Characteristics of hormogonia formation by symbiotic Nostoc spp. in response to the presence of Anthoceros punctatus or its extracellular products

Nostocacean cyanobacteria typically produce gliding filaments termed hormogonia at a low frequency as part of their life cycle. We report here that all Nostoc spp. competent in establishing a symbiotic association with the hornwort Anthoceros punctatus formed hormogonial filaments at a high frequenc...

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Bibliographic Details
Published in:Applied and Environmental Microbiology 1989-01, Vol.55 (1), p.125-131
Main Authors: Campbell, E.L, Meeks, J.C
Format: Article
Language:English
Subjects:
Anthoceros punctatus
AZOTE
Bacteriology
Biogenesis of cell structures, supramolecular organization
Biological and medical sciences
CHAMPIGNON
FISIOLOGIA VEGETAL
Fundamental and applied biological sciences. Psychology
FUNGI
Microbiology
Microorganism-Plant Interactions
NITROGENO
NOSTOC
PHYSIOLOGIE VEGETALE
SIMBIOSIS
SYMBIOSE
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Summary:Nostocacean cyanobacteria typically produce gliding filaments termed hormogonia at a low frequency as part of their life cycle. We report here that all Nostoc spp. competent in establishing a symbiotic association with the hornwort Anthoceros punctatus formed hormogonial filaments at a high frequency in the presence of A. punctatus. The hormogonia-inducing activity was produced by A. punctatus under nitrogen-limited culture conditions. The hormogonia of the symbiotically competent Nostoc spp. were characterized as motile (gliding) filaments lacking heterocysts and with distinctly smaller cells than those of vegetative filaments; the small cells resulted from a continuation of cell division uncoupled from biomass increase. An essentially complete conversion of vegetative filaments to hormogonia occurred within 12 h of exposure of Nostoc sp. strain 7801 to A . punctatus growth-conditioned medium. Hormogonia formation was accompanied by loss of nitrogen fixation (acetylene reduction) and by decreases in photosynthetic CO2 fixation and in vivo NH4+ assimilation of 30% and approximately 40%, respectively. The rates of acetylene reduction and CO2 fixation returned to approximately the control rates within 72 to 96 h after hormogonia induction, as the cultures of Nostoc sp. strain 7801 differentiated heterocysts and reverted to the vegetative growth state. The relationship between hormogonia formation and symbiotic competence is discussed
ISSN:0099-2240
1098-5336
DOI:10.1128/AEM.55.1.125-131.1989