  We introduce various models for cellulose bio-degradation by micro-organisms.
Those models rely on complex chemical mechanisms, involve the structure of the
cellulose chains and are allowed to depend on the phenotypical traits of the
population of micro-organisms. We then use the corresponding models in the
context of multiple-trait populations. This leads to classical, logistic type,
reproduction rates limiting the growth of large populations but also, and more
surprisingly, limiting the growth of populations which are too small in a
manner similar to the effects seen in populations requiring cooperative
interactions (or sexual reproduction). This study hence offers a striking
example of how some mechanisms resembling cooperation can occur in structured
biological populations, even in the absence of any actual cooperation.
