Phages in Anaerobic Systems

Abstract

Since the discovery of phages in 1915, these viruses have been studied mostly in aerobic systems, or without considering the availability of oxygen as a variable that may affect the interaction between the virus and its host. However, with such great abundance of anaerobic environments on the planet, the effect that a lack of oxygen can have on the phage-bacteria relationship is an important consideration. There are few studies on obligate anaerobes that investigate the role of anoxia in causing infection. In the case of facultative anaerobes, it is a well-known fact that their shifting from an aerobic environment to an anaerobic one involves metabolic changes in the bacteria. As the phage infection process depends on the metabolic state of the host bacteria, these changes are also expected to affect the phage infection cycle. This review summarizes the available information on phages active on facultative and obligate anaerobes and discusses how anaerobiosis can be an important parameter in phage infection, especially among facultative anaerobes.

Ecophysiological Features Shape the Distribution of Prophages and CRISPR in Sulfate Reducing Prokaryotes

“…The development of plaques was not observed, however, the presence of iron sulfide precipitates may obscure the observation. Similar results were observed with normal and low iron concentration in the medium, highlighting that this limitation should be overcome to apply the techniques extensively used in phage research in SRP [95].…”

Active virus-host interactions at sub-freezing temperatures in Arctic peat soil

“…Viruses shape the abundance, diversity, and metabolic outputs of their microbial hosts, and the impact viruses can have on an ecosystem depends heavily on the physiological state of the host, their defense mechanisms, and environmental conditions [ 27 ]. Arctic soils predominantly exist under anoxic sub-freezing temperature conditions, which affects microbial growth and metabolism as well as viral dynamics, especially in regard to reprogramming host metabolism [ 27 , 90 ]. We detected many abundant viral genes that can help during an infection such as concanavalin A-like lectin/glucanases that may help in host recognition and attachment [ 91 ], methionine degradation which can help provide missing nutrients [ 92 ], and glycosyltransferases which can help viruses avoid host anti-viral mechanisms [ 83 ].…”

“…Proviruses may also be labeled, but not currently active if they are proviral remnants of a past infection [ 113 ]. These remnants have no negative impact on host metabolism (beyond occupying genome space) but may confer some advantage as a gene transfer agent [ 24 ] or by contributing virulence factors which can still impact host physiology and metabolism [ 90 ]. SIP-enabled metagenomics alone cannot unequivocally identify a virus’ state (e.g., in maintenance mode or a remnant), making it currently difficult to fully assess viral activity.…”

Ecology of active viruses and their bacterial hosts in frozen Arctic peat soil revealed with H218O stable isotope probing metagenomics

“…This is because proviruses do not shut down and redirect host metabolism for progeny production during the lysogenic cycle as compared to the lytic cycle. During lysogeny, viruses still impact host metabolism via host gene regulation and acquisition of new virulence factors, but it is primarily for maintaining the provirus in the host genome [99]. Proviruses may also be labeled, but not currently active if they are proviral remnants of a past infection [100].…”

“…Proviruses may also be labeled, but not currently active if they are proviral remnants of a past infection [100]. These remnants have no negative impact on host metabolism (beyond occupying genome space) but may confer some advantage as a gene transfer agent [51] or by contributing virulence factors which can still impact host physiology and metabolism [99]. SIP-enabled metagenomics alone cannot unequivocally identify a virus’ state (e.g., in maintenance mode or remnant), making it currently difficult to fully assess viral activity.…”