Current knowledge and recent advances in understanding metabolism of the model cyanobacterium Synechocystis sp. PCC 6803

Cyanobacteria are key organisms in the global ecosystem, useful models for studying metabolic and physiological processes conserved in photosynthetic organisms, and potential renewable platforms for production of chemicals. Characterising cyanobacterial metabolism and physiology is key to understanding their role in the environment and unlocking their potential for biotechnology applications. Many aspects of cyanobacterial biology differ from heterotrophic bacteria. For example, most cyanobacteria incorporate a series of internal thylakoid membranes where both oxygenic photosynthesis and respiration occur, while CO2 fixation takes place in specialised compartments termed carboxysomes. In this review, we provide a comprehensive summary of our knowledge on cyanobacterial physiology and the pathways in Synechocystis sp. PCC 6803 (Synechocystis) involved in biosynthesis of sugar-based metabolites, amino acids, nucleotides, lipids, cofactors, vitamins, isoprenoids, pigments and cell wall components, in addition to the proteins involved in metabolite transport. While some pathways are conserved between model cyanobacteria, such as Synechocystis, and model heterotrophic bacteria like Escherichia coli, many enzymes and/or pathways involved in the biosynthesis of key metabolites in cyanobacteria have not been completely characterised. These include pathways required for biosynthesis of chorismate and membrane lipids, nucleotides, several amino acids, vitamins and cofactors, and isoprenoids such as plastoquinone, carotenoids, and tocopherols. Moreover, our understanding of photorespiration, lipopolysaccharide assembly and transport, and degradation of lipids, sucrose, most vitamins and amino acids, and heme, is incomplete. We discuss tools that may aid characterisation of cyanobacterial metabolism, notably CyanoSource, a barcoded library of targeted Synechocystis mutants, which will significantly accelerate characterisation of individual proteins

Development of Synechococcus sp. PCC 11901 as a biotechnology platform

Cyanobacteria are key organisms in the global ecosystem and potential renewable platforms for production of chemicals. Many aspects of cyanobacterial biology are unique to this subset of prokaryotes. Characterising cyanobacterial metabolism and physiology is key to understanding their environmental role and unlocking their potential for biotechnology. This thesis provides a comprehensive summary of our knowledge on cyanobacterial physiology and the pathways in the model organism, Synechocystis sp. PCC 6803 (PCC 6803). One of the main issues within cyanobacterial bioindustry has been the lack of sustained fast-growing strains. The newly discovered Synechococcus sp. PCC 11901 (PCC 11901) reportedly demonstrates the highest, most sustained growth of any known cyanobacterium. Knowledge of PCC 11901 biology, including the factors underlying the sustained fast growth, is limited, which hinders its potential for biotechnology. Genetic tools for generating unmarked mutants in PCC 11901 are not established. This thesis confirms that PCC 11901 displays faster growth than other model cyanobacteria. Comparative genomics between PCC 11901 and PCC 6803 reveal conservation of most metabolic pathways but PCC 11901 has a simplified electron transport chain and reduced light-harvesting complex. This may underlie its efficient light use, reduced photoinhibition, and higher photosynthetic and respiratory rates. Attempts to generate unmarked knockouts using two negative selectable markers were unsuccessful, suggesting that recombinase or CRISPR-based approaches may be necessary for the industry requirement of repeated genetic manipulation. To further cement PCC 11901 as a future industrial strain, biomass and optical density measurements were carried out over a range of light intensities to aid photo-mechanistic modelling of the strain. This thesis establishes PCC 11901 as one of the most promising species currently available for cyanobacterial biotechnology and provides a useful set of bioinformatic tools and strains for advancing this field, in addition to insights into the factors underlying its fast growth phenotype

Functional traits provide new insight into recovery and succession at deep-sea hydrothermal vents

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Dykman, L. N., Beaulieu, S. E., Mills, S. W., Solow, A. R., & Mullineaux, L. S. Functional traits provide new insight into recovery and succession at deep-sea hydrothermal vents. Ecology, 102(8), (2021): e03418, https://doi.org/10.1002/ecy.3418.Investigation of communities in extreme environments with unique conditions has the potential to broaden or challenge existing theory as to how biological communities assemble and change through succession. Deep-sea hydrothermal vent ecosystems have strong, parallel gradients of nutrients and environmental stress, and present unusual conditions in early succession, in that both nutrient availability and stressors are high. We analyzed the succession of the invertebrate community at 9°50′ N on the East Pacific Rise for 11 yr following an eruption in 2006 in order to test successional theories developed in other ecosystems. We focused on functional traits including body size, external protection, provision of habitat (foundation species), and trophic mode to understand how the unique nutritional and stress conditions influence community composition. In contrast to established theory, large, fast-growing, structure-forming organisms colonized rapidly at vents, while small, asexually reproducing organisms were not abundant until later in succession. Species in early succession had high external protection, as expected in the harsh thermal and chemical conditions after the eruption. Changes in traits related to feeding ecology and dispersal potential over succession agreed with expectations from other ecosystems. We also tracked functional diversity metrics over time to see how they compared to species diversity. While species diversity peaked at 8 yr post-eruption, functional diversity was continuing to increase at 11 yr. Our results indicate that deep-sea hydrothermal vents have distinct successional dynamics due to the high stress and high nutrient conditions in early succession. These findings highlight the importance of extending theory to new systems and considering function to allow comparison between ecosystems with different species and environmental conditions.Funding for L. Dykman, L. Mullineaux, and S. Beaulieu was provided by NSF OCE-1829773. The Synthesis Centre of the German Centre for Integrative Biodiversity Research (sDiv) funded the sFDvent working group and database

Exploring psychological characteristic of problem financial trading: The effect of self-control and dispositional greed

Abstract While an increasing body of literature has noted the preponderance of gambling within various financial markets, limited research has been done on the psychological characteristics of traders, such as levels of self-control (i.e., ability to regulate behaviors and emotions) and dispositional greed (i.e., a strong desire to acquire more). Such characteristics may place traders at a disproportionate risk for trading financial assets more problematically. The proposed study explores the association between self-control and problem financial trading and the role of dispositional greed in mediating their association. Participants who identified as having engaged in financial trading during the past year (N = 504; 67.1% male; M = 39.4 years, SD = 12.6) were recruited via Amazon’s Mechanical Turk to complete an online survey. Results from structural equation modeling revealed that self-control is partially negatively related to problematic financial trading behaviors (B = -.21, p \u3c .001; 95%CI[-.28, -.14]). Furthermore, self-control is related to less problem financial trading behaviors through a decrease in dispositional greed (B = -.05, p = .004; 95%CI[-.08, -.02]). These findings are the among the first to explore the interplay between self-control and dispositional greed. The implications of these findings will be discussed. Implication The present study is the first to explore self-control and dispositional greed in relation to problematic financial trading. Findings speak to the unique interplay between self-control and dispositional greed among financial traders, and provide a foundation for further research in this area

Photographic identification guide to larvae at hydrothermal vents

The purpose of this guide is to assist researchers in the identification of larvae of benthic invertebrates at hydrothermal vents. Our work is based on plankton sampling at the East Pacific Rise 9-10°N vent field from 1991-2007, supplemented by benthic collections of juveniles. In addition to images and descriptions of the species, we included frequency data from large-volume plankton pump samples taken between 1998 and 2004 and time-series sediment trap samples from 2004-2005.Funding provided by NSF grants OCE-9619605, OCE-9712233, OCE-0424593 and ATM-0428122 and ChEss Grant #WHOI 1334800

Animal community dynamics at senescent and active vents at the 9° N East Pacific Rise after a volcanic eruption

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gollner, S., Govenar, B., Arbizu, P. M., Mullineaux, L. S., Mills, S., Le Bris, N., Weinbauer, M., Shank, T. M., & Bright, M. Animal community dynamics at senescent and active vents at the 9° N East Pacific Rise after a volcanic eruption. Frontiers in Marine Science, 6, (2020): 832, doi:10.3389/fmars.2019.00832.In 2005/2006, a major volcanic eruption buried faunal communities over a large area of the 9°N East Pacific Rise (EPR) vent field. In late 2006, we initiated colonization studies at several types of post eruption vent communities including those that either survived the eruption, re-established after the eruption, or arisen at new sites. Some of these vents were active whereas others appeared senescent. Although the spatial scale of non-paved (surviving) vent communities was small (several m2 compared to several km2 of total paved area), the remnant individuals at surviving active and senescent vent sites may be important for recolonization. A total of 46 meio- and macrofauna species were encountered at non-paved areas with 33 of those species detected were also present at new sites in 2006. The animals living at non-paved areas represent refuge populations that could act as source populations for new vent sites directly after disturbance. Remnants may be especially important for the meiofauna, where many taxa have limited or no larval dispersal. Meiofauna may reach new vent sites predominantly via migration from local refuge areas, where a reproductive and abundant meiofauna is thriving. These findings are important to consider in any potential future deep-sea mining scenario at deep-sea hydrothermal vents. Within our 4-year study period, we regularly observed vent habitats with tubeworm assemblages that became senescent and died, as vent fluid emissions locally stopped at patches within active vent sites. Senescent vents harbored a species rich mix of typical vent species as well as rare yet undescribed species. The senescent vents contributed significantly to diversity at the 9°N EPR with 55 macrofaunal species (11 singletons) and 74 meiofaunal species (19 singletons). Of these 129 species associated with senescent vents, 60 have not been reported from active vents. Tubeworms and other vent megafauna not only act as foundation species when alive but provide habitat also when dead, sustaining abundant and diverse small sized fauna.We received funding from the Austrian FWF (GrantP20190-B17; MB), the U.S. National Science Foundation (OCE-0424953; to LM, D. McGillicuddy, A. Thurnherr, J. Ledwell, and W. Lavelle; and OCE-1356738 to LM), and the European Union Seventh Framework Programme (FP7/2007-2013) under the MIDAS project, Grant Agreement No. 603418. Ifremer and CNRS (France) supported NL cruise participation and sensor developments. BG was supported by a postdoctoral fellowship from the Deep Ocean Exploration Institute at WHOI (United States). TS was supported by the U.S. National Science Foundation (OCE-0327261 to TS and OCE-0937395 to TS and BG)

Persistent effects of disturbance on larval patterns in the plankton after an eruption on the East Pacific Rise

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 491 (2013): 67-76, doi:10.3354/meps10463.To predict how benthic communities will respond to disturbance, it is necessary to understand how disturbance affects the planktonic larval supply available to recolonize the area. Deep-sea hydrothermal vent fauna along the East Pacific Rise (EPR) experience frequent local extinctions due to tectonic and magmatic events, but the effects on regional larval abundance and diversity are unknown. We had been monitoring larvae at 9° 50' N on the EPR prior to the 2006 eruption and were able to resume collections shortly afterward. We found that many species that were common before the eruption became significantly less so afterward, whereas a few other species experienced a transient spike in abundance. Surprisingly, overall species richness in the plankton was high 9 mo after the eruption, but then decreased sharply after 1 yr and had not returned to pre-eruption levels after 2 yr. These results suggest that recovery from disturbance may continue to be affected by limited larval supply even several years after a disturbance event. This delay in recovery means that larvae of pioneer species may dominate potential colonists, even after benthic habitats have transitioned to conditions that favor later-successional species. Moreover, the combined effects of natural and anthropogenic disturbance (e.g. mining) would be likely to cause more profound and long-lasting changes than either event alone. Our results indicate that we do not have sufficient data to predict the timing of recovery after disturbance in the deep sea, even in a well-studied vent system.Support was provided by National Science Foundation Grant OCE-0424953 and a Woods Hole Oceanographic Institution grant from the Deep Ocean Exploration Institute

Larvae from afar colonize deep-sea hydrothermal vents after a catastrophic eruption

Author Posting. © The Authors, 2010. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 107 (2010): 7829-7834, doi:10.1073/pnas.0913187107.The planktonic larval stage is a critical component of life history in marine benthic species because it confers the ability to disperse, potentially connecting remote populations and leading to colonization of new sites. Larval-mediated connectivity is particularly intriguing in deep-sea hydrothermal vent communities, where the habitat is patchy, transient and often separated by tens or hundreds of kilometers. A recent catastrophic eruption at vents near 9°50’N on the East Pacific Rise created a natural clearance experiment and provided an opportunity to study larval supply in the absence of local source populations. Previous field observations have suggested that established vent populations may retain larvae and be largely self-sustaining. If this hypothesis is correct, the removal of local populations should result in a dramatic change in the flux, and possibly species composition, of settling larvae. Fortuitously, monitoring of larval supply and colonization at the site had been established before the eruption and resumed shortly afterward. We detected a striking change in species composition of larvae and colonists after the eruption, most notably the appearance of the gastropod Ctenopelta porifera, an immigrant from possibly >300 km away, and the disappearance of a suite of species that formerly had been prominent. This switch demonstrates that larval supply can change markedly after removal of local source populations, enabling recolonization via immigrants from distant sites with different species composition. Population connectivity at this site appears to be temporally variable, depending not only on stochasticity in larval supply, but also on the presence of resident populations.Support was provided by NSF grants OCE-969105, OCE-9712233, and OCE-0424953), WHOI grants from DOEI and the Ocean Venture Fund, a NDSEG graduate fellowship to DA, and the WHOI Jannasch Chair for Excellence in Oceanography to LM

Long-Period Giant Companions to Three Compact, Multiplanet Systems

Understanding the relationship between long-period giant planets and multiple smaller short-period planets is critical for formulating a complete picture of planet formation. This work characterizes three such systems. We present Kepler-65, a system with an eccentric (e = 0.28 ± 0.07) giant planet companion discovered via radial velocities (RVs) exterior to a compact, multiply transiting system of sub-Neptune planets. We also use precision RVs to improve mass and radius constraints on two other systems with similar architectures, Kepler-25 and Kepler-68. In Kepler-68 we propose a second exterior giant planet candidate. Finally, we consider the implications of these systems for planet formation models, particularly that the moderate eccentricity in Kepler-65\u27s exterior giant planet did not disrupt its inner system