Localization by scanning immunoelectron microscopy of triosephosphate isomerase, the molecules responsible for contact-mediated killing of Cryptococcus, on the surface of Staphylococcus

Abstract

In our previous studies, TPI were found to be the molecules responsible for contact-killing of C. neoformans by S. aureus cells. Since TPI is a glycolytic protein that functions in the cytoplasm, evidence that TPI is present on the surface of S. aureus was required. In the present study, the presence of TPI on the cell surface of S. aureus was demonstrated by agglutination test and scanning immunoelectron microscopy. Furthermore, TPI was found to be present at a lower density than protein A/G molecules on the surface of S. aureus. Interaction between microbes colonizing mucosal membranes is known to occur. Recently, we discovered that the bacterium S. aureus, found in the nasopharynx of a large proportion of healthy human subjects (1, 2), kills C. neoformans and fragments its DNA, suggesting that S. aureus in human nasal cavities may prevent the entry of C. neoformans (3). Since this killing required contact between the cells, it seemed unlikely that soluble substances, such as bacteriocin or killer toxins, were involved. Key wordsTo investigate the molecules responsible for contactmediated killing, we attempted to identify the candidate adhesion molecules. TPI and α-(1→3)-mannooligosaccharide (larger than triose) in the backbone of GXM, the main component of the cryptococcal capsule, were identified on S. aureus and C. neoformans, respectively (4). Binding between TPI and mannotriose has previously been confirmed by using purified TPI iso- lated from S. aureus (5). Since TPI is a glycolytic protein that functions in the cytoplasm, evidence for the presence on the surface of S. aureus of the molecules recognizing GXM was required.Here, we visualized by scanning immunoelectron microscopy the localization of TPI, the molecules responsible for contact-mediated killing of C. neoformans, on the surface of S. aureus.For the agglutination test, S. aureus ATCC6538P was cultured in trypticase soy broth at 37• C for 18 hr. The cells were harvested by centrifugation at 1700 g for 10 min and washed with PBS three times. The cell suspension was treated with GXM prepared from C. neoformans B-3501 (6) at a concentration of 0.5 mg/ml, and incubated overnight with shaking. After washing twice with PBS, the suspensions (of about McFarland no.10 turbidity) were subjected to a slide agglutination test. On a slide glass, 368

The Extracellular Matrix of Staphylococcus aureus Biofilms Comprises Cytoplasmic Proteins That Associate with the Cell Surface in Response to Decreasing pH

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Interaction of triosephosphate isomerase from Staphylococcus aureus with plasminogen

“…The presence of TPI on the cell surface of S. aureus has been suggested by proteomics analysis (20) and the results of our previous studies (1,21). The secretory pathways of the glycolytic protein to the cell surface are unknown.…”

Fetuin A, a serum component, promotes growth and biofilm formation by Aspergillus fumigatus

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