Lon protease promotes survival of Escherichia coli during anaerobic glucose starvation

Luo, Shen; McNeill, Megan; Myers, Timothy G.; Hohman, Robert J.; Levine, Rodney L.

doi:10.1007/s00203-007-0304-z

Cited by 11 publications

(14 citation statements)

References 33 publications

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“…Then, the AThTP content gradually decreased, but this was probably due to death of the bacteria: indeed, the ability to form colonies after plating on agar plates decreased and became null after 6 days (data not shown), a test generally used to determine bacterial survival [ 6 ]. Luo et al [ 7 ] reported that after two days of glucose starvation, about 54% of BL21 cells survived aerobically, which is in agreement with the present data.…”

Section: Resultssupporting

confidence: 93%

“…During amino acid starvation, E. coli cells accumulate inorganic polyphosphate (poly-P) that activate Lon and redirect their activity towards free ribosomal proteins [ 16 ]. Whilst the survival rate of wild-type and Lon-deficient E. coli is the same under aerobic conditions, Lon-deficient cells are more sensitive to anaerobic conditions [ 7 ]. The degradation of these proteins releases amino acids that can be used to make enzymes required for amino acid metabolism [ 17 ].…”

Section: Resultsmentioning

confidence: 99%

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Adenosine thiamine triphosphate accumulates in Escherichia coli cells in response to specific conditions of metabolic stress

et al. 2010

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BackgroundE. coli cells are rich in thiamine, most of it in the form of the cofactor thiamine diphosphate (ThDP). Free ThDP is the precursor for two triphosphorylated derivatives, thiamine triphosphate (ThTP) and the newly discovered adenosine thiamine triphosphate (AThTP). While, ThTP accumulation requires oxidation of a carbon source, AThTP slowly accumulates in response to carbon starvation, reaching ~15% of total thiamine. Here, we address the question whether AThTP accumulation in E. coli is triggered by the absence of a carbon source in the medium, the resulting drop in energy charge or other forms of metabolic stress.ResultsIn minimal M9 medium, E. coli cells produce AThTP not only when energy substrates are lacking but also when their metabolization is inhibited. Thus AThTP accumulates in the presence of glucose, when glycolysis is blocked by iodoacetate, or in the presence lactate, when respiration is blocked by cyanide or anoxia. In both cases, ATP synthesis is impaired, but AThTP accumulation does not appear to be a direct consequence of reduced ATP levels. Indeed, in the CV2 E. coli strain (containing a thermolabile adenylate kinase), the ATP content is very low at 37°C, even in the presence of metabolizable substrates (glucose or lactate) and under these conditions, the cells produce ThTP but not AThTP. Furthermore, we show that ThTP inhibits AThTP accumulation. Therefore, we conclude that a low energy charge is not sufficient to trigger AThTP accumulation and the latter can only accumulate under conditions where no ThTP is synthesized. We further show that AThTP production can also be induced by the uncoupler CCCP but, unexpectedly, this requires the presence of pyruvate or a substrate yielding pyruvate (such a D-glucose or L-lactate). Under the conditions described, AThTP production is not different when RelA or SpoT mutants are used.ConclusionsIn E. coli, AThTP accumulates in response to two different conditions of metabolic stress: lack of energy substrates (or inhibition of their metabolization) and uncoupled pyruvate oxidation. Both conditions prevent bacterial growth. There is no obvious link with the stringent response or catabolite repression.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Adenosine thiamine triphosphate accumulates in Escherichia coli cells in response to specific conditions of metabolic stress

et al. 2010

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“…Streptomycin-treated mouse is a model of choice for studying intestinal colonization of EHEC strains ( Luo et al, 2008 ) and has been extensively used for this purpose ( Leatham et al, 2009 ). The number of persistent EHEC in streptomycin-treated mouse feces is a representation of their number in the large intestine ( Leatham et al, 2009 ); where intestinal colonization is reduced, the level of EHEC in the feces is proportionately reduced ( Leatham et al, 2009 ).…”

Section: Methodsmentioning

confidence: 99%

“…Streptomycin sulfate was administrated to mice in their drinking water (5 g/liter) over the entire course of these experiments; this selectively removes facultative anaerobic and some strictly anaerobic bacteria ( Hentges et al, 1984 ). However, the overall population of anaerobes in mouse feces following streptomycin treatment remain unchanged ( Luo et al, 2008 ). We used fecal EHEC excretion to measure the relative intestinal colonizing abilities of EHEC O157:H7 strain EDL933 and EHEC O26:H11 strain 21765.…”

Section: Methodsmentioning

confidence: 99%

Milk Fat Globules Hamper Adhesion of Enterohemorrhagic Escherichia coli to Enterocytes: In Vitro and in Vivo Evidence

et al. 2018

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Enterohemorrhagic Escherichia coli (EHEC; E. coli) are food-borne agents associated with gastroenteritis, enterocolitis, bloody diarrhea and the hemolytic-uremic syndrome (HUS). Bovine milk glycans have been shown to contain oligosaccharides which are similar to host epithelial cell receptors and can therefore prevent bacterial adhesion. This study aimed to describe interactions between EHEC O157:H7 EDL933 and O26:H11 21765 and milk fat globules (MFGs) in raw milk and raw milk cheese, and the impact of MFGs on EHEC strains adhesion to the intestinal tract in vitro and in vivo. Both EHEC serotypes clearly associated with native bovine MFGs and significantly limited their adhesion to a co-culture of intestinal cells. The presence of MFGs in raw milk cheese had two effects on the adhesion of both EHEC serotypes to the intestinal tracts of streptomycin-treated mice. First, it delayed and reduced EHEC excretion in mouse feces for both strains. Second, the prime implantation site for both EHEC strains was 6 cm more proximal in the intestinal tracts of mice fed with contaminated cheese containing less than 5% of fat than in those fed with contaminated cheese containing 40% of fat. Feeding mice with 40% fat cheese reduced the intestinal surface contaminated with EHEC and may therefore decrease severity of illness.

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“…A set of proteins involved in arginine, glutamate, lysine and citrate biosynthesis (ArgABCGI, GdhA, LysC, GltA) and periplasmic proteins arginine high-affinity import (ArtJ), histidine high-affinity import (HisJ), molybdate import (ModA), and lysozyme inhibition (PliG) decreased dramatically in SynH2 cells relative to SynH2 − cells without corresponding reductions of their transcripts. GdhA, other biosynthetic enzymes, and other periplasmic binding proteins are degraded by the ClpP protease during C or N starvation (Maurizi and Rasulova, 2002 ; Weichart et al, 2003 ); Lon protease also has been implicated in proteolysis upon C starvation (Luo et al, 2008 ). Thus, we suggest that aromatic inhibitors may enhance degradation of proteins involved in N and C metabolism in stationary phase cells.…”

Section: Resultsmentioning

confidence: 99%

Aromatic inhibitors derived from ammonia-pretreated lignocellulose hinder bacterial ethanologenesis by activating regulatory circuits controlling inhibitor efflux and detoxification

et al. 2014

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Efficient microbial conversion of lignocellulosic hydrolysates to biofuels is a key barrier to the economically viable deployment of lignocellulosic biofuels. A chief contributor to this barrier is the impact on microbial processes and energy metabolism of lignocellulose-derived inhibitors, including phenolic carboxylates, phenolic amides (for ammonia-pretreated biomass), phenolic aldehydes, and furfurals. To understand the bacterial pathways induced by inhibitors present in ammonia-pretreated biomass hydrolysates, which are less well studied than acid-pretreated biomass hydrolysates, we developed and exploited synthetic mimics of ammonia-pretreated corn stover hydrolysate (ACSH). To determine regulatory responses to the inhibitors normally present in ACSH, we measured transcript and protein levels in an Escherichia coli ethanologen using RNA-seq and quantitative proteomics during fermentation to ethanol of synthetic hydrolysates containing or lacking the inhibitors. Our study identified four major regulators mediating these responses, the MarA/SoxS/Rob network, AaeR, FrmR, and YqhC. Induction of these regulons was correlated with a reduced rate of ethanol production, buildup of pyruvate, depletion of ATP and NAD(P)H, and an inhibition of xylose conversion. The aromatic aldehyde inhibitor 5-hydroxymethylfurfural appeared to be reduced to its alcohol form by the ethanologen during fermentation, whereas phenolic acid and amide inhibitors were not metabolized. Together, our findings establish that the major regulatory responses to lignocellulose-derived inhibitors are mediated by transcriptional rather than translational regulators, suggest that energy consumed for inhibitor efflux and detoxification may limit biofuel production, and identify a network of regulators for future synthetic biology efforts.

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Lon protease promotes survival of Escherichia coli during anaerobic glucose starvation

Cited by 11 publications

References 33 publications

Adenosine thiamine triphosphate accumulates in Escherichia coli cells in response to specific conditions of metabolic stress

Adenosine thiamine triphosphate accumulates in Escherichia coli cells in response to specific conditions of metabolic stress

Milk Fat Globules Hamper Adhesion of Enterohemorrhagic Escherichia coli to Enterocytes: In Vitro and in Vivo Evidence

Aromatic inhibitors derived from ammonia-pretreated lignocellulose hinder bacterial ethanologenesis by activating regulatory circuits controlling inhibitor efflux and detoxification

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