The opportunistic coral pathogen Aspergillus sydowii contains dddP and makes dimethyl sulfide from dimethylsulfoniopropionate

Abstract

The ascomycete Aspergillus sydowii is associated with a serious epizootic of sea fan corals in the Caribbean. Corals are rich in the compatible solute, dimethylsulfoniopropionate (DMSP), produced by their symbionts, the dinoflagellate Symbiodinium. As other Aspergillus species can catabolize DMSP, liberating dimethyl sulfide (DMS) in the process, we tested A. sydowii strains, obtained from diseased corals and other environments, for this Ddd þ phenotype. All the strains, irrespective of their geographical or environmental origins, made DMS from DMSP, and all of them contained homologs (487% identical) of the dddP gene, which encodes an enzyme that releases DMS from DMSP and which occurs in other Ddd þ fungi and in some marine bacteria. The dddP gene was likely acquired by the Aspergillus fungi by inter-domain horizontal gene transfer from a-proteobacteria.

The dddP gene of Roseovarius nubinhibens encodes a novel lyase that cleaves dimethylsulfoniopropionate into acrylate plus dimethyl sulfide

“…The cloned dddP gene of R. nubinhibens and of some strains of Aspergillus and Fusarium fungi had previously been shown to confer on E. coli the ability to generate DMS from DMSP (Ddd + phenotype), but the identity of the other catabolite(s) was not established (Todd et al, 2009a;Kirkwood et al, 2010).…”

“…More surprisingly, functional DddP homologues were also found in some Aspergillus and Fusarium spp., pointing to inter-Domain HGT of dddP from bacteria to these eukaryotic ascomycete fungi (Todd et al, 2009a;Kirkwood et al, 2010). The advent of large-scale metagenomic sequencing of microbial subgenomic fragments allows the abundance of any given gene in natural populations to be estimated.…”

Coral-associated micro-organisms and their roles in promoting coral health and thwarting diseases

“…While other functions could be carried on the integrons, they play a key role in the spread of antibiotic resistance in coral-associated bacteria [59]. In addition to acquiring virulence and antibiotic-resistance genes, coral bacteria could gain novel metabolic functions, such as the ability to use dimethylsulfoniopropionate (DMSP), which is produced in abundance by the symbiotic dinoflagellates [62,63].…”

DddY, a periplasmic dimethylsulfoniopropionate lyase found in taxonomically diverse species of Proteobacteria

“…Further evidence for HGT came from the observation that a DMSP lyase in the marine Chlorophyte Ulva curvata cross-reacted with antibody raised against the A. faecalis DMSP lyase . However, the algal polypeptide (78 kDa) was larger than the 48 kDa bacterial lyase, and it will be of interest to compare these two enzymes at a molecular level to see if this represents another case of inter-Domain HGT, as was found with the DddP DMSP lyase (Todd et al, 2009;Kirkwood et al, 2010b).…”

“…The dddD gene is mostly found in marine g-proteobacteria, whereas dddL, dddP and dddQ usually occur in the Roseobacters (Curson et al, 2008Todd et al, 2007Todd et al, , 2009Todd et al, , 2010Todd et al, , 2011. Some ddd genes are subject to horizontal gene transfer (HGT), even extending to interdomain transfer of dddP among bacteria and Ascomycete fungi (Todd et al, 2007(Todd et al, , 2009; Kirkwood et al, 2010b).…”