In:
Applied and Environmental Microbiology, American Society for Microbiology, Vol. 81, No. 22 ( 2015-11-15), p. 7730-7739
Kurzfassung:
Cyanobacteria are generally assumed to be effective competitors at low CO 2 levels because of their efficient CO 2 -concentrating mechanism (CCM), and yet how bloom-forming cyanobacteria respond to rising CO 2 concentrations is less clear. Here, we investigate changes in CCM gene expression at ambient CO 2 (400 ppm) and elevated CO 2 (1,100 ppm) in six strains of the harmful cyanobacterium Microcystis . All strains downregulated cmpA encoding the high-affinity bicarbonate uptake system BCT1, whereas both the low- and high-affinity CO 2 uptake genes were expressed constitutively. Four strains downregulated the bicarbonate uptake genes bicA and/or sbtA , whereas two strains showed constitutive expression of the bicA - sbtA operon. In one of the latter strains, a transposon insert in bicA caused low bicA and sbtA transcript levels, which made this strain solely dependent on BCT1 for bicarbonate uptake. Activity measurements of the inorganic carbon (C i ) uptake systems confirmed the CCM gene expression results. Interestingly, genes encoding the RuBisCO enzyme, structural carboxysome components, and carbonic anhydrases were not regulated. Hence, Microcystis mainly regulates the initial uptake of inorganic carbon, which might be an effective strategy for a species experiencing strongly fluctuating C i concentrations. Our results show that CCM gene regulation of Microcystis varies among strains. The observed genetic and phenotypic variation in CCM responses may offer an important template for natural selection, leading to major changes in the genetic composition of harmful cyanobacterial blooms at elevated CO 2 .
Materialart:
Online-Ressource
ISSN:
0099-2240
,
1098-5336
DOI:
10.1128/AEM.02295-15
Sprache:
Englisch
Verlag:
American Society for Microbiology
Publikationsdatum:
2015
ZDB Id:
223011-2
ZDB Id:
1478346-0
SSG:
12
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