Life Sciences

2 Abstract 14 We have identified a homologue to the Staphylococcal biofilm-associated protein (Bap) 15 in a bloodstream isolate of Acinetobacter baumannii. The fully-sequenced open reading frame is 16 25,863 bp and encodes a protein with a predicted molecular mass of 854 kDa. Analysis of the 17 nucleotide sequence reveals a repetitive structure consistent with bacterial cell-surface adhesins. 18 Bap-specific monoclonal antibody (mAb) 6E3 was generated to an epitope conserved among 19 41 % of A. baumannii strains isolated during a recent outbreak in the US military health care 20 system. Flow cytometry confirms that the mAb 6E3 epitope is surface-exposed. Random 21 transposon mutagenesis was used to generate A. baumannii bap1302::EZ-Tn5, a mutant negative 22 for surface-reactivity to mAb 6E3 in which the transposon disrupts the coding sequence of bap. 23 Time-course confocal laser scanning microscopy and three-dimensional image analysis of 24 actively growing biofilms demonstrates that this mutant is unable to sustain biofilm thickness 25 and volume, suggesting a role for Bap in supporting the development of the mature biofilm 26 structure. This is the first identification of a specific cell-surface protein directly involved in 2