Biodiversity of marine microbes is safeguarded by phenotypic heterogeneity in ecological traits

Why, contrary to theoretical predictions, do marine microbe communities harbor tremendous phenotypic heterogeneity? How can so many marine microbe species competing in the same niche coexist? We discovered a unifying explanation for both phenomena by investigating a non-cooperative game that interpolates between individual-level competitions and species-level outcomes. We identified all equilibrium strategies of the game. These strategies represent the probability distribution of competitive abilities (e.g. traits) and are characterized by maximal phenotypic heterogeneity. They are also neutral towards each other in the sense that an unlimited number of species can co-exist while competing according to the equilibrium strategies. Whereas prior theory predicts that natural selection would minimize trait variation around an optimum value, here we obtained a mathematical proof that species with maximally variable traits are those that endure. This discrepancy may reflect a disparity between predictions from models developed for larger organisms in contrast to our microbe-centric model. Rigorous mathematics proves that phenotypic heterogeneity is itself a mechanistic underpinning of microbial diversity. This discovery has fundamental ramifications for microbial ecology and may represent an adaptive reservoir sheltering biodiversity in changing environmental conditions.

Trophic upgrading and mobilization of wax esters in microzooplankton

Heterotrophic protists play pivotal roles in aquatic ecosystems by transferring matter and energy, including lipids, from primary producers to higher trophic predators. Using Oxyrrhis marina as a model organism, changes to the non-saponifiable protist lipids were investigated under satiation and starvation conditions. During active feeding on the alga Cryptomonas sp., the O. marina hexane soluble non-saponifiable fraction lipid profile reflected its food source with the observed presence of long chain mono-unsaturated fatty alcohols up to C25:1. Evidence of trophic upgrading in O. marina was observed with long chain mono-unsaturated fatty alcohol accumulation of up to C35:1. To the best of our knowledge, this is the first evidence that heterotrophic dinoflagellates are capable of producing ester derived alcohols and that dinoflagellates like O. marina are capable of synthesizing fatty alcohols up to C₃₅. Additionally, we show evidence of trophic upgrading of lipids. During a 20-day resource deprivation, the lipid profile remained constant. During starvation, the mobilization of wax esters as energy stores was observed with long chain fatty alcohols mobilized first. Changes in lipid class profile and utilization of wax esters in O. marina provides insight into the types of lipids available for energy demand, the transfer of lipids through the base of marine food webs, and the catabolic response induced by resource deprivation.

The role of intraspecific variation in the ecological and evolutionary success of diatoms in changing environments

Intraspecific variation in diatoms has been shown to play a key role in species' responses to several important environmental factors such as light, salinity, temperature and nutrients. Furthermore, modelling efforts indicate that this variation within species extends bloom periods, and likely provides sufficient variability in competitive interactions between species under hydrographically variable conditions. The intraspecific variation most likely corresponds to optimal fitness in temporary microhabitats and may help to explain the paradox of the plankton. Here, we examine the implications of intraspecific variation for the ecology and success of diatoms in general and emphasize the potential implications for our understanding of carbon metabolism in these important organisms. Additionally, data from palaeoecological studies have the potential for evaluating genetic variation through past climate changes, going thousands of years back in time. We suggest pathways for future research including the adoption of multiple strains of individual species into studies of diatom carbon metabolism, to refine our understanding of the variation within and between species, and the inclusion of experimental evolution as a tool for understanding potential evolutionary responses of diatom carbon metabolism to climate change.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'.

The Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP): illuminating the functional diversity of eukaryotic life in the oceans through transcriptome sequencing

Current sampling of genomic sequence data from eukaryotes is relatively poor, biased, and inadequate to address important questions about their biology, evolution, and ecology; this Community Page describes a resource of 700 transcriptomes from marine microbial eukaryotes to help understand their role in the world's oceans.

Psychotherapy of bereavement after homicide

The author presents guidelines for the assessment and initial treatment of bereavement after a homicide. Early interventions include nonverbal techniques applied in individual and group therapy. Because patients are over-whelmed and reactive, initial treatment strategy is supportive and focuses on reestablishing resiliency rather than on preexisting vulnerabilities (ambivalence, guilt, repression, denial). Adjustment to homicidal dying is lifelong, and therapist and patient should acknowledge that change may be limited.