Project description:Seawater exposure to the gram negative marine bacterium Vibrio diazotrophicus induces a robust cellular response in sea urchin larvae that includes the migration of pigment cells to the gut epithelium, changes in cell behavior and altered gut morphology (Ho et al., 2016; PMID 27192936). To investigate the transcriptional underpinnings of this response, whole transcriptome sequencing was performed on mRNA isolated from larval samples collected at 0, 6, 12 and 24 hr of exposure to V. diazotrophicus. The morphological simplicity of the sea urchin larva provides a systems-level model for identifying biologically relevant transcriptional state changes in response to dysbiosis in the gut lumen.
Project description:Gluconacetobacter diazotrophicus has been the focus of several studies aiming to understand the mechanisms behind this endophytic diazotrophic bacterium. The present study is the first global analysis of the early transcriptional response of exponentially growing G. diazotrophicus to iron, an essential cofactor for many enzymes involved in various metabolic pathways. RNA-seq, targeted gene mutagenesis and computational motif discovery tools were used to define the G. diazotrophicus Fur regulon. The data analysis showed that genes encoding functions related to iron homeostasis, were significantly upregulated in response to iron limitation. Certain genes involved in the secondary metabolism were overexpressed under iron-limited conditions. In contrast, it was observed that the expression of genes involved in Fe-S cluster biosynthesis, flagellar biosynthesis and type IV secretion systems were downregulated in an iron-depleted culture medium. Our results support a model that control transcription in G. diazotrophicus by Fur function. The G. diazotrophicus Fur protein was able to complement an E. coli fur mutant. These results provide new insights into the effects of iron on the metabolism of G. diazotrophicus, as well as demonstrating the essentiality of this micronutrient for the main characteristic of plant growth promotion by G. diazotrophicus.
