Biological in situ resource utilization: synthetic biology as a key enabling technology

Hi all,
I'm new to the forum, but I'd like to start a discussion on biological in situ resource utilization: synthetic biology as a key enabling technology for utilizing resources on another solar body. I'd like to start by asking if anyone is familiar with any of the previous life-support systems that have been proposed such as CELLS or ESA's Melissa?

http://www.nas.nasa.gov/About/Education/SpaceSettlement/designer/regen.h...
http://ecls.esa.int/ecls/?p=melissa
MELIiSSA (Micro-Ecological Life Support System Alternative)

The question is this: If synthetic biology makes biological organisms easier to engineer, how would this change the previous proposed missions? If you were not limited to naturally occurring plants then what advantages might this give you?

Best,
John