Non-essential MCM-related proteins mediate a response to DNA damage in the archaeon Methanococcus maripaludis

Abstract

The single minichromosome maintenance (MCM) protein found in most archaea has been widely studied as a simplified model for the MCM complex that forms the catalytic core of the eukaryotic replicative helicase. Organisms of the order Methanococcales are unusual in possessing multiple MCM homologues. The Methanococcus maripaludis S2 genome encodes four MCM homologues, McmA-McmD. DNA helicase assays reveal that the unwinding activity of the three MCM-like proteins is highly variable despite sequence similarities and suggests additional motifs that influence MCM function are yet to be identified. While the gene encoding McmA could not be deleted, strains harbouring individual deletions of genes encoding each of the other MCMs display phenotypes consistent with these proteins modulating DNA damage responses. M. maripaludis S2 is the first archaeon in which MCM proteins have been shown to influence the DNA damage response.

Scale-up of biomass production by Methanococcus maripaludis

“…This system has been established for studies of nutrient limitations (Hendrickson et al, 2007(Hendrickson et al, , 2008Costa et al, 2013), where distinct M. maripaludis strains (S2, S52) have been cultivated at low optical density in various media (mineral McN, with or without acetate supplementation, but also defined complex McA and McCas) and their OD has been measured at distinct wavelengths (600 or 660), hence complicating straightforward comparison, due to the Lambert-Beer's law. The application of the chemostat cultivation procedure in a 3 L reactor with 2 L cultures of strain S2, grown in modified rich McCas medium, supplemented with casamino acids, has delivered highest reported OD 600 of around 2.7 and doubling times of 3 to 4 h (Walters and Chong, 2017). Here, doubling time of 4 to 5 h and the highest OD 578 of 3.4 have been reached with strain S0001, grown on gaseous H 2 /CO 2 substrate in reduced 141 medium, supplemented with acetate.…”

“…In contrast, a fed-batch mode of cultivation allows continuous addition of feed for growth, larger culture volumes and more sophisticated control of conditions. Nevertheless, only handful of notable studies have applied chemostat-like systems (Haydock et al, 2004;Hendrickson et al, 2007Hendrickson et al, , 2008Costa et al, 2013;Müller et al, 2021) or carried out scale-up of pure cultures (Walters and Chong, 2017) for biomass generation by of M. maripaludis. All of them have been focused on other fundamental questions and have not developed a detailed pipeline for continuous transfer and scale-up of M. maripaludis cultures.…”

Haloferax volcanii —a model archaeon for studying DNA replication and repair

“…Most archaeal species encode a single MCM homologue thought to act as the replicative helicase [73]. Where species encode more than one mcm homologue, such as Thermococcus kodakarensis and Methanococcus maripaludis, which possess three and four MCM homologues, respectively, only one will be essential for viability [74][75][76]. The essential MCM protein in species with multiple paralogues shares structural and sequence similarity with the single MCM proteins in other species [75,76].…”