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Het archeologisch onderzoek in het Twaalfgemetenbos is een ‘archeologisch onderzoek met het oog op wetenschappelijke vraagstellingen’. Deze opgraving volgt wel uit een toevalsvondst, die door de politie telefonisch werd gemeld in november 2016. Bij de berging van een oorlogsslachtoffer is een gedegen archeologische opgraving en de verdere uitwerking van alle gegevens noodzakelijk om toe te laten kennis te verwerven over het individu, over de omstandigheden van overlijden en over het oorlogsgebeuren. Een volledige verwerkingsstrategie met een gedetailleerde uitwerking van alle gegevens is daarbij noodzakelijk om tot een zinvolle conclusie te kunnen komen van deze vindplaats. De studie beperkt zich tot case-gebonden onderzoeksvragen met betrekking tot de aard van de vindplaats, de datering, de relatie en de fasering van sporen en vondsten. Eigen aan het onderzoek van een beperkte toevalsvondst is dat de uitwerking ervan veel vertelt over deze vindplaats maar weinig over de ruimere context. De vondst van gesneuvelden blijft maatschappelijk enorm belangrijk. Bovendien levert elke vondst van een gesneuvelde ook een puzzelstuk in het grotere verhaal van de Eerste Wereldoorlog. In welke specifieke context van de Eerste Wereldoorlog moet deze gesneuvelde geplaatst worden? Kan een gedetailleerde studie van de vondsten leiden tot identificatie? De uitzonderlijke bewaring van de vele bijvondsten van deze gesneuvelde maakt het bovendien mogelijk om in detail de uitrusting van deze soldaat te reconstrueren. Op basis van de vondstlocatie en het vondstmateriaal dat bij en rond hem werd aangetroffen, moet hij gesneuveld zijn tussen 7 juni 1917 en 29 april 1918. De militair was tussen 19 en 22 jaar oud op het moment dat hij stierf. Het fysisch-antropologisch onderzoek leverde bewijzen op voor een mogelijke doodsoorzaak.

“Hoe lang gaat dit duren?”, Dat is vaak de eerste vraag die archeologen te horen krijgen over het archeologisch onderzoek. Een vraag die vervolgens zelden naar voldoening beantwoord kan worden, omdat ze meteen de complexiteit van het archeologisch onderzoek samenvat: archeologisch erfgoed is per definitie verscholen in de grond en ongekend. Het is dan ook niet verrassend dat de meeste initiatiefnemers, wiens missie het tenslotte is om leidingen aan te leggen, niet geheel enthousiast zijn over het archeologisch traject. Maar, de ervaringen groeien bij alle belanghebbenden, waardoor men het archeologisch onderzoek steeds beter integreert in de geplande werken. Het archeologisch onderzoek op lijntracés wijkt niet significant af van het archeologisch onderzoek bij andere projecten/ontwikkelingen in Vlaanderen. Een archeologisch onderzoek bij de ontwikkeling van lijninfrastructuur is geslaagd als het vlot en efficiënt verloopt. Eén van de sleutels hierbij is een planmatige en uitvoerige communicatie tussen de verschillende partijen.

As a major group of algae, diatoms are responsible for a substantial part of the primary production on the planet. Pennate diatoms have a predominantly benthic lifestyle and are the most species-rich diatom group, with members of the raphid clades being motile and generally having heterothallic sexual reproduction. It was recently shown that the model species Seminavis robusta uses multiple sexual cues during mating, including cyclo(l-Pro-l-Pro) as an attraction pheromone. Elaboration of the pheromone-detection system is a key aspect in elucidating pennate diatom life-cycle regulation that could yield novel fundamental insights into diatom speciation. This study reports the synthesis and bio-evaluation of seven novel pheromone analogs containing small structural alterations to the cyclo(l-Pro-l-Pro) pheromone. Toxicity, attraction, and interference assays were applied to assess their potential activity as a pheromone. Most of our analogs show a moderate-to-good bioactivity and low-to-no phytotoxicity. The pheromone activity of azide- and diazirine-containing analogs was unaffected and induced a similar mating behavior as the natural pheromone. These results demonstrate that the introduction of confined structural modifications can be used to develop a chemical probe based on the diazirine- and/or azide-containing analogs to study the pheromone-detection system of S. robusta.

Sexual reproduction is a fundamental phase in the life cycle of most diatoms. Despite its role as a source of genetic variation, it is rarely reported in natural circumstances and its molecular foundations remain largely unknown. Here, we integrate independent transcriptomic datasets to prioritize genes responding to sex inducing pheromones (SIPs) in the pennate diatom Seminavis robusta. We observe marked gene expression changes associated with SIP treatment in both mating types, including an inhibition of S phase progression, chloroplast division, mitosis, and cell wall formation. Meanwhile, meiotic genes are upregulated in response to SIP, including a sexually induced diatom specific cyclin. Our data further suggest an important role for reactive oxygen species, energy metabolism, and cGMP signaling during the early stages of sexual reproduction. In addition, we identify several genes with a mating type specific response to SIP, and link their expression pattern with physiological specialization, such as the production of the attraction pheromone diproline in mating type − (MT−) and mate-searching behavior in mating type + (MT+). Combined, our results provide a model for early sexual reproduction in pennate diatoms and significantly expand the suite of target genes to detect sexual reproduction events in natural diatom populations.

Benthic diatoms are the main primary producers in shallow freshwater and coastal environments, fulfilling important ecological functions such as nutrient cycling and sediment stabilization. However, little is known about their evolutionary adaptations to these highly structured but heterogeneous environments. Here, we report a reference genome for the marine biofilm-forming diatom Seminavis robusta, showing that gene family expansions are responsible for a quarter of all 36,254 protein-coding genes. Tandem duplications play a key role in extending the repertoire of specific gene functions, including light and oxygen sensing, which are probably central for its adaptation to benthic habitats. Genes differentially expressed during interactions with bacteria are strongly conserved in other benthic diatoms while many species-specific genes are strongly upregulated during sexual reproduction. Combined with re-sequencing data from 48 strains, our results offer insights into the genetic diversity and gene functions in benthic diatoms., Available genomics studies have mostly focused on planktonic centric diatom. Here, the authors report the genome assembly of the marine biofilm-forming diatom Seminavis robusta and the resequencing data of a panel of accessions to reveal their evolutionary adaptations.

In cooperation with many other actors, the Flanders Heritage Agency (Flemish Government) set up a guideline with procedures how to act when human remains are found in the soil of Flanders (the northern part of Belgium). The basic principle is that human remains with an archaeological value always must be excavated by archaeologists and physical anthropologists, according to the Flemish legislation on archaeology. This also applies for casualties of the First and Second World War: excavating using archaeological techniques does not conflict at all with the principles of the Geneva Convention, on the contrary: this way of working guarantees a qualitative research that increases the chance of identification and delivers more details about the battle and war: a win-win.

Benthic diatoms are the main primary producers in shallow freshwater and coastal environments, fulfilling important ecological functions such as nutrient cycling and sediment stabilization. However, little is known about their evolutionary adaptations to these highly structured but heterogeneous environments. Here, we report a reference genome for the marine biofilm-forming diatom Seminavis robusta, showing that gene family expansions are responsible for a quarter of all 36,254 protein-coding genes. Tandem duplications play a key role in extending the repertoire of specific gene functions, including light and oxygen sensing, which are probably central for its adaptation to benthic habitats. Genes differentially expressed during interactions with bacteria are strongly conserved in other benthic diatoms while many species-specific genes are strongly upregulated during sexual reproduction. Combined with re-sequencing data from 48 strains, our results offer insights into the genetic diversity and gene functions in benthic diatoms.

Incomplete reproductive isolation between genetically distinct taxa provides an interesting opportunity for speciation and adaptation studies. This phenomenon is well-described in macro-organisms, but less experimental evidence is available for unicellular eukaryotes. Here, we document the sympatric occurrence of genetically differentiated populations of the pennate model diatom Seminavis robusta in coastal subtidal biofilm communities and show widespread potential for gene flow between them. Based on sequence variation in the plastid-encoded rbcL gene, three distinct clades were identified. Morphological variation between the clades reflected their phylogenetic relationships, with subtle differences in valve morphology in the most distant clade compared to the other two clades, which were indistinguishable. Using a large number of experimental crosses we showed that, although reproductive output was significantly lower compared to the majority of within-clade crosses, approximately 34.5% of the inter-clade crosses resulted in viable and fertile progeny. While the nature of the incomplete reproductive isolation remains unknown, its occurrence in natural diatom populations represents an additional mechanism contributing to population genetic structuring and adaptation and can spur further research into the mechanisms of species divergence and the maintenance of species identity in the presence of gene flow.

Recently the first pheromone of a marine diatom was identified to be the diketopiperazine (S,S)-diproline. This compound facilitates attraction between mating partners in the benthic diatom Seminavis robusta. Interestingly, sexualized S. robusta cells are attracted to both the natural pheromone (S,S)-diproline as well as to its enantiomer (R,R)-diproline. Usually stereospecificity is a prerequisite for successful substrate-receptor interactions, and especially pheromone perception is often highly enantioselective. Here we introduce a structure-activity relationship study, to learn more about the principles of pheromone reception in diatoms. We analyzed the activity of nine different diketopiperazines in attraction and interference assays. The pheromone diproline itself, as well as a pipecolic acid derived diketopiperazine with two expanded aliphatic ring systems, showed the highest attractivity. Hydroxylatoin of the aliphatic rings abolished any bioactivity. Diketopiperazines derived from acyclic amino acids were not attrative as well. All stereoisomers of both the diproline and the pipecolic acid derived diketopiperazine were purified by enantioselective high-performance liquid chromatography, and application in bioactivity tests confirmed that attraction pheromone perception in this diatom is indeed not stereospecific. However, the lack of activity of diketopiperazines derived from acyclic amino acids suggests a specificity that prevents misguidance to sources of other naturally occurring diketopiperazines.

Diatoms constitute the most diverse group of microalgae and have long been recognised for their large biotechnological potential. In the wake of growing research interest in new model species and development of commercial applications, there is a pressing need for long-term preservation of diatom strains. While cryopreservation using dimethylsulfoxide (DMSO) as a cryoprotective agent is the preferred method for long-term strain preservation, many diatom species cannot be successfully cryopreserved using DMSO. Therefore, in this study, we studied cryopreservation success in six different diatom species, representing the major morphological and ecological diatom groups, using a range of DMSO concentrations and Plant Vitrification Solution 2 (PVS2) as an alternative cryoprotectant to DMSO. In addition, we tested whether suppressing bacterial growth by antibiotics accelerates the post-thaw recovery process. Our results show that the effects of cryoprotectant choice, its concentration and the addition of antibiotics are highly species specific. In addition, we showed that PVS2 and antibiotics are useful agents to optimize cryopreservation of algae that cannot survive the traditional cryopreservation protocol using DMSO. We conclude that a species-specific approach will remain necessary to develop protocols for diatom cryopreservation and to increase their representation in public culture collections.

The original version of this article unfortunately contained a mistake. The chemical structure of compound 6 in Fig. 1 was incorrect. The tested compound 6 in this study was (3S,8aS)-3-isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione as shown in the corrected version of Fig. 1 here.

Although sexual reproduction is believed to play a major role in the high diversification rates and species richness of diatoms, a mechanistic understanding of diatom life cycle control is virtually lacking. Diatom sexual signalling is controlled by a complex, yet largely unknown, pheromone system. Here, a sex-inducing pheromone (SIP+) of the benthic pennate diatom Seminavis robusta was identified by comparative metabolomics, subsequently purified and physicochemically characterized. Transcriptome analysis revealed that SIP+ triggers the switch from mitosis-to-meiosis in the opposing mating type, coupled with the transcriptional induction of proline biosynthesis genes and the release of the proline-derived attraction pheromone. The induction of cell cycle arrest by a pheromone, chemically distinct from the one used to attract the opposite mating type, highlights the existence of a sophisticated mechanism to increase chances of mate finding, while keeping the metabolic losses associated with the release of an attraction pheromone to a minimum.