Details:

Journal Title:
BMC Genomics
Personal Author:
Harke, Matthew J. ; Gobler, Christopher J.
Harke, Matthew J. ; Gobler, Christopher J. Less -
NOAA Program & Office:
NOS (National Ocean Service) ; NCCOS (National Centers for Coastal Ocean Science)
NOS (National Ocean Service) ; NCCOS (National Centers for Coastal Ocean Science) Less -
Description:
Background: While transcriptomics have become a valuable tool for linking physiology and ecology in aquatic microbes, the temporal dynamics of global transcriptomic patterns in Microcystis have rarely been assessed. Furthermore, while many microbial studies have explored expression of nutrient transporter genes, few studies have concurrently measured nutrient assimilation rates. Here, we considered how the global transcriptomic patterns and physiology of the cyanobacterium, Microcystis aeruginosa, changed daily as cells were grown from replete to deficient nitrogen (N) conditions and then back to replete conditions.

Results: During N deprivation, Microcystis downregulated genes involved in photosynthesis and respiration, carbon acquisition, lipid metabolism, and amino acid biosynthesis while upregulating genes involved in N acquisition and transport. With increasing N stress, both the strength of expression and number of genes being differentially expressed increased, until N was restored at which point these patterns reversed. Uptake of 15N-labeled nitrate, ammonium and urea reflected differential expression of genes encoding transporters for these nutrients, with Microcystis appearing to preferentially increase transcription of ammonium and urea transporters and uptake of these compounds during N deprivation. Nitrate uptake and nitrate transporter expression were correlated for one set of transporters but not another, indicating these were high and low affinity nitrate transporters, respectively. Concentrations of microcystin per cell decreased during N deprivation and increased upon N restoration. However, the transcript abundance of genes involved in the synthesis of this compound was complex, as microcystin synthetase genes involved in peptide synthesis were downregulated under N deprivation while genes involved in tailoring and transport were upregulated, suggesting modification of the microcystin molecule under N stress as well as potential alternative functions for these genes and/or this toxin.

Conclusions: Collectively, this study highlights the complex choreography of gene expression, cell physiology, and toxin synthesis that dynamic N levels can elicit in this ecologically important cyanobacterium. Differing expression patterns of genes within the microcystin synthetase operon in response to changing N levels revealed the potential limitations drawing conclusions based on only one gene in this operon.


Keywords:
[+]
Microcystis Nitrogen
Source:
BMC Genomics. 2015; 16: 1068.
DOI:
https://dx.doi.org/10.1186/s12864-015-2275-9
Pubmed ID:
26673568
Pubmed Central ID:
PMC4681089
Document Type:
Journal Article
Funding:
Grant no. NA10NOS4780140
Rights Information:
CC BY
Compliance:
PMC
Main Document Checksum:
[+]
urn:sha256:a32c2dc7bb427cc66719af490823788c272ae34f1020b9ed8da8c236c361f85b
Download URL:
https://repository.library.noaa.gov/view/noaa/27667/noaa_27667_DS1.pdf
File Type:

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