Lysozyme activity of the Ruminococcus champanellensis cellulosome

Abstract

Ruminococcus champanellensis is a keystone species in the human gut that produces an intricate cellulosome system of various architectures. A variety of cellulosomal enzymes have been identified, which exhibit a range of hydrolytic activities on lignocellulosic substrates. We describe herein a unique R. champanellensis scaffoldin, ScaK, which is expressed during growth on cellobiose and comprises a cohesin module and a family 25 glycoside hydrolase (GH25). The GH25 is non-autolytic and exhibits lysozyme-mediated lytic activity against several bacterial species. Despite the narrow acidic pH curve, the enzyme is active along a temperature range from 2 to 85°C and is stable at very high temperatures for extended incubation periods. The ScaK cohesin was shown to bind selectively to the dockerin of a monovalent scaffoldin (ScaG), thus enabling formation of a cell-free cellulosome, whereby ScaG interacts with a divalent scaffodin (ScaA) that bears the enzymes either directly or through additional monovalent scaffoldins (ScaC and ScaD). The ScaK cohesin also interacts with the dockerin of a protein comprising multiple Fn3 domains that can potentially promote adhesion to carbohydrates and the bacterial cell surface. A cell-free cellulosomal GH25 lysozyme may provide a bacterial strategy to both hydrolyze lignocellulose and repel eventual food competitors and/or cheaters.

Cell Wall Hydrolases in Bacteria: Insight on the Diversity of Cell Wall Amidases, Glycosidases and Peptidases Toward Peptidoglycan

“…Of note and besides LTG domains, some CWHs can exhibit additional catalytic domains unrelated to CW degradation or CW biosynthesis but this aspect has not been really explored yet. Interestingly, lysozyme activity was recently uncovered in the Ruminococcus champellensis cellulosome (Morais et al, 2016) and several dockerin-containing CWHs enable to associate to the cohesion domains of a scaffoldin were further reported (Bensoussan et al, 2017). Beyond the cellulosome dedicated to the degradation of plant materials (Shoham et al, 1999; Desvaux, 2005; Smith et al, 2017), a new concept could emerge, that is an extracellular multi-enzymes complex dedicated to bacterial cell lysis, i.e.…”

Comparative Genomics of Lactobacillus crispatus from the Gut and Vagina Reveals Genetic Diversity and Lifestyle Adaptation

“…GH73 encodes β-N-acetylglucosaminidases that cleave the β-1,4 glycosidic linkage between the N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc) residues of bacterial cell wall peptidoglycan (PG) [57]. These two GH family lysozymes might provide a bacterial strategy to improve the competitive advantage of L. crispatus by destroying the cell walls of other pathogenic bacteria in the vagina and lysing them [58]. In summary, the above results demonstrate that L. crispatus is adaptable to different environments to improve its ability to survive.…”

The Cellulosome Paradigm in An Extreme Alkaline Environment

“…ScaK and ScaN1-7 could be “adaptor scaffoldins” as ScaC in R. flavefaciens [14] and Ruminococcus champanellensis [51,52], as they contain one to three copies of type I cohesins and a C-terminal type I dockerin module in their sequences, except for ScaN7 that has a type I dockerin at its N-terminus.…”