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Targeted microarray analysis of two symbiotic cyanobacterial diazotroph strains in the western tropical North Atlantic

ABSTRACT: We designed a new specific mRNA microarray targeting a subset of genes (956) of the diazotrophs Richelia intracellularis and Calothrix rhizosoleniae (genomes RintRC01, RintHH01, RintHM01 and CalSC01) which associate with diatom hosts. The aim was to be able to describe the gene expressions of genes related to several metabolic pathways, specifically nitrogen fixation and how they possibly differed between the closely related strains based on environment and host association. In this study we focused on the RintRC01 and RintHH01. To better understand how the gene expression of nitrogen fixation genes relates to nitrogen fixation rates both gene expression and rate measurements were done in parallell.

ORGANISM(S): seawater metagenome Calothrix rhizosoleniae Richelia intracellularis

PROVIDER: GSE139589 | GEO | 2019/10/31

REPOSITORIES: GEO

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Project description:Biological nitrogen fixation, the microbial reduction of atmospheric nitrogen to bioavailable ammonia, represents both a major limitation on biological productivity and a highly desirable engineering target for synthetic biology. However, the engineering of nitrogen fixation requires an integrated understanding of how the gene regulatory dynamics of host diazotrophs respond across sequence-function space of its central catalytic metalloenzyme, nitrogenase. Here, we interrogate this relationship by analyzing the transcriptome of Azotobacter vinelandii engineered with a phylogenetically inferred ancestral nitrogenase protein variant. The engineered strain exhibits reduced cellular nitrogenase activity but recovers wild-type growth rates following an extended lag period. We find that expression of genes within the immediate nitrogen fixation network is resilient to the introduced nitrogenase sequence-level perturbations. Rather the sustained physiological compatibility with the ancestral nitrogenase variant is accompanied by reduced expression of genes that support trace metal and electron resource allocation to nitrogenase. Our results spotlight gene expression changes in cellular processes adjacent to nitrogen fixation as productive engineering considerations to improve compatibility between remodeled nitrogenase proteins and engineered host diazotrophs. IMPORTANCE Azotobacter vinelandii is a key model bacterium for the study of biological nitrogen fixation, an important metabolic process catalyzed by nitrogenase enzymes. Here, we demonstrate that compatibilities between engineered A. vinelandii strains and nitrogenase variants can be modulated at the regulatory level. The engineered strain studied here responds by adjusting the expression of proteins involved in cellular processes adjacent to nitrogen fixation, rather than that of nitrogenase proteins themselves. These insights can inform future strategies to transfer nitrogenase variants to non-native hosts.

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Targeted microarray analysis of two symbiotic cyanobacterial diazotroph strains in the western tropical North Atlantic

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