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Essential oils (EOs) and their individual volatile organic constituents have been an inherent part of our civilization for thousands of years. They are widely used as fragrances in perfumes and cosmetics and contribute to a healthy diet, but also act as active ingredients of pharmaceutical products. Their antibacterial, antiviral, and anti-inflammatory properties have qualified EOs early on for both, the causal and symptomatic therapy of a number of diseases, but also for prevention. Obtained from natural, mostly plant materials, EOs constitute a typical example of a multicomponent mixture (more than one constituent substances, MOCS) with up to several hundreds of individual compounds, which in a sophisticated composition make up the property of a particular complete EO. The integrative use of EOs as MOCS will play a major role in human and veterinary medicine now and in the future and is already widely used in some cases, e.g. , in aromatherapy for the treatment of psychosomatic complaints, for inhalation in the treatment of respiratory diseases, or topically administered to manage adverse skin diseases. The diversity of molecules with different functionalities exhibits a broad range of multiple physical and chemical properties, which are the base of their multi-target activity as opposed to single isolated compounds. Whether and how such a broad-spectrum effect is reflected in natural mixtures and which kind of pharmacological potential they provide will be considered in the context of ONE Health in more detail in this review.

Major biogeographic features of the microbial seascape in the oceans have been established and their underlying ecological mechanisms in the (sub)tropical oceans and the Pacific Ocean identified. However, we still lack a unifying understanding of how prokaryotic communities and biogeographic patterns are affected by large-scale current systems in distinct ocean basins and how they are globally shaped in line with ecological mechanisms. Here we show that prokaryotic communities in the epipelagic Pacific and Atlantic Ocean, in the southern Indian Ocean, and the Mediterranean Sea are composed of modules of co-occurring taxa with similar environmental preferences. The relative partitioning of these modules varies along latitudinal and longitudinal gradients and are related to different hydrographic and biotic conditions. Homogeneous selection and dispersal limitation were identified as the major ecological mechanisms shaping these communities and their free-living (FL) and particle-associated (PA) fractions. Large-scale current systems govern the dispersal of prokaryotic modules leading to the highest diversity near subtropical fronts. This study investigated how ecological mechanisms and large-scale oceanic current systems shape prokaryotic microbial community patterns. They show that prokaryotic communities in the upper 200 m of the Pacific and Atlantic Ocean, the southern Indian Ocean, and the Mediterranean Sea have a modular structure of co-occurring taxa with similar environmental preferences.

Microbial communities are major drivers of global elemental cycles in the oceans due to their high abundance and enormous taxonomic and functional diversity. Recent studies assessed microbial taxonomic and functional biogeography in global oceans but microbial functional biogeography remains poorly studied. Here we show that in the near-surface Atlantic and Southern Ocean between 62°S and 47°N microbial communities exhibit distinct taxonomic and functional adaptations to regional environmental conditions. Richness and diversity showed maxima around 40° latitude and intermediate temperatures, especially in functional genes (KEGG-orthologues, KOs) and gene profiles. A cluster analysis yielded three clusters of KOs but five clusters of genes differing in the abundance of genes involved in nutrient and energy acquisition. Gene profiles showed much higher distance-decay rates than KO and taxonomic profiles. Biotic factors were identified as highly influential in explaining the observed patterns in the functional profiles, whereas temperature and biogeographic province mainly explained the observed taxonomic patterns. Our results thus indicate fine-tuned genetic adaptions of microbial communities to regional biotic and environmental conditions in the Atlantic and Southern Ocean. The taxonomic and functional diversity of marine microbial communities are shaped by both environmental and biotic factors. Here, the authors investigate the functional biogeography of epipelagic prokaryotic communities along a 13,000-km transect in the Southern and Atlantic Oceans, showing finely tuned genetic adaptations to regional conditions.

Dissolved organic matter (DOM) in the oceans constitutes a major carbon pool involved in global biogeochemical cycles. More than 96% of the marine DOM resists microbial degradation for thousands of years. The composition of this refractory DOM (RDOM) exhibits a molecular signature ubiquitously detected in the deep oceans. Surprisingly efficient microbial transformation of labile into stable forms of DOM has been shown previously, implying that microorganisms apparently produce far more RDOM than needed to sustain the global pool. Here we show, by assessing the microbial formation and transformation of DOM in unprecedented molecular detail for 3 years, that most of the microbial DOM is different from RDOM in the ocean. Only <0.4% of the net community production is channelled into a form of DOM that is undistinguishable from oceanic RDOM. Our study provides a molecular background for global models on the production, turnover and accumulation of marine DOM. The extent to which the microbial carbon pump contributes to the generation of marine refractory dissolved organic matter (RDOM) remains a matter of debate. Here, the authors report results from a 3-year mesocosm study, and show that most of the microbial DOM is different from RDOM in the ocean.

In marine pelagic ecosystems energy is often the limiting factor for growth of heterotrophic bacteria. Aerobic anoxygenic photosynthesis (AAP) and oxidation of carbon monoxide (CO) are modes to acquire complementary energy, but their significance in abundant and characteristic pelagic marine bacteria has not been well studied. In long-term batch culture experiments we found that Planktomarina temperata RCA23, representing the largest and most prominent subcluster of the Roseobacter group, maintains 2–3-fold higher cell numbers in the stationary and declining phase when grown in a light-dark cycle relative to dark conditions. Light enables P. temperata to continue to replicate its DNA during the stationary phase relative to a dark control such that when reinoculated into fresh medium growth resumed two days earlier than in control cultures. In cultures grown in the dark and supplemented with CO, cell numbers in the stationary phase remained significantly higher than in an unsupplemented control. Furthermore, repeated spiking with CO until day 372 resulted in significant CO consumption relative to an unsupplemented control. P. temperata represents a prominent marine pelagic bacterium for which AAP and CO consumption, to acquire complementary energy, have been documented.

Cobalamin (vitamin B 12 , herein referred to as B 12 ) is an essential cofactor for most marine prokaryotes and eukaryotes 1 , 2 . Synthesized by a limited number of prokaryotes, its scarcity affects microbial interactions and community dynamics 2 – 4 . Here we show that two bacterial B 12 auxotrophs can salvage different B 12 building blocks and cooperate to synthesize B 12 . A Colwellia sp. synthesizes and releases the activated lower ligand α-ribazole, which is used by another B 12 auxotroph, a Roseovarius sp., to produce the corrin ring and synthesize B 12 . Release of B 12 by Roseovarius sp. happens only in co-culture with Colwellia sp. and only coincidently with the induction of a prophage encoded in Roseovarius sp. Subsequent growth of Colwellia sp. in these conditions may be due to the provision of B 12 by lysed cells of Roseovarius sp. Further evidence is required to support a causative role for prophage induction in the release of B 12 . These complex microbial interactions of ligand cross-feeding and joint B 12 biosynthesis seem to be widespread in marine pelagic ecosystems. In the western and northern tropical Atlantic Ocean, bacteria predicted to be capable of salvaging cobinamide and synthesizing only the activated lower ligand outnumber B 12 producers. These findings add new players to our understanding of B 12 supply to auxotrophic microorganisms in the ocean and possibly in other ecosystems. Two species of auxotrophic marine bacteria are shown to share precursors to synthesize the essential cofactor vitamin B 12 , and such ligand cross-feeding may be a common phenomenon in the ocean and other ecosystems.

The genus Octadecabacter is a member of the ubiquitous marine Roseobacter clade. The two described species of this genus, Octadecabacter arcticus and Octadecabacter antarcticus, are psychrophilic and display a bipolar distribution. Here we provide the manually annotated and finished genome sequences of the type strains O. arcticus 238 and O. antarcticus 307, isolated from sea ice of the Arctic and Antarctic, respectively. Both genomes exhibit a high genome plasticity caused by an unusually high density and diversity of transposable elements. This could explain the discrepancy between the low genome synteny and high 16S rRNA gene sequence similarity between both strains. Numerous characteristic features were identified in the Octadecabacter genomes, which show indications of horizontal gene transfer and may represent specific adaptations to the habitats of the strains. These include a gene cluster encoding the synthesis and degradation of cyanophycin in O. arcticus 238, which is absent in O. antarcticus 307 and unique among the Roseobacter clade. Furthermore, genes representing a new subgroup of xanthorhodopsins as an adaptation to icy environments are present in both Octadecabacter strains. This new xanthorhodopsin subgroup differs from the previously characterized xanthorhodopsins of Salinibacter ruber and Gloeobacter violaceus in phylogeny, biogeography and the potential to bind 4-keto-carotenoids. Biochemical characterization of the Octadecabacter xanthorhodopsins revealed that they function as light-driven proton pumps.

Background The Roseobacter group is a major component of prokaryotic communities in the global oceans. Information on this group is based predominantly on isolates and their genomic features and on the 16S rRNA gene. Assessments of prokaryotic communities in the pelagic of the global oceans indicated an unveiled diversity of this group but studies of the diversity and global biogeography of the entire group are still missing. Hence, we aimed at a comprehensive assessment of the Roseobacter group in the global oceans on the basis of MAGs and SAGs. Results The obtained 610 MAGs and 43 SAGs of high quality were subjected to in-depth analyses of their phylogeny, genomic and functional features. The recruitment locations range from the tropics to polar regions, include all major ocean basins. The phylogenetic analysis delineated the known RCA cluster and five pelagic clusters, two of which were completely novel: TCR (Temperate and Cold Roseobacter ), AAPR (Arctic-Atlantic-Pacific Roseobacter , novel), AAR (Arctic-Atlantic Roseobacter , novel), COR (Central Oceanic Roseobacter ), LUX ( Cand . Luxescamonaceae) cluster. These clusters account for ~ 70% of all Roseobacter MAGs and SAGs in the epipelagic. The TCR, AAPR, AAR, and LUX clusters are among the most deeply branching lineages of the Roseobacter group. These clusters and several sublineages of the RCA and COR clusters exhibit distinct features of genome streamlining, i.e. genome sizes of < 2.9 Mbp and G + C contents of < 40%. The clusters exhibit differences in their functional features and also compared to other lineages of the Roseobacter group. Proteorhodopsin is encoded in most species of the AAPR, AAR, TCR, and RCA clusters and in a few species of the COR cluster, whereas in most species of the latter, the LUX cluster and in a few species of the RCA cluster aerobic anoxygenic photosynthesis is encoded. Biogeographic assessments showed that the AAPR, AAR, TCR and RCA clusters constitute the Roseobacter group in the temperate to polar regions to great extent whereas the COR and LUX clusters in the tropics and subtropics. Conclusions Our comprehensive analyses shed new light on the diversification, genomic features, environmental adaptation, and global biogeography of a major lineage of pelagic bacteria. 38CQ_iBm9T2VLF_Tyinxsd Video Abstract

Algal polysaccharides are an important bacterial nutrient source and central component of marine food webs. However, cellular and ecological aspects concerning the bacterial degradation of polysaccharide mixtures, as presumably abundant in natural habitats, are poorly understood. Here, we contextualize marine polysaccharide mixtures and their bacterial utilization in several ways using the model bacterium Alteromonas macleodii 83-1, which can degrade multiple algal polysaccharides and contributes to polysaccharide degradation in the oceans. Transcriptomic, proteomic and exometabolomic profiling revealed cellular adaptations of A. macleodii 83-1 when degrading a mix of laminarin, alginate and pectin. Strain 83-1 exhibited substrate prioritization driven by catabolite repression, with initial laminarin utilization followed by simultaneous alginate/pectin utilization. This biphasic phenotype coincided with pronounced shifts in gene expression, protein abundance and metabolite secretion, mainly involving CAZymes/polysaccharide utilization loci but also other functional traits. Distinct temporal changes in exometabolome composition, including the alginate/pectin-specific secretion of pyrroloquinoline quinone, suggest that substrate-dependent adaptations influence chemical interactions within the community. The ecological relevance of cellular adaptations was underlined by molecular evidence that common marine macroalgae, in particular Saccharina and Fucus , release mixtures of alginate and pectin-like rhamnogalacturonan. Moreover, CAZyme microdiversity and the genomic predisposition towards polysaccharide mixtures among Alteromonas spp. suggest polysaccharide-related traits as an ecophysiological factor, potentially relating to distinct ‘carbohydrate utilization types’ with different ecological strategies. Considering the substantial primary productivity of algae on global scales, these insights contribute to the understanding of bacteria–algae interactions and the remineralization of chemically diverse polysaccharide pools, a key step in marine carbon cycling.

Antibiotics are typically regarded as microbial weapons, but whereas their function at concentrations lethal for bacteria is often well characterized, the role of antibiotics at much lower concentrations as possibly found under natural conditions remains poorly understood. By using whole-transcriptome analyses and phenotypic screenings of the marine bacterium Phaeobacter inhibens we found that the broad-spectrum antibiotic tropodithietic acid (TDA) causes the same regulatory effects in quorum sensing (QS) as the common signaling molecule N-acyl-homoserine lactone (AHL) at concentrations 100-fold lower than the minimal inhibitory concentration against bacteria. Our results show that TDA has a significant impact on the expression of ~10% of the total genes of P. inhibens , in the same manner as the AHL. Furthermore, TDA needs the AHL associated LuxR-type transcriptional regulator, just as the AHL molecule. Low concentrations of antibiotics can obviously have a strong influence on the global gene expression of the bacterium that produces it and drastically change the metabolism and behaviour of the bacterium. For P. inhibens this includes motility, biofilm formation and antibiotic production, all important for settlement on new host-associated surfaces. Our results demonstrate that bacteria can produce antibiotics not only to antagonise other bacteria, but also to mediate QS like endogenous AHL molecules.