Diversity and Ecology of Viruses in Hyperarid Desert Soils

Abstract

In recent years, remarkable progress has been made in the field of virus environmental ecology. In marine ecosystems, for example, viruses are now thought to play pivotal roles in the biogeochemical cycling of nutrients and to be mediators of microbial evolution through horizontal gene transfer. The diversity and ecology of viruses in soils are poorly understood, but evidence supports the view that the diversity and ecology of viruses in soils differ substantially from those in aquatic systems. Desert biomes cover ϳ33% of global land masses, and yet the diversity and roles of viruses in these dominant ecosystems remain poorly understood. There is evidence that hot hyperarid desert soils are characterized by high levels of bacterial lysogens and low extracellular virus counts. In contrast, cold desert soils contain high extracellular virus titers. We suggest that the prevalence of microbial biofilms in hyperarid soils, combined with extreme thermal regimens, exerts strong selection pressures on both temperate and virulent viruses. Many desert soil virus sequences show low values of identity to virus genomes in public databases, suggesting the existence of distinct and as-yet-uncharacterized soil phylogenetic lineages (e.g., cyanophages). We strongly advocate for amplification-free metavirome analyses while encouraging the classical isolation of phages from dominant and culturable microbial isolates in order to populate sequence databases. This review provides an overview of recent advances in the study of viruses in hyperarid soils and of the factors that contribute to viral abundance and diversity in hot and cold deserts and offers technical recommendations for future studies.

Genetic and functional diversity of ubiquitous DNA viruses in selected Chinese agricultural soils

“…The rapidly growing database of viral environmental sequences has revealed that most sequences (approximately 90%) do not have homologs in public databases, and are typically labeled as viral dark matter38. The same phenomenon occurred that an average of 2/3 of the genes within dsDNA viruses cannot be assigned a biological function or taxonomic affiliation according to a Basic Local Alignment Search Tool homology19. This may be one of the reasons why viral species distribution is similar among viromes from different environmental samples.…”

Sources and contamination routes of microbial pathogens to fresh produce during field cultivation: A review

“…Lower temperatures are more suitable for bacterial and viral survival. The ultraviolet radiation from the sun inactivates viruses on the surface of the soil, but viruses in deeper soil strata are protected from this (Rodríguez-L azaro et al, 2012;Zablocki et al, 2016). In loamy soil samples, at pH 7.5, poliovirus and echovirus were recovered after 110e130 days at 3e10 C compared to recovery 40e90 days at 18e23 C (Bagdasaryan, 1964).…”

Metaviromes of Extracellular Soil Viruses along a Namib Desert Aridity Gradient

“…However, the diversity and ecological functions of viruses in these arid ecosystems are mostly unknown (2). Virus research in arid soils has primarily focused on the taxonomic composition associated with surface soils and soil-lithic interfaces (3–10) and has revealed a wide diversity of virus taxa, mostly composed of tailed phage families (order: Caudovirales ).…”