Linking bacteriophage infection to quorum sensing signalling and bioluminescent bioreporter monitoring for direct detection of bacterial agents

How Broad Is Enough: The Host Range of Bacteriophages and Its Impact on the Agri-Food Sector

Novel bacteriophages (phages) possessing a broad host range are consistently and routinely reported, yet there is presently no consensus on the definition of "broad host range." As phages are increasingly being used in the development of methods for the detection and biocontrol of human pathogens, it is important to address the limitations associated with the host range. For instance, unanticipated host range breadth may result in the detection of nonpathogenic targets, thereby increasing the false-positive rate. Moreover, a broad host range is generally favored in biocontrol applications despite the risk of undesirable ancillary effects against nontarget species. Here, we discuss the research progress, applications, and implications of broad host range phages with a focus on tailed broad host range phages infecting human pathogens of concern in the Agri-Food sector.

The Application of Bacteriophage Diagnostics for Bacterial Pathogens in the Agricultural Supply Chain: From Farm-to-Fork

Bacteriophages (phages) have great potential not only as therapeutics but as diagnostics. Indeed, they have been developed and used to diagnose and detect bacterial infections, primarily in human clinical settings. The ability to rapidly detect and control bacterial pathogens in agriculture is of primary importance to maintain food security, improve animal health, and prevent the passage of zoonotic pathogens into the human population. Culture-based detection methods are often labor-intensive, and require further confirmatory tests, increasing costs and processing times needed for diagnostics. Molecular detection methods such as polymerase chain reaction are commonly used to determine the safety of food, however, a major drawback is their inability to differentiate between viable and nonviable bacterial pathogens in food. Phage diagnostics have been proven to be rapid, capable of identifying viable pathogens and do not require cultivation to detect bacteria. Phage detection takes advantage of the specificity of interaction between phage and their hosts. Furthermore, phage detection is cost effective, which is vitally important in agricultural supply chains where there is a drive to keep costs down to ensure that the cost of food does not increase. The full potential of phage detection/diagnostics is not wholly realized or commercialized. This review explores the current use and potential future scope of phage diagnostics and their application to various bacterial pathogens across agriculture and food supply chains.

Quorum Sensing Communication: Molecularly Connecting Cells, Their Neighbors, and Even Devices

Quorum sensing (QS) is a molecular signaling modality that mediates molecular-based cell–cell communication. Prevalent in nature, QS networks provide bacteria with a method to gather information from the environment and make decisions based on the intel. With its ability to autonomously facilitate both inter- and intraspecies gene regulation, this process can be rewired to enable autonomously actuated, but molecularly programmed, genetic control. On the one hand, novel QS-based genetic circuits endow cells with smart functions that can be used in many fields of engineering, and on the other, repurposed QS circuitry promotes communication and aids in the development of synthetic microbial consortia. Furthermore, engineered QS systems can probe and intervene in interkingdom signaling between bacteria and their hosts. Lastly, QS is demonstrated to establish conversation with abiotic materials, especially by taking advantage of biological and even electronically induced assembly processes; such QS-incorporated biohybrid devices offer innovative ways to program cell behavior and biological function.

Detection of Escherichia coli in ready-to-eat fresh vegetables using broad-host-range recombinant phages

AIM

To construct a simple method to detect Escherichia coli in ready-to-eat fresh vegetables using broad-host-range recombinant phages.

METHODS AND RESULTS

Firstly, a gene encoding cytochrome c peroxidase (CCP) chromogenic enzyme was inserted into genomes of wild-type phages IP008 and IP052 to produce recombinant phages IP008BK and IP052BK. They were then used in the production of the chromogenic enzyme (CCP) through infection into E. coli. The method was then examined in the colorimetric detection of E. coli K12 in broth, and its appearance was confirmed by a significant change in absorbance after a few minutes of the enzyme assay. Secondly, the protocol using the recombinant phages for the detection of E. coli in vegetables, that is, lettuce and mustard greens, was investigated. A low E. coli concentration at 4 CFU per g vegetable was detected within 16·5 h that is of a shorter duration than agar plate methods and in some commonly known phage-based methods.

CONCLUSION

The existence of E. coli as a faecal contamination indicator in two types of ready-to-eat fresh vegetables, that is, lettuce and mustard greens, can be identified by the broad-host-range recombinant phages.

SIGNIFICANCE AND IMPACT OF STUDY

The method is simple and convenient since it enables the detection of E. coli without expensive apparatus. It is applicable to other types of food samples.

Biocontrol and Rapid Detection of Food-Borne Pathogens Using Bacteriophages and Endolysins

Bacteriophages have been suggested as natural food preservatives as well as rapid detection materials for food-borne pathogens in various foods. Since Listeria monocytogenes-targeting phage cocktail (ListShield) was approved for applications in foods, numerous phages have been screened and experimentally characterized for phage applications in foods. A single phage and phage cocktail treatments to various foods contaminated with food-borne pathogens including E. coli O157:H7, Salmonella enterica, Campylobacter jejuni, Listeria monocytogenes, Staphylococcus aureus, Cronobacter sakazakii, and Vibrio spp. revealed that they have great potential to control various food-borne pathogens and may be alternative for conventional food preservatives. In addition, phage-derived endolysins with high host specificity and host lysis activities may be preferred to food applications rather than phages. For rapid detection of food-borne pathogens, cell-wall binding domains (CBDs) from endolysins have been suggested due to their high host-specific binding. Fluorescence-tagged CBDs have been successfully evaluated and suggested to be alternative materials of expensive antibodies for various detection applications. Most recently, reporter phage systems have been developed and tested to confirm their usability and accuracy for specific detection. These systems revealed some advantages like rapid detection of only viable pathogenic cells without interference by food components in a very short reaction time, suggesting that these systems may be suitable for monitoring of pathogens in foods. Consequently, phage is the next-generation biocontrol agent as well as rapid detection tool to confirm and even identify the food-borne pathogens present in various foods.

Phage-based detection of bacterial pathogens

Bacterial pathogens cause significant morbidity and mortality annually to both humans and animals. With the rampant spread of drug resistance and the diminishing effectiveness of current antibiotics, there is a pressing need for effective diagnostics for detection of bacterial pathogens and their drug resistances. Bacteriophages offer several unique opportunities for bacterial detection. This review highlights the means by which bacteriophages have been utilized to achieve and facilitate specific bacterial detection.

Bacteriophages: biosensing tools for multi-drug resistant pathogens

Pathogen detection is of utmost importance in many sectors, such as in the food industry, environmental quality control, clinical diagnostics, bio-defence and counter-terrorism. Failure to appropriately, and specifically, detect pathogenic bacteria can lead to serious consequences, and may ultimately be lethal. Public safety, new legislation, recent outbreaks in food contamination, and the ever-increasing prevalence of multidrug-resistant infections have fostered a worldwide research effort targeting novel biosensing strategies. This review concerns phage-based analytical and biosensing methods targeted towards theranostic applications. We discuss and review phage-based assays, notably phage amplification, reporter phage, phage lysis, and bioluminescence assays for the detection of bacterial species, as well as phage-based biosensors, including optical (comprising SPR sensors and fiber optic assays), electrochemical (comprising amperometric, potentiometric, and impedimetric sensors), acoustic wave and magnetoelastic sensors.

Bacteriophage-based pathogen detection

Considered the most abundant organism on Earth, at a population approaching 10(31), bacteriophage, or phage for short, mediate interactions with myriad bacterial hosts that has for decades been exploited in phage typing schemes for signature identification of clinical, food-borne, and water-borne pathogens. With over 5,000 phage being morphologically characterized and grouped as to susceptible host, there exists an enormous cache of bacterial-specific sensors that has more recently been incorporated into novel bio-recognition assays with heightened sensitivity, specificity, and speed. These assays take many forms, ranging from straightforward visualization of labeled phage as they attach to their specific bacterial hosts to reporter phage that genetically deposit trackable signals within their bacterial hosts to the detection of progeny phage or other uniquely identifiable elements released from infected host cells. A comprehensive review of these and other phage-based detection assays, as directed towards the detection and monitoring of bacterial pathogens, will be provided in this chapter.

Development of an engineered bioluminescent reporter phage for the sensitive detection of viable Salmonella typhimurium

Because foodborne illnesses continuously threaten public health, rapid and sensitive detection of pathogens in food has become an important issue. As an alternative to time-consuming and laborious conventional detection methods, a technique using recombinant reporter phages has been developed. Here, we developed an advanced bioluminescent reporter phage SPC32H-CDABE by inserting a bacterial luxCDABE operon into the Salmonella temperate phage SPC32H genome. Whole SPC32H genome sequencing enabled the selection of nonessential genes, which can be replaced with approximately 6-kb luxCDABE operon, which provides both luciferase (LuxAB) and its substrate, fatty aldehyde, as generated by fatty acid reductase (LuxCDE). Thus, the SPC32H-CDABE detection assay is simpler and more efficient compared to the luxAB-based assay because the substrate addition step is excluded. At least 20 CFU/mL of pure S. Typhimurium culture was detectable using SPC32H-CDABE within 2 h, and the signals increased proportionally to the number of cells contaminated in lettuce, sliced pork, and milk. These results thereby demonstrate that this phage successfully detects live Salmonella without appreciable interference from food components. Furthermore, the presented data suggest that SPC32H-CDABE represents a promising easy-to-use diagnostic tool for the detection of Salmonella contamination in food.

Detection of bacteria with bioluminescent reporter bacteriophage

Bacteriophages are viruses that exclusively infect bacteria. They are ideally suited for the development of highly specific diagnostic assay systems. Bioluminescent reporter bacteriophages are designed and constructed by integration of a luciferase gene in the virus genome. Relying on the host specificity of the phage, the system enables rapid, sensitive, and specific detection of bacterial pathogens. A bioluminescent reporter phage assay is superior to any other molecular detection method, because gene expression and light emission are dependent on an active metabolism of the bacterial cell, and only viable cells will yield a signal. In this chapter we introduce the concept of creating reporter phages, discuss their advantages and disadvantages, and illustrate the advances made in developing such systems for different Gram-negative and Gram-positive pathogens. The application of bioluminescent reporter phages for the detection of foodborne pathogens is emphasized.

Application of bacteriophages for detection of foodborne pathogens

Bacterial contamination of food products presents a challenge for the food industry and poses a high risk for the consumer. Despite increasing awareness and improved hygiene measures, foodborne pathogens remain a threat for public health, and novel methods for detection of these organisms are needed. Bacteriophages represent ideal tools for diagnostic assays because of their high target cell specificity, inherent signal-amplifying properties, easy and inexpensive production, and robustness. Every stage of the phage lytic multiplication cycle, from the initial recognition of the host cell to the final lysis event, may be harnessed in several ways for the purpose of bacterial detection. Besides intact phage particles, phage-derived affinity molecules such as cell wall binding domains and receptor binding proteins can serve for this purpose. This review provides an overview of existing phage-based technologies for detection of foodborne pathogens, and highlights the most recent developments in this field, with particular emphasis on phage-based biosensors.

Bacteriophages for detection and control of bacterial pathogens in food and food-processing environment

This chapter presents recent advances in bacteriophage research and their application in the area of food safety. Section 1 describes general facts on phage biology that are relevant to their application for control and detection of bacterial pathogens in food and environmental samples. Section 2 summarizes the recently acquired data on application of bacteriophages to control growth of bacterial pathogens and spoilage organisms in food and food-processing environment. Section 3 deals with application of bacteriophages for detection and identification of bacterial pathogens. Advantages of bacteriophage-based methods are presented and their shortcomings are discussed. The chapter is intended for food scientist and food product developers, and people in food inspection and health agencies with the ultimate goal to attract their attention to the new developing technology that has a tremendous potential in providing means for producing wholesome and safe food.

Acylhomoserine lactone production by bacteria associated with cultivated mushrooms

The main bacterial pathogens of cultivated mushroom as well as mushroom-associated bacteria, which were isolated from Agaricus bisporus, Pleurotus ostreatus and Pleurotus eryngii mushroom niches, were evaluated for the production of N-acyl-L-homoserine lactones (AHLs) by using four bioreporters. Furthermore, identification of AHLs by LC-ESI-FTICR MS was performed on culture filtrates of selected pathogens and mushroom-associated bacteria strains, which resulted in inducing at least one of the four bioreporters. Strains of Burkolderia gladioli pv. agariciola, Pseudomonas agarici and Pseudomonas gingeri, but not those of Pseudomonas tolaasii and Pseudomonas reactans, produced an array of AHLs depending on the strain. This is the first report of AHL production by mushroom bacterial pathogens. Forty-four of 236 bacterial isolates obtained from different niches of cultivated mushrooms, in part identified by the Biolog identification system, were demonstrated to produce AHLs. Among them, seven mushroom-associated bacterial species were for the first time demonstrated to produce the above signal molecules. In the culture filtrates of a certain number of isolates/strains the AHL-hydrolyzed forms were also present. The minimal signal inducing concentration (MSIC) of selected pure AHLs was also determined for the four bioreporters used in this study.

Recent advances in recognition elements of food and environmental biosensors: a review

A sensitive monitoring of contaminants in food and environment, such as chemical compounds, toxins and pathogens, is essential to assess and avoid risks for both, human and environmental health. To accomplish this, there is a high need for sensitive, robust and cost-effective biosensors that make real time and in situ monitoring possible. Due to their high sensitivity, selectivity and versatility, affinity-based biosensors are interesting for monitoring contaminants in food and environment. Antibodies have long been the most popular affinity-based recognition elements, however recently a lot of research effort has been dedicated to the development of novel recognition elements with improved characteristics, like specificity, stability and cost-efficiency. This review discusses three of these innovative affinity-based recognition elements, namely, phages, nucleic acids and molecular imprinted polymers and gives an overview of biosensors for food and environmental applications where these novel affinity-based recognition elements are applied.

Virus-based chemical and biological sensing

Viruses have recently proven useful for the detection of target analytes such as explosives, proteins, bacteria, viruses, spores, and toxins with high selectivity and sensitivity. Bacteriophages (often shortened to phages), viruses that specifically infect bacteria, are currently the most studied viruses, mainly because target-specific nonlytic phages (and the peptides and proteins carried by them) can be identified by using the well-established phage display technique, and lytic phages can specifically break bacteria to release cell-specific marker molecules such as enzymes that can be assayed. In addition, phages have good chemical and thermal stability, and can be conjugated with nanomaterials and immobilized on a transducer surface in an analytical device. This Review focuses on progress made in the use of phages in chemical and biological sensors in combination with traditional analytical techniques. Recent progress in the use of virus-nanomaterial composites and other viruses in sensing applications is also highlighted.

Genome sequence of the Bacteroides fragilis phage ATCC 51477-B1

The genome of a fecal pollution indicator phage, Bacteroides fragilis ATCC 51477-B1, was sequenced and consisted of 44,929 bases with a G+C content of 38.7%. Forty-six putative open reading frames were identified and genes were organized into functional clusters for host specificity, lysis, replication and regulation, and packaging and structural proteins.

Bacteriophage-based bioluminescent bioreporter for the detection of Escherichia coli 0157:H7

The rapid detection of pathogenic bacteria in food and water is vital for the prevention of foodborne illness. In this study, the lux reporter genes were used in a new bioassay that allows pathogen monitoring without multiple sample manipulations or the addition of exogenous substrate. A recombinant phage specific for Escherichia coli 0157:H7 was constructed that, upon infection, catalyzes the synthesis of N-(3-oxohexanoyl)-L-homoserine lactone (OHHL). This phage PP01 derivative carries the luxI gene from Vibrio fischeri under the control of the phage promoter PL. OHHL produced by infected E. coli 0157:H7 induces bioluminescence in bioreporter cells carrying the V. fischeri lux operon. The ability of phage PP0-luxl to detect several strains of E. coli 0157:H7 was confirmed in a 96-well plate assay. In this assay, luxCDABE bioreporter cells capable of detecting OHHL were mixed with phage PPOI-luxl and E. coli 0157:H7, and luminescence was monitored. Reporter phages induced light in bioreporter cells within I h when exposed to 10(4) CFU/ml of E. coli 0157:H7 and were able to detect 10 CFU/ml in pure culture with a preincubation step (total detection time, 4 h). The detection method was also applied to contaminated apple juice and was able to detect 10(4) CFU/ml of E. coli 0157:H7 in 2 h after a 6-h preincubation.

Biotechnological exploitation of bacteriophage research

The experimentally amenable nature of phage and their use in testing fundamental biological questions have meant that phage research has had a profound effect on modern molecular biology. Phage research has also fuelled multiple biotechnological developments. For example, phage display has recently been harnessed in a multidisciplinary approach for the generation of novel nanotechnologies. In addition, with the emerging threat of antibiotic-resistant bacterial infections, phage have begun to provide technologies to combat these problems. Finally, recent data acquired from genome sequencing and advances in phage biology research have aided the development of phage-derived bacterial detection and treatment strategies in addition to methods to control the detrimental effects of phage in industry. Here, we examine the promising uses of phage in these important areas of biotechnology.