Amazing stuff!
Should the cyanophages ever takeover the cyanobacteria then we have a real climate crisis and worse!
"Marine viruses deploy a sophisticated Trojan horse maneuver that enables them to dismantle the energy systems of ocean bacteria and use the breakdown products for self-replication. ...
Tiny cyanobacterial cells that live in the oceans play a crucial role in the global ecosystem, as they carry out photosynthesis to produce the organic carbon that serves as the basis of the oceanic food web. In the process they contribute significantly to oxygen production and carbon dioxide draw down from the atmosphere, influencing the global carbon cycle.
These essential bacteria are frequently attacked by viruses called cyanophages, which specialize in infecting and destroying marine cyanobacteria. During evolution, these viruses capture genes from cyanobacteria they had previously infected and integrated them into their own genome. The researchers focused on a gene called nblA, which is activated in cyanobacteria under stress conditions such as nutrient starvation. In such situations, it dismantles the cyanobacterial photosynthetic energy-harvesting systems to release amino acids vital for survival. Technion researchers have now shown for the first time that this process gives the viruses a significant advantage.
In cyanophages, a unique mechanism evolved whereby infection of the cyanobacterium triggers the same gene in the virus – nblA – to dismantle the energy-harvesting systems, but this time to the bacterium’s detriment. The amino acids released from this breakdown are used by the hostile virus for rapid self-replication. Thus, the virus converts the cyanobacterial host’s energy-harvesting system into resources for expanding its own population. This represents a sophisticated evolutionary move in which the virus harnesses the bacterium’s survival mechanism for its own benefit, exploiting the host’s resources and ultimately destroying it from within. ..."
From the abstract:
"Marine picocyanobacteria are abundant photosynthetic organisms of global importance. They coexist in the ocean with cyanophages—viruses that infect cyanobacteria. Cyanophages carry many auxiliary metabolic genes acquired from their hosts that are thought to redirect host metabolism for the phage’s benefit.
One such gene is nblA, which is present in multiple cyanophage families. Under nutrient deprivation cyanobacterial NblA is responsible for inducing proteolytic degradation of the phycobilisome, the large cyanobacterial photosynthetic light-harvesting complex. This increases the pool of amino acids available for essential tasks, serving as a survival mechanism.
Ectopic expression of different cyanophage nblA genes results in host pigment protein degradation. However, the benefit of the virus-encoded NblA for cyanophages and the broader impact on the host are unclear.
Here, using a recently developed genetic manipulation system for marine cyanophages, we reveal that viral NblA significantly accelerates the cyanophage infection cycle, directs degradation of the host phycobilisome and other proteins, and reduces host photosynthetic light-harvesting efficiency.
Metagenomic analysis revealed that cyanophages carrying nblA are widespread in the oceans and comprise 35% and 65% of oceanic T7-like cyanophages in surface and deep photic zones, respectively.
Our results show a large benefit of NblA to the cyanophage, while it exerts a negative effect on the host photosynthetic apparatus and host photosynthesis. These findings suggest that cyanophage NblA has an adverse global impact on light harvesting by oceanic picocyanobacteria."
Fig. 1: The influence of nblA on S-TIP37 cyanophage infection dynamics.
Fig. 5: The global distribution of T7-like cyanophages with and without nblA genes.
