of uroplakin 1a on the urinary epithelium
( 4 , 14 , 27 ). The intrinsic flexibility of UMOD
filaments allows their adaptation to the bac-
terial surface, multivalent binding to pili from
the same bacterium, and eventually encap-
sulation of entire cells. Analogous to the
mechanism by which antibody–cross-linked
clumps of enchainedSalmonellacells facili-
tate the removal of pathogens from the gut
( 28 ), UMOD-mediated cell aggregation may have
a role in the efficient clearance of bacteria
through micturition.Our study also sheds light on interactions
between UMOD and pathogens other than
type 1–piliated UPEC. UPEC genomes, for
example, encode up to 16 fimbrial gene clusters,
and UPEC switch expression between pilus types
with distinct receptor specificities ( 24 , 29 – 31 ).Weisset al.,Science 369 , 1005–1010 (2020) 21 August 2020 4of6
Fig. 3. UMOD associates with piliated bacteria and can lead to cell aggre-
gation.(AandB) The type 1 pilus–deficient strainE. coliAAEC189 was
transformed with the type 1 pilus expression plasmid pSH2, coincubated with
UMOD filaments (1mM UMOD monomers and ~1.6 × 10^9 E. colicells/ml) and
imaged with cryo-ET. A slice (8.6-nm thick) through a cryotomogram (A) and a
segmentation of the same tomogram (B) are shown. Piliated bacteria (cell,
brown; pili, orange) were always seen in close association with a loose mesh of
UMOD filaments (blue lines or arrows). Note the contact site of the pilus tip with
the UMOD filament. A partly lysed cell that resulted in higher image quality is
shown. See fig. S13, A and B, for more examples. Scale bars, 100 nm.
(C) Quantification of UMOD-mediated formation of cell aggregates with light
microscopy. The bar graph shows the normalized clump area observed upon
incubation (2 hours) at 37°C of a constant amount of type 1–piliatedE. coli
HB101 (FimAra) (~10^8 cells/mL), with different concentrations of UMOD
filaments (0.08 to 5.0mM; concentrations refer to the UMOD monomer). The
presence of 10 mMD-mannose inhibited aggregation across all UMOD
concentrations tested. Representative light microscopy images are shown on the
right (without and with 10 mM Man). Bars represent the means of biological
triplicates ± SEM. *P< 0.05 difference between groups [two-way analysis of
variance (ANOVA), post hoc Tukey test]. Scale bars, 10mm. (D) Cell aggregates
colocalized with UMOD filaments. Bright-field and TIRF microscopy images of
type 1–piliatedE. coliHB101 (FimAra) cells (excitation at 405 nm, green) that
were incubated with fluorescent UMOD-Alexa647 filaments (red) are shown.
Scale bars, 10mm. (E) UMOD-inducedE. coliaggregates were plunge-frozen,
thinned by cryo-FIB milling, and imaged with cryo-ET (an 8.6-nm tomographic
slice is shown).E. colicells (brown) were always seen embedded in a highly
dense meshwork of UMOD filaments (blue arrows). For further examples,
see fig. S19. Scale bar, 100 nm.RESEARCH | REPORT