Wagstaff, B. A. | Search bioRxiv

bioRxiv2021

N-glycan core synthesis by Alg24 strengthens the hypothesis of an archaeal origin of eukaryal N-glycosylation

Protein N-glycosylation is the most common posttranslational modifications found in all three domains of life. The crenarchaeal N-glycosylation begins with the synthesis of a lipid-linked chitobiose core structure, identical to that in eukaryotes. Here, we report the identification of a thermostable archaeal beta-1,4-N-acetylglucosaminyltransferase, named archaeal glycosylation enzyme 24 (Agl24), responsible for the synthesis of the N-glycan chitobiose core. Biochemical characterization confirmed the function as an inverting {beta}-D-GlcNAc-(1[->]4)--D-GlcNAc-diphosphodolichol glycosyltransferase. Substitution of a conserved histidine residue, found also in the eukaryotic and bacterial homologs, demonstrated its functional importance for Agl24. Furthermore, bioinformatics and structural modeling revealed strong similarities between Agl24 and both the eukaryotic Alg14/13 and a distant relation to the bacterial MurG, which catalyze the identical or a similar process, respectively. Our data, complemented by phylogenetic analysis of Alg13 and Alg14, revealed similar sequences in Asgardarchaeota, further supporting the hypothesis that the Alg13/14 homologs in eukaryotes have been acquired during eukaryogenesis. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC="FIGDIR/small/427365v2_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@13d1ffdorg.highwire.dtl.DTLVardef@1ff48d0org.highwire.dtl.DTLVardef@1056e75org.highwire.dtl.DTLVardef@196ff58_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIFirst identification and characterization of a thermostable {beta}-D-GlcNAc-(1[->]4)--D-GlcNAc-diphosphodolichol glycosyltransferase (GT family 28) in Archaea. C_LIO_LIA highly conserved histidine, within a GGH motif in Agl24, Alg14, and MurG, is essential for function of Agl24. C_LIO_LIAgl24-like homologs are broadly distributed among Archaea. C_LIO_LIThe eukaryotic Alg13 and Alg14 are closely related to the Asgard homologs, suggesting their acquisition during eukaryogenesis. C_LI

microbiology↗

bioRxiv2020

Dissecting the toxicity and mitigating the impact of harmful Prymnesium blooms in the UK waters of the Norfolk Broads

Prymnesium parvum is a toxin-producing microalga that causes harmful algal blooms (HABs) globally, frequently leading to massive fish kills that have adverse ecological and economic implications for natural waterways and aquaculture alike. The dramatic effects observed on fish are likely due to algae-produced polyether toxins, known as the prymnesins, but these compounds had not been detected in environmental samples, which has resulted in ambiguity about the true ichthyotoxic entities. Using qPCR, we found elevated levels of both P. parvum and its lytic virus, PpDNAV-BW1, in a fish-killing bloom on the Norfolk Broads, United Kingdom, in March 2015, a site historically plagued by P. parvum blooms. 16S rRNA gene sequencing confirmed that P. parvum dominated the bloom microbial community and that the microbial species diversity changed after recovery of the ecosystem. We also detected, for the first time, the recently discovered B-type prymnesin toxins in Broads waterway samples and gill tissue isolated from a dead fish taken from the study site. Furthermore, Norfolk Broads P. parvum isolates unambiguously produced B-type toxins in laboratory-grown cultures. In addition, a 2-year longitudinal study of the Broads study site showed P. parvum blooms positively correlated with increased temperature and that PpDNAV plays a significant role in P. parvum bloom demise in this natural setting. Finally, we used a field trial to show that treatment with low doses of hydrogen peroxide represents an effective strategy to mitigate blooms of P. parvum in enclosed water bodies.

microbiology↗