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Appl. Environ. Microbiol., Nov 1997, 4479-4484, Vol 63, No. 11
NJ West and DG Adams
PCR amplification techniques were used to compare cyanobacterial symbionts
from a cyanobacterium-bryophyte symbiosis and free-living cyanobacteria
from the same field site. Thirty-one symbiotic cyanobacteria were isolated
from the hornwort Phaeoceros sp. at several closely spaced locations, and
40 free-living cyanobacteria were isolated from the immediate vicinity of
the same plants. One of the symbiotic isolates was a species of Calothrix,
a genus not previously known to form bryophyte symbioses, and the remainder
were Nostoc spp. Of the free-living strains, two were Calothrix spp., three
were Chlorogloeopsis spp. and the rest were Nostoc spp. All of the
symbiotic and all but one of the free-living strains were able to
reconstitute the symbiosis with axenic cultures of both Phaeoceros and the
liverwort Blasia sp. Axenic cyanobacterial strains were compared by DNA
amplification using PCR with either short arbitrary primers or primers
specific for the regions flanking the 16S-23S rRNA internal transcribed
spacer. With one exception, the two techniques produced complementary
results and confirmed for the first time that a diversity of symbiotic
cyanobacteria infect Phaeoceros in the field. Symbionts from adjacent
colonies were different as often as they were the same, showing that the
same thallus could be infected with many different cyanobacterial strains.
Strains found to be identical by the techniques employed here were often
found as symbionts in different thalli at the same locale but were never
found free-living. Only one of the free-living strains, and none of the
symbiotic strains, was found at more than one sample site, implying a
highly localized distribution of strains.
Copyright © 1997, American Society for Microbiology
Phenotypic and Genotypic Comparison of Symbiotic and Free-Living Cyanobacteria from a Single Field Site
Department of Microbiology, University of Leeds, Leeds LS2 9JT, United Kingdom
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