SPRINT-TB Theme 1 researchers had another look at this adaptation. Rather than shock starving the bacilli in saline, they added traces of a carbon source to the saline and observed the response of the bacteria. Interestingly, providing traces of a carbon source to M. smegmatis in saline (as opposed to shock-starving the microorganism), resulted in the formation of a small-cell morphotype: reductive cell division generated very short rodshaped cells with increased long-term viability. Upon addition of rich medium, these small resting cells grew back to larger standard cells before commencement of the regular cell division cycle. The fact that a new morphotype can be so easily generated by slight changes in culture conditions supports the notion of a surprising morphological plasticity of mycobacteria.
These observations were described in Future Microbiology in April 2015 (Wu ML, Dick T. Metabolic flexibility and morphological plasticity in mycobacteria. Future Microbiol. 2015 Apr;10:449-52).