Cellular chain formation in Escherichia coli biofilms

• Published in: Microbiology (Society for General Microbiology) 2009-05, Vol.155 (5), p.1407-1417
• Main Authors: Vejborg, Rebecca Munk, Klemm, Per
• Format: Article
• Language: English
• Subjects: Bacteriology; Biofilms - growth & development; Biological and medical sciences; Escherichia coli; Escherichia coli - chemistry; Escherichia coli - cytology; Escherichia coli - genetics; Escherichia coli - physiology; Escherichia coli Infections - microbiology; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Fundamental and applied biological sciences. Psychology; Humans; Hydrophobic and Hydrophilic Interactions; Microbiology; Miscellaneous
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.026419-0

Microbial Genomics Group, Centre for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Building 301, DK-2800 Kgs. Lyngby, Denmark In this study we report on a novel structural phenotype in Escherichia coli biofilms: cellular chain formation. Biofilm chaining in E. coli K-12 was found to occur primarily by clonal expansion, but was not due to filamentous growth. Rather, chain formation was the result of intercellular interactions facilitated by antigen 43 (Ag43), a self-associating autotransporter (SAAT) protein, which has previously been implicated in auto-aggregation and biofilm formation. Immunofluorescence microscopy suggested that Ag43 was concentrated at or near the cell poles, although when the antigen was highly overexpressed, a much more uniform distribution was seen. Immunofluorescence microscopy also indicated that other parameters, including dimensional constraints (flow, growth alongside a surface), may also affect the final biofilm architecture. Moreover, chain formation was affected by other surface structures; type I fimbriae expression significantly reduced cellular chain formation, presumably by steric hindrance. Cellular chain formation did not appear to be specific to E. coli K-12. Although many urinary tract infection (UTI) isolates were found to form rather homogeneous, flat biofilms, three isolates, including the prototypic asymptomatic bacteriuria strain, 83972, formed highly elaborate cellular chains during biofilm growth in human urine. Combined, these results illustrate the diversity of biofilm architectures that can be observed even within a single microbial species. Correspondence Per Klemm pkl{at}cbs.dtu.dk Abbreviations: ABU, asymptomatic bacteriuria; Ag43, antigen 43; FLIP, fluorescence loss in photo-bleaching; UPEC, uropathogenic E. coli ; UTI, urinary tract infection Details of minimal media and primers are available as supplementary material with the online version of this paper.