Contribution of the Mannan Backbone of Cryptococcal Glucuronoxylomannan and a Glycolytic Enzyme ofStaphylococcus aureusto Contact-Mediated Killing ofCryptococcus neoformans

Abstract

The fungal pathogen Cryptococcus neoformans is killed by the bacterium Staphylococcus aureus, and the killing is inhibited by soluble capsular polysaccharides. To investigate the mechanism of killing, cells in coculture were examined by scanning and transmission electron microscopy. S. aureus attached to the capsule of C. neoformans, and the ultrastructure of the attached C. neoformans cells was characteristic of dead cells. To identify the molecules that contributed to the fungal-bacterial interaction, we treated each with NaIO 4 or protease. Treatment of C. neoformans with NaIO 4 promoted adherence. It was inferred that cleavage of xylose and glucuronic acid side chains of glucuronoxylomannan (GXM) allowed S. aureus to recognize mannose residues in the backbone, which resisted periodate oxidation. On the other hand, treatment of S. aureus with protease decreased adherence, suggesting that protein contributed to attachment in S. aureus. In confirmation, side chain-cleaved polysaccharide or defined ␣-(133)-mannan inhibited the killing at lower concentrations than native GXM did. Also, these polysaccharides reduced the adherence of the two species and induced clumping of pure S. aureus cells. ␣-(133)-Mannooligosaccharides with a degree of polymerization (DP) of >3 induced cluster formation of S. aureus in a dose-dependent manner. Surface plasmon resonance analyses showed interaction of GXM and surface protein from S. aureus; the interaction was inhibited by oligosaccharides with a DP of >3. Conformations of ␣-(133) oligosaccharides were predicted. The three-dimensional structures of mannooligosaccharides larger than triose appeared curved and could be imagined to be recognized by a hypothetical staphylococcal lectin. Native polyacrylamide gel electrophoresis of staphylococcal protein followed by electroblotting, enzyme-linked immunolectin assay, protein staining, and N-terminal amino acid sequencing suggested that the candidate protein was triosephosphate isomerase (TPI). The enzymatic activities were confirmed by using whole cells of S. aureus. TPI point mutants of S. aureus decreased the ability to interact with C. neoformans. Thus, TPI on S. aureus adheres to the capsule of C. neoformans by recognizing the structure of mannotriose units in the backbone of GXM; we suggest that this contact is required for killing of C. neoformans.

Interaction of triosephosphate isomerase from Staphylococcus aureus with plasminogen

“…aureus to C . neoformans induces apoptosis‐like cell death of the fungal pathogen (1, 31, 32). TPI recognizes at least three mannose residues in the α‐1,3‐linked mannan backbone of GXM.…”

“…Because TPI has been shown to bind cryptococcal GXM, the membrane was incubated with GXM, followed by anti‐ C . neoformans rabbit antibody, a conjugate of anti‐rabbit IgG and alkaline phosphatase, and then the substrate (1).…”

“…Triosephosphate isomerase displayed on the cell surface of S. aureus acts as an adhesion molecule that binds to the capsule of C. neoformans , a fungal pathogen (1, 2). Previously, we have shown that TPI recognizes α‐1,3‐linked mannooligosaccharides of a size equal to or greater than that of triose.…”

Ability of Candida albicans Mutants To Induce Staphylococcus aureus Vancomycin Resistance during Polymicrobial Biofilm Formation

“…There are several possible fungal and bacterial moieties that could mediate interspecies attachment: (i) a combination of known candidal adhesins, (ii) an unidentified candidal adhesin, (iii) a candidal cell wall component, and/or (iv) an unknown staphylococcal adhesin. It has been demonstrated previously that an S. aureus surface protein mediates binding to mannooligosaccharides (MOS) in the Cryptococcus neoformans capsule (18). Similar MOS are present in the candidal cell wall and are increased by hyphal versus yeast forms (1).…”

Growth Inhibition of an Opportunistic Yeast Pathogen <i>Trichosporon asahii</i> by <i>Staphylococcus epidermidis</i>

“…Triosephosphate isomerase, a glycolytic enzyme, on the cell surface of S. aureus and mannose residues in the capsule surrounding C. neoformans were identified as the adhesion molecules. [2][3][4][5][6] By investigating other combinations of microbes that threaten human health, we noticed that Trichosporon asahii did not grow in co-cultures with S. epidermidis using solid medium. Therefore, we speculated that the active substances might be soluble.…”