Morphological and physiological properties of symbiotic cyanobacteria

Abstract

SUM MARVThe main morphological and physiological characters of several symbiotic cyanobacterial strains, isolated from different plant-cyanobacteria associations {Anthoceros, Azalla, cycads and Gunnerd) were investigated. All the strains showed heterocystous immotile filaments and motile hormogonia, typical of the genus Nostoc. In accordance with their symbiotic origin, all were found capable of photoheterotrophic growtb. On the basis of the morphological and physiological properties and tbe phycobiliprotein content, the isolates from Asolla appeared very close to eacb otber and quite distinct from tbe otber cyanobionts. The latter sbowed many characteristics in common, sucb as marked tendency to produce bormogonia, synthesis of C-pbycoerytbrin and ratber small dimensions of the akinetes. With regard to the cycad cyanobionts, there vias no coTre\atwn between the properties of the isolates and tbe bast plants.

Colonization of wheat (Triticum vulgare L.) by N2‐fixing cyanobacteria: III. The role of a hormogonia‐promoting factor

“…Thus, microorganisms (Al-Mallah, Davey & Cocking, the infection process will probably depend on Cockmget al, 1990;Quispel, 1990), including motility in the cyanobacterium, which may, at least cyanobacteria (Gusev & Korzhenevskaya, 1990). We partly, explain why cyanobacteria associated symhave described the colonization of wheat roots by biotically with plants are almost invariably Nostoc certain N.^-fixing cyanobacteria when co-cultivated species (Peters, 1990;Vagnoli et al, 1992). The in a liquid medium (Gantar, Kerby & Rowell, possession of hormogonia, which is the main charac-1991 a; Gantar et al, 1991 b).…”

Characterization by genotypic methods of symbiotic Nostoc strains isolated from five species of Gunnera

“…In the classification system of cyanobacteria proposed by Rippka et al (1979), the genus Nostoc is classified to section IV, which is defined as filamentous cyanobacteria able to differentiate specialized N 2 -fixing cells (heterocysts), and are in addition characterized by division in one plane only. However, the extreme morphological flexibility of Nostoc species, which is influenced by the life cycle stage and environmental conditions (Vagnoli et al 1992;Mollenhauer et al 1994;Dodds et al 1995), makes identification and taxonomy based on morphology alone problematic. Therefore, supplementary genetic information should be incorporated to give a polyphasic classification system for the genus Nostoc.…”

“…The genus Nostoc dominates in terrestrial systems and includes cyanobacteria with the capacity to form symbioses with an exceptionally broad range of plants such as bryophytes (liverworts and hornworts), fungi, Azolla (a water fern), cycads (gymnosperms) and Gunnera (an angiosperm) (Bergman et al 1996;Rai et al 2000). Traditionally, the taxonomy of Nostoc species has been based on morphological and physiological observations (Vagnoli et al 1992). In the classification system of cyanobacteria proposed by Rippka et al (1979), the genus Nostoc is classified to section IV, which is defined as filamentous cyanobacteria able to differentiate specialized N 2 -fixing cells (heterocysts), and are in addition characterized by division in one plane only.…”

Artificial Cyanobacterium-Plant Symbioses

“…Media for cultivation of plant tissues contain 5 times more mineral nitrogen than BG-11 medium, and 10 to 35 times more sucrose, than required for photoheterotrophic growth of Nostoc cyanobionts (Vagnoli et al, 1992). Increased CG content, lack of and modest amounts of other carbon containing inclusions (PHB-like and indicate a shift in intracellular N:C balance towards nitrogen.…”