Young Algologist Reveals Ancient History of Cyanobacteria

The scientific community has gained a clearer understanding of the evolution of cyanobacteria of the Synechococcus group. It is one of the largest groups of cyanobacteria, widespread from the poles to the equator, in the sea as well as on land. Petr Dvořák, a phycologist from the Faculty of Science, has compared their genes and constructed, with the help of molecular biology, the first complex phylogenetic tree of this group, an interpretation of its evolution. It shows that cyanobacteria have been living on the Earth for more than 3 billion years.

Although most of us would associate cyanobacteria with the unwanted “water blooms”, which make bathing and swimming in many ponds and lakes problematic, cyanobacteria are vital in nature. They survive everywhere where sunlight is available, even in extreme temperatures. They function as primary producers, conducting oxygenic photosynthesis as well as plants. Their metabolism produces oxygen and sugar and fixates nitrogen, which is utilised by other organisms.

Investigated genes and the tree of life

Petr Dvořák from the Department of Botany has been shedding light in the last two years mainly on the Synechococcus group dominant in the maritime environment. It is one of the most important components of photosynthetic picoplankton under the ocean surface. “We have used various molecular methods to reconstruct the evolutionary tree of this genus. Phylogenetic analyses are most commonly used for this purpose. On the basis of algorithms of DNA sequences, we can estimate the hierarchical timeline of evolution,” explained Dvořák.

Evolution of cyanobacteria differs from that of plants or humans. Cyanobacteria live in huge populations, and genetic exchange occurs very frequently. And it is not by means of reproduction, since they do not reproduce sexually, their genetic material is transferred among the cells themselves. Scientists have discovered that the quantity of these exchanges depends on time. The newer the lineage is, the more gene transfers occurred.

“The research has confirmed that cyanobacteria of the Synechococcus group have been on the Earth for about 3 billion years. They alter genetically and develop various evolutionary lines. They have survived here for a uniquely long time. Their existence is many times longer than that of plants or animals, not mentioning humans. This has been a matter of speculation in the past, but now we have another proof it’s really so,” said Dvořák, hardly concealing his enthusiasm. Scientists have described thousands of cyanobacteria species to date; however, dozens of thousands exist on the Earth according to estimations.

Unique plenitude of data

Dvořák and his colleagues utilised also a genome sequence of a new genus of cyanobacteria found in a peatbog in Slovakia. It was named Neosynechococcus. Along with it, genes of another 200 cyanobacteria species were analysed. “Until now, scientists have explored only the maritime or freshwater cyanobacteria within each group. I’ve put them all together,” explained Dvořák. Their latest findings were published in the journal Molecular Ecology in September 2014. Olomouc botanists conducted the research jointly with the University of North Florida in Jacksonville and the Stazione Zoologica Anton Dohrn in Naples.

Important fragment for understanding the ecosystem

Concerning how very widespread cyanobacteria are in the world, the research findings are precious. “They appear in immense quantities in the world, possibly thousands of billions of cells. They greatly affect the global ecosystem, so it’s vital to know their evolution. This may be of significance in the future, too. The occurrence and quantity of maritime cyanobacteria of this genus keep changing in relation to global warming,” said Dvořák.

For instance, maritime Synechococcus and Prochlorococcus, belonging to the same group, are responsible for 25 percent of primary production of energy in the oceans. Produced sugars and oxygen are subsequently utilised by other organisms in the food chain. Some cyanobacteria are used in agriculture to make up for the lack of nitrogen in the soil. In rice fields, chemical fertilisers can be replaced with cyanobacteria that fixate nitrogen from the air. As a result, rice plants can thrive.

Cyanobacteria are able to survive extreme conditions. They live in Antarctica as well as in mountain springs. One species was isolated even from polar bear hairs.

Cyanobacteria

The oldest photosynthetic organisms on the planet. Their simple structure allows them to survive extremely adverse conditions. They often live in symbiosis with other organisms. Their reproduction is asexual. Their name comes from the Greek word for blue, cyanos.

Algology (from algae) is a branch of biology studying algae and cyanobacteria. It deals with the systematisation, phylogenesis, and ecology of these organisms. It also includes physiology, biochemistry, and genetics.

 

Figure 1: Cyanobacteria Synechococcus sp. PCC 6717 living in thermal springs in Yellowstone National Park in the United States. Individual cells form simple “threads”, consisting of two cells.

Figure 2: Cyanobacterium sp. PCC 7202, occurring in stagnant waters in Africa. This group is related to the Synechococcus genus.

Figure 3: Neosynechococcus sphagnicola (cyanobacteria). This genus was recently described in the laboratory at the Department of Botany where its genome was also later sequenced. Elongated cells can be seen between cellular walls of peat moss.

Mgr. Petr Dvořák, Ph.D. (b. 1984)

He graduated Palacký University, where he defended his Ph.D. thesis in 2013. He gained experience during scholarships at John Carroll University in Cleveland and the University of North Florida in Jacksonville.

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