Silicified virus‐like nanoparticles in an extreme thermal environment: implications for the preservation of viruses in the geological record

Abstract

Biofilms that grow around Gumingquan hot spring (T = 71 °C, pH = 9.2) in the Rehai geothermal area, Tengchong, China, are formed of various cyanobacteria, Firmicutes, Aquificae, Thermodesulfobacteria, Desulfurococcales, and Thermoproteales. Silicified virus-like nanoparticles, 40-200 nm in diameter, are common inside the microbial cells and the extracellular polymeric substances around the cells. These nanoparticles, which are formed of a core encased by a silica cortex, are morphologically akin to known viruses and directly comparable to silicified virus-like particles that were produced in biofilms cultured in the laboratory. The information obtained from examination of the natural and laboratory-produced samples suggests that viruses can be preserved by silicification, especially while they are still encased in their host cells. These results expand our views of virus-host mineral interaction in extreme thermal environments and imply that viruses can be potentially preserved and identified in the geological record.

Precipitation of Calcium Carbonate Mineral Induced by Viral Lysis of Cyanobacteria

“…When Ca 2+ access to intracellular space, the existence of capsid synthetized by viral DNA provides nucleation site for initial calcification (Fig 10). This heterogeneous calcification involves addition of material to the preexisting viral surface, which may similar to mineralized virus in microbial mat from hot spring (Peng et al, 2013) or hypersaline lakes (Pacton et al, 2014;De Wit et al, 2015;Perri et al, 2017). The pathway that viral induced calcification during the lysis of the 15 host cells retrieved by experimental study expands roles of viruses in marine carbonate precipitation.…”

“…1) was harvested via centrifugation (13000 g, 5 min) for electronic microscopy and mineral study with the methods adopted from Peng et al (2013). In brief, 20 subsamples for TEM study were fixed by the addition of glutaraldehyde (to 4% final concentration), rinsed in distilled water to remove salt, mounted on copper grids and air-dried.…”

“…Furthermore, viral particles could act as nucleation sites for different mineral precipitation. In the past few years, researchers have investigated that the capsid of viruses can interact directly with elements in solutions and thus potentially mediate the formation and precipitation of different minerals (Daughney et al, 2004;Kyle et al, 2008;Peng et al, 2013;Pacton et al, 2014;De Wit et al, 2015;Laidler and Stedman, 2010). It has been widely 5 studied that viruses can interact with iron minerals under both marine system (including experimental conditions) (Daughney et al, 2004;Bonnain et al, 2016) and in the natural low pH acid mine drainage environment (Kyle et al, 2008;Kyle and Ferris, 2013).…”

“…Long-term and short-term experimental silicification was also studied for the simulation of hot spring mineralization and checking the preservation of viruses in the mineralized structure (Laidler 10 and Stedman, 2010;Orange et al, 2011). The study of the hot spring biofilm by Peng et al (2013) proved that viruses can be preserved in the natural environment. Recent studies have shown that hypersaline carbonate minerals can precipitate at the surface of viral particles and have implication to the nano-sized calcium carbonate structures in various geological settings (Pacton et al, 2014;Lisle and Robbins, 2016;Perri et al, 2017).…”

Hydrated Silica Exterior Produced by Biomimetic Silicification Confers Viral Vaccine Heat-Resistance

“…11,12 According to fossil records, these ancient thermophiles were usually encased in silica because the concentration of silica in the Archean oceans and hydrothermal fluids was high. 11,13 Various modern organisms, ranging from hot-spring bacteria 13 to deep-sea sponges 14 and from lower unicellular diatoms 15 to higher multicellular rice plants, 16,17 retain their ability for silicification, which is used to protect themselves against environmental aggressions.…”