Chloroplast-stealing (a.k.a., "kleptoplastidic") plankton transiently obtain and integrate prey metabolic machinery into their own cells. To do so, they must address a series of challenges, including physical localization of acquired machinery, metabolic integration of organelles and their products, and maintenance of machinery. Here, we study this transient integration in the marine ciliate Mesodinium chamaeleon by pulse feeding the ciliate with cryptophyte algal prey (Storeatula major) and then tracking changes in ciliate cellular ultrastructure, physiology (growth and photosynthesis), and gene expression over time. We demonstrate a predictable series of changes, from the reconfiguration of metabolic activity fueled by recent ingestion, to a period of rapid growth, to a reduction in physiological performance as prey organelle number and functionality become limiting. Because M. chamaeleon also steals transcriptionally active prey nuclei, gene expression is a complex milieu of host and cryptophyte expression, with much of prey metabolism apparently intact in the new host, albeit at low levels. Collectively, our results highlight the holistic orchestration of stolen organelles to produce rapid-yet transient-growth in a new host.
Julian M Jacobs, Zachary L. Reitz, E. Lasek-Nesselquist et al.· The ISME Journal· 0 citations
Iron is widely considered the first metallocofactor, evolving as iron-sulfur clusters in early life. While iron-chelating siderophores have been widely characterized across microbial life, the lanthanide-chelating metallophore, methylolanthanin, has only recently been described in Methylobacterium extorquens AM1. Methylolanthanin shares structural similarities to the siderophore rhodopetrobactin but contains 4-hydroxybenzoate chelating moieties in place of canonical 3,4-dihydroxybenzoates. Here we compare M. extorquens AM1, which produces methylolanthanin, and the closely related M. extorquens PA1, which produces rhodopetrobactin. We present a pathway for the biosynthesis of both metallophores and describe the unusual synthesis of methylolanthanin’s 4-HB moieties from tyrosine. We uncover a frameshift mutation in the predicted 3-dehydroshikimate dehydratase, mllF, that prevents production of rhodopetrobactin in AM1 through truncation of the catalytically essential N-terminus. We find that deletion of the uncharacterized gene mllG reveals a cryptic branch of the pathway, leading to production of both methylolanthanin and rhodopetrobactin. Finally, we discover that rhodopetrobactin production in this mutant is enabled through the activity of a 3-dehydroshikimate dehydratase in a separate biosynthetic gene cluster. These insights highlight an evolutionary mechanism for metallophore diversification through pseudogenization and regulation of distinct biosynthetic gene clusters with shared aromatic intermediates.
Alexa M. Zytnick, Marquis T. Yazzie, Tashi C. E. Liebergesell et al.· bioRxiv· 0 citations