Combination of statistical methods for easy analysis and classification of virus-host environmental dynamics in the saltern of Sfax, Tunisia

Investigations of virus-host interactions depend heavily either on their cultivation or on metagenomics. In this study, we combined complementary statistical methods and culture-independent methods to gain deeper insight into virus-host interactions in the Sfax saltern, Tunisia. Samples were collected and the data were statistically evaluated. Hierarchical cluster analysis classified the ponds into two main groups with a sharp cutoff: type A with a salinity value <24% and type B with salinity > 24%. Redundancy analysis demonstrated a strong correlation between viral abundance, virus-to-prokaryote ratio, and archaea in type B ponds. Head-tailed viruses with medium-small genome size were often predicted to preferentially infect the most abundant hosts in high-salinity ponds, Salinibacter and Haloquadratum, which are both strongly correlated with high Mg2+ concentrations. Based on the redundancy analysis, type A ponds were defined by relatively high Ca2+ content and were dominated by spherical viruses, with the largest genomes infecting either the potential bacterial host Halopeptonella or the archaeal host Halogeometricum. Interestingly, the low-salinity pond M1Oct09 displayed a special viral community pattern. The receiver operating characteristic curve clarified the criteria that could not discriminate between pond types A and B, including Na+ , pH, and bacterial abundance. Parameters including the viral and archaeal diversity index and the virus morphotype showed a correlation with salinity but could not be used to discriminate between these types. Combining the complementary statistical and culture-independent methods could serve as suitable evaluation tools for providing clear and easily understandable information on virus-host interactions.