A step on the way to "grey goo"
Perhaps but I think we are quite a ways off from the horror scenario of nanotech and bacteria gone mad.
A journey of a 1000 miles begins with a single step.
Its the combination of dangers. First you tailor a bacterium to eat certain things. Thats ok. Then you tune it up in the lab to be REALLY efficient at eating and reproducing and eating and...... Some Dr Evil builds on that technology to tailor it to eat something else.... maybe you end up with the thing being able to eat ALL the rice/millet/sorghum/wheat/maize crop. AFAIK there are not all that many varieties any more in commercial use of these food plants.
The only nanotech you need is the old fashioned biological kind.