Investigation into virus-bacterium interactions in Lake Cadagno, Switzerland

Lake Cadagno (1921m alt.), is a meromictic lake originated 10’000 years ago—located in the Southern Alps of Switzerland. The difference in density of water in Lake Cadagno divides it into three water-layers; Mixolimnion (low density, oxic), Monilimnion (high density, anoxic), chemocline (oxic-anoxic interface). The interface between Mixolimnion and Monimolimnion possesses physicochemical differences, which has contributed to the formation of chemocline between 11 to 14m depth. This water layer is occupying diverse microbial communities including purple sulphur bacteria—PSB (Chromatium okenii) and green sulphur bacteria—GSB (e.g., Chlorobium clathratiforme)[1] which are responsible for maintaining Carbon and Sulfur cycles of Meromictic Lake Cadagno. These bacteria regulate the sulphur cycle in this lake, which may be ancient. In support, the fossil record suggests that the bacteria associated with sulphur cycle was reported around 2.5 billion-year-old showing similarity with modern sulphur bacteria)[2].

Viruses act as a critical controller of bacterial abundance and biodiversity[3]. Despite bacterial diversity from Lake Cadagno is being studied from more than two decades, no information is yet available about the abundance and functionality of viruses. This thesis would be the first extensive report to fulfil this gap of knowledge in the field of viral ecology.