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Astrobiology Graduates in Europe (AbGradE, pronounced ab-grad-ee) is an association of early-career scientists working in fields relevant to astrobiological research. Conceptualized in 2013, it was initially designed as a mini-conference or workshop dedicated to early-career researchers, providing a friendly environment where early-career minds would be able to present their research without being intimidated by the possibility of facing a more traditional audience, composed mainly of senior scientists. Within the last couple of years, AbGradE became the first point of call for European, but also for an increasing number of non-European, early-career astrobiologists. This article aims to present how AbGradE has evolved over the years (in its structure and in its way of organizing events), how it has adapted with the COVID-19 pandemic, and what future developments are considered.

Introduction: Astrobiology Graduates in Europe (AbGradE, pronounced ab-grad-ee) is an association of early-career scientists working in fields relevant to astrobiological research. Conceptualized in 2013, it was initially designed as a mini-conference dedicated to early-career researchers (ECAs) in a more relaxed environment than that of traditional conferences. Our meetings act as a networking opportunity, as well as a practice round and steppingstone for ECAs entering the world of academic research.Audience & topics engaged: Our audience is mostly composed of graduate students and post-doctoral fellows, but not only: undergraduates, senior scientists, and researchers from different disciplines with a strong interest in astrobiology are also welcome to attend our meetings. The topics engaged at our events, both symposia and workshops, naturally include the obvious themes related to astrobiology, and go beyond them by delving into social sciences and humanities (e.g., an online Space law and governance meeting in 2021). Specific workshops were organized on more practical issues like science communication, space mission design, networking, and navigating post-graduate research. Other issues, like mental health in a research context, are also considered for future editions.Collaborations: AbGradE has been involved in astrobiology schools, such as the EANA International hydrothermal spring school. As the spiritual daughter organization of EANA, AbGradE maintains strong ties with it while developing on its own into an organization by ECAs, for ECAs, in a similar fashion to how AbGradCon operates. Over the years, AbGradE also teamed up with other organizations, like the European Astrobiology Campus (EAC), the European Astrobiology Institute (EAI), and the Europlanet Early Career (EPEC) Network.Online presence: In the spirit of the “work from home” attitude prevalent during the COVID-19 pandemic, AbGradE has attempted to provide more online resources. Apart from moving meetings online, we have built a website and sent out a quarterly newsletter to keep ECAs engaged, and to encourage a sense of community during the lockdown-ridden time of the pandemic.Scope: Within the last couple of years, AbGradE became the first point of call for European, but also for an increasing number of non-European ECAs, especially with the recent development of online resources. This presentation aims to present how AbGradE has evolved over the years (in its structure and in its way of organizing events), how it has adapted with the COVID-19 pandemic, and what future developments are considered.

ATP is universally conserved as the principal energy currency in cells, driving metabolism through phosphorylation and condensation reactions. Such deep conservation suggests that ATP arose at an early stage of biochemical evolution. Yet purine synthesis requires six phosphorylation steps linked to ATP hydrolysis. This autocatalytic requirement for ATP to synthesize ATP implies the need for an earlier prebiotic ATP-equivalent, which could drive protometabolism before purine synthesis. Why this early phosphorylating agent was replaced, and specifically with ATP rather than other nucleotide triphosphates, remains a mystery. Here we show that the deep conservation of ATP reflects its prebiotic chemistry in relation to another universally conserved intermediate, acetyl phosphate, which bridges between thioester and phosphate metabolism by linking acetyl CoA to the substrate-level phosphorylation of ADP. We confirm earlier results showing that acetyl phosphate can phosphorylate ADP to ATP at nearly 20 % yield in water in the presence of Fe3+ions. We then show that Fe3+and acetyl phosphate are surprisingly favoured: a panel of other prebiotically relevant ions and minerals did not catalyze ADP phosphorylation; nor did a number of other potentially prebiotic phosphorylating agents. Only carbamoyl phosphate showed some modest phosphorylating activity. Critically, we show that acetyl phosphate does not phosphorylate other nucleotide diphosphates or free pyrophosphate in water. The phosphorylation of ADP monomers seems to be favoured by the interaction between the N6 amino group on the adenine ring with Fe3+coupled to acetyl phosphate. Our findings suggest that the reason ATP is universally conserved across life is that its formation is chemically favoured in aqueous solution under mild prebiotic conditions.

ATP is universally conserved as the principal energy currency in cells, driving metabolism through phosphorylation and condensation reactions. Such deep conservation suggests that ATP arose at an early stage of biochemical evolution. Yet purine synthesis requires 6 phosphorylation steps linked to ATP hydrolysis. This autocatalytic requirement for ATP to synthesize ATP implies the need for an earlier prebiotic ATP equivalent, which could drive protometabolism before purine synthesis. Why this early phosphorylating agent was replaced, and specifically with ATP rather than other nucleoside triphosphates, remains a mystery. Here, we show that the deep conservation of ATP might reflect its prebiotic chemistry in relation to another universally conserved intermediate, acetyl phosphate (AcP), which bridges between thioester and phosphate metabolism by linking acetyl CoA to the substrate-level phosphorylation of ADP. We confirm earlier results showing that AcP can phosphorylate ADP to ATP at nearly 20% yield in water in the presence of Fe3+ ions. We then show that Fe3+ and AcP are surprisingly favoured. A wide range of prebiotically relevant ions and minerals failed to catalyse ADP phosphorylation. From a panel of prebiotic phosphorylating agents, only AcP, and to a lesser extent carbamoyl phosphate, showed any significant phosphorylating potential. Critically, AcP did not phosphorylate any other nucleoside diphosphate. We use these data, reaction kinetics, and molecular dynamic simulations to infer a possible mechanism. Our findings might suggest that the reason ATP is universally conserved across life is that its formation is chemically favoured in aqueous solution under mild prebiotic conditions.

Metabolism is primed through the formation of thioesters via acetyl CoA and the phosphorylation of substrates by ATP. Prebiotic equivalents such as methyl thioacetate and acetyl phosphate have been proposed to catalyse analogous reactions at the origin of life, but their propensity to hydrolyse challenges this view. Here we show that acetyl phosphate (AcP) can be synthesised in water within minutes from thioacetate (but not methyl thioacetate) under ambient conditions. AcP is stable over hours, depending on temperature, pH and cation content, giving it an ideal poise between stability and reactivity. We show that AcP can phosphorylate nucleotide precursors such as ribose to ribose-5-phosphate and adenosine to adenosine monophosphate, at modest (~2%) yield in water, and at a range of pH. AcP can also phosphorylate ADP to ATP in water over several hours at 50 °C. But AcP did not promote polymerization of either glycine or AMP. The amino group of glycine was preferentially acetylated by AcP, especially at alkaline pH, hindering the formation of polypeptides. AMP formed small stacks of up to 7 monomers, but these did not polymerise in the presence of AcP in aqueous solution. We conclude that AcP can phosphorylate biologically meaningful substrates in a manner analogous to ATP, promoting the origins of metabolism, but is unlikely to have driven polymerization of macromolecules such as polypeptides or RNA in free solution. This is consistent with the idea that a period of monomer (cofactor) catalysis preceded the emergence of polymeric enzymes or ribozymes at the origin of life. Electronic supplementary material The online version of this article (10.1007/s11084-018-9555-8) contains supplementary material, which is available to authorized users.