DaveO -

Starting with a glop of sea water, a normal procedure would be to add a culture medium so that the critter you're looking for grows and multiplies, preferably faster than the other critters in your sample. Once you have enough of them to see them and play around with them, you add something to the soup to kill of "everything else."

The cyanobacteria, unfortunately, has been impossible to "culture" in this way.

On the assumption that it exists, and is in the sample, with the new DNA replication process(es), you can make selected DNA bits replicate to get larger samples of just the DNA "pieces."

The article doesn't give details, but it might be expected that the researchers have then "subtracted out" (probably via computer analysis) the DNA bits known to be parts of the "genetics" for any other organisms they found in the sample.

What's left over must have come from the cyanobactera.

(A problem not mentioned is how they decided what to do for the bits that may be in both the cyanobacteria and in other "organisms" that might have been in the sample; but other research has suggested quantative methods for estimating the probabilities - if they had a big enough computer.)

The value of what's (maybe) been done is that it revealed that the cyanobacteria (probably) lacks any photosynthesis mechanism, so light exposure (possibly) should be omitted from new attempts to culture it directly. It also (maybe) is adversely affected by oxygen, so an anearobic condition (perhaps) is needed. The results cited (appear to) confirm that genetic mechanisms exist (probably) in this critter for benefiting from lots of nitrogen.

The results, if confirmed, may suggest ways to actually "grow" the bacterium in question so that sufficient (and sufficiently pure) samples can be cultured. If that can be done, eventually someone may be actually able to "see" this particular varmint and learn what it can do.

Similar(?) nitrogen fixing organisms are found in soils, and my impression is that a little more is known about them. If enough can be learned about these sea-faring organisms, the vast areas of the sea suggest that we may learn ways to make them "healthier" so that more available nitrogen can stimulate the phytoplanktons that may help with CO₂ sequestering.

Present knowledge doesn't tell us how we can stimulate this critter, and of course the next (eventual) question will be whether we should try to help it along.

John