Accelerated rock erosion

In examining the variety of life around us we have discovered bacteria suited for every niche, and this method merely accelerates a natural process which results in the excavation of rock, forming subterranean caverns, or unusual surface lakes, this process has also been used to hollow out asteroids, in more modern space applications.

The organisms responsible are not just a single species of bacteria, but a community of many different types of bacteria, who live around one process, eating rock. Some of these bacteria excrete very powerful acids, and these acids dissolve the rock. The bacteria themselves are tolerant of the pH and live quite happily in an environment that is stronger than battery acid, and they obtain their energy from chemical manipulation of the dissolved rock chemicals. It is at this stage where we begin to see the real complexity in the system, some bacteria act as a scaffold holding the community to the rock face, and providing organic compounds to the more specialized bacteria which process the minerals into a biologically accessible form. These kind of natural systems survive independently of sunshine or other energy sources, though they prefer marine environments.

However there remains one problem before we can put these organisms to work for shaping rock, they are tortuously slow, and very often very choosy about their substrates (nearly all examples within the federation rely mainly on carbonates), these limiting factors have somewhat been subverted by modern genetic engineering.

The resulting bacteria can now can eat rock surfaces away at perhaps metres per year, depending on rock type, though still very slow work, caverns can be rapidly excavated by fracturing up the rock beforehand greatly expanding the working surface. Also as the bacteria get established the ambient pH of the space decreases rapidly, and to levels lower than even their original extremes, so much so that even non-colonized rock is rapidly broken down.

Though this acceleration is magnificent it also poses problems, firstly in containing the bacteria, secondly to stop the acid water leaking into local ecosystems and destroying what already exists.

To limit the spread of the bacteria, a number of different techniques have been established. The first, and simplest method is to make the organisms dependent on a particular substance which is administered controllably by site coordinators, bacteria spreading beyond the main body of the growth medium are in solutions containing very little of the dependent chemical, and so their growth is arrested. A problem in this method is the threat of bacteria becoming able to synthesize the substance themselves again, usually by incorporating foreign DNA.

Another method is making the bacteria dependent on a symbiote, whose numbers can be very precisely controlled, without the symbiotic organisms present the working population declines, as by itself it can not survive. A common example is use of virus in a eukaryotic system. The virus itself can interact with the cells in one of two ways, the first is a destructive lytic cycle, which destroys the cell but releases replicated copies of the virus, the second is a lysogenic cycle in which the virus incorporates into the cell, and both exist together.

If the cell is programmed to depend upon the virus for regulation (in the lysogenic mode) of a particular function, say the lengthening of telomeres (which in turn govern the number of times the organisms can replicate), then the removal of the virus, or switching the virus to lytic cycle (triggered by certain conditions) will destroy the organism population, as those resistant to the virus lack its regulation, and therefore cease to function, and those who able to be infected by the virus are destroyed in lysis. Tailored virii as mentioned above can reliably control large populations of cells, with their altered genomes there is relatively little risk of bacteria taking the genes necessary to survive independently of the virus.

The oldest method which is still very much in use, involves the incorporation of suicide genes, genes which when a certain condition is met destroy the cell, and release potent chemicals that destroy other nearby cells. This method has been refined to such a degree than even if some cells in the population have corrupted control genes, the sheer release of toxic compounds from the other ‘normal’ cells guarantees sterilization of the working environment.

            In any modern application many of these control methods are used back to back to reliably control the population, but with nearly all things in bioforming there is a risk of loss of containment, which is more severe the more hospitable the environment. It is partly for this reason why bioforming is used in terraforming projects, as beyond the nurtured conditions provided the organisms cannot survive.