Bacteriophages as Biosensors

Definition of Bacteriophages

Bacteriophages, also known as phages or bacterial viruses, are a group of viruses that are capable of infecting bacteria. Being ubiquitous, bacteriophages are present within every known environment, generating endless potential for enhancing biological interactions and processes.

Although bacteriophages reside in a simple structure, they are morphologically varied with a high genomic diversity, which is influenced largely by their specific local environment. Here – we will take a look at how bacteriophages have optimised biomolecular developments towards bacterial identification in a range of field applications, and how phages have come to be a large contributor to the most promising biosensor entity in discovery.

Overview of Bacteriophage Uses

Remarkably, the most omnipresent organisms on Earth are bacteriophages. Because of this, these biological agents are heavily engrained across all ecosystems and have proven to be an invaluable molecular vehicle for driving research and development in a variety of field applications. 

Well-established is the field of human and animal disease. Bacteriophages have contributed significantly to the treatment of disease because of their distinctive ability to infect colonising bacterium with great specificity, without disturbing neighbouring microbial populations. This is commercially known as phage therapy, and it is this bio-engineered paradigm that has revolutionised the pathogenesis of many microbial diseases; by boosting population equilibrium and regulating immunity. Other uses of bacteriophages across the biotechnology industry can be seen in the biocontrol of agriculture, aquaculture and environmental monitoring. 

Bacteriophages as Biosensors

Standard bacterial infection monitors, which were historically the only functional method of identifying pathogenic communities, are reliant on labour-intensive microbiological assays which can often take multiple days to obtain results. Consequently, the landscape supporting biotechnology research has marked a definitive urgency to develop a more reliable, effectively functioning and cheaper biosensor model – with increased diagnostic capabilities to match the ever-evolving number of microbial communities. 

A biosensor is an analytical device used for chemical substance detection that includes a biological component for sensory identification – for example, an implement used for the detection of foodborne pathogens. Due to the high environmental presence, narrow host range, and easily manipulative biostructure of bacteriophages, phage-based biosensors are retrieving increasing attention as a bio-recognition molecule. 

Biosensors are frequently used throughout medical diagnostics, quality control, food safety, drug protection and industrial wastewater control. Using bacteriophages as the bio-probe component of a biosensor promotes increased signal processing and accuracy in pathogenic identification, allowing different strains of the same pathogenic species to be reliably identified. This is largely due to the natural specificity of phages to their host bacterium – an attribute that sets these microorganisms apart from alternative biosensor forms.

Advantages of Bacteriophages as Biosensors

Previously devised biosensors, whereby the bio-probe is stimulated through enzymatic reactions or antibody attachment, have lacked diagnostic accuracy and socio-economical security due to their limiting scope for wide-ranging detectability. This is where bacteriophages dominate the field, with phage-based biosensors paving the way for a more effective sensory model for microbial detection. 

As we have mentioned, the most significant to the success of phage-driven biosensors is the increased specificity bacteriophages have towards their host. This allows for high strain selectivity and is a promising movement toward achieving accurate diagnoses of microbial species in food production and agriculture for public safety. Additionally, bacteriophages show resistance to extreme external interferences, such as organic solvents, high temperatures and wide pH ranges – again – promoting phage-based biosensors as stable modifications of previously used biosensor machinery. Comparably to antibodies, phages can be produced in large quantities and extremely quickly, with a relatively cheap production cost, making these bioengineered constructs highly desirable for commercial use. 

Methods for Engineering Bacteriophages as Biosensors

For a bacteriophage to successfully infect its host, several features can initiate, guide and effectively carry out this interaction. Receptor binding proteins (RBPs), seen visually on the tail of a bacteriophage known as tail spike proteins, are the primary determinant of phage specificity, initiating a phage-host adsorption interaction. RBPs are capable of binding to proteins and other receptor sites on the host bacterium, allowing a stable and secure interaction between the phage and its host. During bioengineering, RBPs can be modified through gene replacement techniques to direct specificity and increase phage infection. This provides phage-led biosensors with a custom host range for an optimal attack on their host. 

Applications of Bacteriophage Biosensors

Phage-based biosensors hold many applications in the fields of food safety and environmental regulation. Due to the many benefits bacteriophage-led biosensors hold over conventional pathogenic screening devices, such as their elevated compatibility with their host, they have quickly become a leading microbial detection tool. 

Detection of Biotoxins

Biotoxins are relatively new and emerging natural threats to human health, produced by animals, plants, fungi and bacteria. In addition to this, many bioactive molecules produced as a by-product of the pharmaceutical are considered highly toxic to human health. Due to the proposed risk of biotoxins to living organisms such as ourselves, early identification is essential for putting processes in place to deter their damage streams. Using phage-based biosensors as a method to screen for biotoxins will allow for rapid intervention measures to take place against them. 

Detection of Antibiotic Resistance

With a larger number of bacterial species developing resistance to bacterial-specific drug therapies, a method to detect these resistant strains early to enable secondary control measures to be introduced is critical to public health. Phage-based biosensors have provided us with unique capabilities to do just that – to detect antibiotic-resistance bacteria quickly, efficiently, and with greater accuracy. 

Detection of Food Contaminants

Antimicrobial-resistance bacteria can also be spread through food sources and travel long lengths through the food supply chain. For example, outbreaks of antibiotic-resistant infections can occur through many processes contributing to the food supply chain, such as through contact with contaminated animal faeces, drinking contaminated water, and through agricultural growth whereby contaminants are taken up by plants through soil. 

Foodborne pathogens pose an unprecedented risk to public health, with mild to severe infections arising as a consequence to the consumer. This makes bacteriophage-driven biosensors a critical tool for early detection of such microbial communities to prevent foodborne infections, particularly those carrying antibiotic resistance tendencies, from entering the food supply chain. Pathogens responsible for the most ominous outcomes of food contaminants are Listeria monocytogenes, Staphylococcus aureus, Salmonella, Campylobacter, Cryptosporidium and E.coli 0157:H7. 

Conclusion

Taking a wider look at universal concerns, the future of food safety and environmental monitoring is undoubtedly at the forefront. Pathogenic infections continue to impose on human and animal health, as well as the wider stability of the environment, with antimicrobial resistance only making this worry greater. Phage-based biosensors have demonstrated vast potential as a diagnostic tool for hazardous pathogen screening in a range of promising fields: human disease, the food supply chain, environmental stability process, agriculture and aquaculture. Moving forward, the use of bacteriophages in biosensor equipment will modernise the speed at which we can detect pathogenic communities in our food and environment.