GROWTH AND NITROGEN FIXATION OF THE DIAZOTROPHIC FILAMENTOUS NONHETEROCYSTOUS CYANOBACTERIUM TRICHODESMIUM SP. IMS 101 IN DEFINED MEDIA: EVIDENCE FOR A CIRCADIAN RHYTHM¹

Abstract

Trichodesmium sp. IMS 101, originally isolated from coastal western Atlantic waters by Prufert‐Bebout and colleagues and maintained in seawater‐based media, was successfully cultivated in two artificial media. Its characteristics of growth, nitrogen fixation, and regulation of nitrogen fixation were compared to those of natural populations and Trichodesmium sp. NIBB 1067. Results indicate that the culture grown in artificial media had nitrogen fixation characteristics similar to those when the culture is grown in seawater‐based medium and to those of Trichodesmium sp. in the natural habitat. The study provides practical artificial media to facilitate the physiological studies of these important diazotrophic cyanobacteria, as well as the cultivation of other Trichodesmium species in future studies. Manipulations of the light/dark cycle were performed to determine whether or not the daily cycle of nitrogen fixation is a circadian rhythm. Cultures grown under continuous light maintained the cycle for up to 6 days. We demonstrated that the daily cycle of nitrogen fixation in Trichodesmium sp. IMS 101 was at least partially under the control of a circardian rhythm.

A novel cohabitation between two diazotrophic cyanobacteria in the oligotrophic ocean

“…YBCII media (Chen et al, 1996) were not conducive to reconstitution. However, SO media, consisting of 75% seawater and 25% MilliQ water, and devoid of a fixed nitrogen source (Webb et al, 2001), exhibited repeated success.…”

“…All cultures were grown in autoclaved, sterilized YBCII media with no added nitrogen sources according to the protocol described in Chen et al, 1996. Nitrogen fixation was measured on the hetDA batch culture over a 26-h incubation period (Capone, 1993;Fu et al, 2008).…”

Gammaproteobacterial diazotrophs and nifH gene expression in surface waters of the South Pacific Ocean

“…Diel patterns of N 2 fixation activity in the marine cyanobacteria Trichodesmium, UCYN-A, and Crocosphaera watsonii have been reported, and while probably partially regulated by circadian rhythms (Chen et al, 1996), the cycles of nitrogenase activity are directly linked with access to energy supporting the enzyme and strategies for protection against inhibition by O 2 (Postgate, 1990;Rabouille et al, 2006). The diel cycle in the marine filamentous cyanobacterium Trichodesmium is well characterized, with the majority of the N 2 fixation occurring during the day (Staal et al, 2007b).…”

Spatial variation in N<sub>2</sub>-fixation rate and diazotroph activity in the Tropical Atlantic

“…Trichodesmium often forms dense surface blooms of large spatial extent and can clearly make a significant contribution to the local and global budget of oceanic nitrogen (Capone et al, 2005;Karl et al, 2002). Because of its size and prominence at sea, Trichodesmium has received a great deal of attention in both field (Capone et al, 1997;Carpenter, 1992;Capone et al, 2005) and laboratory studies (Ohki et al, 1986;Chen et al, 1996;Mulholland and Capone, 1999;Mulholland et al, 2004). As a result, we now have a much better understanding of the environmental factors and physiological underpinnings of N 2 -fixation by Trichodesmium than we do for any other marine diazotroph.…”