Abundance and Diversity of Viruses in Six Delaware Soils

Abstract

The importance of viruses in marine microbial ecology has been established over the past decade. Specifically, viruses influence bacterial abundance and community composition through lysis and alter bacterial genetic diversity through transduction and lysogenic conversion. By contrast, the abundance and distribution of viruses in soils are almost completely unknown. This study describes the abundance and diversity of autochthonous viruses in six Delaware soils: two agricultural soils, two coastal plain forest soils, and two piedmont forest soils. Viral abundance was measured using epifluorescence microscopy, while viral diversity was assessed from morphological data obtained through transmission electron microscopy. Extracted soil virus communities were dominated by bacteriophages that demonstrated a wide range of capsid diameters (20 nm to 160 nm) and morphologies, including filamentous forms and phages with elongated capsids. The reciprocal Simpson's index suggests that forest soils harbor more diverse assemblages of viruses, particularly in terms of morphological distribution. Repeated extractions of virus-like particles (VLPs) from soils indicated that the initial round of extraction removes approximately 70% of extractable viruses. Higher VLP abundances were observed in forest soils (1.31 ؋ 10 9 to 4.17 ؋ 10 9 g ؊1 dry weight) than in agricultural soils (8.7 ؋ 10 8 to 1.1 ؋ 10 9 g ؊1 dry weight). Soil VLP abundance was significantly correlated to moisture content (r ‫؍‬ 0.988) but not to soil texture. Land use (agricultural or forested) was significantly correlated to both bacterial (r ‫؍‬ 0.885) and viral (r ‫؍‬ 0.812) abundances, as were soil organic matter and water content. Thus, land use is a significant factor influencing viral abundance and diversity in soils.

Occurrence of Bacillus thuringiensis and their phages in Yemen soil

“…Results indicated that, phage active against Bt may be present in soil or integrated with host genome (lysogeny) or as independent linear replica within the cell. These results are in accordance with finding of [19,26,27,41,43,48]. Electron microscopic studies of the isolated phages (Fig.…”

Methods of Virus Detection in Soils and Sediments

“…It was speculated that this may happen because viruses persist longer at cooler temperatures (Yates et al 1990). Williamson et al (2005) verified that viruses persist infectious for longer times under wetland soils. This may be due to the presence of thicker water films and smaller interfacial areas, since such interfaces may inactivate viral particles (Zhuang & Jin 2003).…”

“…It is a general consensus that the transport of pathogens in the subsurface depends on the extent of their retention of soil particles and their environmental resistance (Keeley et al 2003). The maintenance of these agents may also be affected by the isoelectric point and hydrophobicity of capsid proteins (Williamson et al 2005). It was demonstrated that clay minerals in soil may protect viral particles (Nasser et al 2002).…”

“…The first estimates of viral abundances were made by EfM used DAPI (4' , 6-diamidino-2-phenylindole) (Suttle et al 1990). Other fluorescent dyes, such as YO-PRO {4-[3-methyl-2,3-dihydro-(benzo-1,3-oxazole)-2-methylmethyledene]-1-(3'-trimethylammoniumpropyl)-quinolinium -diiodide} (Hennes & Suttle 1995), SYBR Green and SYBR Gold (N' ,N'- (Noble & Fuhrman 1998, Williamson et al 2005) are also available. The major disadvantage of EfM is that it is not possible to infer about virus diversity present in the samples, unlike the flow cytometry (FC) method.…”

Physiology and Pathology of Multidrug-Resistant Bacteria: Phage-Related Therapy

“…For instance, agricultural soils usually harbor a phage count of approximately 10 /mL [25][26][27][28].…”