Changes in Escherichia coli outer membrane subproteome under environmental conditions inducing the viable but nonculturable state

Muela, A.; Seco, Carolina; Camafeita, Emilio; Arana, Inés; Orruño, Maite; López, Juan Antonio; Barcina, Isabel

doi:10.1111/j.1574-6941.2008.00453.x

Cited by 74 publications

(73 citation statements)

References 67 publications

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“…Alternatively, the overexpression of efflux pumps may also result in the loss of nutrients and metabolic intermediates necessary for growth or survival (67), which are likely to be particularly important in stationary phase. For instance, TolC protein expression levels have been reported to be lower than the maximum levels during starvation in PBS at 20°C when E. coli cells are in a viable-but-nonculturable (VBNC) state (68); this reduction in TolC expression may be due to the posttranscriptional regulation by SdsR.…”

Section: Discussionmentioning

confidence: 99%

Small RNA Regulation of TolC, the Outer Membrane Component of Bacterial Multidrug Transporters

Parker

Gottesman

2016

J Bacteriol

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Bacteria use multidrug efflux pumps to export drugs and toxic compounds out of the cell. One of the most important efflux pumps in Escherichia coli is the AcrAB-TolC system. Small regulatory RNAs (sRNAs) are known to be major posttranscriptional regulators that can enhance or repress translation by binding to the 5= untranslated region (UTR) of mRNA targets with the help of a chaperone protein, Hfq. In this study, we investigated the expression of acrA, acrB, and tolC translational fusions using 27 Hfq-dependent sRNAs overexpressed from plasmids. No significant sRNA regulation of acrA or acrB was detected. SdsR (also known as RyeB), an abundant and well-conserved stationary-phase sRNA, was found to repress the expression of tolC, the gene encoding the outer membrane protein of many multidrug resistance efflux pumps. This repression was shown to be by direct base pairing occurring upstream from the ribosomal binding site. SdsR overexpression and its regulation of tolC were found to reduce resistance to novobiocin and crystal violet. Our results suggest that additional targets for SdsR exist that contribute to increased antibiotic sensitivity and reduced biofilm formation. In an effort to identify phenotypes associated with single-copy SdsR and its regulation of tolC, the effect of a deletion of sdsR or mutations in tolC that should block SdsR pairing were investigated using a Biolog phenotypic microarray. However, no significant phenotypes were identified. Therefore, SdsR appears to modulate rather than act as a major regulator of its targets. IMPORTANCEAcrAB-TolC is a major efflux pump present in E. coli and Gram-negative bacteria used to export toxic compounds; the pump confers resistance to many antibiotics of unrelated classes. In this study, we found that SdsR, a small RNA expressed in stationary phase, repressed the expression of tolC, resulting in increased sensitivity to some antibiotics. This extends the findings of previous studies showing that sRNAs contribute to the regulation of many outer membrane proteins; manipulating or enhancing their action might help in sensitizing bacteria to antibiotics.

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Section: Discussionmentioning

confidence: 99%

Small RNA Regulation of TolC, the Outer Membrane Component of Bacterial Multidrug Transporters

Parker

Gottesman

2016

J Bacteriol

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“…Discrepancies between the total heterotrophic cell counts and gene abundances could be due to a number of reasons such as the E. coli cells entering a VBNC state upon inoculation into drinking water (60). No differentiation can be made between DNA from viable and nonviable cells.…”

Section: Discussionmentioning

confidence: 99%

Survival, Biofilm Formation, and Growth Potential of Environmental and Enteric Escherichia coli Strains in Drinking Water Microcosms

Abberton

Bereschenko

Wielen

et al. 2016

Appl Environ Microbiol

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Escherichia coli is the most commonly used indicator for fecal contamination in drinking water distribution systems (WDS). The assumption is that E. coli bacteria are of enteric origin and cannot persist for long outside their host and therefore act as indicators of recent contamination events. This study investigates the fate of E. coli in drinking water, specifically addressing survival, biofilm formation under shear stress, and regrowth in a series of laboratory-controlled experiments. We show the extended persistence of three E. coli strains (two enteric isolates and one soil isolate) in sterile and nonsterile drinking water microcosms at 8 and 17°C, with T 90 (time taken for a reduction in cell number of 1 log 10 unit) values ranging from 17.4 ؎ 1.8 to 149 ؎ 67.7 days, using standard plate counts and a series of (reverse transcription-)quantitative PCR [(RT-)Q-PCR] assays targeting 16S rRNA, tuf, uidA, and rodA genes and transcripts. Furthermore, each strain was capable of attaching to a surface and replicating to form biofilm in the presence of nutrients under a range of shear stress values (0.6, 2.0, and 4.4 dynes [dyn] cm ؊2 ; BioFlux system; Fluxion); however, cell numbers did not increase when drinking water flowed over the biofilm (P > 0.05 by t test). Finally, E. coli regrowth within drinking water microcosms containing polyethylene PE-100 pipe wall material was not observed in the biofilm or water phase using a combination of culturing and Q-PCR methods for E. coli. The results of this work highlight that when E. coli enters drinking water it has the potential to survive and attach to surfaces but that regrowth within drinking water or biofilm is unlikely. IMPORTANCEThe provision of clean, safe drinking water is fundamental to society. WDS deliver water to consumers via a vast network of pipes. E. coli is used as an indicator organism for recent contamination events based on the premise that it cannot survive for long outside its host. A key public health concern therefore arises around the fate of E. coli on entering a WDS; its survival, ability to form a biofilm, and potential for regrowth. In particular, if E. coli bacteria have the ability to incorporate and regrow within the pipe wall biofilm of a WDS, they could reinoculate the water at a later stage. This study sheds light on the fate of environmental and enteric strains of E. coli in drinking water showing extended survival, the potential for biofilm formation under shear stress, and importantly, that regrowth in the presence of an indigenous microbial community is unlikely. S afe, clean drinking water is the foundation of society. However, even in developed countries, drinking water quality failures occur and have considerable public health impact. In particular, microbiological quality failures can be a significant threat to the supply of drinking water. The exact cause of these water quality malfunctions can be difficult to determine. In public water supplies, inefficient water treatment of the source could result in unwanted micr...

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“…Although these microorganisms are not recoverable in standard culture media, they demonstrate metabolic activity and maintain their pathogenic features. 13 Stress factors which are responsible for the VBNC state may include UV exposure, antimicrobial agents, pH and temperature changes, and carbon and energy starvation.…”

Section: 7-10mentioning

confidence: 99%

Disinfection of water and wastewater by UV-A and UV-C irradiation: application of real-time PCR method

Chatzisymeon

Droumpali

Mantzavinos

et al. 2011

Photochem Photobiol Sci

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PapersPerformance of the photo-Fenton process in the degradation of a model azo dye mixture J. Macías-Sánchez et al., Photochem. Photobiol. Sci., 2011, 10 The disinfection efficiency of synthetic and real wastewater by means of UV-A and UV-C irradiation in the presence or absence of TiO 2 was investigated. A reference strain of Escherichia coli suspended in sterile 0.8% (w/v) NaCl aqueous solution was used as a synthetic wastewater, while real wastewater samples were collected from the outlet of the secondary treatment of a municipal wastewater treatment plant. E. coli inactivation was monitored both by the conventional culture technique and by the real-time PCR method. Culture method showed that UV-C irradiation (11 W lamp) achieved total E. coli inactivation of 100% within 3 min of photolytic treatment. On the other hand, UV-A (9 W lamp)/TiO 2 ; [TiO 2 ] = 200 mg L -1 (i.e. best operating conditions) required 60 min to achieve total disinfection of the synthetic wastewater. Real time PCR revealed compatible results, regarding the better efficiency of UV-C. However, it showed different times of bacterial inactivation, probably due to the phenomenon of "viable but not culturable bacteria". Disinfection durability tests in the dark and under natural sunlight irradiation showed that there is cell repair when UV-C irradiation is used for synthetic wastewater disinfection. Regarding real wastewater it was observed that only UV-C irradiation was capable of totally inactivating E. coli population in short time. Comparing results obtained from both methods, real time PCR proved to be more reliable and accurate, concerning the bacterial detection and enumeration in aquatic samples after the application of UV irradiation.

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Changes in Escherichia coli outer membrane subproteome under environmental conditions inducing the viable but nonculturable state

Cited by 74 publications

References 67 publications

Small RNA Regulation of TolC, the Outer Membrane Component of Bacterial Multidrug Transporters

Small RNA Regulation of TolC, the Outer Membrane Component of Bacterial Multidrug Transporters

Survival, Biofilm Formation, and Growth Potential of Environmental and Enteric Escherichia coli Strains in Drinking Water Microcosms

Disinfection of water and wastewater by UV-A and UV-C irradiation: application of real-time PCR method

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