ppGpp

The stringent response of bacteria to starvation and stress also fulfills a role in addressing the threat of antibiotics. Within this stringent response, (p)ppGpp, synthesized by RelA or SpoT, functions as a global alarmone. However, the effect of this (p)ppGpp on resistance development is poorly understood. Here, we show that knockout of relA or rpoS curtails resistance development against bactericidal antibiotics. The emergence of mutated genes associated with starvation and (p)ppGpp, among others, indicates the activation of stringent responses...

Pseudomonas aeruginosa is a major cause of nosocomial infections and the leading cause of chronic lung infections in cystic fibrosis and chronic obstructive pulmonary disease patients. Antibiotic treatment remains challenging because P. aeruginosa is resistant to high concentrations of antibiotics and has a remarkable ability to acquire mutations conferring resistance to multiple groups of antimicrobial agents. Here we report that when P. aeruginosa is plated on ciprofloxacin (cipro) plates, the majority of cipro-resistant (ciproR) colonies observed at and after 48 h of incubation carry mutations in genes related to the Stringent Response (SR)...

The stringent response exerted by (p)ppGpp and RNA-polymerase binding protein DksA regulates gene expression in diverse bacterial species. To control gene expression (p)ppGpp, synthesized by enzymes RelA and SpoT, interacts with two sites within the RNA polymerase; site 1, located in the interphase between subunits β' and ω (rpoZ), and site 2 located in the secondary channel that is dependent on DksA protein. In Escherichia coli, inactivation of dksA results in a reduced sigma factor RpoS expression...

Ionic silver (Ag+ ) is being investigated as a residual biocide for use in NASA spacecraft potable water systems on future crewed missions. This water will be used to irrigate future spaceflight crop production systems. We have evaluated the impact of three concentrations (31 ppb, 125 ppb, and 500 ppb) of ionic silver biocide solutions on lettuce in an arcillite (calcinated clay particle substrate) and hydroponic (substrate-less) growth setup after 28 days. Lettuce plant growth was reduced in the hydroponic samples treated with 31 ppb silver and severely stunted for samples treated at 125 ppb and 500 ppb silver...

Resistance evolution during exposure to non-lethal levels of antibiotics is influenced by various stress responses of bacteria which are known to affect growth rate. Here, we aim to disentangle how the interplay between resistance development and associated fitness costs is affected by stress responses. We performed de novo resistance evolution of wild-type strains and single-gene knockout strains in stress response pathways using four different antibiotics. Throughout resistance development, the increase in minimum inhibitory concentration (MIC) is accompanied by a gradual decrease in growth rate, most pronounced in amoxicillin or kanamycin...

Bacterial stress adaptive response is formed due to changes in the cell gene expression profile in response to alterations in environmental conditions through the functioning of regulatory networks. The mutual influence of network signaling molecules represented by cells' natural metabolites, including indole and second messengers (p) ppGpp and cAMP, is hitherto not well understood, being the aim of this study. E. coli parent strain BW25141 ((p) ppGpp+) and deletion knockout BW25141ΔrelAΔspoT which is unable to synthesize (p)ppGpp ((p)ppGpp0) were cultivated in M9 medium supplemented with different glucose concentrations (5...

(p)ppGpp is a nucleotide alarmone that controls bacterial response to nutrient deprivation. Since elevated (p)ppGpp levels confer mecillinam resistance and are essential for broad-spectrum β-lactam resistance as mediated by the β-lactam-insensitive transpeptidase YcbB (LdtD), we hypothesized that (p)ppGpp might affect cell wall peptidoglycan metabolism. Here we report that (p)ppGpp-dependent β-lactam resistance does not rely on any modification of peptidoglycan metabolism, as established by analysis of Escherichia coli peptidoglycan structure using high-resolution mass spectrometry...

As an important alarmone nucleotide, guanosine 3'-diphosphate-5'-diphosphate (ppGpp) can regulate the survival of bacteria under strict environmental conditions. Direct detection of ppGpp in bacteria with high sensitivity and selectivity is crucial for elucidating the role of ppGpp in bacterial stringent response. Herein, the terbium-carbon dots nanocomposite (CDs-Tb) modified glass nanopipet was developed for the recognition of ppGpp. The CDs-Tb in glass nanopipette preserved their fluorescence properties as well as the coordination capacity of Tb3+ toward ppGpp...

The export of peptides or proteins is essential for a variety of important functions in bacteria. Among the diverse protein-translocation systems, peptidase-containing ABC transporters (PCAT) are involved in the maturation and export of quorum-sensing or antimicrobial peptides in Gram-positive bacteria and of toxins in Gram-negative organisms. In the multicellular and diazotrophic cyanobacterium Nostoc PCC 7120, the protein HetC is essential for the differentiation of functional heterocysts, which are micro-oxic and non-dividing cells specialized in atmospheric nitrogen fixation...

Infective endocarditis (IE) caused by Enterococcus spp. represents the third most common cause of IE, with high rates of relapse compared with other bacteria. Interestingly, late relapses (>6 months) have only been described in Enterococcus faecalis, but here we describe the first reported IE relapse with Enterococcus faecium more than a year (17 months) after the initial endocarditis episode. Firstly, by multi locus sequence typing (MLST), we demonstrated that both isolates (EF646 and EF641) belong to the same sequence type (ST117)...

To thrive in nature, bacteria have to reproduce efficiently under favorable conditions and persist during stress. The global strategy that integrates the growth control and stress response remains to be explored. Here, we find that a moderate induction of (p)ppGpp reduces growth rate but significantly enhances the stress tolerance of E. coli , resulting from a global resource re-allocation from ribosome synthesis to the synthesis of stress-responsive proteins. Strikingly, the activation of stress response by (p)ppGpp is still largely retained in the absence of RpoS...

Guanosine tetra- and pentaphosphate nucleotides, (p)ppGpp, function as central secondary messengers and alarmones in bacterial cell biology, signalling a range of stress conditions, including nutrient starvation and exposure to cell-wall-targeting antibiotics, and are critical for survival. While activation of the stringent response and alarmone synthesis on starved ribosomes by members of the RSH (Rel) class of proteins is well understood, much less is known about how single-domain small alarmone synthetases (SASs) and their corresponding alarmone hydrolases, the small alarmone hydrolases (SAHs), are regulated and contribute to (p)ppGpp homeostasis...

In response to starvation, virtually all bacteria pyrophosphorylate the 3'-hydroxy group of GTP or GDP to produce two messenger nucleotides collectively denoted as (p)ppGpp. Also known as alarmones, (p)ppGpp reprograms bacterial physiology to arrest growth and promote survival. Intriguingly, although cellular concentration of dGTP is two orders of magnitude lower than that of GTP, alarmone synthetases are highly selective against using 2'-deoxyguanosine (2dG) nucleotides as substrates. We thus hypothesize that production of 2dG alarmone, (p)pp(dG)pp, is highly deleterious, which drives a strong negative selection to exclude 2dG nucleotides from alarmone signaling...

UNLABELLED: In response to nutrient deprivation, bacteria activate a conserved stress response pathway called the stringent response (SR). During SR activation in Caulobacter crescentus , SpoT synthesizes the secondary messengers (p)ppGpp, which affect transcription by binding RNA polymerase to downregulate anabolic genes. (p)ppGpp also impacts expression of anabolic genes by controlling the levels and activities of their transcriptional regulators. In Caulobacter , a major regulator of anabolic genes is the transcription factor CdnL...

In the ongoing battle against antimicrobial resistance, phenotypic drug tolerance poses a formidable challenge. This adaptive ability of microorganisms to withstand drug pressure without genetic alterations further complicating global healthcare challenges. Microbial populations employ an array of persistence mechanisms, including dormancy, biofilm formation, adaptation to intracellular environments, and the adoption of L-forms, to develop drug tolerance. Moreover, molecular mechanisms like toxin-antitoxin modules, oxidative stress responses, energy metabolism, and (p)ppGpp signaling contribute to this phenomenon...

S. lividans and S. coelicolor are phylogenetically closely related strains with different abilities to produce the same specialized metabolites. Previous studies revealed that the strong antibiotic producer, S. coelicolor, had a lower ability to assimilate nitrogen and phosphate than the weak producer, S. lividans, and this resulted into a lower growth rate. A comparative proteomic dataset was used to establish the consequences of these nutritional stresses on the abundance of proteins of the translational apparatus of these strains, grown in low and high phosphate availability...

The cyanobacterium Synechococcus elongatus PCC 7942 accumulates alarmone guanosine tetraphosphate (ppGpp) under stress conditions, such as darkness. A previous study observed that artificial ppGpp accumulation under photosynthetic conditions led to the downregulation of genes involved in the nitrogen assimilation system, which is activated by the global nitrogen regulator NtcA, suggesting that ppGpp regulates NtcA activity. However, the details of this mechanism have not been elucidated. Here, we investigate the metabolic responses associated with ppGpp accumulation by heterologous expression of the ppGpp synthetase RelQ...

In addition to comprising monomers of nucleic acids, nucleotides have signaling functions and act as second messengers in both prokaryotic and eukaryotic cells. The most common example is cyclic AMP (cAMP). Nucleotide signaling is a focus of great interest in bacteria. Cyclic di-AMP (c-di-AMP), cAMP, and cyclic di-GMP (c-di-GMP) participate in biological events such as bacterial growth, biofilm formation, sporulation, cell differentiation, motility, and virulence. Moreover, the cyclic-di-nucleotides (c-di-nucleotides) produced in pathogenic intracellular bacteria can affect eukaryotic host cells to allow for infection...

Infection by the enteric pathogen Shigella flexneri requires transit through the gastrointestinal tract and invasion of and replication within the cells of the host colonic epithelium. This process exposes the pathogen to a range of diverse microenvironments. Furthermore, the unique composition and physical environment of the eukaryotic cell cytosol represents a stressful environment for S. flexneri , and extensive physiological adaptations are needed for the bacterium to thrive. In this work, we show that disrupting synthesis of the stringent response alarmone (p)ppGpp in S...

Nucleotide second messengers play an important role in bacterial adaptation to environmental changes. Recent evidence suggests that some of these regulatory molecular pathways were conserved upon the degenerative evolution of the wall-less mycoplasmas. We have recently reported the occurrence of a phosphodiesterase (PDE) in the ruminant pathogen Mycoplasma bovis , which was involved in c-di-AMP metabolism. In the present study, we demonstrate that the genome of this mycoplasma species encodes a PDE of the GdpP family with atypical DHH domains...