TY - JOUR
T1 - Carotenoid production and phenotypic variation in Azospirillum brasilense
AU - Brenholtz, Gal Reem
AU - Tamir-Ariel, Dafna
AU - Okon, Yaacov
AU - Burdman, Saul
N1 - Publisher Copyright:
© 2017 Institut Pasteur
PY - 2017/6
Y1 - 2017/6
N2 - We assessed the occurrence of phenotypic variation in Azospirillum brasilense strains Sp7, Cd, Sp245, Az39 and phv2 during growth in rich media, screening for variants altered in colony pigmentation or extracellular polysaccharide (EPS) production. Previous studies showed that EPS-overproducing variants of Sp7 appear frequently following starvation or growth in minimal medium. In contrast, no such variants were detected during growth in rich media in the tested strains except for few variants of phv2. Regarding alteration in colony pigmentation (from pink to white in strain Cd and from white to pink in the others), strain Sp7 showed a relatively high frequency of variation (0.009–0.026%). Strain Cd showed a lower frequency of alteration in pigmentation (0–0.008%), and this type of variation was not detected in the other strains. In A. brasilense, carotenoid synthesis is controlled by two RpoE sigma factors and their cognate ChrR anti-sigma factors, the latter acting as negative regulators of carotenoid synthesis. Here, all tested (n = 28) pink variants of Sp7 carried mutations in one of the anti-sigma factor genes, chrR1. Our findings indicate that, in A. brasilense, phenotypic variation is strain- and environment-dependent and support the central role of ChrR1 in regulation of carotenoid production.
AB - We assessed the occurrence of phenotypic variation in Azospirillum brasilense strains Sp7, Cd, Sp245, Az39 and phv2 during growth in rich media, screening for variants altered in colony pigmentation or extracellular polysaccharide (EPS) production. Previous studies showed that EPS-overproducing variants of Sp7 appear frequently following starvation or growth in minimal medium. In contrast, no such variants were detected during growth in rich media in the tested strains except for few variants of phv2. Regarding alteration in colony pigmentation (from pink to white in strain Cd and from white to pink in the others), strain Sp7 showed a relatively high frequency of variation (0.009–0.026%). Strain Cd showed a lower frequency of alteration in pigmentation (0–0.008%), and this type of variation was not detected in the other strains. In A. brasilense, carotenoid synthesis is controlled by two RpoE sigma factors and their cognate ChrR anti-sigma factors, the latter acting as negative regulators of carotenoid synthesis. Here, all tested (n = 28) pink variants of Sp7 carried mutations in one of the anti-sigma factor genes, chrR1. Our findings indicate that, in A. brasilense, phenotypic variation is strain- and environment-dependent and support the central role of ChrR1 in regulation of carotenoid production.
KW - Anti-sigma factor
KW - Azospirillum
KW - Carotenoids
KW - Extracellular polysaccharides
KW - Phase variation
KW - Phenotypic variation
UR - http://www.scopus.com/inward/record.url?scp=85017190012&partnerID=8YFLogxK
U2 - 10.1016/j.resmic.2017.02.008
DO - 10.1016/j.resmic.2017.02.008
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C2 - 28263905
AN - SCOPUS:85017190012
SN - 0923-2508
VL - 168
SP - 493
EP - 501
JO - Research in Microbiology
JF - Research in Microbiology
IS - 5
ER -