Biology subjects

Goehlich, H.

Publications and source records attributed to Goehlich, H..

5 recordsLinked to original sources

bioRxiv2026

Parallel phenotypes underpinned by different genes in the visual system of two trans-isthmian coral reef fish species pairs

Understanding the genetic basis of adaptation in natural populations to changing environmental conditions is challenging. The relatively simple genotype-to-phenotype relationship between opsin genes and visual pigments offers a particularly informative model to explore the molecular mechanisms underpinning adaptive phenotypic change in natural populations. Here we leveraged the natural experiment provided by the tectonic closure of the Central American seaway that created allopatric, sister taxa in multiple, independent lineages of marine organisms and exposed them to distinct underwater light environments: either the more turbid Tropical Eastern Pacific (TEP), or the spectrally broader Caribbean Sea. Using two species pairs of planktivorous teleosts, the Azurina multilineata/A. atrilobata damselfish and the Cephalopholis (Paranthias) furcifer/C. colonus groupers, we explore to what extent visual sensitivity converged to similar adaptations in response to similar foraging strategies and shared underwater light in each marine basin. We found that the compression of the underwater light field towards the central portion of the spectrum from Caribbean to TEP waters is reflected in similar shifts towards the centre of the light spectrum in overall single and double cone sensitivities in both families. Both TEP species have single (short-wavelength) cone sensitivities shifted to longer wavelengths and double (long-wavelength) cone sensitivities shifted to shorter wavelengths, compared to their Caribbean counterparts. These parallel shifts in visual sensitivities observed in response to shared underwater light environments are accomplished by different underlying opsin gene toolsets in the two lineages. Similarly, expression changes in pathways associated with the visual system revealed limited parallelism at the molecular level.

evolutionary biology↗

bioRxiv2023

COMPLETE GENOME SEQUENCE OF VIBRIO SYNGNATHI SP. NOV., A FISH PATHOGEN, ISOLATED FROM THE KIEL FJORD

A new Vibrio strain K08M4T was isolated from the broad-nosed pipefish Syngnathus typhle in the Kiel Fjord. Infection experiments revealed that K08M4T is highly virulent for juvenile pipefish. Cells of strain K08M4T are Gram-stain-negative, curved rod-shaped and motile by means of a single polar flagellum. The strain can grow aerobically at 9 to 40{degrees}C, at pH 4 to 10.5 and tolerates up to 12% (w/v) NaCl. The most prevalent (> 10%) cellular fatty acids of K08M4T were C16:1{omega} 7c and C16:0. Whole-genome comparisons revealed that K08M4T represents a separate evolutionary lineage which is distinct from other Vibrio species and falls within the Vibrio Splendidus clade. The genome is 4,886,292 bp in size, consists of two circular chromosomes (3,298,328 bp, 1,587,964 bp), and comprises 4,178 protein-coding genes and 175 RNA genes. In this study, we describe the phenotypic features of the new isolate and present the annotation and analysis of its complete genome sequence. Based on these data, the new isolate represents a new species for which we propose the name Vibrio syngnathi. The type strain is K08M4T (=DSM 109818T). Supplementary materialOne supplementary figure and six supplementary table are available with the online version of the Manuscript.

microbiology↗

bioRxiv2022

SUB-OPTIMAL ENVIRONMENTAL CONDITIONS PROLONG PHAGE EPIDEMICS IN BACTERIAL POPULATIONS

Infections by filamentous phages influence bacterial fitness in various ways. While phage-encoded accessory genes, e.g., virulence genes, can be highly beneficial, the production of viral particles is energetically costly and often reduces bacterial growth. Consequently, if costs outweigh benefits, bacteria evolve resistance which can shorten phage epidemics. Abiotic conditions are known to influence the net-fitness effect for infected bacteria. Their impact on the dynamics and trajectories of host resistance evolution, however, remains yet unknown. To address this, we experimentally evolved the bacterium Vibrio alginolyticus in the presence of a filamentous phage at three different salinity levels, i.e., (1) ambient (2) 50% reduction, and (3) fluctuations between reduced and ambient. In all three salinities, bacteria rapidly acquired resistance through super infection exclusion (SIE), whereby phage-infected cells acquired immunity at the cost of reduced growth. Over time, SIE was gradually replaced by evolutionary fitter surface receptor mutants (SRM). This replacement was significantly faster at ambient and fluctuating conditions compared to the low saline environment. Our experimentally parameterized mathematical model explains that suboptimal environmental conditions, in which bacterial growth is slower, slow down phage resistance evolution ultimately prolonging phage epidemics. Our results imply that, if filamentous phages encode virulence genes, these may persist longer in bacterial populations at sub-optimal environmental conditions, which, in times of climate change, are becoming more frequent. Thus, our future ocean may favour the emergence of phage-born pathogenic bacteria, and impose a greater risk for disease outbreaks, impacting not only marine animals but also humans.

evolutionary biology↗

bioRxiv2021

HIGH VIRULENCE SELECTS FOR FAST HOST RESISTANCE EVOLUTION

Parasites and pathogens vary strikingly in their virulence and the resulting selection they impose on their hosts. While the evolution of different virulence levels is well studied, the evolution of host resistance in response to different virulence levels is less understood and as of now mainly based on observations and theoretical predictions with few experimental tests. Increased virulence can increase selection for host resistance evolution if resistance costs are outweighed by the benefits of avoiding infection. To test this, we experimentally evolved the bacterium Vibrio alginolyticus in the presence of two variants of the filamentous phage, VALG{Phi}8, that differ in their virulence. The bacterial host exhibited two alternative defence strategies against future phage infection: (1) super infection exclusion (SIE) whereby phage-infected cells were immune to subsequent infection at a cost of reduced growth, and (2) surface receptor mutations (SRM) in genes encoding the MSHA type-IV pilus providing resistance to infection by preventing phage attachment. While SIE emerged rapidly against both phages, SRM evolved faster against the high virulence compared to the low virulence phage. Using a mathematical model of our system we show that increasing virulence strengthens selection for SRM due to the higher costs of infection suffered by SIE immune hosts. In both the experiments and the model, higher levels of SRM in the host population drove more rapid phage extinction. Thus, by accelerating the evolution of host resistance, more virulent phages caused shorter epidemics.

evolutionary biology↗

bioRxiv2020

Pipefish locally adapted to low salinity in the Baltic Sea retain phenotypic plasticity to cope with ancestral salinity levels.

Genetic adaptation and phenotypic plasticity facilitate the invasion of new habitats and enable organisms to cope with a rapidly changing environment. In contrast to genetic adaptation that spans multiple generations as an evolutionary process, phenotypic plasticity allows acclimation within the life-time of an organism. Genetic adaptation and phenotypic plasticity are usually studied in isolation, however, only by including their interactive impact, we can understand acclimation and adaptation in nature. We aimed to explore the contribution of adaptation and plasticity in coping with an abiotic (salinity) and a biotic (Vibrio bacteria) stressor using six different populations of the broad-nosed pipefish Syngnathus typhle that originated from either high or low saline environments. We hypothesized that wild S. typhle populations are locally adapted to the salinity and prevailing pathogens of their native environment, and that short-term acclimation of parents to a novel salinity may aid in buffering offspring phenotypes in a matching environment. To test these hypotheses, we exposed all wild caught animals, to either high or low salinity, representing native and novel salinity conditions and allowed animals to mate. After male pregnancy, offspring was split and each half was exposed to one of the two salinities and infected with Vibrio alginolyticus bacteria that were evolved at either of the two salinities in a fully reciprocal design. We investigated life history traits of fathers (offspring survival, offspring size) and expression of 47 target genes in mothers and offspring. Pregnant males originating from high salinity exposed to low salinity were highly susceptible to opportunistic fungi infections resulting in decreased offspring size and number. In contrast, no signs of fungal infection were identified in fathers originating from low saline conditions suggesting that genetic adaptation has the potential to overcome the challenging conditions of low salinity. Genetic adaptation increased survival rates of juveniles from parents in lower salinity (in contrast to those from high salinity). Juvenile gene expression indicated patterns of local adaptation, trans-generational plasticity and developmental plasticity. The results of our study suggest that pipefish locally adapted to low salinity retain phenotypic plasticity, which allows them to also cope with ancestral salinity levels and prevailing pathogens.

evolutionary biology↗