Bacteriophages in Natural and Artificial Environments

Abstract

Bacteriophages (phages) are biological entities that have attracted a great deal of attention in recent years. They have been reported as the most abundant biological entities on the planet and their ability to impact the composition of bacterial communities is of great interest. In this review, we aim to explore where phages exist in natural and artificial environments and how they impact communities. The natural environment in this review will focus on the human body, soils, and the marine environment. In these naturally occurring environments there is an abundance of phages suggesting a role in the maintenance of bacterial community homeostasis. The artificial environment focuses on wastewater treatment plants, industrial processes, followed by pharmaceutical formulations. As in natural environments, the existence of bacteria in manmade wastewater treatment plants and industrial processes inevitably attracts phages. The presence of phages in these environments can inhibit the bacteria required for efficient water treatment or food production. Alternatively, they can have a positive impact by eliminating recalcitrant organisms. Finally, we conclude by describing how phages can be manipulated or formulated into pharmaceutical products in the laboratory for use in natural or artificial environments.

Keywords: bacteriophage; environment; human body; phage biocontrol; phage therapy; pharmaceutical products; soil; wastewater; water.

Figure 1

Bacteriophage Lifecycle: Lytic phages attach and infect a bacterial cell which results in the reproduction of phages and lysis of the cell host and this lysogenic cycle results in the integration of a phage genome into the bacterial genome. Some lysogenic phages do not integrate into the genome and remain in the cell as a circular or linear plasmid (not depicted here).

Figure 2

Bacteriophages in natural and artificial environments: The significance of phages in natural environments lies in their ability to replicate within their host, thus impacting the diversity of bacterial communities. Within the human body, phages function to protect against pathogenic bacteria. Ocean waters contain 4 × 10³⁰ viruses, making it the largest phage reservoir. Soil phages influence nutrient cycling capabilities and symbioses between plant roots and bacteria. In artificial environments, the ability of phages to mediate bacterial growth can be exploited for a range of uses, due to their specificity and how readily they can be genetically modified. In wastewater treatment, phages can be used to impact the bacterial communities present, thus increasing the efficiency of this process. Industrial applications of phages include control of foodborne pathogens and decreasing the number of problematic bacteria in the petroleum industry. Pharmaceutical uses for phages are currently limited, but this is likely to change as the efficacy of antibiotics reduces and phage efficacy and specificity are improved in the laboratory.