Viruses in bottom sediments in a eutrophic reservoir (Ivankovo Reservoir, Upper Volga)

The total number of viruses, morphological and size composition of viriobenthos, number of bacterial cells infected by viruses, number of mature phages inside bacterial cells, and virus-induced mortality of bacteriobenthos have been estimated in bottom sediments of the Ivankovo Reservoir. The total number of viriobenthos in the reservoir range from 10.3 to 83.2 (31.5 +/- 6.2 on average) billion particles/cm(3). The total number of virus-to-bacteria ratio in the Ivan'kovo reservoir varies between 0.3 and 1.7 (0.7 +/- 0.1 on average). A positive correlation between viral and bacterial abundance is found (R = 0.61, p = 0.05). In different parts of the reservoir, viral infection of bacteria is not observed or is very low. The number of infected bacteria ranges from 1.0 to 3.5% (1.7 +/- 0.2% on average) of the total viriobenthos abundance and mortality due to viral lysis accounts for 1.0-3.7% (1.8 +/- 0.2% on average) of the total bacterial mortality. The number of phages found inside bacterial cells average 8 +/- 1 phages/cell. Thus, a phenomenon known as "infection paradox" is observed in the Ivankovo Reservoir when, at a very high viral abundance, no viral infection of bacteria is recorded or it was very low.