FIG. 2.

Effect of rpoS on X. nematophilus-nematode mutualism. (A) Schematic diagram illustrating nematode cultivation on X. nematophilus lawns. The circle represents an LA petri dish seeded with a lawn of a test bacterial strain. Bacteria-free S. carpocapsae nematode eggs are applied and monitored for development through their life cycle of four juvenile stages (J1 to J4) and adults that mate and lay eggs. After multiple rounds of development, the nematodes exhaust available nutrients and develop into the alternate infective juvenile stage that migrates off the plate. (B) Schematic diagram of infective-juvenile-stage nematode morphology, with key structures indicated. The rectangle indicates the portion of the nematode's internal organs, including the normal site of bacterial colonization, which are shown in the images in panel C. (C) Microscopic images of representative intestines of infective juvenile nematodes cultivated on lawns of wild-type (a), rpoS::kan (b), wild-type/pBCSK+ (c), rpoS::kan/pBCSK+ (d), wild-type/pBCrpoS (e), and rpoS::kan/pBCrpoS (f) cells. The percentage of nematodes (out of at least 30 visible foreguts for each cocultivation) harboring bacteria is indicated within each image and represents the mean of at least three independent experiments. The size bar represents 10 μm and applies to all images in panel C.