The Life Cycle Transitions of Temperate Phages: Regulating Factors and Potential Ecological Implications

Abstract

Phages are viruses that infect bacteria. They affect various microbe-mediated processes that drive biogeochemical cycling on a global scale. Their influence depends on whether the infection is lysogenic or lytic. Temperate phages have the potential to execute both infection types and thus frequently switch their infection modes in nature, potentially causing substantial impacts on the host-phage community and relevant biogeochemical cycling. Understanding the regulating factors and outcomes of temperate phage life cycle transition is thus fundamental for evaluating their ecological impacts. This review thus systematically summarizes the effects of various factors affecting temperate phage life cycle decisions in both culturable phage-host systems and natural environments. The review further elucidates the ecological implications of the life cycle transition of temperate phages with an emphasis on phage/host fitness, host-phage dynamics, microbe diversity and evolution, and biogeochemical cycles.

Viral impacts on microbial activity and biogeochemical cycling in a seasonally anoxic freshwater lake

“…We also found phages infecting Chloroflexota and Gammaproteobacteria (orders Burkholderiales, Methylococcacea, and GCA_2729495). In lakes, Chloroflexota is often associated with hypolimnion 39 and can make up to abundance up to ~25% in lakes 40 . Gammaproteobacteria phages have also been found in the Baltic Sea 41 , and Methylococcaccea phages have been found in Lake Baikal 13 .…”

Emerging applications of phage therapy and fecal virome transplantation for treatment of Clostridioides difficile infection: challenges and perspectives

“…In general, bacteriophages exhibit four life cycles, including lytic, lysogenic, bacterial budding, and pseudolysogenic cycles (Fig. 1 B) [ 28 , 29 ]. In the lytic cycle, the phage injects its genome into the host cell cytoplasm and produces new phage particles within 30–60 min by using the bacterial cell machinery.…”

“…Temperate phages are able to integrate their genome into the chromosome of their host bacteria as a prophage, or remains as a stable extra-chromosomal genetic element, instead of immediately producing new phage particles. This life cycle helps temperate phages to profit from the survival of their host bacteria in unfavorable environmental conditions [ 29 ]. Virulent phages exploit exclusively the lytic life cycle, whereas temperate phages can benefit both the lytic and lysogenic pathways [ 32 ].…”

“…Therefore, the prophage form can be advantageous to the survival or proliferation of a temperate phage when faced with different external challenges [ 30 ]. Generally, the prophage induction is both phage - and inducer-dependent and can be triggered by harsh environmental conditions such as nutrient limitation, phagocytosis, antibiotics, alterations in pH and temperature, ultraviolet radiation, chemical/diet inducers, oxidative/inflammatory stressors, or even superinfection of the host cell by other strains of phages [ 29 , 33 , 34 ]. Recently, short-chain fatty acids (SCFAs) and fructose-enriched diets were added to the list of prophage inducers in bacteria, particularly lactobacilli [ 35 ].…”

“…Depending on the conditions, phages can adapt their life cycle typically to either lytic or lysogenic cycles [ 21 ]. The lytic phages can benefit from predator-prey relationships with their host, leading to altering the functional composition of microbial communities [ 29 ]. Therefore, virulent phages can exert detrimental impacts on their bacterial host cells via cell lysis, and consequently balance the overall population of the gut microbiota [ 45 ].…”