10 region. This demonstrates that an extended -10 sequence alone is not sufficient for low-temperature opening. Additionally, we report the temperature dependence of a hybrid galP1–cysG promoter, the related galP2 and galP3 promoters and a derivative of galP1 with an improved -10 hexamer sequence.

scholarly journals The organization of open complexes between Escherichia coli RNA polymerase and DNA fragments carrying promoters either with or without consensus −35 region sequences

1990 ◽  
Vol 270 (1) ◽  
pp. 141-148 ◽  
Author(s):  
B Chan ◽  
A Spassky ◽  
S Busby
Keyword(s):  
Escherichia Coli ◽  
Complex Formation ◽  
Rna Polymerase ◽  
Transcription Initiation ◽  
Point Mutations ◽  
Dna Fragments ◽  
Transcription Start ◽  
Footprint Analysis ◽  
Open Complex Formation ◽  
Promoter Dna

Transcription initiation at the Escherichia coli galP1 promoter does not depend on specific nucleotide sequences in the -35 region. Footprint analysis of transcriptionally competent complexes between E. coli RNA polymerase and DNA fragments carrying galP1 shows that RNA polymerase protects sequences as far upstream as -55, whereas sequences around the -35 region are exposed. In contrast, with galP1 derivatives carrying -35 region sequences resembling the consensus, RNA polymerase protects bases as far as -45, and the -35 region is fully protected. Taken together, our data suggest that the overall architecture of RNA polymerase-promoter complexes can vary according to whether or not consensus -35 region sequences are present; in the absence of these sequences, open complex formation requires distortion of the promoter DNA. However, the unwinding of promoter DNA around the transcription start is not affected by the nature of the -35 region sequence. With a galP1 derivative carrying point mutations in the spacer region that greatly reduce promoter activity, the protection of bases by RNA polymerase around the -10 sequence and transcription start site is reduced. In contrast, protection of the region upstream of -25 is unaffected by the spacer mutations, although sequences from -46 to -54 become hypersensitive to attack by potassium permanganate, indicating severe distortion or kinking of this zone. We suggest that, with this galP1 derivative, RNA polymerase is blocked in a complex that is an intermediate on the path to open complex formation.

Changes in Aerobic Plate and Escherichia coli–Coliform Counts and in Populations of Inoculated Foodborne Pathogens on Inshell Walnuts during Storage

2016 ◽  
Vol 79 (7) ◽  
pp. 1143-1153 ◽  
Author(s):  
JOHN C. FRELKA ◽  
GORDON R. DAVIDSON ◽  
LINDA J. HARRIS
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Relative Humidity ◽  
Low Temperature ◽  
Foodborne Pathogens ◽  
Limit Of Detection ◽  
Sampling Time ◽  
E Coli ◽  
Plate Counts ◽  
Forced Air

ABSTRACT After harvest, inshell walnuts are dried using low-temperature forced air and are then stored in bins or silos for up to 1 year. To better understand the survival of bacteria on inshell walnuts, aerobic plate counts (APCs) and Escherichia coli–coliform counts (ECCs) were evaluated during commercial storage (10 to 12°C and 63 to 65% relative humidity) over 9 months. APCs decreased by 1.4 to 2.0 log CFU per nut during the first 5 months of storage, and ECCs decreased by 1.3 to 2.2 log CFU per nut in the first month of storage. Through the remaining 4 to 8 months of storage, APCs and ECCs remained unchanged (P > 0.05) or decreased by <0.15 log CFU per nut per month. Similar trends were observed on kernels extracted from the inshell walnuts. APCs and ECCs were consistently and often significantly higher on kernels extracted from visibly broken inshell walnuts than on kernels extracted from visibly intact inshell walnuts. Parameters measured in this study were used to determine the survival of five-strain cocktails of E. coli O157:H7, Listeria monocytogenes, and Salmonella inoculated onto freshly hulled inshell walnuts (~8 log CFU/g) after simulated commercial drying (10 to 12 h; 40°C) and simulated commercial storage (12 months at 10°C and 65% relative humidity). Populations declined by 2.86, 5.01, and 4.40 log CFU per nut for E. coli O157:H7, L. monocytogenes, and Salmonella, respectively, after drying and during the first 8 days of storage. Salmonella populations changed at a rate of −0.33 log CFU per nut per month between days 8 and 360, to final levels of 2.83 ± 0.79 log CFU per nut. E. coli and L. monocytogenes populations changed by −0.17 log CFU per nut per month and −0.26 log CFU per nut per month between days 8 and 360, respectively. For some samples, E. coli or L. monocytogenes populations were below the limit of detection by plating (0.60 log CFU per nut) by day 183 or 148, respectively; at least one of the six samples was positive at each subsequent sampling time by either plating or by enrichment.

scholarly journals Induction of Viable but Nonculturable Escherichia coli O157:H7 in the Phyllosphere of Lettuce: a Food Safety Risk Factor

2011 ◽  
Vol 77 (23) ◽  
pp. 8295-8302 ◽  
Author(s):  
Laura-Dorina Dinu ◽  
Susan Bach
Keyword(s):  
Escherichia Coli ◽  
Food Safety ◽  
Low Temperature ◽  
Cell Density ◽  
Prolonged Storage ◽  
Potential Hazard ◽  
Vbnc State ◽  
Viable But Nonculturable ◽  
Content Type ◽  
E Coli

ABSTRACTEscherichia coliO157:H7 continues to be an important human pathogen and has been increasingly linked to food-borne illness associated with fresh produce, particularly leafy greens. The aim of this work was to investigate the fate ofE. coliO157:H7 on the phyllosphere of lettuce under low temperature and to evaluate the potential hazard of viable but nonculturable (VBNC) cells induced under such stressful conditions. First, we studied the survival of six bacterial strains following prolonged storage in water at low temperature (4°C) and selected two strains with different nonculturable responses for the construction ofE. coliO157:H7 Tn7gfptransformants in order to quantitatively assess the occurrence of human pathogens on the plant surface. Under a suboptimal growth temperature (16°C), bothE. coliO157:H7 strains maintained culturability on lettuce leaves, but under more stressful conditions (8°C), the bacterial populations evolved toward the VBNC state. The strain-dependent nonculturable response was more evident in the experiments with different inoculum doses (109and 106E. coliO157:H7 bacteria per g of leaf) when strain BRMSID 188 lost culturability after 15 days and strain ATCC 43895 lost culturability within 7 days, regardless of the inoculum dose. However, the number of cells entering the VBNC state in high-cell-density inoculum (approximately 55%) was lower than in low-cell-density inoculum (approximately 70%). We recorded the presence of verotoxin for 3 days in samples that contained a VBNC population of 4 to 5 log10cells but did not detect culturable cells. These findings indicate thatE. coliO157:H7 VBNC cells are induced on lettuce plants, and this may have implications regarding food safety.

scholarly journals Temperature Dependence of MinD Oscillation in Escherichia coli: Running Hot and Fast

2006 ◽  
Vol 188 (21) ◽  
pp. 7661-7667 ◽  
Author(s):  
Ahmed Touhami ◽  
Manfred Jericho ◽  
Andrew D. Rutenberg
Keyword(s):  
Escherichia Coli ◽  
Temperature Dependence ◽  
Growth Curve ◽  
Oscillation Period ◽  
Quantitative Model ◽  
Temperature Dependent ◽  
E Coli ◽  
Temperature Range ◽  
Characteristic Wavelength ◽  
Dependent Growth

ABSTRACT We observed that the oscillation period of MinD within rod-like and filamentous cells of Escherichia coli varied by a factor of 4 in the temperature range from 20°C to 40°C. The detailed dependence was Arrhenius, with a slope similar to the overall temperature-dependent growth curve of E. coli. The detailed pattern of oscillation, including the characteristic wavelength in filamentous cells, remained independent of temperature. A quantitative model of MinDE oscillation exhibited similar behavior, with an activated temperature dependence of the MinE-stimulated MinD-ATPase rate.

Peotoemission Study of Si (001) Surfaces Exposed to as Flux

1989 ◽  
Vol 148 ◽  
Author(s):  
H. Okumura ◽  
K. Miki ◽  
K. Sakamoto ◽  
T. Sakamoto ◽  
S. Misawa ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Electronic Structures ◽  
Low Temperatures ◽  
Dimer Model ◽  
Surface And Interface ◽  
High And Low Temperatures ◽  
Interface Structures ◽  
Temperature Sample

ABSTRACTPhotoemission spectra (XPS and UPS) of As-covered Si (001) surfaces prepared at high (>600ºC) and low (<450ºC) temperatures and GaAs epilayers subsequently grown on them were measured without exposing to air. It was found that the surface electronic structures of As/Si prepared at the low temperature are different from those of the high temperature sample, the spectra of which can be interpreted as a symmetric dimer model. Differences were also observed between the GaAs epilayers on the As—covered Si surfaces prepared at the high and low temperatures. The temperature dependence of the surface and interface structures are discussed.

scholarly journals Polysialic and colanic acids metabolism in Escherichia coli K92 is regulated by RcsA and RcsB

2013 ◽  
Vol 33 (3) ◽  
Author(s):  
Nicolás Navasa ◽  
Leandro Rodríguez-Aparicio ◽  
Miguel Ángel Ferrero ◽  
Andrea Monteagudo-Mera ◽  
Honorina Martínez-Blanco
Keyword(s):  
Escherichia Coli ◽  
Low Temperatures ◽  
Regulatory Mechanism ◽  
Polysialic Acid ◽  
Negative Regulators ◽  
Surface Appearance ◽  
E Coli ◽  
Colanic Acid

We have shown previously that Escherichia coli K92 produces two different capsular polymers known as CA (colanic acid) and PA (polysialic acid) in a thermoregulated manner. The complex Rcs phosphorelay is largely related to the regulation of CA synthesis. Through deletion of rscA and rscB genes, we show that the Rcs system is involved in the regulation of both CA and PA synthesis in E. coli K92. Deletion of either rcsA or rcsB genes resulted in decreased expression of cps (CA biosynthesis cluster) at 19°C and 37°C, but only CA production was reduced at 19°C. Concerning PA, both deletions enhanced its synthesis at 37°C, which does not correlate with the reduced kps (PA biosynthesis cluster) expression observed in the rcsB mutant. Under this condition, expression of the nan operon responsible for PA catabolism was greatly reduced. Although RcsA and RcsB acted as negative regulators of PA synthesis at 37°C, their absence did not reestablish PA expression at low temperatures, despite the deletion of rcsB resulting in enhanced kps expression. Finally, our results revealed that RcsB controlled the expression of several genes (dsrA, rfaH, h-ns and slyA) involved in the thermoregulation of CA and PA synthesis, indicating that RcsB is part of a complex regulatory mechanism governing the surface appearance in E. coli.

scholarly journals Transcriptomic Analysis of Viable but Non-Culturable Escherichia coli O157:H7 Formation Induced by Low Temperature

2019 ◽  
Vol 7 (12) ◽  
pp. 634 ◽  
Author(s):  
Junliang Zhong ◽  
Xihong Zhao
Keyword(s):  
Escherichia Coli ◽  
Low Temperature ◽  
Differentially Expressed Genes ◽  
Pathogenic Bacteria ◽  
Differentially Expressed ◽  
Transmembrane Transport ◽  
Pathway Enrichment Analysis ◽  
Escherichia Coli O157 ◽  
Vbnc State ◽  
E Coli

Escherichia coli O157:H7 is one of the most common pathogenic bacteria that pose a threat to food safety. The aim of this study was to investigate the mechanisms of the formation of viable but non-culturable (VBNC) E. coli O157:H7 induced by low temperature (−20 °C) using RNA sequencing (RNA-Seq) transcriptomics analysis. The results of the present investigation revealed the presence of 2298 differentially expressed genes in VBNC cells, accounting for 46.03% of the total number of genes. Additionally, GO function and KEGG pathway enrichment analysis were performed to investigate the functional and related metabolic pathways of the differentially expressed genes. We found that the ion transport, protein synthesis, and protein transmembrane transport activities were significantly improved in the VBNC cells, indicating that E. coli O157:H7 cells synthesized a considerable amount of protein to maintain the levels of their functional metabolic processes and life activities in the VBNC state. In conclusion, we suggest that the increased synthesis of proteins such as SecY, FtsY, and Ffh might indicate that they are the key proteins involved in the improvement of the transmembrane transport activities in VBNC E. coli O157:H7 cells, maintaining their functional metabolism in the VBNC state and enhancing their survival ability under low temperatures.

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