Bacteriophage infection has profound effects on bacterial biology. Clustered regular interspaced short palindromic repeats (CRISPRs) and cas (CRISPR-associated) genes are found in most archaea and many bacteria and have been reported to play a role in resistance to bacteriophage infection. We observed that lysogenic infection of Pseudomonas aeruginosa PA14 with bacteriophage DMS3 inhibits biofilm formation and swarming motility, both important bacterial group behaviors. This inhibition requires the CRISPR region in the host. Mutation or deletion of five of the six cas genes and one of the two CRISPRs in this region restored biofilm formation and swarming to DMS3 lysogenized strains. Our observations suggest a role for CRISPR regions in modifying the effects of lysogeny on P. aeruginosa.Bacteriophages are probably best known for their role as tools used to study bacteria. Phages have also served as important models for the study of mechanisms of transcription, recombination, and transposition (8). Bacteriophages also shape microbial populations both by impacting the size and structure of bacterial communities and through the transfer of genetic material between bacterial strains (6, 39, 52). It is estimated that phages can lyse as many as 20% of all bacterial cells daily; therefore, these infectious particles can have a profound impact on the evolution of microbes (53).While some bacteriophage infections are primarily lytic, temperate or lysogenic bacteriophages often integrate into the bacterial genome as a prophage causing a chronic infection of the host bacterium (52). In some cases, genes carried by a bacteriophage confer a new function upon a bacterium, typically not directly related to the phage life cycle, through a process known as lysogenic conversion. Lysogenic conversion likely supports phage survival indirectly by increasing the fitness of the host microbe, thus promoting the continued persistence of the phage genome within the host population. Examples of this phenomenon include the phage-mediated introduction of secreted virulence factors such as cholera toxin (30), altered lipopolysaccharide profile (35), and improved adhesion to epithelial cells (50).Here we report that infection of Pseudomonas aeruginosa PA14 by phage DMS3 results in lysogenized strains unable to form a biofilm or undergo swarming motility-two key group behaviors of this bacterium. Furthermore, we show that the loss of biofilm formation and swarming motility requires clustered regular interspaced short palindromic repeats (CRISPRs) and five of six cas (CRISPR-associated) genes. Our data suggest a complex interaction between microbe and bacteriophage impacts the group behaviors of P. aeruginosa. MATERIALS AND METHODSBacterial and phage culture preparation. Strains and plasmids used in this study are shown in Table 1. Overnight cultures were streaked from glycerol stocks stored at Ϫ80°C onto lysogeny broth (LB) agar (1.5%) and incubated overnight at 37°C to isolated single colonies. These colonies were then used to inoculate plankt...

Pseudomonas aeruginosa is a ubiquitous bacterium capable of twitching, swimming, and swarming motility. In this study, we present evidence that P. aeruginosa has two flagellar stators, conserved in all pseudomonads as well as some other gram-negative bacteria. Either stator is sufficient for swimming, but both are necessary for swarming motility under most of the conditions tested, suggesting that these two stators may have different roles in these two types of motility.

Heparin, known for its anticoagulant activity, is commonly used in catheter locks. Staphylococcus aureus, a versatile human and animal pathogen, is commonly associated with catheter-related bloodstream infections and has evolved a number of mechanisms through which it adheres to biotic and abiotic surfaces. We demonstrate that heparin increased biofilm formation by several S. aureus strains. Surface coverage and the kinetics of biofilm formation were stimulated, but primary attachment to the surface was not affected. Heparin increased S. aureus cell-cell interactions in a protein synthesis-dependent manner. The addition of heparin rescued biofilm formation of hla, ica, and sarA mutants. Our data further suggest that heparin stimulation of biofilm formation occurs neither through an increase in sigB activity nor through an increase in polysaccharide intracellular adhesin levels. These finding suggests that heparin stimulates S. aureus biofilm formation via a novel pathway.