Transcriptional response of Nautella italica R11 towards its macroalgal host uncovers new mechanisms of host–pathogen interaction

Abstract

Macroalgae (seaweeds) are essential for the functioning of temperate marine ecosystems, but there is increasing evidence to suggest that their survival is under threat from anthropogenic stressors and disease. Nautella italica R11 is recognized as an aetiological agent of bleaching disease in the red alga, Delisea pulchra. Yet, there is a lack of knowledge surrounding the molecular mechanisms involved in this model host-pathogen interaction. Here we report that mutations in the gene encoding for a LuxR-type quorum sensing transcriptional regulator, RaiR, render N. italica R11 avirulent, suggesting this gene is important for regulating the expression of virulence phenotypes. Using an RNA sequencing approach, we observed a strong transcriptional response of N. italica R11 towards the presence of D. pulchra. In particular, genes involved in oxidative stress resistance, carbohydrate and central metabolism were upregulated in the presence of the host, suggesting a role for these functions in the opportunistic pathogenicity of N. italica R11. Furthermore, we show that RaiR regulates a subset of genes in N. italica R11, including those involved in metabolism and the expression of phage-related proteins. The outcome of this research reveals new functions important for virulence of N. italica R11 and contributes to our greater understanding of the complex factors mitigating microbial diseases in macroalgae.

Bacterial Communities Associated With Four Blooming Scyphozoan Jellyfish: Potential Species-Specific Consequences for Marine Organisms and Humans Health

“…Genus Nautella , identified in the umbrella of N. nomurai , was dominated by N. italica , an etiological agent of bleaching in the red alga Delisea pulchra ( Case et al, 2011 ; Gardiner et al, 2017 ; Hudson et al, 2018 ). The most abundant species of genus Acinetobacter , detected in the oral arms of C. nozakii , was A. schindleri , a human pathogen ( McGann et al, 2013 ; Jani et al, 2019 ).…”

Global Metabolome Analysis of Dunaliella tertiolecta, Phaeobacter italicus R11 Co-cultures using Thermal Desoprtion - Comprehensive Two-dimensional Gas Chromatography - Time-of-Flight Mass Spectrometry (TD-GC×GC-TOFMS)

“…Previously, Schaffer et al have identified a plant metabolite, coumaric acid, that can replace the HSL tail to form a hybrid material-host signal [26], and so an analogous system with the HSL ring structure being host derived warrants further investigation. Alternatively, the Dunaliella teriolecta metabolite could be an HSL antagonist as Phaeobacter italicus R11 is known to produce HSLs which are antagonised by the algal metabolites, furanores [11] [27] [28].…”

Introduction: The host‐associated microbiome: Pattern, process and function

“…Induction of bacteriophage by plants is one means of plant defence against bacterial pathogens (Gill & Abedon, ). These results suggest Delisea may protect itself in the same way and that N. italica subverts this defence by repressing prophage, through a quorum‐sensing‐dependent mechanism (Hudson, Gardiner, Deshpande, & Egan, ).…”