Cover photograph (Copyright © 2013, American Society for Microbiology. All Rights Reserved.): Streptococcus pneumoniae biofilms (purple) formed, for 8 h, on living cultures of human lung A549 cells were visualized by scanning electron microscopy. Unidentified fibers surrounding those bacteria appear to embrace pneumococcal cells within the biofilm matrix. Otitis media and pneumonia caused by S. pneumoniae strains, and persistence in the nasopharynx, are related to biofilm structures produced on human epithelia. In this study, a bioreactor was developed to demonstrate that S. pneumoniae produces more-robust biofilms on human respiratory cells, and this phenomenon was controlled by quorum-sensing molecules. The image was pseudocolored using Adobe Photoshop software. (See related article on p. 1341.)