Evidence for cyanophages active against bloom‐forming freshwater cyanobacteria

Abstract

1. A total of 35 putative cyanophages able to infect non-axenic cultures of bloom-forming freshwater cyanobacteria in the genera Microcystis, Anabaena and Planktothrix were isolated from Lake Zurich (Switzerland) and lakes in the Cotswold Water Park (U.K.). Eleven lytic cyanophage isolates were isolated on Microcystis and 12 each on Anabaena and Planktothrix. Cyanophage isolation protocols varied when using these different cyanobacterial hosts. 2. The collection of putative cyanophage isolates encompassed a variety of morphotypes, including the first filamentous cyanophage from any environment and the second siphocyanophage reported from fresh water. 3. PCR primer sets for gp20, gp23 and MCP genes, which have been previously found to be conserved in other cyanophages, were used in an attempt to determine genetic diversity among the phage isolates. The failure to obtain specific amplification products from most isolates suggests that the cyanophages isolated in this study were different from those previously characterized from both marine and freshwater environments. 4. Some putative cyanophages within the collection of isolates proved to have a very broad host range and were able to infect Anabaena, Microcystis and Planktothrix. The ability to infect a wide range of host taxa extends the potential reproductive period for lytic propagation, and also has implications for the transfer of genetic information between deeply separated cyanobacterial lineages.

Biotic factors in induced defence revisited: cell aggregate formation in the toxic cyanobacterium Microcystis aeruginosa PCC 7806 is triggered by spent Daphnia medium and disrupted cells

“…In the Laurentian Great Lakes (North America), for example, toxic blooms persist despite huge remediation efforts during the past few decades that have led to reduced off-shore nutrient levels; and in these lakes, no robust relationships are observed between algal/cyanobacterial biomass and toxins (Watson et al, 2008). Among other abiotic and biotic factors, cyanophages active against freshwater cyanobacteria (Deng & Hayes, 2008) may influence the natural population dynamics of Microcystis. The abundance dynamics and diversity of coexisting Microcystis genotypes (Kurmayer et al, 2002;Rinta-Kanto et al, 2005) or chemotypes (Welker et al, 2007) are regarded as major factors that influence the microcystin concentration in natural Microcystis blooms and communities.…”

Virus-Bacterium Coupling Driven by both Turbidity and Hydrodynamics in an Amazonian Floodplain Lake

“…Viruses were reported in host-specific parasites that infect one or a few species of the same genus. However, there are few examples of bacteriophage and cyanophage with relatively broad host ranges (3,16,17). In fact, high abundances of host species are necessary to promote the random virus-host cell encounter.…”

Putative Antiparasite Defensive System Involving Ribosomal and Nonribosomal Oligopeptides in Cyanobacteria of the Genus Planktothrix

“…The success of cyanobacteria is typically attributed to adaptations that ensure a competitive advantage in utilization of growth resources (2,3) and to a low susceptibility to zooplankton grazing (4). However, freshwater cyanobacteria are also targeted by potent pathogens (5,6), and it has yet to be explained why these frequently fail to keep cyanobacterial dominance and bloom formation in check.…”