REVERSAL OF HELIX ORIENTATION IN THE CYANOBACTERIUM ARTHROSPIRA¹

Abstract

A survey of the morphological characters of 36 clonal axenic strains of Arthrospira showed that 34 had helical and 2 had straight trichomes. Of those with helical trichomes, five were right‐handed and 29 left‐handed. After repeated subculture for 1 year, the orientation of one helical strain (D893) had changed from right‐ to left‐handed, suggesting a probable genetic shift. The influence of environmental factors on helix orientation was tested on a subset of 10 strains. A temperature upshift from 30 to 32–34° C for 7 days led to a change in orientation in three strains (D918/H, D923, D925). Incubation at 32° C (D918/H, D923) or 34° C (D925) for periods less than needed for the morphological change to show still permitted the change to take place subsequently, when the temperature was reduced to 30° C; however, further subculture at 30° C led to the orientation reverting to its original state. In strain D925, but not the other nine strains, continuous shaking at 30° C also led to a change in helix orientation. In this case, some trichomes showed both orientations in a single trichome, with a snag at the point of reversion. A repeat survey of the stock cultures of all 34 strains after 2 years showed that another strain (D918/H) had now changed orientation from right‐handed to left‐handed. These observations are compared with the behavior of other helical structures in the literature, including filamentous Bacillus subtilis mutants and helix reversal in tendrils of climbing plants.

The Selective Value of Bacterial Shape

“…An unusual but similar phenomenon is exhibited by the cyanobacterium Arthrospira, which grows as helical trichomes, i.e., long filaments of individual cells encased and aligned within a common tubular structure (224). When exposed to protistan grazing, two helical Arthrospira trichomes began the experiment growing as right-handed spiral trichomes.…”

“…When exposed to protistan grazing, two helical Arthrospira trichomes began the experiment growing as right-handed spiral trichomes. However, at the end of the experiments these had changed so that left-handed spiral filaments dominated (224). In fact, while grazing, the ciliate predator rotates to follow the Arthrospira spiral during feeding (224) and turns on its axis while sucking in up to six complete bacterial coils (A. Belay, personal communication).…”

“…However, at the end of the experiments these had changed so that left-handed spiral filaments dominated (224). In fact, while grazing, the ciliate predator rotates to follow the Arthrospira spiral during feeding (224) and turns on its axis while sucking in up to six complete bacterial coils (A. Belay, personal communication). Also, the helical pitch of the spirals seems to matter, because no grazing is observed if the Arthrospira trichomes are tightly coiled (A. Belay, personal communication).…”

Photosynthesis and growth of Arthrospira (Spirulina) platensis (Cyanophyta) in response to solar UV radiation, with special reference to its minor variant

“…can alter according to environmental changes. Mühling et al (2003) found that the helix orientation could be reversed by temperature changes. Wang and Zhao (2005) proved that the morphogenesis of Arthrospira filaments from spiral to linear was due to DNA mutation.…”

Avaliação da utilização do dióxido de carbono proveniente da fermentação alcoólica no cultivo de Spirulina (Arthrospira) platensis: uso simultâneo de nitrato de sódio e sulfato de amônio como fontes de nitrogênio em fotobiorreator aberto

“…Destacam-se principalmente pela natureza dos pigmentos fotossintéticos -a clorofila "a" e as ficobiliproteínas, e pela estrutura e composição química da parede celular, As espécies do gênero Arthrospira são formadas principalmente por tricomascadeias de células cilíndricas dispostas em forma helicoidal, que variam de tamanho e morfologia conforme as condições de crescimento (CIFERRI, 1983;TIBONI, 1985). A orientação desses tricomas, por exemplo, pode ser afetada pela temperatura a qual as células são submetidas, ou por qualquer tipo de estresse mecânico, como a agitação contínua durante um cultivo (MÜHLING et al, 2003 As espécies do gênero Arthrospira ocorrem naturalmente no solo, na areia, nas marismas, em água doce, em água salobra e em água do mar (CIFERRI, 1983;TIBONI, 1985). São tipicamente encontradas em alguns lagos alcalinos e salinos do México e da África, especialmente na região africana de Chad (ABDULQADER; BARSANTI; TREDICI, 2000), onde crescem naturalmente junto a outras cianobactérias em lagos com concentração salina inferior a 30 g L -1 e com pH entre 7,0 e 9,5 (CIFERRI, 1983;TIBONI, 1985).…”