A Proteomic Signature of Dormancy in the Actinobacterium Micrococcus luteus

ABSTRACT Dormancy is a protective state in which diverse bacteria, including Mycobacterium tuberculosis, Staphylococcus aureus, Treponema pallidum (syphilis), and Borrelia burgdorferi (Lyme disease), curtail metabolic activity to survive external stresses, including antibiotics. Evidence suggests dormancy consists of a continuum of interrelated states, including viable but nonculturable (VBNC) and persistence states. VBNC and persistence contribute to antibiotic tolerance, reemergence from latent infections, and even quorum sensing and biofilm formation. Previous studies indicate that the protein mechanisms regulating persistence and VBNC states are not well understood. We have queried the VBNC state of Micrococcus luteus NCTC 2665 (MI-2665) by quantitative proteomics combining gel electrophoresis, high-performance liquid chromatography, and tandem mass spectrometry to elucidate some of these mechanisms. MI-2665 is a nonpathogenic actinobacterium containing a small (2.5-Mb), high-GC-content genome which exhibits a well-defined VBNC state induced by nutrient deprivation. The MI-2665 VBNC state demonstrated a loss of protein diversity accompanied by increased levels of 18 proteins that are conserved across actinobacteria, 14 of which have not been previously identified in VNBC. These proteins implicate an anaplerotic strategy in the transition to VBNC, including changes in the glyoxylate shunt, redox and amino acid metabolism, and ribosomal regulatory processes. Our data suggest that MI-2665 is a viable model for dissecting the protein mechanisms underlying the VBNC stress response and provide the first protein-level signature of this state. We expect that this protein signature will enable future studies deciphering the protein mechanisms of dormancy and identify novel therapeutic strategies effective against antibiotic-tolerant bacterial infections. IMPORTANCE Dormancy is a protective state enabling bacteria to survive antibiotics, starvation, and the immune system. Dormancy is comprised of different states, including persistent and viable but nonculturable (VBNC) states that contribute to the spread of bacterial infections. Therefore, it is imperative to identify how bacteria utilize these different dormancy states to survive antibiotic treatment. The objective of our research is to eliminate dormancy as a route to antibiotic tolerance by understanding the proteins that control dormancy in Micrococcus luteus NCTC 2665. This bacterium has unique advantages for studying dormancy, including a small genome and a well-defined and reproducible VBNC state. Our experiments implicate four previously identified and 14 novel proteins upregulated in VBNC that may regulate this critical survival mechanism.

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Induction of Viable but Nonculturable Escherichia coli O157:H7 in the Phyllosphere of Lettuce: a Food Safety Risk Factor

Applied and Environmental Microbiology ◽

10.1128/aem.05020-11 ◽

2011 ◽

Vol 77 (23) ◽

pp. 8295-8302 ◽

Cited By ~ 81

Author(s):

Laura-Dorina Dinu ◽

Susan Bach

Keyword(s):

Escherichia Coli ◽

Food Safety ◽

Low Temperature ◽

Cell Density ◽

Prolonged Storage ◽

Potential Hazard ◽

Vbnc State ◽

Viable But Nonculturable ◽

Content Type ◽

E Coli

ABSTRACTEscherichia coliO157:H7 continues to be an important human pathogen and has been increasingly linked to food-borne illness associated with fresh produce, particularly leafy greens. The aim of this work was to investigate the fate ofE. coliO157:H7 on the phyllosphere of lettuce under low temperature and to evaluate the potential hazard of viable but nonculturable (VBNC) cells induced under such stressful conditions. First, we studied the survival of six bacterial strains following prolonged storage in water at low temperature (4°C) and selected two strains with different nonculturable responses for the construction ofE. coliO157:H7 Tn7gfptransformants in order to quantitatively assess the occurrence of human pathogens on the plant surface. Under a suboptimal growth temperature (16°C), bothE. coliO157:H7 strains maintained culturability on lettuce leaves, but under more stressful conditions (8°C), the bacterial populations evolved toward the VBNC state. The strain-dependent nonculturable response was more evident in the experiments with different inoculum doses (109and 106E. coliO157:H7 bacteria per g of leaf) when strain BRMSID 188 lost culturability after 15 days and strain ATCC 43895 lost culturability within 7 days, regardless of the inoculum dose. However, the number of cells entering the VBNC state in high-cell-density inoculum (approximately 55%) was lower than in low-cell-density inoculum (approximately 70%). We recorded the presence of verotoxin for 3 days in samples that contained a VBNC population of 4 to 5 log10cells but did not detect culturable cells. These findings indicate thatE. coliO157:H7 VBNC cells are induced on lettuce plants, and this may have implications regarding food safety.

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Characterization and Genomic Analysis of ValSw3-3, a New Siphoviridae Bacteriophage Infecting Vibrio alginolyticus

Journal of Virology ◽

10.1128/jvi.00066-20 ◽

2020 ◽

Vol 94 (10) ◽

Author(s):

Ling Chen ◽

Quan Liu ◽

Jiqiang Fan ◽

Tingwei Yan ◽

Haoran Zhang ◽

...

Keyword(s):

Phylogenetic Analysis ◽

In Silico ◽

Bacterial Infections ◽

Phage Therapy ◽

Gc Content ◽

Vibrio Alginolyticus ◽

Lytic Bacteriophage ◽

Sequence Alignments ◽

Content Type ◽

Link Type

ABSTRACT A novel lytic bacteriophage, ValSw3-3, which efficiently infects pathogenic strains of Vibrio alginolyticus, was isolated from sewage water and characterized by microbiological and in silico genomic analyses. Transmission electron microscopy indicated that ValSw3-3 has the morphology of siphoviruses. This phage can infect four species in the Vibrio genus and has a latent period of 15 min and a burst size of 95 ± 2 PFU/infected bacterium. Genome sequencing results show that ValSw3-3 has a 39,846-bp double-stranded DNA genome with a GC content of 43.1%. The similarity between the genome sequences of ValSw3-3 and those of other phages recorded in the GenBank database was below 50% (42%), suggesting that ValSw3-3 significantly differs from previously reported phages at the DNA level. Multiple genome comparisons and phylogenetic analysis based on the major capsid protein revealed that phage ValSw3-3 is grouped in a clade with five other phages, including Listonella phage phiHSIC (GenBank accession no. NC_006953.1), Vibrio phage P23 (MK097141.1), Vibrio phage pYD8-B (NC_021561.1), Vibrio phage 2E1 (KX507045.1), and Vibrio phage 12G5 (HQ632860.1), and is distinct from all known genera within the Siphoviridae family that have been ratified by the International Committee on Taxonomy of Viruses (ICTV). An in silico proteomic comparison of diverse phages from the Siphoviridae family supported this clustering result and suggested that ValSw3-3, phiHSIC, P23, pYD8-B, 2E1, and 12G5 should be classified as a novel genus cluster of Siphoviridae. A subsequent analysis of core genes also revealed the common genes shared within this new cluster. Overall, these results provide a characterization of Vibrio phage ValSw3-3 and support our proposal of a new viral genus within the family Siphoviridae. IMPORTANCE Phage therapy has been considered a potential alternative to antibiotic therapy in treating bacterial infections. For controlling the vibriosis-causing pathogen Vibrio alginolyticus, well-documented phage candidates are still lacking. Here, we characterize a novel lytic Vibrio phage, ValSw3-3, based on its morphology, host range and infectivity, growth characteristics, stability under various conditions, and genomic features. Our results show that ValSw3-3 could be a potent candidate for phage therapy to treat V. alginolyticus infections due to its stronger infectivity and better pH and thermal stability than those of previously reported Vibrio phages. Moreover, genome sequence alignments, phylogenetic analysis, in silico proteomic comparison, and core gene analysis all support that this novel phage, ValSw3-3, and five unclassified phages form a clade distant from those of other known genera ratified by the ICTV. Thus, we propose a new viral genus within the Siphoviridae family to accommodate this clade, with ValSw3-3 as a representative member.

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Viable-but-NonculturableListeria monocytogenesandSalmonella entericaSerovar Thompson Induced by Chlorine Stress Remain Infectious

mBio ◽

10.1128/mbio.00540-18 ◽

2018 ◽

Vol 9 (2) ◽

pp. e00540-18 ◽

Cited By ~ 31

Author(s):

Callum J. Highmore ◽

Jennifer C. Warner ◽

Steve D. Rothwell ◽

Sandra A. Wilks ◽

C. William Keevil

Keyword(s):

Listeria Monocytogenes ◽

Caenorhabditis Elegans ◽

Life Span ◽

Fresh Produce ◽

Environmental Stresses ◽

Vbnc State ◽

Viable But Nonculturable ◽

Content Type ◽

Food Borne Pathogens ◽

Food Borne

ABSTRACTThe microbiological safety of fresh produce is monitored almost exclusively by culture-based detection methods. However, bacterial food-borne pathogens are known to enter a viable-but-nonculturable (VBNC) state in response to environmental stresses such as chlorine, which is commonly used for fresh produce decontamination. Here, complete VBNC induction of green fluorescent protein-taggedListeria monocytogenesandSalmonella entericaserovar Thompson was achieved by exposure to 12 and 3 ppm chlorine, respectively. The pathogens were subjected to chlorine washing following incubation on spinach leaves. Culture data revealed that total viableL. monocytogenesandSalmonellaThompson populations became VBNC by 50 and 100 ppm chlorine, respectively, while enumeration by direct viable counting found that chlorine caused a <1-log reduction in viability. The pathogenicity of chlorine-induced VBNCL. monocytogenesandSalmonellaThompson was assessed by usingCaenorhabditis elegans. Ingestion of VBNC pathogens byC. elegansresulted in a significant life span reduction (P= 0.0064 andP< 0.0001), and no significant difference between the life span reductions caused by the VBNC and culturableL. monocytogenestreatments was observed.L. monocytogeneswas visualized beyond the nematode intestinal lumen, indicating resuscitation and cell invasion. These data emphasize the risk that VBNC food-borne pathogens could pose to public health should they continue to go undetected.IMPORTANCEMany bacteria are known to enter a viable-but-nonculturable (VBNC) state in response to environmental stresses. VBNC cells cannot be detected by standard laboratory culture techniques, presenting a problem for the food industry, which uses these techniques to detect pathogen contaminants. This study found that chlorine, a sanitizer commonly used for fresh produce, induces a VBNC state in the food-borne pathogensListeria monocytogenesandSalmonella enterica. It was also found that chlorine is ineffective at killing total populations of the pathogens. A life span reduction was observed inCaenorhabditis elegansthat ingested these VBNC pathogens, with VBNCL. monocytogenesas infectious as its culturable counterpart. These data show that VBNC food-borne pathogens can both be generated and avoid detection by industrial practices while potentially retaining the ability to cause disease.

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The Arginine Deiminase Pathway Impacts Antibiotic Tolerance during Biofilm-Mediated Streptococcus pyogenes Infections

mBio ◽

10.1128/mbio.00919-20 ◽

2020 ◽

Vol 11 (4) ◽

Author(s):

Jeffrey A. Freiberg ◽

Yoann Le Breton ◽

Janette M. Harro ◽

Devon L. Allison ◽

Kevin S. McIver ◽

...

Keyword(s):

Treatment Failure ◽

Antibiotic Treatment ◽

Streptococcus Pyogenes ◽

Bacterial Infections ◽

Bacterial Species ◽

Arginine Deiminase ◽

Antibiotic Tolerance ◽

Human Pathogen ◽

Biofilm Growth ◽

Content Type

ABSTRACT Bacterial biofilms are responsible for a variety of serious human infections and are notoriously difficult to treat due to their recalcitrance to antibiotics. Further work is necessary to elicit a full understanding of the mechanism of this antibiotic tolerance. The arginine deiminase (ADI) pathway is responsible for bacterial pH maintenance and is highly expressed during biofilm growth in multiple bacterial species. Using the group A Streptococcus (GAS) as a model human pathogen, the ADI pathway was demonstrated to contribute to biofilm growth. The inability of antibiotics to reduce GAS populations when in a biofilm was demonstrated by in vitro studies and a novel animal model of nasopharyngeal infection. However, disruption of the ADI pathway returned GAS biofilms to planktonic levels of antibiotic sensitivity, suggesting the ADI pathway is influential in biofilm-related antibiotic treatment failure and provides a new strategic target for the treatment of biofilm infections in GAS and potentially numerous other bacterial species. IMPORTANCE Biofilm-mediated bacterial infections are a major threat to human health because of their recalcitrance to antibiotic treatment. Through the study of Streptococcus pyogenes, a significant human pathogen that is known to form antibiotic-tolerant biofilms, we demonstrated the role that a bacterial pathway known for responding to acid stress plays in biofilm growth and antibiotic tolerance. This not only provides some insight into antibiotic treatment failure in S. pyogenes infections but also, given the widespread nature of this pathway, provides a potentially broad target for antibiofilm therapies. This discovery has the potential to impact the treatment of many different types of recalcitrant biofilm infections.

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Urinary Concentrations of Colistimethate and Formed Colistin after Intravenous Administration in Patients with Multidrug-Resistant Gram-Negative Bacterial Infections

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02595-16 ◽

2017 ◽

Vol 61 (8) ◽

Cited By ~ 12

Author(s):

Sonia Luque ◽

Carol Escaño ◽

Luisa Sorli ◽

Jian Li ◽

Nuria Campillo ◽

...

Keyword(s):

Urinary Excretion ◽

Intravenous Administration ◽

Bacterial Infections ◽

High Performance ◽

Multidrug Resistant ◽

Limited Information ◽

Urinary Recovery ◽

Gram Negative ◽

Content Type ◽

Colistimethate Sodium

ABSTRACT Limited information is available on the urinary excretion of colistin in infected patients. This study aimed to investigate the pharmacokinetics of colistimethate sodium (CMS) and formed colistin in urine in patients with multidrug-resistant (MDR) Gram-negative bacterial infections. A pharmacokinetic study was conducted on 12 patients diagnosed with an infection caused by an extremely drug-resistant (XDR) P. aeruginosa strain and treated with intravenous CMS. Fresh urine samples were collected at 2-h intervals, and blood samples were collected predose (C min ss) and at the end of the CMS infusion (C max ss) for measurement of concentrations of CMS and formed colistin using high-performance liquid chromatography (HPLC). CMS urinary recovery was determined as the summed amount of CMS and formed colistin recovered in urine for each 2-h interval divided by the CMS dose. There were 12 enrolled patients, 9 of whom were male (75%). Data [median (range)] were as follows: age, 65.5 (37 to 86) years; colistimethate urinary recovery 0 to 6 h, 42.6% (2.9% to 72.8%); range of concentrations of colistin in urine, <0.1 to 95.4 mg/liter; C min ss and C max ss of colistin in plasma, 0.9 (<0.2 to 1.4) and 0.9 (<0.2 to 1.4) mg/liter, respectively. In 6/12 (50%) patients, more than 40% of the CMS dose was recovered in the urine within the first 6 h after CMS administration. This study demonstrated rapid urinary excretion of CMS in patients within the first 6 h after intravenous administration. In all but one patient, the concentrations of formed colistin in urine were above the MIC for the most predominant isolate of P. aeruginosa in our hospital. Future studies are warranted for optimizing CMS dosage regimens in urinary tract infection (UTI) patients.

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Nonthermal Plasma Induces the Viable-but-Nonculturable State in Staphylococcus aureus via Metabolic Suppression and the Oxidative Stress Response

Applied and Environmental Microbiology ◽

10.1128/aem.02216-19 ◽

2019 ◽

Vol 86 (5) ◽

Cited By ~ 2

Author(s):

Xinyu Liao ◽

Donghong Liu ◽

Tian Ding

Keyword(s):

Oxidative Stress ◽

Staphylococcus Aureus ◽

Stress Response ◽

Nonthermal Plasma ◽

Energy Allocation ◽

Oxidative Stress Response ◽

Vbnc State ◽

Viable But Nonculturable ◽

Content Type ◽

Energy Dependent

ABSTRACT As a novel nonthermal technology, nonthermal plasma (NTP) has attracted a lot of attention. However, it could induce microorganisms into a viable but nonculturable (VBNC) state, posing a potential risk to food safety and public health. In this study, the molecular mechanisms of VBNC Staphylococcus aureus induced by NTP were investigated. With the use of a propidium monoazide quantitative PCR (PMA-qPCR) technique combined with a plate count method, we confirmed that 8.1 to 24.3 kJ NTP induced S. aureus into a VBNC state at a level of 7.4 to 7.6 log10 CFU/ml. The transcriptomic analysis was conducted and revealed that most energy-dependent physiological activities (e.g., metabolism) were arrested in VBNC S. aureus, while the oxidative stress response-related genes (katA, dps, msrB, msrA, and trxA) were significantly upregulated. In addition, this study showed that the ATP depletion by carbonyl cyanide m-chlorophenyl hydrazone (CCCP) pretreatment could accelerate the formation of VBNC S. aureus. The NTP-generated oxidative stress triggers the staphylococcal oxidative stress response, which consumes part of cellular energy (e.g., ATP). The energy allocation is therefore changed, and the energy assigned for other energy-dependent physiological activities (cell growth and division, etc.) is reduced, subsequently forcing S. aureus into a VBNC state. Therefore, the alterations of energy allocation should be some of the major contributors to the induction of VBNC S. aureus with NTP exposure. This study provides valuable knowledge for controlling the formation of VBNC S. aureus during NTP treatment. IMPORTANCE In recent years, nonthermal plasma (NTP) technology has received a lot of attention as a promising alternative to thermal pasteurization in the food industry. However, little is known about the microbial stress response toward NTP, which could be a potential risk to food safety and impede the development of NTP. A viable but nonculturable (VBNC) state is one of the most common survival strategies employed by microorganisms against external stress. This study investigated the mechanisms of the formation of VBNC Staphylococcus aureus by NTP in a more comprehensive and systematic aspect than had been done before. Our work confirmed that the NTP-generated oxidative stress induced changes in energy allocation as a driving force for the formation of VBNC S. aureus. This study could provide better knowledge for controlling the occurrence of VBNC S. aureus induced by NTP, which could lead to more rational design and ensure the development of safe foods.

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Nitric Oxide Levels Regulate the Immune Response of Drosophila melanogaster Reference Laboratory Strains to Bacterial Infections

Infection and Immunity ◽

10.1128/iai.02318-14 ◽

2014 ◽

Vol 82 (10) ◽

pp. 4169-4181 ◽

Cited By ~ 30

Author(s):

Ioannis Eleftherianos ◽

Kareen More ◽

Stephanie Spivack ◽

Ethan Paulin ◽

Arman Khojandi ◽

...

Keyword(s):

Nitric Oxide ◽

Immune Response ◽

Drosophila Melanogaster ◽

Bacterial Infections ◽

Pathogenic Bacteria ◽

Micrococcus Luteus ◽

The Other ◽

Reference Laboratory ◽

Content Type ◽

Reference Strains

ABSTRACTStudies on the innate immune response against microbial infections inDrosophila melanogasterinvolve mutant strains and their reference strains that act as experimental controls. We used five standardD. melanogasterlaboratory reference strains (Oregon R, w1118, Canton-S, Cinnabar Brown, and Yellow White [YW]) and investigated their response against two pathogenic bacteria (Photorhabdus luminescensandEnterococcus faecalis) and two nonpathogenic bacteria (Escherichia coliandMicrococcus luteus). We detected high sensitivity among YW flies to bacterial infections and increased bacterial growth compared to the other strains. We also found variation in the transcription of certain antimicrobial peptide genes among strains, with Oregon and YW infected flies showing the highest and lowest gene transcription levels in most cases. We show that Oregon and w1118 flies possess more circulating hemocytes and higher levels of phenoloxidase activity than the other strains upon infection with the nonpathogenic bacteria. We further observed reduced fat accumulation in YW flies infected with the pathogenic bacteria, which suggests a possible decline in physiological condition. Finally, we found that nitrite levels are significantly lower in infected and uninfected YW flies compared to w1118 flies and that nitric oxide synthase mutant flies in YW background are more susceptible to bacterial infection compared to mutants in w1118 background. Therefore, increased sensitivity of YW flies to bacterial infections can be partly attributed to lower levels of nitric oxide. Such studies will significantly contribute toward a better understanding of the genetic variation betweenD. melanogaster reference strains.

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Draft Genome Sequence of Pseudarthrobacter sp. Strain ATCC 49442 (Formerly Micrococcus luteus), a Pyridine-Degrading Bacterium

Microbiology Resource Announcements ◽

10.1128/mra.00299-20 ◽

2020 ◽

Vol 9 (38) ◽

Author(s):

Nidhi Gupta ◽

Kelly A. Skinner ◽

Zarath M. Summers ◽

Janaka N. Edirisinghe ◽

Pamela B. Weisenhorn ◽

...

Keyword(s):

Genome Sequence ◽

Micrococcus Luteus ◽

Draft Genome ◽

Gc Content ◽

Draft Genome Sequence ◽

Strain Atcc ◽

Genome Length ◽

Content Type ◽

Degrading Bacterium

ABSTRACT We present here the draft genome sequence of a pyridine-degrading bacterium, Micrococcus luteus ATCC 49442, which was reclassified as Pseudarthrobacter sp. strain ATCC 49442 based on its draft genome sequence. Its genome length is 4.98 Mbp, with 64.81% GC content.

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Viable but Nonculturable Escherichia coli O157:H7 and Salmonella enterica in Fresh Produce: Rapid Determination by Loop-Mediated Isothermal Amplification Coupled with a Propidium Monoazide Treatment

Applied and Environmental Microbiology ◽

10.1128/aem.02566-19 ◽

2020 ◽

Vol 86 (7) ◽

Cited By ~ 2

Author(s):

Lu Han ◽

Kaidi Wang ◽

Lina Ma ◽

Pascal Delaquis ◽

Susan Bach ◽

...

Keyword(s):

Escherichia Coli ◽

Pure Culture ◽

Fresh Produce ◽

Isothermal Amplification ◽

Propidium Monoazide ◽

Vbnc State ◽

Viable But Nonculturable ◽

Content Type ◽

E Coli ◽

Detection And Quantification

ABSTRACT Escherichia coli O157:H7 and Salmonella enterica are leading causes of foodborne outbreaks linked to fresh produce. Both species can enter the “viable but nonculturable” (VBNC) state that precludes detection using conventional culture-based or molecular methods. In this study, we assessed propidium monoazide-quantitative PCR (PMA-qPCR) assays and novel methods combining PMA and loop-mediated isothermal amplification (LAMP) for the detection and quantification of VBNC E. coli O157:H7 and S. enterica in fresh produce. The performance of PMA-LAMP assays targeting the wzy gene of E. coli O157:H7 and the agfA gene of S. enterica and the performance of PMA-qPCR assays were compared in pure culture and spiked tomato, lettuce, and spinach. No cross-reaction was observed in the specificity tests. The values representing the limit of detection (LOD) seen with PMA-LAMP were 9.0 CFU/reaction for E. coli O157:H7 and 4.6 CFU/reaction for S. enterica in pure culture and were 5.13 × 103 or 5.13 × 104 CFU/g for VBNC E. coli O157:H7 and 1.05 × 104 or 1.05 × 105 CFU/g for VBNC S. enterica in fresh produce, representing results comparable to those obtained by PMA-qPCR. Standard curves showed correlation coefficients ranging from 0.925 to 0.996, indicating a good quantitative capacity of PMA-LAMP for determining populations of both bacterial species in the VBNC state. The PMA-LAMP assay was completed with considerable economy of time (30 min versus 1 h) and achieved sensitivity and quantitative capacity comparable to those seen with a PMA-qPCR assay. PMA-LAMP is a rapid, sensitive, and robust method for the detection and quantification of VBNC E. coli O157:H7 and S. enterica in fresh produce. IMPORTANCE VBNC pathogenic bacteria pose a potential risk to the food industry because they do not multiply on routine microbiological media and thus can evade detection in conventional plating assays. Both E. coli O157:H7 and S. enterica have been reported to enter the VBNC state under a range of environmental stress conditions and to resuscitate under favorable conditions and are a potential cause of human infections. PMA-LAMP methods developed in this study provide a rapid, sensitive, and specific way to determine levels of VBNC E. coli O157:H7 and S. enterica in fresh produce, which potentially decreases the risks related to the consumption of fresh produce contaminated by enteric pathogens in this state. PMA-LAMP can be further applied in the field study to enhance our understanding of the fate of VBNC pathogens in the preharvest and postharvest stages of fresh produce.

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Importance of Pyruvate Sensing and Transport for the Resuscitation of Viable but NonculturableEscherichia coliK-12

Journal of Bacteriology ◽

10.1128/jb.00610-18 ◽

2018 ◽

Vol 201 (3) ◽

Cited By ~ 8

Author(s):

Cláudia Vilhena ◽

Eugen Kaganovitch ◽

Alexander Grünberger ◽

Magdalena Motz ◽

Ignasi Forné ◽

...

Keyword(s):

Response Regulator ◽

Bacterial Species ◽

Microfluidic System ◽

Vbnc State ◽

Viable But Nonculturable ◽

Content Type ◽

E Coli ◽

High Affinity ◽

Vbnc Bacteria ◽

K 12

ABSTRACTEscherichia coliand many other bacterial species can enter into a viable but nonculturable (VBNC) state, which is a survival strategy adopted by cells exposed to adverse environmental conditions. Pyruvate is known to be one factor that promotes resuscitation of VBNC cells. Here we studied the role of a pyruvate-sensing network, composed of the histidine kinase-response regulator systems BtsS/BtsR and YpdA/YpdB and the target genebtsT, encoding the high-affinity pyruvate/H+symporter BtsT, in the resuscitation of VBNCE. coliK-12 cells after exposure to cold for 120 days. Analysis of the proteome of VBNC cells revealed upregulation, relative to exponentially growing cells, of BtsT and other proteins involved in pyruvate metabolism. Provision of pyruvate stimulated protein and DNA biosynthesis, and thus resuscitation, in wild-type but notbtsSR ypdABmutant VBNC cells. This result was corroborated by time-dependent tracking of the resuscitation of individual VBNCE. colicells observed in a microfluidic system. Finally, transport assays revealed that14C-labeled pyruvate was rapidly taken up into VBNC cells by BtsT. These results provide the first evidence that pyruvate is taken up as a carbon source for the resuscitation of VBNCE. colicells.IMPORTANCEViable but nonculturable (VBNC) bacteria do not form colonies in standard medium but otherwise retain their metabolic activity and can express toxic proteins. Many bacterial genera, includingEscherichia,Vibrio, andListeria, have been shown to enter the VBNC state upon exposure to adverse conditions, such as low temperature, radiation, and starvation. Ultimately, these organisms pose a public health risk with potential implications for the pharmaceutical and food industries, as dormant organisms are especially difficult to selectively eliminate and VBNC bacteria can be resuscitated if placed in an environment with appropriate nutrition and temperature. Here we used a microfluidic system to monitor the resuscitation of single VBNC cells over time. We provide new molecular insights into the initiation of resuscitation by demonstrating that VBNCE. colicells rapidly take up pyruvate with an inducible high-affinity transporter, whose expression is triggered by the BtsSR-YpdAB sensing network.

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