Phenotypic variability between closely related Trichodesmium strains as a means to making the most out of heterogeneous microenvironments

Abstract

The cynobacteria Trichodesmium spp., play an important role in oceanic carbon and nitrogen cycles. Forming colonies that host diverse microorganisms likely enhances Trichodesmiums metabolic flexibility and resilience. Combining single-colony metagenomics and metatranscriptomics with a novel bioinformatic approach we investigated the community composition and transcriptional activity of 69 individual Trichodesmium thiebautii colonies collected from the northern Red Sea, Israel. Three Trichodesmium strains were detected in all colonies, each with a heterogenous yet distinct transcriptional-activity profile. N-fixation, superoxide dismutase, and ATPase activities were similar among colonies, while P and Fe uptake, as well as photosynthesis, were high in only few colonies. Colonies had no core microbiome with >70% dissimilarity in the associated microbial communities, yet, the abundance of some species was correlated with the activity of specific Trichodesmium strains. We propose Trichodesmium occupies heterogeneous microenvironments with which it deals through inter-strain phenotypic variability further fine-tuned through interactions with beneficial, non-fixed, heterotrophic colonizers.