Fig. 5.

Testing the ability of P. vortex to cross air gaps with the assistance of A. fumigatus. (A) Experimental setup. A 90-mm diameter agar plate was filled with RMHA. A sterile razor blade was used to remove the RMHA from the right-hand one-half of the plate, leaving the inoculation region (Start). A second RMHA block (Target) was positioned to create an air gap (Gap) 0.5 or 0.8 mm wide. P. vortex with A. fumigatus conidia (or as a control, the bacteria alone) were inoculated at either position X (3.5 cm from air gap) or position Y (adjacent to air gap) in the inoculation region. This setup was incubated in a humidity chamber at 37 °C for 5 d. (B) Mycelial growth across a 0.5-mm air gap (Gap) from the starting region (S) to the target region (T). The left-hand edge of the air gap is obscured by fungal growth and is indicated by a vertical orange line. (C) Same as B but a smaller number of mycelia (black arrows) crosses a 0.8-mm air gap. (D) Fluorescence microscopy of target region (T) showing mycelia growing from the air gap (from the left) with associated P. vortex 3 d after inoculation. The bacteria are labeled with hexidium iodide, and the fungal mycelia are not stained but are visible as a negative image because of the surrounding bacteria (white). (E) Section of a mycelium crossing an air gap imaged by transmission light microscopy. (F) Same section of mycelia imaged by fluorescence microscopy revealing clusters of P. vortex associated with the fungus (labeled with hexidium iodide; e.g., white arrow). (G) Merged image combining E and F. (Scale bar: A, 17 mm; B and C, 0.3 mm; D, 80 μm; E–G, 25 μm.)