Autecology, allelopathy and toxicity of Limnothrix (strain AC0243): Multiple-organism studies using laboratory cultures

This study examines the growth, allelopathy and toxicity of laboratory cultures of the cyanobacterium Limnothrix (strain AC0243). Key findings of the research show evidence that this strain demonstrates ecological plasticity and should be considered as a potentially dangerous invasive species. General observations of the strain under normal (non-experimental) conditions showed extensive plasticity in terms of colony morphology. These forms included floating and non-floating ‘ball’ colonies, well structured colonies attached to the tissue culture flasks, sheets of intertwined trichomes loosely attached to the flasks or planktonic masses. No specific trigger could be attributed to the changes in morphology. Trials were performed to determine if allelopathy occurred between some species of microfungi and Limnothrix (strain AC0243), both of which are commonly recovered from the same niche. The results of these experiments suggested symbiotic or commensual relationships with Fusarium species and Acremonium species but not Cladosporium sphaerospermum. Cladosporium sphaerospermum inhibited growth of the cyanobacterium, although no allelopathy occurred, as determined by the lack of inhibition zones surrounding the colony. Allelopathy occurred when Limnothrix (strain AC0243) was grown Page 5 of 312 with ‘self’ inoculum, suggesting a quorum sensing mediated recognition of antagonism.