Literature Review on Viral Ecology
Introduction
Viruses can respond to environmental changes or create variations in their ecosystem. Knowledge of virus ecology is essential in establishing transformation and balance in a viral ecosystem. It is also helpful in understanding antigenic shifts that emanate from environmental changes. A vital element for virus ecology is its association with plants, their vectors, and interaction with insects. This paper seeks to analyze the existing literature on viral ecology and later identify existing gaps which act as avenues of future research work.
Literature Review
According to Hurst (2011), viral ecology is best described by studying archaea, bacteria, and eukaryotes. Though this is not exhaustive, it gives a good representation of interactions between viruses and hosts. In a similar approach, Hyman and Abedon (2012) agree that viruses of microorganisms (VoMs) are best encapsulated within the three domains, and with technology, researchers can establish their symbiotic relationships. Often, ecological relationships occur when there is a disturbance in an ecosystem or as a result of evolution.
Environmental changes in aquatic ecosystems are known to cause major viral effects. Storms cause disturbances that create variations in different layers in water, which causes imbalances in microbial activities. This is true for both particulate and planktonic viral communities. Some disturbances in an environmental system can happen in the hosts creating further complexities in the virus ecology. A spatiotemporal analysis of lytic activities and viral abundance revealed a close relationship between viral dynamism and environmental and microbial communities (Payet and Suttle 2008).
Weinbauer (2004) explains that the cumulative viral abundance in an ecosystem is significantly higher than prokaryotic abundance. Further, this prokaryotic community is highly phage-infected, which stimulates the need for viral ecological studies. These effects cut across freshwater, marine, and soil ecosystems. The intensity of viruses in those ecosystems shows extreme variations and closely tied to bacterial activities, which means the central part of the viruses are phages.
Existing data on the prevalence of phages depict a rather diverse survival strategy and environmental niche but is not exhaustive. Viruses induce transience of prokaryotes as one of the survival mechanisms. The mortalities vary on a spatial and temporal scale which is an indicator that phages form a chain of predators in bacterioplankton environment (Weinbauer 2004). Additionally, the mortality releases cell lysis outputs that influence the state of the food web in microbial niches and the diversity of hosts. These ecological processes also lead to the domination of some of the species in the ecosystem (Hyman and Abedon 2012). The implication is the extinction of less competitive species.
It is important to note that viral ecology features different interactive processes depending on the life cycle of the viruses. In lytic cycles, phages interact with the host in metabolism and the creation of new phages (Weinbauer 2004). In lysogenic cycle, the phage is dormant within the host and only multiplies as the host does. It only transits to the next phase after a lysogenic decision, which induces lytic cycle. Psedolysogenic cycle is a carrier state whose role is the propagation of the virus. In all these cycles, there are different degrees of virus-ecosystem relationships, with the sole purpose being the survival of the virus (Hyman and Abedon 2012).
Viruses play a critical role in moderation and regulation of both freshwater and saltwater ecosystems. The major players in this are the bacteriophages whose function is the destruction of bacteria in microbial communities. They are harmless to both animals and plants and come in handy during the recycling of carbon products in marine ecosystems. During this process, new molecules of organic compounds are produced, promoting the development of algae and bacteria. Microorganisms represent nearly 90% of the entire sea biomass (Weinbauer 2004). Viruses kill about 20% of the biomass daily, which is crucial in maintaining a balanced ecosystem. They kill the most dangerous algal blooms that would otherwise cause harm to marine life (Allen and Abedon 2014). The distribution of viruses in marine life varies depending on the constitution of organisms. They decrease on the offshore and in the deepest regions where hosts are minimal.
An understanding of viral ecology leads to the appreciation of the role played by viruses during photosynthesis (Hyman and Abedon 2012). They feed marine plants with carbon dioxide, which is an essential component in photosynthesis. This, in turn, helps in the provision of oxygen to aquatic animals. Despite the positive contribution of viruses in an ecosystem, it essential to note that some mammals fall victim to viral infections(Owens 2011). Some viruses such as phocine distemper are known to cause deaths.
Viruses and insects show a close collaboration in establishing viral ecological balance. This is most evident in plant viruses where the latter relies on insects for transmission (Weitz 2016). For example, aphids carry parasitoids, creating a form of symbiotic relationship. The yellow mosaic virus depends non-persistently on the activities of aphids. Gemini viruses are predominantly transmitted by whiteflies, and the flies have been linked to the emergence of the virus. It is worth noting that the relationship between insects and viruses can range from mutualistic to antagonistic (Weinbauer 2004). The nature of the relationship determines the fecundity and longevity of the carrier insects. These viral relationships are also dependent on plants because they act as hosts of the insects. This means that if plants do not serve as perfect hosts, the viruses are equally affected. For example, tobacco plants are repellants of whiteflies. However, after infection with geminivirus, they improve in their hosting capabilities. As such, there is a mutual relationship between geminivirus and whiteflies (Weinbauer 2004).
Some insects use plants as a vector of transmission. The reoviruses that occur in insects that feed on plants rely on a horizontal transmission mechanism where insects deposit viruses from plants. After the completion of this process, viruses move to other insects in the chain. By doing so, a continuous and self-contained chain of the virus life cycle is developed (Weinbauer 2004). As such, viral ecology in plants is closely tied to the vectors, and it is equally affected by pathogens in plants.
Another important aspect of viral ecology is evolution. It has led to multiple studies different from those of ancient times. The models used in earlier research studies were anchored on a known response of viruses. However, some eukaryotic genomes have displayed a different viral-like sequence, which leaves a significant research gap. Ecologists have embarked on extensive research that focuses on viral genotype and its relationship with the environment, but evidence gathered so far is limited (Hyman and Abedon 2012). The same is true for plant viruses. This widens the virus ecology gap even further.
Conclusion
The literature reviewed in this research work appreciates various studies on viral ecology that have been of great help in scientific research and discoveries. However, the viral dynamics due to mutations and discoveries necessitates the need for further research on viral ecology to understand better how new and mutated genotypes respond. Besides, the theoretical perceptions provided in some of the literature developed during the olden days require new technological verification to cement the proposals. This research paper seeks to fill the existing gaps.
