Characterization of Arthrospira (Spirulina) strains
A culture collection of clonal, axenic cultures of 35 Arthrospira strains and five strains,
which were duplicate subcultures of the original isolates, was established. In addition, eight
morphological mutants were isolated from cultures of these strains. All strains are different
from those belonging to the genus Spirulina as concluded from TEM and PyMS studies. All
Arthrospira strains, duplicates and different morphotypes were screened for variation in
morphological, ultrastructural, physiological and biochemical characters for taxonomic
Special emphasis was put on the analysis of factors which influence the morphology of the
trichome helix, as this is the feature most characteristic forArthrospira strains. For
example, the orientation of coiling was found to be influenced by genetic drift or the growth
temperature, but can also be reversed by mechanical impact.
Studies were also made on the ability to utilize sugars for growth. None of the strains
grew on sucrose, but many grew on glucose and/or fructose. Growth in the presence of
sucrose under photoheterotrophic conditions required an adaptation process, though sucrose
is not being utilized for growth.
Analysis of fatty acid composition of all strains revealed quantitative differences between
strains, most markedly in the unsaturated fatty acid fraction. Repeat experiments showed the
same results each time, indicating the value of this approach for identification purposes.
Similarly, lectin-binding to cell surface structures proved to be a useful approach for
differentiation between strains.
Analysis of the whole cell composition by pyrolysis mass spectrometry (PyMS) did not
confirm the clusters based on other phenotypic characters, but showed that there is a high
similarity between duplicate strains or different morphotypes derived from the same stock.
Numerical analysis of the data for 28 characters resolved the helical strains in two
phenotypic clusters which show a high correlation to the two molecular clusters based on
ARDRA of the ITS of the same set of strains.
The helical trichome morphology of the strains showed the highest correlation to either of
the clusters. Comparison of species descriptions and morphological characters of the strains,
as determined in the presented work, indicate, that phenotypic cluster I is composed of
Arthrospira maxima, A. fusiformis and A. indica, while A. platensis forms phenotypic