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Blooming cyanobacteria!

One of the consequences of declining water quality is an increase in cyanobacteria – these are photosynthetic bacteria that live in a wide variety of aquatic or wet habitats.

Understanding blooms a key to improving water quality

Cyanobacterial blooms in rivers cause a reduction in water quality and are a threat to animal and human health. The project (in collaboration with the Cawthron Institute) determined key genetic mechanisms (diverse nutrient acquisition strategies) that enable members of the cyanobacterial genus Microcoleus to proliferate in freshwater habitats.

So, how do cyanobacteria live in their natural habitat, how do they coexist with other bacteria and microbial life forms, and what makes them so good at forming blooms?

underwater mats

Underwater mats

Genomics Aotearoa has been funding stream-to-ocean microbiome research to better understand microbial life. Through a collaboration between the University of Auckland School of Biological Sciences and the Cawthron Institute, Genomics Aotearoa researchers have studied the genes and proteins in Microcoleus proliferating in our rivers.

While globally common and problematic, Microcoleus forms a type of bloom that is less well-studied than other cyanobacteria – it coats the benthic environment (along river or lake beds) in thick cohesive mats. Microcoleus proliferations are composed of either non-toxic species, or mixtures of co-occurring non-toxic and the toxic species that are responsible for animal deaths.

Research reveals that diverse genomic mechanisms underlie blooms

Research by the group shows that Microcoleus are equipped with diverse mechanisms for acquiring nitrogen and phosphorus, enabling them to proliferate and out-compete others in low-phosphorus waters, while taking advantage of nitrogen compounds likely introduced by agricultural runoff.

Further genomic research by the group has determined important differences in the abilities of toxin producing and non-toxic Microcoleus species to store and acquire nutrients. These differences are associated with substantial differences in metabolic capabilities. Genetic evidence indicates that the toxic species are metabolically less versatile, less able to withstand fluctuating nutrient supply, and unable to synthesize an essential vitamin for self-sustained growth.

Understanding the mechanisms for co-occurrence of toxic and non-toxic species an important next step

Future work will investigate the project’s prediction that toxic species are dependent on non-toxic counterparts for this vitamin, which would explain why toxic species are invariably found to co-occur with non-toxic Microcoleus. Understanding the conditions needed for these bacteria to grow and thrive, and those that select for toxic species, will potentially help us predict and manage bloom formations, and better manage water quality and safety.