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.

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Abstract. The Plasmodium falciparum gene encoding erythrocyte binding antigen-175 (EBA-175), a putative receptor for red cell invasion (Camus, D., and T. J. Hadley. 1985. Science (Wash. DC). 230:553-556.), has been isolated and characterized. DNA sequencing demonstrated a single open reading frame encoding a translation product of 1,435 amino acid residues. Peptides corresponding to regions on the deduced amino acid sequence predicted to be B cell epitopes were assessed for immunogenicity. Immunization of mice and rabbits with EBA-peptide 4, a synthetic peptide encompassing amino acid residues 1,062-1,103, produced antibodies that recognized P. falciparum merozoites in an indirect fluorescent antibody assay. When compared to sera from rabbits immunized with the same adjuvant and carrier protein, sera from rabbits immunized with EBA-peptide 4 inhibited merozoite invasion of erythrocytes in vitro by 80% at a 1:5 dilution. Furthermore, these sera inhibited the binding of purified, authentic EBA-175 to erythrocytes, suggesting that their activity in inhibiting merozoite invasion of erythrocytes is mediated by blocking the binding of EBA-175 to erythrocytes. Since the nucleotide sequence of EBA-peptide 4 is conserved among seven strains of P. falciparum from throughout the world (Sim, B. K. L. 1990. Mol. Biochem. Parasitol. 41:293-296.), these data identify a region of the protein that should be a focus of vaccine development efforts.

This large outbreak of conjunctivitis on a college campus was caused by an atypical, unencapsulated strain of S. pneumoniae that was identical to strains that had caused outbreaks two decades earlier.

Objective-To conduct a therapeutic exploratory clinical trial comparing clinical outcomes of treatment with topical natamycin vs topical voriconazole for fungal keratitis.Methods-The multicenter, double-masked, clinical trial included 120 patients with fungal keratitis at Aravind Eye Hospital in India who were randomized to receive either topical natamycin or topical voriconazole and either had repeated scraping of the epithelium or not.Main Outcome Measures-The primary outcome was best spectacle-corrected visual acuity (BSCVA) at 3 months. Other outcomes included scar size, perforations, and a sub-analysis of BSCVA at 3 months in patients with an enrollment visual acuity of 20/40 to 20/400.Results-Compared with those who received natamycin, voriconazole-treated patients had an approximately 1-line improvement in BSCVA at 3 months after adjusting for scraping in a multivariate regression model but the difference was not statistically significant (P=.29). Scar size at 3 months was slightly greater with voriconazole after adjusting for scraping (P=.48). Corneal perforations in the voriconazole group (10 of 60 patients) were not significantly different than in the natamycin-treated group (9 of 60 patients) (P>.99). Scraping was associated with worse BSCVA at 3 months after adjusting for drug (P=.06). Patients with baseline BSCVA of 20/40 to 20/400 showed a trend toward a 2-line improvement in visual acuity with voriconazole (P=.07).Conclusions-Overall, there were no significant differences in visual acuity, scar size, and perforations between voriconazole-and natamycin-treated patients. There was a trend toward scraping being associated with worse outcomes.