FIG 1.

Identification of PA3898 as essential for biofilm formation. (A) Spatial expression pattern of PA3898 in the surface, middle, and interior of a biofilm from a previous study (38). Fold changes of spatially expressed genes are shown with a red-black-green double-color gradient. Green indicates upregulation and red indicates downregulation compared to levels under planktonic growth conditions, as shown in the color gradient bar at the top (log₂ fold change, 2 to −2). For each location within the biofilm, the first three boxes represent the results from three biological replicates, and the fourth box represents the average fold changes of the replicates. (B) The PA3898::Tn mutant strain has significantly reduced biofilm formation via a crystal violet assay compared to wild-type (WT) PAO1 and the complemented strain (***, P < 0.0005 based on Student’s t test). The biofilm assay was performed in triplicate, and average amounts of biofilm and standard errors of the means are shown. (C) Defects in biofilm were observed and validated by confocal microscopy. Microscopic imaging was done in triplicate, and representative images are shown. (D) The PA3898::Tn mutant strain shows no in vitro growth defect compared to its complemented strain and wild-type PAO1.