Effect offurmutation on acid-tolerance response and in vivo virulence of avian septicemicEscherichia coli

2002 ◽  
Vol 48 (5) ◽  
pp. 458-462 ◽  
Author(s):  
Chengru Zhu ◽  
Musangu Ngeleka ◽  
Andrew A Potter ◽  
Brenda J Allan
Keyword(s):  
Parent Strain ◽  
Acid Tolerance ◽  
Wild Type ◽  
Acid Tolerance Response ◽  
E Coli ◽  
Regulator Protein ◽  
In The Wild ◽  
Tolerance Response ◽  
Wild Type Parent

The Fur (ferric uptake regulator) protein is a master regulator of iron metabolism in gram-negative bacteria. In the present study, the effect of a partial deletion of the fur gene on the acid-tolerance response and in vivo virulence of avian Escherichia coli was examined. The fur mutant was unable to trigger the acid-tolerance response as observed in the wild-type parent strain. However, the mutant was as virulent as the wild-type parent strain when tested in 1-day-old chickens by subcutaneous inoculation. These data indicate that the fur gene is involved in the acid-tolerance response but not involved in the virulence of E. coli, as detected by the ability to cause septicemia in our experimental infection.Key words: E. coli, fur, acid-tolerance response.

High-Salt Preadaptation of Vibrio parahaemolyticus Enhances Survival in Response to Lethal Environmental Stresses

2014 ◽  
Vol 77 (2) ◽  
pp. 246-253 ◽  
Author(s):  
SAI SIDDARTH KALBURGE ◽  
W. BRIAN WHITAKER ◽  
E. FIDELMA BOYD
Keyword(s):  
Stress Response ◽  
Marine Environment ◽  
Vibrio Parahaemolyticus ◽  
High Salinity ◽  
Acid Stress ◽  
Acid Tolerance ◽  
High Salt ◽  
Wild Type ◽  
Acid Tolerance Response ◽  
Tolerance Response

Adaptation to changing environmental conditions is an important strategy for survival of foodborne bacterial pathogens. Vibrio parahaemolyticus is a gram-negative seafoodborne enteric pathogen found in the marine environment both free living and associated with oysters. This pathogen is a moderate halophile, with optimal growth at 3% NaCl. Among the several stresses imposed upon enteric bacteria, acid stress is perhaps one of the most important. V. parahaemolyticus has a lysine decarboxylase system responsible for decarboxylation of lysine to the basic product cadaverine, an important acid stress response system in bacteria. Preadaptation to mild acid conditions, i.e., the acid tolerance response, enhances survival under lethal acid conditions. Because of the variety of conditions encountered by V. parahaemolyticus in the marine environment and in oyster postharvest facilities, we examined the nature of the V. parahaemolyticus acid tolerance response under high-salinity conditions. Short preadaptation to a 6% salt concentration increased survival of the wild-type strain but not that of a cadA mutant under lethal acid conditions. However, prolonged exposure to high salinity (16 h) increased survival of both the wild-type and the cadA mutant strains. This phenotype was not dependent on the stress response sigma factor RpoS. Although this preadaptation response is much more pronounced in V. parahaemolyticus, this characteristic is not limited to this species. Both Vibrio cholerae and Vibrio vulnificus also survive better under lethal acid stress conditions when preadapted to high-salinity conditions. High salt both protected the organism against acid stress and increased survival under −20°C cold stress conditions. High-salt adaptation of V. parahaemolyticus strains significantly increases survival under environmental stresses that would otherwise be lethal to these bacteria.

scholarly journals Defects in d-Alanyl-Lipoteichoic Acid Synthesis in Streptococcus mutans Results in Acid Sensitivity

2000 ◽  
Vol 182 (21) ◽  
pp. 6055-6065 ◽  
Author(s):  
David A. Boyd ◽  
Dennis G. Cvitkovitch ◽  
Arnold S. Bleiweis ◽  
Michael Y. Kiriukhin ◽  
Dmitri V. Debabov ◽  
...  
Keyword(s):  
Streptococcus Mutans ◽  
Growth Yield ◽  
Acid Tolerance ◽  
Lipoteichoic Acid ◽  
Wild Type ◽  
Lower Growth ◽  
Acid Tolerance Response ◽  
Acid Sensitivity ◽  
Permeabilized Cells ◽  
Tolerance Response

ABSTRACT In the cariogenic organism, Streptococcus mutans, low pH induces an acid tolerance response (ATR). To identify acid-regulated proteins comprising the ATR, transposon mutagenesis with the thermosensitive plasmid pGh9:ISS1 was used to produce clones that were able to grow at neutral pH, but not in medium at pH 5.0. Sequence analysis of one mutant (IS1A) indicated that transposition had created a 6.3-kb deletion, one end of which was indltB of the dlt operon encoding four proteins (DltA-DltD) involved in the synthesis ofd-alanyl-lipoteichoic acid. Inactivation of thedltC gene, encoding the d-alanyl carrier protein (Dcp), resulted in the generation of the acid-sensitive mutant, BH97LC. Compared to the wild-type strain, LT11, the mutant exhibited a threefold-longer doubling time and a 33% lower growth yield. In addition, it was unable to initiate growth below pH 6.5 and unadapted cells were unable to survive a 3-h exposure in medium buffered at pH 3.5, while a pH of 3.0 was required to kill the wild type in the same time period. Also, induction of the ATR in BH97LC, as measured by the number of survivors at a pH killing unadapted cells, was 3 to 4 orders of magnitude lower than that exhibited by the wild type. While the LTA of both strains contained a similar average number of glycerolphosphate residues, permeabilized cells of BH97LC did not incorporated-[14C]alanine into this amphiphile. This defect was correlated with the deficiency of Dcp. Chemical analysis of the LTA purified from the mutant confirmed the absence ofd-alanine-esters. Electron micrographs showed that BH97LC is characterized by unequal polar caps and is devoid of a fibrous extracellular matrix present on the surface of the wild-type cells. Proton permeability assays revealed that the mutant was more permeable to protons than the wild type. This observation suggests a mechanism for the loss of the characteristic acid tolerance response in S. mutans.

Influence of Incubation Conditions on Survival and Acid Tolerance Response of Escherichia coliO157:H7 and Non-O157:H7 Isolates Exposed to Acetic Acid

1998 ◽  
Vol 61 (5) ◽  
pp. 542-546 ◽  
Author(s):  
LESLYE BRUDZINSKI ◽  
MARK A. HARRISON
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Organic Acids ◽  
Adaptive System ◽  
Acid Tolerance ◽  
Effect Of Temperature ◽  
Escherichia Coli O157 ◽  
Acid Tolerance Response ◽  
E Coli ◽  
Tolerance Response

The increasing frequency of Escherichia coli O157:H7 outbreaks, especially in acidic foods, raises the concern of an acid tolerance response (ATR). Organic acids can be present in processed and preserved foods: shifts in the acid levels of foods due to these acids may allow E. coli to adapt and later tolerate pH levels that would normally inactivate the organism. The effect of temperature and agitation on the ATRs of three E. coli O157:H7 and two non-O157:H7 isolates were determined. Triggered at pH 5.0, the adaptive System of the ATR allowed for up to nearly 1,000-fold enhanced survival of E. coli O157:H7 cells in some cases compared to survival of nonadapted cells at pH 4.0. E. coli O157:H7 isolates revealed greater acid tolerance responses when incubated statically at 32°C, whereas the non-O157:H7 coli isolates exhibited a greater acid tolerance response with orbital agitation at 25°C. The magnitude of response changed over the incubation period.

scholarly journals HtrA Is Essential for Efficient Secretion of Recombinant Proteins by Lactococcus lactis

2008 ◽  
Vol 74 (23) ◽  
pp. 7442-7446 ◽  
Author(s):  
Kalpana Sriraman ◽  
Guhan Jayaraman
Keyword(s):  
Recombinant Protein ◽  
Lactococcus Lactis ◽  
Protein Secretion ◽  
Recombinant Proteins ◽  
Acid Tolerance ◽  
Wild Type ◽  
Acid Tolerance Response ◽  
Recombinant Protein Secretion ◽  
Tolerance Response ◽  
Secretion Of Recombinant Proteins

ABSTRACT HtrA is a unique protease on the extracellular surface of Lactococcus lactis. It is known to take part in the proteolysis of many secreted recombinant proteins, and the mutation of htrA can lead to the complete stabilization of recombinant proteins. In this work, we have shown that htrA mutation also leads to significant reduction of the efficiency of recombinant-protein secretion. We also show that the level of HtrA can be lowered by the suppression of the acid tolerance response (ATR) in L. lactis. Instead of using an L. lactis htrA mutant, the reduction of the HtrA level in wild-type recombinant cultures of L. lactis by ATR suppression may serve as a better strategy for the production of secreted recombinant proteins.

scholarly journals Characterization of a Glutamate Transporter Operon, glnQHMP, in Streptococcus mutans and Its Role in Acid Tolerance

2009 ◽  
Vol 192 (4) ◽  
pp. 984-993 ◽  
Author(s):  
Kirsten Krastel ◽  
Dilani B. Senadheera ◽  
Richard Mair ◽  
Jennifer S. Downey ◽  
Steven D. Goodman ◽  
...  
Keyword(s):  
Streptococcus Mutans ◽  
Glutamate Transporter ◽  
Acid Tolerance ◽  
Wild Type ◽  
Acid Tolerance Response ◽  
Gram Positive Bacteria ◽  
Oral Bacterium ◽  
Tolerance Response ◽  
Kinetics Of

ABSTRACT Glutamate contributes to the acid tolerance response (ATR) of many Gram-negative and Gram-positive bacteria, but its role in the ATR of the oral bacterium Streptococcus mutans is unknown. This study describes the discovery and characterization of a glutamate transporter operon designated glnQHMP (Smu.1519 to Smu.1522) and investigates its potential role in acid tolerance. Deletion of glnQHMP resulted in a 95% reduction in transport of radiolabeled glutamate compared to the wild-type UA159 strain. The addition of glutamate to metabolizing UA159 cells resulted in an increased production of acidic end products, whereas the glnQHMP mutant produced less lactic acid than UA159, suggesting a link between glutamate metabolism and acid production and possible acid tolerance. To investigate this possibility, we conducted a microarray analysis with glutamate and under pH 5.5 and pH 7.5 conditions which showed that expression of the glnQHMP operon was downregulated by both glutamate and mild acid. We also measured the growth kinetics of UA159 and its glnQHMP-negative derivative at pH 5.5 and found that the mutant doubled at a much slower rate than the parent strain but survived at pH 3.5 significantly better than the wild type. Taken together, these findings support the involvement of the glutamate transporter operon glnQHMP in the acid tolerance response in S. mutans.

scholarly journals Global Analysis of Escherichia coli Gene Expression during the Acetate-Induced Acid Tolerance Response

2001 ◽  
Vol 183 (7) ◽  
pp. 2178-2186 ◽  
Author(s):  
Carrie N. Arnold ◽  
Justin McElhanon ◽  
Aaron Lee ◽  
Ryan Leonhart ◽  
Deborah A. Siegele
Keyword(s):  
Escherichia Coli ◽  
Global Analysis ◽  
Acid Tolerance ◽  
Short Chain Fatty Acids ◽  
Low Ph ◽  
Insertion Mutation ◽  
Acid Tolerance Response ◽  
E Coli ◽  
Serovar Typhimurium ◽  
Tolerance Response

ABSTRACT The ability of Escherichia coli to survive at low pH is strongly affected by environmental factors, such as composition of the growth medium and growth phase. Exposure to short-chain fatty acids, such as acetate, proprionate, and butyrate, at neutral or nearly neutral pH has also been shown to increase acid survival of E. coli and Salmonella enterica serovar Typhimurium. To investigate the basis for acetate-induced acid tolerance in E. coli O157:H7, genes whose expression was altered by exposure to acetate were identified using gene arrays. The expression of 60 genes was reduced by at least twofold; of these, 48 encode components of the transcription-translation machinery. Expression of 26 genes increased twofold or greater following treatment with acetate. This included six genes whose products are known to be important for survival at low pH. Five of these genes, as well as six other acetate-induced genes, are members of the E. coli RpoS regulon. RpoS, the stress sigma factor, is known to be required for acid tolerance induced by growth at nonlethal low pH or by entry into stationary phase. Disruption of therpoS gene by a transposon insertion mutation also prevented acetate-induced acid tolerance. However, induction of RpoS expression did not appear to be sufficient to activate the acid tolerance response. Treatment with either NaCl or sodium acetate (pH 7.0) increased expression of anrpoS::lacZ fusion protein, but only treatment with acetate increased acid survival.

scholarly journals Identification of Gene Products Involved in the Oxidative Stress Response ofMoraxella catarrhalis

2010 ◽  
Vol 79 (2) ◽  
pp. 745-755 ◽  
Author(s):  
Todd C. Hoopman ◽  
Wei Liu ◽  
Stephanie N. Joslin ◽  
Christine Pybus ◽  
Chad A. Brautigam ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Parent Strain ◽  
Dilution Effect ◽  
Dependent Manner ◽  
Wild Type ◽  
Gene Encoding ◽  
Reverse Transcription Pcr ◽  
Genes Encoding ◽  
In The Wild ◽  
Wild Type Parent

ABSTRACTMoraxella catarrhalisis subjected to oxidative stress from both internal and environmental sources. A previous study (C. D. Pericone, K. Overweg, P. W. Hermans, and J. N. Weiser, Infect. Immun.68:3990-3997, 2000) indicated that a wild-type strain ofM. catarrhaliswas very resistant to killing by exogenous hydrogen peroxide (H2O2). The gene encoding OxyR, a LysR family transcriptional regulator, was identified and inactivated inM. catarrhalisstrain O35E, resulting in an increase in sensitivity to killing by H2O2in disk diffusion assays and a concomitant aerobic serial dilution effect. Genes encoding a predicted catalase (KatA) and an alkyl hydroperoxidase (AhpCF) showed dose-dependent upregulation in wild-type cells exposed to H2O2. DNA microarray and real-time reverse transcription-PCR (RT-PCR) analyses identifiedM. catarrhalisgenes whose expression was affected by oxidative stress in an OxyR-dependent manner. Testing ofM. catarrhalisO35EkatAandahpCmutants for their abilities to scavenge exogenous H2O2showed that the KatA catalase was responsible for most of this activity in the wild-type parent strain. The introduction of the same mutations intoM. catarrhalisstrain ETSU-4 showed that the growth of a ETSU-4katAmutant was markedly inhibited by the addition of 50 mM H2O2but that this mutant could still form a biofilm equivalent to that produced by its wild-type parent strain.

scholarly journals Role of Listeria monocytogenes σB in Survival of Lethal Acidic Conditions and in the Acquired Acid Tolerance Response

2003 ◽  
Vol 69 (5) ◽  
pp. 2692-2698 ◽  
Author(s):  
Adriana Ferreira ◽  
David Sue ◽  
Conor P. O'Byrne ◽  
Kathryn J. Boor
Keyword(s):  
Listeria Monocytogenes ◽  
Stationary Phase ◽  
Growth Phase ◽  
Brain Heart Infusion ◽  
Relative Survival ◽  
Acid Tolerance ◽  
Inorganic Acid ◽  
Wild Type ◽  
Acid Tolerance Response ◽  
Tolerance Response

ABSTRACT The food-borne pathogen Listeria monocytogenes can acquire enhanced resistance to lethal acid conditions through multiple mechanisms. We investigated contributions of the stress-responsive alternative sigma factor, σB, which is encoded by sigB, to growth phase-dependent acid resistance (AR) and to the adaptive acid tolerance response in L. monocytogenes. At various points throughout growth, we compared the relative survival of L. monocytogenes wild-type and ΔsigB strains that had been exposed to either brain heart infusion (pH 2.5) or synthetic gastric fluid (pH 2.5) with and without prior acid adaptation. Under these conditions, survival of the ΔsigB strain was consistently lower than that of the wild-type strain throughout all phases of growth, ranging from 4 orders of magnitude less in mid-log phase to 2 orders of magnitude less in stationary phase. Survival of both ΔsigB and wild-type L. monocytogenes strains increased by 6 orders of magnitude upon entry into stationary phase, demonstrating that the L. monocytogenes growth phase-dependent AR mechanism is σB independent. σB-mediated contributions to acquired acid tolerance appear to be greatest in early logarithmic growth. Loss of a functional σB reduced the survival of L. monocytogenes at pH 2.5 to a greater extent in the presence of organic acid (100 mM acetic acid) than in the presence of inorganic acid alone (HCl), suggesting that L. monocytogenes protection against organic and inorganic acid may be mediated through different mechanisms. σB does not appear to contribute to pHi homeostasis through regulation of net proton movement across the cell membrane or by regulation of pHi buffering by the GAD system under the conditions examined in this study. In summary, a functional σB protein is necessary for full resistance of L. monocytogenes to lethal acid treatments.

scholarly journals Arabidopsis Disulfide Reductase, Trx-h2, Functions as an RNA Chaperone under Cold Stress

2021 ◽  
Vol 11 (15) ◽  
pp. 6865
Author(s):  
Eun Seon Lee ◽  
Joung Hun Park ◽  
Seong Dong Wi ◽  
Ho Byoung Chae ◽  
Seol Ki Paeng ◽  
...  
Keyword(s):  
Cold Stress ◽  
Wild Type ◽  
Rna Chaperone ◽  
E Coli ◽  
Cold Sensitive ◽  
Thioredoxin H ◽  
Functional Rnas

The thioredoxin-h (Trx-h) family of Arabidopsis thaliana comprises cytosolic disulfide reductases. However, the physiological function of Trx-h2, which contains an additional 19 amino acids at its N-terminus, remains unclear. In this study, we investigated the molecular function of Trx-h2 both in vitro and in vivo and found that Arabidopsis Trx-h2 overexpression (Trx-h2OE) lines showed significantly longer roots than wild-type plants under cold stress. Therefore, we further investigated the role of Trx-h2 under cold stress. Our results revealed that Trx-h2 functions as an RNA chaperone by melting misfolded and non-functional RNAs, and by facilitating their correct folding into active forms with native conformation. We showed that Trx-h2 binds to and efficiently melts nucleic acids (ssDNA, dsDNA, and RNA), and facilitates the export of mRNAs from the nucleus to the cytoplasm under cold stress. Moreover, overexpression of Trx-h2 increased the survival rate of the cold-sensitive E. coli BX04 cells under low temperature. Thus, our data show that Trx-h2 performs function as an RNA chaperone under cold stress, thus increasing plant cold tolerance.

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