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PHOTOAUTOTROPHIC GROWTH OF A RECENTLY ISOLATED N 2 ‐FIXING MARINE NON‐HETEROCYSTOUS FILAMENTOUS CYANOBACTERIUM, SYMPLOCA SP. (CYANOBACTERIA)
Author(s) -
Kumazawa Shuzo,
Yumura Shinichi,
Yoshisuji Hidekazu
Publication year - 2001
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1046/j.1529-8817.2001.037004482.x
Subject(s) - cyanobacteria , biology , photosynthesis , dcmu , darkness , photon flux , botany , diazotroph , photosystem ii , biophysics , physics , photon , bacteria , nitrogen fixation , optics , genetics
Photoautotrophic growth of a marine non‐heterocystous filamentous cyanobacterium, Symploca sp. strain S84, was examined under nitrate‐assimilating and N 2 ‐fixing conditions. Under continuous light, photon flux density of 55 μmol photons·m −2 ·s −1 was at a saturating level for growth, and light did not inhibit the growth rate under N 2 ‐fixing conditions even when the photon flux density was doubled (110 μmol photons·m −2 ·s −1 ). Doubling times of the N 2 ‐fixing cultures under 55 and 110 μmol photons·m −2 ·s −1 were about 30 and 31 h, respectively. Under 110 μmol photons·m −2 ·s −1 during the light phase of an alternating 12:12‐h light:dark (L:D) cycle, the doubling time of the N 2 ‐fixing culture was also about 30 h. When grown diazotrophically under a 12:12‐h L:D regime, C 2 H 2 reduction activity was observed mainly during darkness. In continuous light, relatively large cyclic fluctuations in C 2 H 2 reduction were observed during growth. The short‐term (<4 h) effect of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU; 5 μM) indicated that C 2 H 2 reduction activity was not influenced by photosynthetic O 2 evolution. Long‐term (24 h) effects of DCMU indicated that photosynthesis and C 2 H 2 reduction activity occur simultaneously. These results indicate that strain S84 grows well under diazotrophic conditions when saturating light is supplied either continuously or under a 12:12‐h L:D diel light regime.