There is currently much interest in developing technology to use microlgae or cyanobacteria for the
production of bioenergy and biomaterials. Here, we summarize some remarkable achievements in
strains improvement by traditional genetic engineering and discuss common drawbacks for further
progress. We present general knowledge on natural microalgal-bacterial mutualistic interactions
and discuss the potential of recent developments in genetic engineering of multispecies microbial
cell factories. This synthetic biology approach would rely on the assembly of complex metabolic
networks from optimized metabolic modules such as photosynthetic or nitrogen-fixing parts.