Notwithstanding plants’ rightly applauded self-sufficiency, and remarkable life-sustaining synthetic abilities using basic inorganic ingredients, some plant-like organisms need a little extra help in the form of organic compounds. Such organisms are known as auxotrophs and a common requirement is for certain vitamins (those ‘vital amines’ of days gone by) in the case of certain algae. The good news is that vitamins such as B12 are provided by bacteria, which the algae happily ‘appropriate’. The bad news is that work by Sergio Sañudo-Wilhelmy et al. reveals that coastal waters of large areas of the eastern Pacific Ocean are vitamin-deficient. Which is really bad news because the algae dependent upon such external sources of vitamins are major players on the world stage, both in terms of their primary production – hence knock-on effects on the ecosystems they would otherwise support – and their being significant producers of the oxygen we rely on for life. But, the – potential (let’s be scientifically cautious about this…) – good news is that Erin Bertrand and colleagues have identified a ‘cobalamin acquisition protein’ in diatoms. So? Well, cobalamin is an alternative name for cobalt-containing Vitamin B12, which appears to be required by those unicellular algae (which are particularly abundant in the oceans and which are reputedly responsible for approximately 40% of marine primary productivity). This so-called ‘B12 claw’ is located in the cell wall and binds to B12, helping it to be taken up into the cell. Now here’s the really important bit: when external B12 supplies are scarce more of the cobalamin acquisition protein is made. So, all that’s necessary is to engineer the gene for this protein into algae in vitamin-deficient areas of the Pacific (and elsewhere) and the deficiency is overcome. Simple! Not quite… Sergio Sañudo-Wilhelmy et al. found multiple vitamin deficiency… Hmmm, claws for thought?
PS. I know you’re wondering (or should be!), so to put your collective minds at rest: higher plants neither make nor need vitamin B12 because their version of the enzyme for which this is otherwise a co-factor – methionine synthase – is cobalamin-independent.