Cyanophages infecting the oceanic cyanobacterium Prochlorococcus

Area of Science:

• Marine microbiology
• Virology
• Oceanography

Background:

• Prochlorococcus is the dominant phototroph in tropical and subtropical oceans.
• It accounts for a significant portion of marine photosynthetic biomass.
• Understanding its interactions with viruses is crucial for marine ecosystem dynamics.

Purpose of the Study:

• To isolate and characterize cyanophages infecting Prochlorococcus.
• To investigate the host range and gene transfer potential of these phages.
• To determine cyanophage titers in open ocean environments.

Main Methods:

• Isolation of cyanophages from marine environments.
• Host range determination through cross-infection experiments.
• Quantification of cyanophage and cyanobacterial populations.

Main Results:

• Cyanophages infecting Prochlorococcus were isolated.
• Some phages exhibited cross-infection capabilities between Prochlorococcus and Synechococcus strains.
• Podoviridae were exclusively found in high-light Prochlorococcus, while Myoviridae were dominant in low-light Prochlorococcus and Synechococcus.
• Cyanophage titers were low in stratified oligotrophic waters despite high host abundance.

Conclusions:

• Cyanophages play a role in horizontal gene transfer among marine cyanobacteria.
• Phage family (Podoviridae, Myoviridae) correlates with host adaptation (high-light vs. low-light).
• Low cyanophage titers in open oceans may be linked to microbial population diversity, growth rates, or lysogeny.