Lichenized unicellular cyanobacteria fix nitrogen in the light
2007; Canadian Science Publishing; Volume: 85; Issue: 10 Linguagem: Inglês
10.1139/b07-092
ISSN1480-3305
AutoresP. D. Crittenden, Xavier Llimona, Leopoldo G. Sancho,
Tópico(s)Biocrusts and Microbial Ecology
ResumoDiurnal variation in N 2 -fixation (acetylene reduction) rate was measured in Thyrea girardii (Durieu & Mont.) Bagl. & Carestia and Thyrea confusa Henssen, lichens containing a unicellular cyanobacterial photobiont. In field assays, mean acetylene-reduction rates in the light were 25.8 ± 8.9 (n = 11) and 21.0 ± 5.6 nmol C 2 H 4 ·g –1 ·h –1 (n = 13) for T. girardii and T. confusa, respectively, and the respective mean rates in the dark were 8.2 ± 1.8 (n = 26) and 13.5 ± 5.4 (n = 8) nmol C 2 H 4 ·g –1 ·h –1 . In laboratory assays under relatively isothermal conditions (ca. 19–22 °C), the maximum acetylene reduction rate (52.0 ± 6.0 nmol C 2 H 4 ·g –1 ·h –1 ) was recorded in the light and the minimum rate (20.2 ± 6.0 nmol C 2 H 4 ·g –1 ·h –1 ) in the dark. This diurnal pattern is contrary to expectations for unicellular cyanobacteria. We suggest carbon flow to the fungal symbiont reduces the potential for nitrogenase activity in the dark.
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