Pyrolysis mass spectrometry analysis of free-living and symbiotic cyanobacteria

The potential of pyrolysis mass spectrometry to distinguish closely related cyanobacterial strains was assessed by using the technique to compare symb iotic cyanobacteria isolated from the hornwort Phaeoceros laevis and free-l iving cyanobacterial strains at the same field site. The same strains had p reviously been compared using polymerase chain reaction-based DNA fingerpri nting techniques (West & Adams 1997, Appl. Environ. Microbiol. 63: 4479-448 4). Many of the strains were grouped identically by the two techniques, alt hough there were some differences, possibly resulting from the ability of t hese cyanobacteria to develop a range of specialised cell types having diff erent chemical compositions to the vegetative cells. Although growth condit ions were chosen to suppress cellular differentiation, this may not always have been completely successful. With careful control of growth conditions pyrolysis mass spectrometry has considerable potential as an additional too l for the phenetic comparison of cyanobacterial strains. It has the advanta ge that analysis is directly derived from whole cells, and hence is simpler and cheaper than DNA-based methods, although it does require the growth of axenic strains. The technique may be particularly useful in the study of s ome of the more cryptic unicellular and non-heterocystous filamentous cyano bacterial groups, in which the lack of cellular differentiation should mini mise any variability in the chemical composition of cells.