[2][3] Chlorovirus was discovered in 1981 by Russel H. Meints, James L. Van Etten, Daniel Kuczmarski, Kit Lee, and Barbara Ang while attempting to culture Chlorella-like algae.

[1][8] Natural hosts of chloroviruses include various types of unicellular eukaryotic Chlorella-like algae, with individual virus species typically infecting only within a distinct strain.

[9] While an individual protist can harbour up to several hundred algal cells at any given time, free-floating algae are highly susceptible to chloroviruses, indicating that such endosymbiosis serves to provide resistance from infection.

Due to the rich genetic diversity and high specialization of individual species with respect to infectious range, variations in their ecology are not unusual, resulting in unique spatio-temporal patterns, which ultimately depend on lifestyle and nature of the host.

[1] Additionally, studies revealed that chloroviruses demonstrate some resilience in response to decreased temperatures observed during the winter season, characterized by presence of infectious particles under ice layers in a stormwater management pond in Ontario, Canada.

[11] Further, DeLong et al. (2016) suggest that predation by small crustaceans can play an indirect role in titer fluctuations, as degradation of protist cells passing through the digestive tract results in liberation of large numbers of unicellular algae that become susceptible to viral infection due to disruption of endosymbiosis.

Chlorella, in co-occurrence with other types of microscopic algae like Microcystis aeruginosa, are known to cause toxic algal blooms that typically last from February to June in the Northern hemisphere, resulting in oxygen depletion and deaths of larger organisms in freshwater habitats.

[13][14] Lytic infection of unicellular algae by chloroviruses results in termination of algal blooms and the subsequent release of carbon, nitrogen and phosphorus trapped in the cells, transporting them to lower trophic levels and, ultimately, fueling the food chain.

[17][16] Chloroviruses infect certain unicellular, eukaryotic chlorella-like green algae, called zoochlorellae, and are very species and even strain specific.

The virus exits the host cell by lysis via lytic phospholipids, with passive diffusion being the mechanism behind transmission routes.

[19] Because PBCV-1 does not have an RNA polymerase gene, its DNA and viral-associated proteins move to the nucleus where transcription begins 5–10 minutes post infection.

This component is assumed to be a product of the PBCV-a443r gene, which obtains structures resembling proteins involved in nuclear trafficking in mammalian cells.

As such, Chloroviruses are an important mechanism to the termination of algal blooms and play a vital role in the supply of nutrients to the water column[17] (See Ecology section for more information).

The test mice were also less able to recognize an object that had been moved from its previous location, showing a decrease in spatial reference memory.

[7] Chloroviruses, as well as the remaining members of the family Phycodnaviridae, are considered part of the broader group of microbes called nucleocytoplasmic large DNA viruses (NCLDVs).

Phylogenetic analysis of the major capsid protein within the group indicates great likelihood of close relatedness, as well as prior divergence from a single common ancestor, which is believed to be a small DNA virus.

[26] Infection cycle studies in PBCV-1 revealed that the virus relies on a unique capsid glycosylation process independent of the host's ER or Golgi machinery.

This feature has not yet been observed in any other virus currently known to science and potentially represents an ancient and conserved pathway, which could have evolved before eukaryogenesis, which was estimated to occur around 2.0-2.7 billion years ago.

[26] Recent discovery regarding presence of DNA sequences homologous to ATCV-1 in the human oropharyngeal virome, as well as the subsequent studies demonstrating successful infection of mammalian animal model by ATCV-1, also point to the likelihood of ancient evolutionary history of chloroviruses, which possess structural features and utilize molecular mechanisms that potentially allow for replication within diverse animal hosts.