scholarly journals Biocide Exposure Induces Changes in Susceptibility, Pathogenicity, and Biofilm Formation in Uropathogenic Escherichia coli

2019 ◽  
Vol 63 (3) ◽  
Author(s):  
E. L. Henly ◽  
J. A. R. Dowling ◽  
J. B. Maingay ◽  
M. M. Lacey ◽  
T. J. Smith ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Silver Nitrate ◽  
Biofilm Formation ◽  
Galleria Mellonella ◽  
Bacterial Colonization ◽  
Fibroblast Cell ◽  
Cross Resistance ◽  
Coating Agent ◽  
Content Type

ABSTRACT Uropathogenic Escherichia coli (UPEC) is a frequent cause of catheter-associated urinary tract infection (CAUTI). Biocides have been incorporated into catheter coatings to inhibit bacterial colonization while, ideally, exhibiting low cytotoxicity and mitigating the selection of resistant bacterial populations. We compared the effects of long-term biocide exposure on susceptibility, biofilm formation, and relative pathogenicity in eight UPEC isolates. MICs, minimum bactericidal concentrations (MBCs), minimum biofilm eradication concentrations (MBECs), and antibiotic susceptibilities were determined before and after long-term exposure to triclosan, polyhexamethylene biguanide (PHMB), benzalkonium chloride (BAC), and silver nitrate. Biofilm formation was quantified using a crystal violet assay, and relative pathogenicity was assessed via a Galleria mellonella waxworm model. Cytotoxicity and the resulting biocompatibility index values were determined by use of an L929 murine fibroblast cell line. Biocide exposure resulted in multiple decreases in biocide susceptibility in planktonic and biofilm-associated UPEC. Triclosan exposure induced the largest frequency and magnitude of susceptibility decreases at the MIC, MBC, and MBEC, which correlated with an increase in biofilm biomass in all isolates. Induction of antibiotic cross-resistance occurred in 6/84 possible combinations of bacteria, biocide, and antibiotic. Relative pathogenicity significantly decreased after triclosan exposure (5/8 isolates), increased after silver nitrate exposure (2/8 isolates), and varied between isolates for PHMB and BAC. The biocompatibility index ranked the antiseptic potential as PHMB > triclosan > BAC > silver nitrate. Biocide exposure in UPEC may lead to reductions in biocide and antibiotic susceptibility, changes in biofilm formation, and alterations in relative pathogenicity. These data indicate the multiple consequences of biocide adaptation that should be considered when selecting an anti-infective catheter-coating agent.

scholarly journals Loss of Function inEscherichia coliExposed to Environmentally Relevant Concentrations of Benzalkonium Chloride

2018 ◽  
Vol 85 (4) ◽  
Author(s):  
Sarah Forbes ◽  
Nicola Morgan ◽  
Gavin J. Humphreys ◽  
Alejandro Amézquita ◽  
Hitesh Mistry ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Biofilm Formation ◽  
Benzalkonium Chloride ◽  
Loss Of Function ◽  
Free Medium ◽  
Content Type ◽  
Expression Of Genes ◽  
Repeated Passage

ABSTRACTAssessing the risk of resistance associated with biocide exposure commonly involves exposing microorganisms to biocides at concentrations close to the MIC. With the aim of representing exposure to environmental biocide residues,Escherichia coliMG1655 was grown for 20 passages in the presence or absence of benzalkonium chloride (BAC) at 100 ng/liter and 1,000 ng/liter (0.0002% and 0.002% of the MIC, respectively). BAC susceptibility, planktonic growth rates, motility, and biofilm formation were assessed, and differentially expressed genes were determined via transcriptome sequencing. Planktonic growth rate and biofilm formation were significantly reduced (P< 0.001) following BAC adaptation, while BAC minimum bactericidal concentration increased 2-fold. Transcriptomic analysis identified 289 upregulated and 391 downregulated genes after long-term BAC adaptation compared with the respective control organism passaged in BAC-free medium. When the BAC-adapted bacterium was grown in BAC-free medium, 1,052 genes were upregulated and 753 were downregulated. Repeated passage solely in biocide-free medium resulted in 460 upregulated and 476 downregulated genes compared with unexposed bacteria. Long-term exposure to environmentally relevant BAC concentrations increased the expression of genes associated with efflux and reduced the expression of genes associated with outer-membrane porins, motility, and chemotaxis. This was manifested phenotypically through the loss of function (motility). Repeated passage in a BAC-free environment resulted in the upregulation of multiple respiration-associated genes, which was reflected by increased growth rate. In summary, repeated exposure ofE. colito BAC residues resulted in significant alterations in global gene expression that were associated with minor decreases in biocide susceptibility, reductions in growth rate and biofilm formation, and loss of motility.IMPORTANCEExposure to very low concentrations of biocides in the environment is a poorly understood risk factor for antimicrobial resistance. Repeated exposure to trace levels of the biocide benzalkonium chloride (BAC) resulted in loss of function (motility) and a general reduction in bacterial fitness but relatively minor decreases in susceptibility. These changes were accompanied by widespread changes in theEscherichia colitranscriptome. These results demonstrate the importance of including phenotypic characterization in studies designed to assess the risks of biocide exposure.

scholarly journals Short- and Long-Term Transcriptomic Responses of Escherichia coli to Biocides: a Systems Analysis

2020 ◽  
Vol 86 (14) ◽  
Author(s):  
Beatriz Merchel Piovesan Pereira ◽  
Xiaokang Wang ◽  
Ilias Tagkopoulos
Keyword(s):  
Escherichia Coli ◽  
Stress Response ◽  
Stress Responses ◽  
Zinc Homeostasis ◽  
Cross Resistance ◽  
Transcriptional Responses ◽  
Systematic Analysis ◽  
Content Type ◽  
Short Term Exposure

ABSTRACT The mechanisms of the bacterial response to biocides are poorly understood, despite their broad application. To identify the genetic basis and pathways implicated in the biocide stress response, we exposed Escherichia coli populations to 10 ubiquitous biocides. By comparing the transcriptional responses between a short-term exposure (30 min) and a long-term exposure (8 to 12 h) to biocide stress, we established the common gene and pathway clusters that are implicated in general and biocide-specific stress responses. Our analysis revealed a temporal choreography, starting from the upregulation of chaperones to the subsequent repression of motility and chemotaxis pathways and the induction of an anaerobic pool of enzymes and biofilm regulators. A systematic analysis of the transcriptional data identified a zur-regulated gene cluster to be highly active in the stress response against sodium hypochlorite and peracetic acid, presenting a link between the biocide stress response and zinc homeostasis. Susceptibility assays with knockout mutants further validated our findings and provide clear targets for downstream investigation of the implicated mechanisms of action. IMPORTANCE Antiseptics and disinfectant products are of great importance to control and eliminate pathogens, especially in settings such as hospitals and the food industry. Such products are widely distributed and frequently poorly regulated. Occasional outbreaks have been associated with microbes resistant to such compounds, and researchers have indicated potential cross-resistance with antibiotics. Despite that, there are many gaps in knowledge about the bacterial stress response and the mechanisms of microbial resistance to antiseptics and disinfectants. We investigated the stress response of the bacterium Escherichia coli to 10 common disinfectant and antiseptic chemicals to shed light on the potential mechanisms of tolerance to such compounds.

PBP4 and PBP5 are involved in regulating exopolysaccharide synthesis during Escherichia coli biofilm formation

Microbiology ◽  
2021 ◽  
Vol 167 (3) ◽  
Author(s):  
Sathi Mallick ◽  
Shanti Kiran ◽  
Tapas Kumar Maiti ◽  
Anindya S. Ghosh
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Type Species ◽  
Pentose Phosphate ◽  
Bacterial Cells ◽  
Surface Adhesion ◽  
Content Type ◽  
Penicillin Binding Proteins ◽  
E Coli ◽  
Link Type

Escherichia coli low-molecular-mass (LMM) Penicillin-binding proteins (PBPs) help in hydrolysing the peptidoglycan fragments from their cell wall and recycling them back into the growing peptidoglycan matrix, in addition to their reported involvement in biofilm formation. Biofilms are external slime layers of extra-polymeric substances that sessile bacterial cells secrete to form a habitable niche for themselves. Here, we hypothesize the involvement of Escherichia coli LMM PBPs in regulating the nature of exopolysaccharides (EPS) prevailing in its extra-polymeric substances during biofilm formation. Therefore, this study includes the assessment of physiological characteristics of E. coli CS109 LMM PBP deletion mutants to address biofilm formation abilities, viability and surface adhesion. Finally, EPS from parent CS109 and its ΔPBP4 and ΔPBP5 mutants were purified and analysed for sugars present. Deletions of LMM PBP reduced biofilm formation, bacterial adhesion and their viability in biofilms. Deletions also diminished EPS production by ΔPBP4 and ΔPBP5 mutants, purification of which suggested an increased overall negative charge compared with their parent. Also, EPS analyses from both mutants revealed the appearance of an unusual sugar, xylose, that was absent in CS109. Accordingly, the reason for reduced biofilm formation in LMM PBP mutants may be speculated as the subsequent production of xylitol and a hindrance in the standard flow of the pentose phosphate pathway.

scholarly journals Evolution of Rifampin Resistance in Escherichia coli and Mycobacterium smegmatis Due to Substandard Drugs

2018 ◽  
Vol 63 (1) ◽  
Author(s):  
Zohar B. Weinstein ◽  
Muhammad H. Zaman
Keyword(s):  
Escherichia Coli ◽  
Mycobacterium Smegmatis ◽  
Degradation Products ◽  
Treatment Options ◽  
Poor Quality ◽  
Cross Resistance ◽  
Standard Drug ◽  
Content Type ◽  
Drug Degradation ◽  
Rifampin Resistance

ABSTRACT Poor-quality medicines undermine the treatment of infectious diseases, such as tuberculosis, which require months of treatment with rifampin and other drugs. Rifampin resistance is a critical concern for tuberculosis treatment. While subtherapeutic doses of medicine are known to select for antibiotic resistance, the effect of drug degradation products on the evolution of resistance is unknown. Here, we demonstrate that substandard drugs that contain degraded active pharmaceutical ingredients select for gene alterations that confer resistance to standard drugs. We generated drug-resistant Escherichia coli and Mycobacterium smegmatis strains by serially culturing bacteria in the presence of the rifampin degradation product rifampin quinone. We conducted Sanger sequencing to identify mutations in rifampin-resistant populations. Strains resistant to rifampin quinone developed cross-resistance to the standard drug rifampin, with some populations showing no growth inhibition at maximum concentrations of rifampin. Sequencing of the rifampin quinone-treated strains indicated that they acquired mutations in the DNA-dependent RNA polymerase B subunit. These mutations were localized in the rifampin resistance-determining region (RRDR), consistent with other reports of rifampin-resistant E. coli and mycobacteria. Rifampin quinone-treated mycobacteria also had cross-resistance to other rifamycin class drugs, including rifabutin and rifapentine. Our results strongly suggest that substandard drugs not only hinder individual patient outcomes but also restrict future treatment options by actively contributing to the development of resistance to standard medicines.

scholarly journals Novel regulators of the csgD gene encoding the master regulator of biofilm formation in Escherichia coli K-12

Microbiology ◽  
2020 ◽  
Vol 166 (9) ◽  
pp. 880-890 ◽  
Author(s):  
Hiroshi Ogasawara ◽  
Toshiyuki Ishizuka ◽  
Shuhei Hotta ◽  
Michiko Aoki ◽  
Tomohiro Shimada ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Cell Aggregation ◽  
Master Regulator ◽  
Gene Encoding ◽  
Content Type ◽  
Promoter Probe ◽  
K 12 ◽  
Specific Environmental Condition

Under stressful conditions, Escherichia coli forms biofilm for survival by sensing a variety of environmental conditions. CsgD, the master regulator of biofilm formation, controls cell aggregation by directly regulating the synthesis of Curli fimbriae. In agreement of its regulatory role, as many as 14 transcription factors (TFs) have so far been identified to participate in regulation of the csgD promoter, each monitoring a specific environmental condition or factor. In order to identify the whole set of TFs involved in this typical multi-factor promoter, we performed in this study ‘promoter-specific transcription-factor’ (PS-TF) screening in vitro using a set of 198 purified TFs (145 TFs with known functions and 53 hitherto uncharacterized TFs). A total of 48 TFs with strong binding to the csgD promoter probe were identified, including 35 known TFs and 13 uncharacterized TFs, referred to as Y-TFs. As an attempt to search for novel regulators, in this study we first analysed a total of seven Y-TFs, including YbiH, YdcI, YhjC, YiaJ, YiaU, YjgJ and YjiR. After analysis of curli fimbriae formation, LacZ-reporter assay, Northern-blot analysis and biofilm formation assay, we identified at least two novel regulators, repressor YiaJ (renamed PlaR) and activator YhjC (renamed RcdB), of the csgD promoter.

scholarly journals Evaluation of Changes Induced in the Probiotic Escherichia coli M17 Following Recurrent Exposure to Antimicrobials

2021 ◽  
pp. 158-167
Author(s):  
M. J. A. Mbarga ◽  
I. V. Podoprigora ◽  
E. G. Volina ◽  
A. V. Ermolaev ◽  
L. A. Smolyakova
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Silver Nanoparticles ◽  
Biofilm Formation ◽  
Fold Increase ◽  
Bacterial Attachment ◽  
Diffusion Method ◽  
Cross Resistance ◽  
Microdilution Method ◽  
Similar Work

Introduction: It is already well known that the exposure of certain bacteria, pathogenic or not, to antimicrobials is likely to increase their virulence and induce the development of direct or cross resistance to antimicrobials, but there is almost no information available regarding probiotics. Aim: To assess the changes induced in susceptibility to antibiotics, biofilm formation, growth rate and relative pathogenicity in the probiotic Escherichia coli M17 (EC-M17) after long exposure to antimicrobials namely ampicillin, kanamycin, cefazolin and silver nanoparticles (AgNPs). Methods: After determining the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of the 4 antimicrobials above-mentioned by the microdilution method, EC-M17 was exposed to increasing subinhibitory doses ranging from MIC/8 to MIC for 8 days. The susceptibility to antibiotics of the mutants obtained was assessed by the Kirby Bauer disc diffusion method, biofilm formation by the Congo red agar method and with crystal violet bacterial attachment assay, and relative pathogenicity was assessed using a Galleria melonella waxworm model. Results: Exposure to antimicrobials induces noticeable changes in EC-M17. The highest adaptation to antimicrobials was observed on AgNPs with 8-fold increase in MIC and 16-fold increase in MBC of AgNPs. EC-M17 exposed to ampicillin, kanamycin and silver nanoparticles became resistant to ampicillin, ceftazidime, ceftazidime/clavulanate and tetracycline while exposure to cefazolin induced a significant decrease in sensitivity to tetracycline and ampicillin and resistance to ceftazidime/clavulanate and ceftazidime. The strain exposed to ampicillin was the only one to produce more biofilm than the control strain and except the EC-M17 exposed to cefazolin, all other EC-M17 strains were more pathogenic on G. melonella model than the control. Conclusion: Data in this investigation suggest that repeated exposure of the probiotic EC-M17 to antimicrobials may induce changes in antimicrobials susceptibility, biofilm formation, growth rate, and relative pathogenicity. Therefore, as far as possible, the probiotic E. coli M17 should not be used in combination with antibiotics and further investigations are required to expand similar work on more probiotics in order to avoid resistance build-up which might be transmitted by horizontal transfer.

scholarly journals Influence of Type I Fimbriae and Fluid Shear Stress on Bacterial Behavior and Multicellular Architecture of Early Escherichia coli Biofilms at Single-Cell Resolution

2018 ◽  
Vol 84 (6) ◽  
Author(s):  
Liyun Wang ◽  
Robert Keatch ◽  
Qi Zhao ◽  
John A. Wright ◽  
Clare E. Bryant ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Shear Stress ◽  
Single Cell ◽  
Biofilm Formation ◽  
Fluid Shear Stress ◽  
Cell Membrane Permeability ◽  
Type I ◽  
Fluid Shear ◽  
Content Type ◽  
Type I Fimbriae

ABSTRACT Biofilm formation on abiotic surfaces in the food and medical industry can cause severe contamination and infection, yet how biological and physical factors determine the cellular architecture of early biofilms and the bacterial behavior of the constituent cells remains largely unknown. In this study, we examined the specific role of type I fimbriae in nascent stages of biofilm formation and the response of microcolonies to environmental flow shear at the single-cell resolution. The results show that type I fimbriae are not required for reversible adhesion from plankton, but they are critical for the irreversible adhesion of Escherichia coli strain MG1655 cells that form biofilms on polyethylene terephthalate (PET) surfaces. Besides establishing firm cell surface contact, the irreversible adhesion seems necessary to initiate the proliferation of E. coli on the surface. After the application of shear stress, bacterial retention is dominated by the three-dimensional architecture of colonies, independent of the population size, and the multilayered structure could protect the embedded cells from being insulted by fluid shear, while the cell membrane permeability mainly depends on the biofilm population size and the duration of the shear stress. IMPORTANCE Bacterial biofilms could lead to severe contamination problems in medical devices and food processing equipment. However, biofilms are usually studied at a rough macroscopic level; thus, little is known about how individual bacterium behavior within biofilms and the multicellular architecture are influenced by bacterial appendages (e.g., pili/fimbriae) and environmental factors during early biofilm formation. We applied confocal laser scanning microscopy (CLSM) to visualize Escherichia coli microcolonies at a single-cell resolution. Our findings suggest that type I fimbriae are vital to the initiation of bacterial proliferation on surfaces. We also found that the fluid shear stress affects the biofilm architecture and cell membrane permeability of the constituent bacteria in a different way: the onset of the biofilm is linked with the three-dimensional morphology, while membranes are regulated by the overall population of microcolonies.

scholarly journals A Light-Regulated Type I Pilus Contributes toAcinetobacter baumanniiBiofilm, Motility, and Virulence Functions

2018 ◽  
Vol 86 (9) ◽  
Author(s):  
Cecily R. Wood ◽  
Emily J. Ohneck ◽  
Richard E. Edelmann ◽  
Luis A. Actis
Keyword(s):  
Biofilm Formation ◽  
Galleria Mellonella ◽  
Alveolar Epithelial Cells ◽  
Ecological Niches ◽  
Type I ◽  
Pellicle Formation ◽  
Content Type ◽  
Alveolar Epithelial ◽  
Abiotic Surfaces ◽  
Cells Cultured

ABSTRACTTranscriptional analyses ofAcinetobacter baumanniiATCC 17978 showed that the expression of A1S_2091 was enhanced in cells cultured in darkness at 24°C through a process that depended on the BlsA photoreceptor. Disruption of A1S_2091, a component of the A1S_2088-A1S_2091 polycistronic operon predicted to code for a type I chaperone/usher pilus assembly system, abolished surface motility and pellicle formation but significantly enhanced biofilm formation on plastic by bacteria cultured in darkness. Based on these observations, the A1S_2088-A1S_2091 operon was named thephotoregulatedpilus ABCD (prpABCD) operon, with A1S_2091 coding for the PrpA pilin subunit. Unexpectedly, comparative analyses of ATCC 17978 andprpAisogenic mutant cells cultured at 37°C showed the expression of light-regulated biofilm biogenesis and motility functions under a temperature condition that drastically affects BlsA production and its light-sensing activity. These assays also suggest that ATCC 17978 cells produce alternative light-regulated adhesins and/or pilus systems that enhance bacterial adhesion and biofilm formation at both 24°C and 37°C on plastic as well as on the surface of polarized A549 alveolar epithelial cells, where the formation of bacterial filaments and cell chains was significantly enhanced. The inactivation ofprpAalso resulted in a significant reduction in virulence when tested by using theGalleria mellonellavirulence model. All these observations provide strong evidence showing the capacity ofA. baumanniito sense light and interact with biotic and abiotic surfaces using undetermined alternative sensing and regulatory systems as well as alternative adherence and motility cellular functions that allow this pathogen to persist in different ecological niches.

scholarly journals Bioinformatic and Molecular Analysis of Inverse Autotransporters from Escherichia coli

mSphere ◽  
2019 ◽  
Vol 4 (4) ◽  
Author(s):  
Kelvin G. K. Goh ◽  
Danilo G. Moriel ◽  
Steven J. Hancock ◽  
Minh-Duy Phan ◽  
Mark A. Schembri
Keyword(s):  
Escherichia Coli ◽  
Cell Surface ◽  
Biofilm Formation ◽  
Secretion System ◽  
Content Type ◽  
E Coli ◽  
Wide Range ◽  
Type V Secretion ◽  
K 12 ◽  
Type V

ABSTRACT Proteins secreted by the type V secretion system possess multiple functions, including the capacity to mediate adhesion, aggregation, and biolfilm formation. The type V secretion system can be divided into five subclasses, one of which is the type Ve system. Proteins of the type Ve secretion system are also referred to as inverse autotransporters (IATs). In this study, we performed an in silico analysis of 126 completely sequenced Escherichia coli genomes available in the NCBI database and identified several distinct IAT-encoding gene families whose distribution varied throughout the E. coli phylogeny. The genes included three characterized IATs (intimin, fdeC, and yeeJ) and four uncharacterized IATs (here named iatA, iatB, iatC, and iatD). The four iat genes were cloned from the completely sequenced environmental E. coli strain SMS-3-5 and characterized. Three of these IAT proteins (IatB, IatC, and IatD) were expressed at the cell surface and possessed the capacity to mediate biofilm formation in a recombinant E. coli K-12 strain. Further analysis of the iatB gene, which showed a unique association with extraintestinal E. coli strains, suggested that its regulation is controlled by the LeuO global regulator. Overall, this study provides new data describing the prevalence, sequence variation, domain structure, function, and regulation of IATs found in E. coli. IMPORTANCE Escherichia coli is one of the most prevalent facultative anaerobes of the human gut. E. coli normally exists as a harmless commensal but can also cause disease following the acquisition of genes that enhance its pathogenicity. Adhesion is an important first step in colonization of the host and is mediated by an array of cell surface components. In E. coli, these include a family of adhesins secreted by the type V secretion system. Here, we identified and characterized new proteins from an emerging subclass of the type V secretion system known as the inverse autotransporters (IATs). We found that IAT-encoding genes are present in a wide range of strains and showed that three novel IATs were localized on the E. coli cell surface and mediated biofilm formation. Overall, this study provides new insight into the prevalence, function, and regulation of IATs in E. coli.

scholarly journals Proteorhodopsin Overproduction Enhances the Long-Term Viability of Escherichia coli

2019 ◽  
Vol 86 (1) ◽  
Author(s):  
Yizhi Song ◽  
Michaël L. Cartron ◽  
Philip J. Jackson ◽  
Paul A. Davison ◽  
Mark J. Dickman ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Raman Spectroscopy ◽  
Cell Membrane ◽  
Single Cell ◽  
Marine Bacteria ◽  
Membrane Area ◽  
Content Type ◽  
E Coli ◽  
Wide Range

ABSTRACT Genes encoding the photoreactive protein proteorhodopsin (PR) have been found in a wide range of marine bacterial species, reflecting the significant contribution that PR makes to energy flux and carbon cycling in ocean ecosystems. PR can also confer advantages to enhance the ability of marine bacteria to survive periods of starvation. Here, we investigate the effect of heterologously produced PR on the viability of Escherichia coli. Quantitative mass spectrometry shows that E. coli, exogenously supplied with the retinal cofactor, assembles as many as 187,000 holo-PR molecules per cell, accounting for approximately 47% of the membrane area; even cells with no retinal synthesize ∼148,000 apo-PR molecules per cell. We show that populations of E. coli cells containing PR exhibit significantly extended viability over many weeks, and we use single-cell Raman spectroscopy (SCRS) to detect holo-PR in 9-month-old cells. SCRS shows that such cells, even incubated in the dark and therefore with inactive PR, maintain cellular levels of DNA and RNA and avoid deterioration of the cytoplasmic membrane, a likely basis for extended viability. The substantial proportion of the E. coli membrane required to accommodate high levels of PR likely fosters extensive intermolecular contacts, suggested to physically stabilize the cell membrane and impart a long-term benefit manifested as extended viability in the dark. We propose that marine bacteria could benefit similarly from a high PR content, with a stabilized cell membrane extending survival when those bacteria experience periods of severe nutrient or light limitation in the oceans. IMPORTANCE Proteorhodopsin (PR) is part of a diverse, abundant, and widespread superfamily of photoreactive proteins, the microbial rhodopsins. PR, a light-driven proton pump, enhances the ability of the marine bacterium Vibrio strain AND4 to survive and recover from periods of starvation, and heterologously produced PR extends the viability of nutrient-limited Shewanella oneidensis. We show that heterologously produced PR enhances the viability of E. coli cultures over long periods of several weeks and use single-cell Raman spectroscopy (SCRS) to detect PR in 9-month-old cells. We identify a densely packed and consequently stabilized cell membrane as the likely basis for extended viability. Similar considerations are suggested to apply to marine bacteria, for which high PR levels represent a significant investment in scarce metabolic resources. PR-stabilized cell membranes in marine bacteria are proposed to keep a population viable during extended periods of light or nutrient limitation, until conditions improve.

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