The <i>Escherichia coli</i> replication inhibitor CspD is subject to growth‐regulated degradation by the Lon protease

Langklotz, Sina; Narberhaus, Franz

doi:10.1111/j.1365-2958.2011.07646.x

Cited by 43 publications

(46 citation statements)

References 69 publications

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“…Also upregulated was the gene coding for cold shock protein D (cspD), which is induced in the stationary phase in an rpoSindependent manner. CspD is responsible for inhibiting replication by binding to single-stranded DNA (ssDNA), and its overexpression is implicated in increased persister cell formation (46). With upregulation of both hipB and cspD, it is possible that there are an increased number of persister cells found in imipenemtreated biofilms, potentially giving insight into the ability of these biofilms to remain viable even with a carbapenem treatment of 1,000ϫ the MIC.…”

Section: Discussionmentioning

confidence: 99%

Sublethal Concentrations of Carbapenems Alter Cell Morphology and Genomic Expression of Klebsiella pneumoniae Biofilms

Laar

Chen²,

You

et al. 2015

Antimicrob Agents Chemother

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b Klebsiella pneumoniae, a Gram-negative bacterium, is normally associated with pneumonia in patients with weakened immune systems. However, it is also a prevalent nosocomial infectious agent that can be found in infected surgical sites and combat wounds. Many of these clinical strains display multidrug resistance. We have worked with a clinical strain of K. pneumoniae that was initially isolated from a wound of an injured soldier. This strain demonstrated resistance to many commonly used antibiotics but sensitivity to carbapenems. This isolate was capable of forming biofilms in vitro, contributing to its increased antibiotic resistance and impaired clearance. We were interested in determining how sublethal concentrations of carbapenem treatment specifically affect K. pneumoniae biofilms both in morphology and in genomic expression. Scanning electron microscopy showed striking morphological differences between untreated and treated biofilms, including rounding, blebbing, and dimpling of treated cells. Comparative transcriptome analysis using RNA sequencing (RNA-Seq) technology identified a large number of open reading frames (ORFs) differentially regulated in response to carbapenem treatment at 2 and 24 h. ORFs upregulated with carbapenem treatment included genes involved in resistance, as well as those coding for antiporters and autoinducers. ORFs downregulated included those coding for metal transporters, membrane biosynthesis proteins, and motility proteins. Quantitative real-time PCR validated the general trend of some of these differentially regulated ORFs. Treatment of K. pneumoniae biofilms with sublethal concentrations of carbapenems induced a wide range of phenotypic and gene expression changes. This study reveals some of the mechanisms underlying how sublethal amounts of carbapenems could affect the overall fitness and pathogenic potential of K. pneumoniae biofilm cells.

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Section: Discussionmentioning

confidence: 99%

Sublethal Concentrations of Carbapenems Alter Cell Morphology and Genomic Expression of Klebsiella pneumoniae Biofilms

Laar

Chen²,

You

et al. 2015

Antimicrob Agents Chemother

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“…Thus far, conditional proteolysis has only been reported for a few substrates. For instance, (i) increasing temperatures trigger the degradation of the homoserine transsuccinylase HTS (MetA), which catalyzes the first step in the de novo methionine biosynthesis and thereby affects the rate of translation (18), (ii) the stability of the DNA-binding replication inhibitor CspD is adjusted according to the growth rate and growth phase of E. coli cells (19), (iii) anti-sigma factor guided degradation controls the amount of the stationary phase sigma factor RpoS (33), and (iv) the formate dehydrogenase subunit FdoH and the uncharacterized YfgM protein are degraded by FtsH in response to various growth conditions (12).…”

Section: Discussionmentioning

confidence: 99%

“…Although about 15 different FtsH substrates are known, there are many open questions concerning their precise degradation mechanism. Usually, proteolysis of key enzymes or regulatory proteins is not constitutive but tightly controlled to allow adaptation to changing growth conditions (16)(17)(18)(19)(20). Assuming that the stability of LpxC might be coordinated with the cellular demand for LPS under different growth conditions, we set out to monitor LpxC stability at different generation times.…”

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confidence: 99%

FtsH-Mediated Coordination of Lipopolysaccharide Biosynthesis in Escherichia coli Correlates with the Growth Rate and the Alarmone (p)ppGpp

2013

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The outer membrane is the first line of defense for Gram-negative bacteria and serves as a major barrier for antibiotics and other harmful substances. The biosynthesis of lipopolysaccharides (LPS), the essential component of the outer membrane, must be tightly controlled as both too much and too little LPS are toxic. In Escherichia coli, the cellular level of the key enzyme LpxC, which catalyzes the first committed step in LPS biosynthesis, is adjusted by proteolysis carried out by the essential and membrane-bound protease FtsH. Here, we demonstrate that LpxC is degraded in a growth rate-dependent manner with half-lives between 4 min and >2 h. According to the cellular demand for LPS biosynthesis, LpxC is degraded during slow growth but stabilized when cells grow rapidly. Disturbing the balance between LPS and phospholipid biosynthesis in favor of phospholipid production in an E. coli strain encoding a hyperactive FabZ protein abolishes growth rate dependency of LpxC proteolysis. Lack of the alternative sigma factor RpoS or inorganic polyphosphates, which are known to mediate growth rate-dependent gene regulation in E. coli, did not affect proteolysis of LpxC. In contrast, absence of RelA and SpoT, which synthesize the alarmone (p)ppGpp, deregulated LpxC degradation resulting in rapid proteolysis in fast-growing cells and stabilization during slow growth. Our data provide new insights into the essential control of LPS biosynthesis in E. coli.

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“…MqsR relies on Hha and CspD to form persister cells (39); Hha is a putative toxin with antitoxin TomB (24), and CspD is a stress-induced cold shock protein that is a DNA replication inhibitor (79). Furthermore, since the protease Lon degrades CspD primarily during the stationary phase, it has been hypothesized that degradation of CspD may be related to persister cell awakening (i.e., when growth resumes) (46). Additional findings linking toxin MqsR to persistence include those that mqsR is the most highly induced gene in persister cells compared to nonpersisters (67) and that, in transcriptome studies to probe the impact of kanamycin on cell physiology, mqsRA was found to be one of the most highly induced operons (41).…”

Section: Ta Systems and Biofilm Formationmentioning

confidence: 99%

Toxin-Antitoxin Systems Influence Biofilm and Persister Cell Formation and the General Stress Response

Wang

Wood

2011

Appl Environ Microbiol

370

363

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2In many genomes, toxin-antitoxin (TA) systems have been identified; however, their role in cell physiology has been unclear. Here we examine the evidence that TA systems are involved in biofilm formation and persister cell formation and that these systems may be important regulators of the switch from the planktonic to the biofilm lifestyle as a stress response by their control of secondary messenger 3,5-cyclic diguanylic acid. Specifically, upon stress, the sequence-specific mRNA interferases MqsR and MazF mediate cell survival. In addition, we propose that TA systems are not redundant, as they may have developed to respond to specific stresses.Toxin-antitoxin (TA) systems typically consist of two genes in an operon which encode a stable toxin that disrupts an essential cellular process (e.g., translation via mRNA degradation) and a labile antitoxin (either RNA or a protein) that prevents toxicity (73). RNA antitoxins are known as type I if they inhibit toxin translation as antisense RNA or type III if they inhibit toxin activity; type II antitoxins are proteins that inhibit toxin activity (48). For type II systems (Fig. 1), the antitoxin also acts as a transcriptional repressor and negatively autoregulates the operon by a conserved palindromic motif in the operator region. TA systems were initially discovered in 1983 as plasmid addiction systems on low-copy-number plasmids due to their ability to stabilize plasmids by postsegregational killing (55). TA systems are also ubiquitous as chromosomal elements; for example, of the 126 prokaryotic genomes (16 archaea and 110 bacteria) searched, 671 TA loci were identified (56). Since this report, their prevalence and diversity have increased; for example, in Escherichia coli alone, the number of TA systems has increased from 5 to 37 (71). However, their role in cell physiology is controversial, with nine possible roles identified (51): addictive genomic debris, stabilization of genomic parasites, selfish alleles, gene regulation, growth control, persister cell formation (persister cells are a small fraction of bacteria that demonstrate resistance to antibiotics without genetic change [50]), programmed cell arrest, programmed cell death, and antiphage measures (28, 57). Although they were first thought to be related to cell death, it remains controversial whether TA systems result in cell death (51, 56); hence, the primary role of these systems has been enigmatic. In this review, we present evidence that TA systems regulate genes other than their own operons, mediate the general stress response, and help direct cells toward the formation of biofilm and persister cells.

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The Escherichia coli replication inhibitor CspD is subject to growth‐regulated degradation by the Lon protease

Cited by 43 publications

References 69 publications

Sublethal Concentrations of Carbapenems Alter Cell Morphology and Genomic Expression of Klebsiella pneumoniae Biofilms

Sublethal Concentrations of Carbapenems Alter Cell Morphology and Genomic Expression of Klebsiella pneumoniae Biofilms

FtsH-Mediated Coordination of Lipopolysaccharide Biosynthesis in Escherichia coli Correlates with the Growth Rate and the Alarmone (p)ppGpp

Toxin-Antitoxin Systems Influence Biofilm and Persister Cell Formation and the General Stress Response

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