The secret life of algae

A fundamental process that has puzzled researchers for many years has been explained by UK scientists. Some simple plants that are crucial in maintaining the balance of carbon in the Earth’s atmosphere require vitamin B12 to grow properly but it has been a mystery to scientists why some types needed external sources and others did not. Now researchers at the Universities of Cambridge and Kent have discovered that half of all algae have a dependent but beneficial relationship with bacteria that make the vitamin for them.

The researchers, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), found that no algae have the necessary genes to produce vitamin B12. Those that do not require a supply are like higher plants; they have an alternative metabolic process that does not need the vitamin. However, algae that need vitamin B12 cannot make it themselves and must get it from somewhere else.

The scientists realised that the amount of vitamin B12 required to grow the types of algae that do need the vitamin in the laboratory is much higher than natural levels in the seas and rivers. They discovered that in the natural environment were bacteria that could supply the necessary vitamin B12 the algae needed. However, the relationship between the bacteria and algae was not one-way. The scientists found that the algae supported the bacteria by providing them with carbon from their own photosynthesis.

Dr Alison Smith, one of the research leaders at the University of Cambridge, said, “What these observations demonstrate is that, although algae live by harvesting the sun’s energy through photosynthesis, many of them are like animals in that they need another organism to supply them with a vital nutrient. This has implications for how we consider the ecosystems in the world’s oceans.”

Professor Julia Goodfellow, BBSRC Chief Executive, said, “Algae fix around half of the world’s carbon so it is vital that we can understand what affects their growth and wellbeing. Research into fundamental relationships and microscopic bacteria may not seem important at first but it is only by improving our understanding at this level that we can discover how to maintain the health of ecosystems at a global level.”