Are fish immunocompetent enough to face climate change?

Ongoing climate change has already been associated with increased disease outbreaks in wild and farmed fish. Here, we evaluate the current knowledge of climate change-related ecoimmunology in teleosts with a focus on temperature, hypoxia, salinity and acidification before exploring interactive effects of multiple stressors. Our literature review reveals that acute and chronic changes in temperature and dissolved oxygen can compromise fish immunity which can lead to increased disease susceptibility. Moreover, temperature and hypoxia have already been shown to enhance the infectivity of certain pathogens/parasites and to accelerate disease progression. Too few studies exist that have focussed on acidification, but direct immune effects seem to be limited while salinity studies have led to contrasting results. Likewise, multi-stressor experiments essential for unravelling the interactions of simultaneously changing environmental factors are still scarce. This ultimately impedes our ability to estimate to what extent climate change will hamper fish immunity. Our review about epigenetic regulation mechanisms highlights the acclimation potential of the fish immune response to changing environments. However, due to the limited number of epigenetic studies, overarching conclusions cannot be drawn. Finally, we provide an outlook on how to better estimate the effects of realistic climate change scenarios in future immune studies in fish

Biparental immune priming in the broad-nosed pipefish (Syngnathus typhle)

All living organisms are permanently exposed to harmful parasites and pathogens. The immune system and with it sophisticated strategies arose to face challenging pathogens such as bacteria and viruses. One outstanding strategy is the transfer of immunity from mothers to offspring known as “trans-generational immune priming” (TGIP). Through the transfer of acquired immunological protection mothers can boost the immune defense of their offspring and facilitate resistance against bacteria present in the maternal environment. Commonly, TGIP is limited to females and was considered to be a maternal trait. Yet, in the sex-role reversed pipefish Syngnathus typhle fathers are closely connected to the embryos during male pregnancy over a placenta-like structure. This intimate physical connection between fathers and offspring may mechanistically facilitate additional paternal immune priming and provides an exclusive chance to study biparental investment into offspring immunity. In my thesis, I explored multi-generational biparental immune priming in the sex-role reversed pipefish S. typhle and discussed its evolutionary and ecological consequences as well as the mechanistic basis.Alle lebenden Organismen sind permanent allgegenwärtigen infektiösen Parasiten und Pathogenen ausgesetzt. Ausgelöst durch ihre schädliche Wirkung auf die Fitness ihres Wirtes evolvierten sich mit dem Immunsystem verschiedene Abwehrmechanismen, um einen Schutz zu gewährleisten. Eine raffinierte Strategie ist die Übertragung von erworbener Immunität von Müttern auf die Nachkommen über die Plazenta oder Muttermilch, bekannt als „generationsübergreifende Immunprägung". Mit der Weitergabe von erworbenem Immunschutz können somit Mütter die Immunabwehr ihrer Nachkommen in der frühen embryonalen Entwicklung gewährleisten. Zudem ermöglicht es den Nachkommen schneller eine Resistenz gegen die in der mütterlichen Umgebung vorhandenen Krankheitserreger aufzubauen. Daher wurde bisher davon ausgegangen, dass Immunprägung nur durch das weibliche Geschlecht verwirklicht wird. Doch in dem seltenen Fall der Grasnadel Syngnathus typhle ist die Rollenverteilung der Geschlechter vertauscht. Bei dieser besonderen Fischart brüten die Männchen während einer männlichen Schwangerschaft ihre Embryonen in einer Bruttasche und sind über eine plazenta-ähnliche Struktur so eng mit ihnen verbunden, dass mechanistisch eine väterliche Immunprägung möglich wäre. In meiner Doktorarbeit habe ich die Aspekte der biparentalen Immunprägung über zwei Generationen in der Grasnadel erforscht und ihre evolutionären und ökologischen Folgen, sowie mechanistische Grundlage näher untersucht

Biparental immune priming in the pipefish Syngnathus typhle

Highlights: • In a sex-role reversed pipefish, fathers have a major impact on offspring immunity. • Maternal effects are effective early in life but cease upon maturation. • Fathers provide long-term protection that comes with immunological specificity. • Long-term protection could be based on parental epigenetic traces. • Biparental immunological transfer comes with additive costs but lacks additive advantages. Abstract: The transfer of immunity from parents to offspring (trans-generational immune priming (TGIP)) boosts offspring immune defence and parasite resistance. TGIP is usually a maternal trait. However, if fathers have a physical connection to their offspring, and if offspring are born in the paternal parasitic environment, evolution of paternal TGIP can become adaptive. In Syngnathus typhle, a sex-role reversed pipefish with male pregnancy, both parents invest into offspring immune defence. To connect TGIP with parental investment, we need to know how parents share the task of TGIP, whether TGIP is asymmetrically distributed between the parents, and how the maternal and paternal effects interact in case of biparental TGIP. We experimentally investigated the strength and differences but also the costs of maternal and paternal contribution, and their interactive biparental influence on offspring immune defence throughout offspring maturation. To disentangle maternal and paternal influences, two different bacteria were used in a fully reciprocal design for parental and offspring exposure. In offspring, we measured gene expression of 29 immune genes, 15 genes associated with epigenetic regulation, immune cell activity and life-history traits. We identified asymmetric maternal and paternal immune priming with a dominating, long-lasting paternal effect. We could not detect an additive adaptive biparental TGIP impact. However, biparental TGIP harbours additive costs as shown in delayed sexual maturity. Epigenetic regulation may play a role both in maternal and paternal TGIP

A modular approach to the antifungal sphingofungin family: concise total synthesis of sphingofungin A and C

Sphingofungins are fungal natural products known to inhibit the biosynthesis of sphingolipids which play pivotal roles in various cell functions. Here, we report a short and flexible synthetic approach towards the sphingofungin family. Key step of the synthesis was a decarboxylative cross-coupling reaction of chiral sulfinyl imines with a functionalized tartaric acid derivative, which yielded the core motive of sphingofungins carrying four consecutive stereocenters and a terminal double bond. Subsequent metathesis reaction allowed for the introduction of different side chains of choice resulting in a total of eight sphingofungins, including for the first time sphingofungin C (eight steps from commercially available protected tartaric acid with an overall yield of 6%) and sphingofungin A (ten steps). All newly synthesized derivatives were tested for their antifungal, cell proliferative and antiparasitic activity unraveling their structure-activity relations

Actinomadura rubteroloni sp. nov. and Actinomadura macrotermitis sp. nov., isolated from the gut of the fungus growing-termite Macrotermes natalensis

The taxonomic positions of two novel aerobic, Gram-positive actinobacteria, designated strains RB29$^{T}$ and RB68T, were determined using a polyphasic approach. Based on 16S rRNA gene sequence analysis, the closest phylogenetic neighbours of RB29$^{T}$ were identified as Actinomadura rayongensis DSM 102126$^{T}$ (99.2 % similarity) and Actinomadura atramentaria DSM 43919$^{T}$ (98.7 %), and for strain RB68$^{T}$ was Actinomadura hibisca DSM 44148$^{T}$ (98.3 %). Digital DNA–DNA hybridization (dDDH) between RB29$^{T}$ and its closest phylogenetic neighbours, A. rayongensis DSM 102126$^{T}$ and A. atramentaria DSM 43919$^{T}$, resulted in similarity values of 53.2 % (50.6–55.9 %) and 26.4 % (24.1–28.9 %), respectively. Additionally, the average nucleotide identity (ANI) was 93.2 % (94.0 %) for A. rayongensis DSM 102126$^{T}$ and 82.3 % (78.9 %) for A. atramentaria DSM 43919$^{T}$. dDDH analysis between strain RB68$^{T}$ and A. hibisca DSM 44148$^{T}$ gave a similarity value of 24.5 % (22.2–27.0 %). Both strains, RB29$^{T}$ and RB68$^{T}$, revealed morphological characteristics and chemotaxonomic features typical for the genus Actinomadura, such as the presence of meso-diaminopimelic acid in the cell wall, galactose and glucose as major sugar components within whole-cell hydrolysates and the absence of mycolic acids. The major phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannoside. Predominant menaquinones were MK-9(H$_{6}$) and MK-9(H$_{8}$) for RB29$^{T}$ and MK-9(H$_{4}$) and MK-9(H$_{6}$) for RB68T. The main fatty acids were identified as 10-methyloctadecanoic acid (10-methyl C$_{18:0}$), 14-methylpentadecanoic acid (iso-C$_{16:0}$), hexadecanoic acid (C$_{16:0}$) and cis-9-octadecanoic acid (C$_{18:1}$ ω9c). Here, we propose two novel species of the genus Actinomadura: Actinomadura rubteroloni sp. nov. with the type strain RB29$^{T}$ (=CCUG 72668$^{T}$=NRRL B-65537$^{T}$) and Actinomadura macrotermitis sp. nov. with the type strain RB68$^{T}$ (=CCUG 72669$^{T}$=NRRL B-65538$^{T}$)

Comparative Genomics Reveals Prophylactic and Catabolic Capabilities of Actinobacteria within the Fungus-Farming Termite Symbiosis

Actinobacteria, one of the largest bacterial phyla, are ubiquitous in many of Earth’s ecosystems and often act as defensive symbionts with animal hosts. Members of the phylum have repeatedly been isolated from basidiomycete-cultivating fungus-farming termites that maintain a monoculture fungus crop on macerated dead plant substrate. The proclivity for antimicrobial and enzyme production of Actinobacteria make them likely contributors to plant decomposition and defense in the symbiosis. To test this, we analyzed the prophylactic (biosynthetic gene cluster [BGC]) and metabolic (carbohydrate-active enzyme [CAZy]) potential in 16 (10 existing and six new genomes) termite-associated Actinobacteria and compared these to the soil-dwelling close relatives. Using antiSMASH, we identified 435 BGCs, of which 329 (65 unique) were similar to known compound gene clusters, while 106 were putatively novel, suggesting ample prospects for novel compound discovery. BGCs were identified among all major compound categories, including 26 encoding the production of known antimicrobial compounds, which ranged in activity (antibacterial being most prevalent) and modes of action that might suggest broad defensive potential. Peptide pattern recognition analysis revealed 823 (43 unique) CAZymes coding for enzymes that target key plant and fungal cell wall components (predominantly chitin, cellulose, and hemicellulose), confirming a substantial degradative potential of these bacteria. Comparison of termite-associated and soil-dwelling bacteria indicated no significant difference in either BGC or CAZy potential, suggesting that the farming termite hosts may have coopted these soil-dwelling bacteria due to their metabolic potential but that they have not been subject to genome change associated with symbiosis. IMPORTANCE Actinobacteria have repeatedly been isolated in fungus-farming termites, and our genome analyses provide insights into the potential roles they may serve in defense and for plant biomass breakdown. These insights, combined with their relatively higher abundances in fungus combs than in termite gut, suggest that they are more likely to play roles in fungus combs than in termite guts. Up to 25% of the BGCs we identify have no similarity to known clusters, indicating a large potential for novel chemistry to be discovered. Similarities in metabolic potential of soil-dwelling and termite-associated bacteria suggest that they have environmental origins, but their consistent presence with the termite system suggests their importance for the symbiosis

Streptomyces smaragdinus sp. nov., isolated from the gut of the fungus growing-termite Macrotermes natalensis

The taxonomic position of a novel aerobic, Grampositive actinobacteria, designated strain RB5(T), was determined using a poly phasic approach. The strain, isolated from the gut of the fungusfarming termite Macrotermes natalensis, showed morphological, physiological and chemotaxonomic properties typical of the genus Streptomyces. Based on 16S rRNA gene sequence analysis, the closest phylogenetic neighbour of RB5(T) was Streptomyces polyrhachis DSM 42102(T) (98.87 %). DNA-DNA hybridization experiments between strain RB5(T) and S. polyrhachis DSM 42102(T) resulted in a value of 27.4 % (26.8 %). The cell wall of strain RB5(T) contained iota iota diaminopimelic acid as the diagnostic amino acid. Mycolic acids and diagnostic sugars in whole cell hydrolysates were not detected. The strain produced the following major phospholipids: diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositolmannoside and phosphatidylserine. The menaquinone profile showed hexaand octahydrogenated menaquinones containing nine isoprene units [MK-9(H-6) and MK-9(H-8)]. The strain exhibited a fatty acid profile containing the following major fatty acids: 12methyltridecanoic acid (isoC(14:0)) 12-methyltetradecanoic acid (anteiso-C-15:0), 13-methyltetradecanoic acid (isoC(15:0)) and 14-methylpentadecanoic acid (isoC(16:0)). Here, we propose a novel species of the genus Streptomyces - Streptomyces smaragdinus with the type strain RB5(T) (=VKM Ac-2839(T)=NRRL B65539(T))

Nocardia macrotermitis sp. nov. and Nocardia aurantia sp. nov., isolated from the gut of the fungus-growing termite Macrotermes natalensis

The taxonomic positions of two novel aerobic, Gram-stain-positive Actinobacteria, designated RB20$^{T}$ and RB56$^{T}$, were determined using a polyphasic approach. Both were isolated from the fungus-farming termite Macrotermes natalensis. Results of 16S rRNA gene sequence analysis revealed that both strains are members of the genus Nocardia with the closest phylogenetic neighbours Nocardia miyunensis JCM12860$^{T}$ (98.9 %) and Nocardia nova DSM44481$^{T}$ (98.5 %) for RB20$^{T}$ and Nocardia takedensis DSM 44801$^{T}$ (98.3 %), Nocardia pseudobrasiliensis DSM 44290$^{T}$ (98.3 %) and Nocardia rayongensis JCM 19832$^{T}$ (98.2 %) for RB56$^{T}$. Digital DNA–DNA hybridization (DDH) between RB20$^{T}$ and N. miyunensis JCM12860$^{T}$ and N. nova DSM 44481$^{T}$ resulted in similarity values of 33.9 and 22.0 %, respectively. DDH between RB56$^{T}$ and N. takedensis DSM44801$^{T}$ and N. pseudobrasiliensis DSM44290$^{T}$ showed similarity values of 20.7 and 22.3 %, respectively. In addition, wet-lab DDH between RB56$^{T}$ and N. rayongensis JCM19832$^{T}$ resulted in 10.2 % (14.5 %) similarity. Both strains showed morphological and chemotaxonomic features typical for the genus Nocardia , such as the presence of meso-diaminopimelic acid (A$_{2}$pm) within the cell wall, arabinose and galactose as major sugar components within whole cell-wall hydrolysates, the presence of mycolic acids and major phospholipids (diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol), and the predominant menaquinone MK-8 (H4, ω-cyclo). The main fatty acids for both strains were hexadecanoic acid (C$_{16 : 0}$), 10-methyloctadecanoic acid (10-methyl C$_{18 : 0}$) and cis-9-octadecenoic acid (C$_{18 : 1}$ ω9c). We propose two novel species within the genus Nocardia : Nocardia macrotermitis sp. nov. with the type strain RB20$^{T}$ (=VKM Ac-2841$^{T}$=NRRL B65541$^{T}$) and Nocardia aurantia sp. nov. with the type strain RB56$^{T}$ (=VKM Ac-2842$^{T}$=NRRL B65542$^{T}$)

Trans-generational plasticity in response to immune challenge is constrained by heat stress

Trans-generational plasticity is the adjustment of phenotypes to changing habitat conditions that persist longer than the individual lifetime. Fitness benefits (adaptive TGP) are expected upon matching parent-offspring environments. In a global change scenario, several performance-related environmental factors are changing simultaneously. This lowers the predictability of offspring environmental conditions, potentially hampering the benefits of trans-generational plasticity. For the first time, we here explore how the combination of an abiotic and a biotic environmental factor in the parental generation plays out as trans-generational effect in the offspring. We fully reciprocally exposed the parental generation of the pipefish Syngnathus typhle to an immune challenge and elevated temperatures simulating a naturally occurring heatwave. Upon mating and male pregnancy, offspring were kept in ambient or elevated temperature regimes combined with a heat-killed bacterial epitope treatment. Differential gene expression (immune genes and DNA- and histone-modification genes) suggests that the combined change of an abiotic and a biotic factor in the parental generation had interactive effects on offspring performance, the temperature effect dominated over the immune challenge impact. The benefits of certain parental environmental conditions on offspring performance did not sum up when abiotic and biotic factors were changed simultaneously supporting that available resources that can be allocated to phenotypic trans-generational effects are limited. Temperature is the master regulator of trans-generational phenotypic plasticity, which potentially implies a conflict in the allocation of resources towards several environmental factors. This asks for a reassessment of trans-generational plasticity as a short-term option to buffer environmental variation in the light of climate change