Terraformation motifs involving closed cooperation among players. Two main classes ofpotential engineered synthetic microbes (SYN) interacting with their hosts (H) are indicated. Assuming that theengineered species has been obtained from an existing one in the same environment, the wild type (hereindicated as WT) can be obtained from SYN if the engineered construct is lost by mutation (here indicated as afray arrow, and as a rate μ) As SYN and WT are in essence the same organisms, they compete for the sameresources. In (a) we display a logic diagram of positive interactions among both partners defining a mutualdependency. In (b) such cooperative interaction is mediated through some class of physical factor, such aswater (W). These two classes correspond, for example, to exclusive mutualistic interactions displayed by plantcells within root nodules (c) where nitrogen-fixing bacteria are physically embedded (image from http://en.wikipedia.org/wiki/Rootnodule). On the other hand, the need for survival under stressful conditions,as those common in arid ecosystems, makes water a major player and limiting resource. An engineeredmicrobe capable of improving moisture retention can have a very strong effect on the underlying plantspecies, expanding their populations. In soil crusts (d) a whole range of species exist, adapted to water-poorconditions (drawing adapted from Belnap et al 2001). Here we indicate (1) mosses (2,3) lichens, (4,5,7,9) cyanobacteria, (6) fungi and (8) green algae.