Lake Bled is home to an annual bloom of the cyanobacterium Planktothrix rubescens. There are several causes for the rapid decrease in cyanobacterial concentrations as the bloom ends, one hypothesis is the presence of cyanophage which infects cyanobacteria. We sampled the surface water from December 2020 to April 2021, trying to capture as much algal mass as possible. Based on the genome of the only sequenced cyanophage which attacks the genus Planktothrix we designed oligonucleotides that could provide evidence for the presence of a related cyanophage in Lake Bled.
The presence of Planktothrix rubescens was proven by microscopic observation. We tried to isolate a single filament of cyanobacteria on the basis of phototropism and by isolating single strands in microcentrifuge tubes. We tried to culture Planktothrix rubescens in BG-11 liquid medium and regularly monitored the turbidity. Multi-stage filtration with a final pore size of 0.2 μm was used to obtain a phage-enriched fraction. We determined UV-VIS spectra and observed how contaminants were reduced during filtration. We have proven the presence of cyanobacterial DNA in our environmental samples and in the final filtrate by polymerase chain reaction and agarose gel. In addition, using our oligonucleotides, we detected presence of cyanophage DNA in the same samples.
|
