FIG. 6.

H. volcanii adheres to glass in a FlgA1/FlgA2-independent, PibD-dependent manner. Adhesion to glass coverslips was tested using a modified ALI assay (42). Light micrographs of the coverslips taken at ×10 and ×35 magnifications are shown. Coverslips were placed in individual wells of 12-well plates, each containing 3 ml of a mid-log phase H. volcanii liquid culture (H98, wt, MT1, ΔflgA1 ΔflgA2; MT3, ΔpibD; and MT7, ΔpibD ptna-pibD). After overnight incubation, cells were fixed with 2% acetic acid, stained with 0.1% crystal violet, and observed by light microscopy. Attachment of H98 and MT1 to coverslips was observed within 10 min of incubation (data not shown). Multicellular structures reminiscent of microcolonies (a subset indicated by arrows) were observed.