Sabrina Borusak ^1,2,3* Karin Denger ¹ Till Dorendorf ^1,2 Corentin Fournier ^1,3 Harry Lerner ^1,3 Olga Mayans ¹ Dieter Spiteller ¹ David Schleheck ^1,2,3*

• ¹ University of Konstanz, Konstanz, Germany
• ² Konstanz Research School Chemical Biology, University of Konstanz, Konstanz, Baden-Württemberg, Germany
• ³ Limnological Institute, Department of Biology, Faculty of Mathematics and Natural Sciences, University of Konstanz, Konstanz, Baden-Württemberg, Germany

Sulfoquinovose (SQ, 6-deoxy-6-sulfoglucose) produced by plants is one of the most abundant sulfur-containing compounds in nature and its bacterial degradation plays an important role in the biogeochemical sulfur and carbon cycles and in all habitats where SQ is produced and degraded, particularly in gut microbiomes. Here, we report the enrichment and characterization of a strictly anaerobic SQ-degrading bacterial consortium that produces the C2-sulfonate isethionate (ISE) as the major product but also the C3-sulfonate 2,3-dihydroxypropanesulfonate (DHPS), concomitant with production of acetate and hydrogen (H2). In a second step, the ISE was degraded completely to hydrogen sulfide (H2S) if an additional electron donor was supplied to the consortium (external H2). Through growth experiments, analytical chemistry, genomics, proteomics and transcriptomics, we found evidence for a combination of the 6-deoxy-6-sulfofructose (SF) transketolase (sulfo-TK) and SF transaldolase (sulfo-TAL) pathways in a SQ-degrading Faecalicatena-phylotype (family Lachnospiraceae) of the consortium, and for the ISE-desulfonating glycyl-radical enzyme pathway, as described for Bilophila wadsworthia, in an Anaerospora-phylotype (Sporomusaceae). Furthermore, by total proteomics, a new gene cluster for a bifurcated SQ pathway was also detected in Faecalicatena sp. DSM22707, which grew with SQ in pure culture, producing mainly ISE, but also 3-sulfolacate (SL) 3-sulfolacaldehyde (SLA), acetate, butyrate, succinate and formate, but not H2. We then reproduced the growth of the consortium with SQ in a defined co-culture model consisting of Faecalicatena sp. DSM22707 and Bilophila wadsworthia 3.1.6. Our findings provide the first description of an additional sulfoglycolytic, bifurcated SQ pathway. Furthermore, we expand on the knowledge about sulfidogenic SQ-degradation by strictly anaerobic co-cultures, comprising SQ-fermenting bacteria and cross-feeding of the sulfonate-intermediate to H2S-producing organisms, a process in gut microbiomes with relevance for human health and disease.