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Transcriptional and translational regulation of nitrogenase in light-dark- and continuous-light-grown cultures of the unicellular cyanobacterium Cyanothece sp. strain ATCC 51142.

Abstract：

:Cyanothece sp. strain ATCC 51142 is a unicellular, diazotrophic cyanobacterium which demonstrated extensive metabolic periodicities of photosynthesis, respiration, and nitrogen fixation when grown under N2-fixing conditions. N2 fixation and respiration peaked at 24-h intervals early in the dark or subjective-dark period, whereas photosynthesis was approximately 12 h out of phase and peaked toward the end of the light or subjective-light phase. Gene regulation studies demonstrated that nitrogenase is carefully controlled at the transcriptional and posttranslational levels. Indeed, Cyanothece sp. strain ATCC 51142 has developed an expensive mode of regulation, such that nitrogenase was synthesized and degraded each day. These patterns were seen when cells were grown under either light-dark or continuous-light conditions. Nitrogenase mRNA was synthesized from the nifHDK operon during the first 4 h of the dark period under light-dark conditions or during the first 6 h of the subjective-dark period when grown in continuous light. The nitrogenase NifH and NifDK subunits reached a maximum level at 4 to 10 h in the dark or subjective-dark periods and were shown by Western blotting and electron microscopy immunocytochemistry to be thoroughly degraded toward the end of the dark periods. An exception is the NifDK protein (MoFe-protein), which appeared not to be completely degraded under continuous-light conditions. We hypothesize that cellular O2 levels were kept low by decreasing photosynthesis and by increasing respiration in the early dark or subjective-dark periods to permit nitrogenase activity. The subsequent increase in O2 levels resulted in nitrogenase damage and eventual degradation.

journal_name

J Bacteriol

journal_title

Journal of bacteriology

authors

Colón-López MS,Sherman DM,Sherman LA

doi

10.1128/jb.179.13.4319-4327.1997

subject

Has Abstract

pub_date

1997-07-01 00:00:00

pages

4319-27

issue

eissn

0021-9193

issn

1098-5530

journal_volume

179

pub_type

杂志文章

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Transcriptional and translational regulation of nitrogenase in light-dark- and continuous-light-grown cultures of the unicellular cyanobacterium Cyanothece sp. strain ATCC 51142.