Persisters Formation and Resuscitation.

is a commonly used probiotic, and many researchers have focused on its stress response to improve its functionality and survival. However, studies on persister cells, dormant cells that aid bacteria in surviving general stress, have focused on pathogenic bacteria that cause infection, not . Thus, understanding persister cells will provide essential clues for understanding how survives and maintains its function under various environmental conditions.

Single-cell analysis reveals that cryptic prophage protease LfgB protects during oxidative stress by cleaving antitoxin MqsA.

Although toxin/antitoxin (TA) systems are ubiquitous, beyond phage inhibition and mobile element stabilization, their role in host metabolism is obscure. One of the best-characterized TA systems is MqsR/MqsA of , which has been linked previously to protecting gastrointestinal species during the stress it encounters from the bile salt deoxycholate as it colonizes humans. However, some recent whole-population studies have challenged the role of toxins such as MqsR in bacterial physiology since the locus is induced over a hundred-fold during stress, but a phenotype was not found upon its deletion.

CRISPR-Cas Controls Cryptic Prophages.

The bacterial archetypal adaptive immune system, CRISPR-Cas, is thought to be repressed in the best-studied bacterium, K-12. We show here that the CRISPR-Cas system is active and serves to inhibit its nine defective (i.e.

Escherichia coli cryptic prophages sense nutrients to influence persister cell resuscitation.

Cryptic prophages are not genomic junk but instead enable cells to combat myriad stresses as an active stress response. How these phage fossils affect persister cell resuscitation has, however, not been explored. Persister cells form as a result of stresses such as starvation, antibiotics and oxidative conditions, and resuscitation of these persister cells likely causes recurring infections such as those associated with tuberculosis, cystic fibrosis and Lyme disease.

'Viable but non-culturable cells' are dead.

Most bacteria lead lives of quiet desperation, so they sleep. By sleeping, bacteria survive ubiquitous stress, such as antibiotics, and can resuscitate to reconstitute infections. As for other nearly universal and highly regulated processes such as biofilm formation, in persistence, a small population of cells have an elegantly-regulated pathway to become dormant.

The Primary Physiological Roles of Autoinducer 2 in Are Chemotaxis and Biofilm Formation.

Autoinducer 2 (AI-2) is a ubiquitous metabolite but, instead of acting as a "universal signal," relatively few phenotypes have been associated with it, and many scientists believe AI-2 is often a metabolic byproduct rather than a signal. Here, the aim is to present evidence that AI-2 influences both biofilm formation and motility (swarming and chemotaxis), using as the model system, to establish AI-2 as a true signal with an important physiological role in this bacterium. In addition, AI-2 signaling is compared to the other primary signal of , indole, and it is shown that they have opposite effects on biofilm formation and virulence.

Forming and waking dormant cells: The ppGpp ribosome dimerization persister model.

Procaryotes starve and face myriad stresses. The bulk population actively resists the stress, but a small population weathers the stress by entering a resting stage known as persistence. No mutations occur, and so persisters behave like wild-type cells upon removal of the stress and regrowth; hence, persisters are phenotypic variants.

A Primary Physiological Role of Toxin/Antitoxin Systems Is Phage Inhibition.

Toxin/antitoxin (TA) systems are present in most prokaryote genomes. Toxins are almost exclusively proteins that reduce metabolism (but do not cause cell death), and antitoxins are either RNA or proteins that counteract the toxin or the RNA that encodes it. Although TA systems clearly stabilize mobile genetic elements, after four decades of research, the physiological roles of chromosomal TA systems are less clear.

Combatting Persister Cells With Substituted Indoles.

Given that a subpopulation of most bacterial cells becomes dormant due to stress, and that the resting cells of pathogens can revive and reconstitute infections, it is imperative to find methods to treat dormant cells to eradicate infections. The dormant bacteria that are not spores or cysts are known as persister cells. Remarkably, in contrast to the original report that incorrectly indicated indole increases persistence, a large number of indole-related compounds have been found in the last few years that kill persister cells.

Toxin/Antitoxin System Paradigms: Toxins Bound to Antitoxins Are Not Likely Activated by Preferential Antitoxin Degradation.

Periodically, a scientific field should examine its early premises. For ubiquitous toxin/antitoxin (TA) systems, several initial paradigms require adjustment based on accumulated data. For example, it is now clear that under physiological conditions, there is little evidence that toxins of TA systems cause cell death and little evidence that TA systems cause persistence.

ppGpp ribosome dimerization model for bacterial persister formation and resuscitation.

Stress is ubiquitous for bacteria and can convert a subpopulation of cells into a dormant state known as persistence, in which cells are tolerant to antimicrobials. These cells revive rapidly when the stress is removed and are likely the cause of many recurring infections such as those associated with tuberculosis, cystic fibrosis, and Lyme disease. However, how persister cells are formed is not understood well.

Persister Cells Resuscitate Using Membrane Sensors that Activate Chemotaxis, Lower cAMP Levels, and Revive Ribosomes.

Persistence, the stress-tolerant state, is arguably the most vital phenotype since nearly all cells experience nutrient stress, which causes a sub-population to become dormant. However, how persister cells wake to reconstitute infections is not understood well. Here, using single-cell observations, we determined that Escherichia coli persister cells resuscitate primarily when presented with specific carbon sources, rather than spontaneously.

Comment on Metabolomics for a Millenniums-Old Crop: Tea Plant ().

Metabolomics is the study of metabolite profiles at the system level. Since its introduction in the early 2000s, metabolomics has greatly contributed to the understanding of the distribution of metabolites in organisms under various physiological conditions. In this comment, we show our research on the temporal development of metabolomics in general and in agricultural, food, and nutritional sciences.

Persister cells resuscitate via ribosome modification by 23S rRNA pseudouridine synthase RluD.

Upon a wide range of stress conditions (e.g. nutrient, antibiotic, oxidative), a subpopulation of bacterial cells known as persisters survives by halting metabolism.

Identification of a potent indigoid persister antimicrobial by screening dormant cells.

The subpopulation of bacterial cells that survive myriad stress conditions (e.g., nutrient deprivation and antimicrobials) by ceasing metabolism, revive by activating ribosomes.

Phages Mediate Bacterial Self-Recognition.

Cells are social, and self-recognition is a conserved aspect of group behavior where cells assist kin and antagonize non-kin. However, the role of phage in self-recognition is unexplored. Here we find that a demarcation line is formed between different swimming Escherichia coli strains but not between identical clones; hence, motile cells discriminate between self and non-self.

Ribosome dependence of persister cell formation and resuscitation.

Since most bacterial cells are starving, they must enter a resting stage. Persister is the term used for metabolically-dormant cells that are not spores, and these cells arise from stress such as that from antibiotics as well as that from starvation. Because of their lack of metabolism, persister cells survive exposure to multiple stresses without undergoing genetic change; i.

Serine Hydroxymethyltransferase ShrA (PA2444) Controls Rugose Small-Colony Variant Formation in .

causes many biofilm infections, and the rugose small-colony variants (RSCVs) of this bacterium are important for infection. We found here that inactivation of PA2444, which we determined to be a serine hydroxymethyltransferase (SHMT), leads to the RSCV phenotype of PA14. In addition, loss of PA2444 increases biofilm formation by two orders of magnitude, increases exopolysaccharide by 45-fold, and abolishes swarming.

Single cell observations show persister cells wake based on ribosome content.

Since persister cells survive antibiotic treatments through dormancy and resuscitate to reconstitute infections, it is imperative to determine the rate at which these cells revive. Using two sets of Escherichia coli persister cells, those arising after antibiotic treatment at low levels and those generated at high levels by ceasing transcription via rifampicin pretreatment (shown to be bona fide persisters through eight sets of experiments), we used microscopy of single cells to determine that the resuscitation of dormant persisters is heterogeneous and includes cells that grow immediately. In all, five phenotypes were found during the observation of persister cells when fresh nutrients were added: (i) immediate division, (ii) immediate elongation followed by division, (iii) immediate elongation but no division, (iv) delayed elongation/division and (v) no growth.