Sulphate‐limited growth in the N₂‐fixing unicellular cyanobacterium Gloeothece (Nägeli) sp. PCC 6909

Abstract

SUMMARYThe utiicellular diazotrophic cyanobacterium Gloeothece PCC 6909 v\'as grown in batch and continuous culture. It was found that the organism scavenged sulphate from the medium and incorporated it in the poiysaccharide sheath. As a result batch cultures became sulphur-depleted whilst continuous cultures were sulphur-limited. This was observed regardless of the nitrogen source of the culture. Sulphur-depletion was the reason for the low nitrogenase activities usually obsenxd in hatch cultures of Gloeothece. Sulphate-amended cultures showed sustained high nitrogenase activity in the light. Sulphate uptake from the medium was light-dependent. Earlier work on N^ fixation in Gloeothece is discussed in the hght of possible sulphur limitation.

Complexity of cyanobacterial exopolysaccharides: composition, structures, inducing factors and putative genes involved in their biosynthesis and assembly

“…Despite some evidence, this last point is still controversial. Differences in the sulphur content and in the monosaccharidic composition reported for the sheath and RPS of some cyanobacteria strongly support the hypothesis of different biosynthetic pathways (Tease et al, 1991;Ortega-Calvo & Stal, 1994;Li et al, 2002;Micheletti et al, 2008b). However, further studies are needed to fully elucidate these pathways in cyanobacteria.…”

Aerobic nitrogen fixation is confined to a subset of cells in the non‐heterocystous cyanobacterium Symploca PCC 8002

“…Other non-heterocystous species such as the unicellular Gloeothece (Mullineaux et al, 1981) and the filamentous Oscillatoria (Stal & Heyer, 1987) initiate N # fixation in the dark and perform N # fixation primarily in the absence of light. Under certain growth and nutrient conditions however, Gloeothece performs nitrogenase activity in the light even during light\dark cycles (Ortega-Calvo & Stal, 1991 ;Du & Gallon, 1993 ;Ortega-Calvo & Stal, 1994). It should therefore be kept in mind that the N # fixation patterns observed in the laboratory might be influenced by specific growth conditions and may not reflect the actual activity patterns in nature.…”

A spatial investigation of the environmental controls over cryoconite aggregation on Longyearbreen glacier, Svalbard

“…Cyanobacterial EPS has been found to be particularly complex (De Phillipis and Vincenzini, 1998;Pereira et al, 2009). In low-nutrient environments, EPS production can, perhaps surprisingly, be stimulated (Myklestad and Haug, 1972), particularly in phototrophic microorganisms (Ortega-Calvo and Stal, 1994). Furthermore, EPS has been found to actively promote flocculation and aggregation (Bar-Or and Shilo, 1988;Zulpa de Caire et al, 1997).…”