A current question in biofilm research is whether biofilm-specific genetic processes can lead to differentiation in physiology and function among biofilm cells. In Pseudomonas aeruginosa, phenotypic variants which exhibit a small-colony phenotype on agar media and a markedly accelerated pattern of biofilm development compared to that of the parental strain are often isolated from biofilms. We grew P. aeruginosa biofilms in glass flow cell reactors and observed that the emergence of small-colony variants (SCVs) in the effluent runoff from the biofilms correlated with the emergence of plaque-forming Pf1-like filamentous phage (designated Pf4) from the biofilm. Because several recent studies have shown that bacteriophage genes are among the most highly upregulated groups of genes during biofilm development, we investigated whether Pf4 plays a role in SCV formation during P. aeruginosa biofilm development. We carried out immunoelectron microscopy using antiPf4 antibodies and observed that SCV cells, but not parental-type cells, exhibited high densities of Pf4 filaments on the cell surface and that these filaments were often tightly interwoven into complex latticeworks surrounding the cells. Moreover, infection of P. aeruginosa planktonic cultures with Pf4 caused the emergence of SCVs within the culture. These SCVs exhibited enhanced attachment, accelerated biofilm development, and large regions of dead and lysed cells inside microcolonies in a manner identical to that of SCVs obtained from biofilms. We concluded that Pf4 can mediate phenotypic variation in P. aeruginosa biofilms. We also performed partial sequencing and analysis of the Pf4 replicative form and identified a number of open reading frames not previously recognized in the genome of P. aeruginosa, including a putative postsegregational killing operon.

Accessibility to abundant sources of high-quality water is integral to the production of safe and wholesome fresh produce. However, access to safe water is becoming increasingly difficult in many parts of the world, and this can lead to the production of fresh produce contaminated with pathogenic microorganisms, resulting in increased risk of human disease. Water, an important raw material in the fresh produce chain, is used in considerable amounts in many operations, including irrigation and application of pesticides and fertilizers, but also as a transport medium and for cooling and washing in postharvest practices. In several reported outbreaks related to uncooked fruit and vegetable products, water has been identified as a likely source of the outbreak. The present study, initiated by the ILSI Europe Emerging Microbiological Issues Task Force in collaboration with 8 other ILSI branches and support of WHO/FAO, was undertaken to review the status of, and provide suggestions for, consideration by different stakeholders on water and sanitation and its impact on food safety and public health. A limited number of guidelines and regulations on water quality for agricultural production are available, and many of them are still heavily based on microbial standards and (debated) parameters such as fecal coliforms. Data gaps have been identified with regard to baseline studies of microbial pathogens in water sources in many regions, the need for agreement on methods and microbial parameters to be used in assessing water quality, the fate of pathogens in water, and their transfer and persistence on irrigated/processed produce.

The in vitro cytotoxic studies of a series of salicylaldehyde semicarbazones, HOC₆H₄CH=N-NHCONR₂ (H₂R₂) and their Cu(II) complexes on a number of human tumor cell lines were conducted and it was observed that their cytotoxicities were enhanced following complexation to copper. These copper(II) complexes also demonstrated higher in vitro activities than the reference drug, cisplatin, on the tumor cell lines at micro molar range. Apoptotic assays and cell cycle analysis of the copper complexes, [Cu(HBnz₂)Cl] and [Cu(HBu₂)Cl] revealed that they mediated cytotoxicity in MOLT-4 cells via apoptosis. Further proteomic investigation of [Cu(HBnz₂)Cl] and [Cu(HBu₂)Cl] with respect to their protein expression profiles associated with their mode of action was conducted. By comparing the expression levels of 33 identified protein spots amongst the respective compound-treated profiles, we identified similarities in protein expression patterns between the two copper(II) complexes. The possible roles of the identified proteins in the execution of apoptosis by these copper(II) complexes are discussed.

Role-emerging fieldwork placements are increasingly being used in entry-level occupational therapy programs. However, published reviews have yet to focus on synthesizing the experiences and perspectives of students. This review aims to identify the opportunities, challenges, and future directions of role-emerging fieldwork placements based on the student perspective. A literature review using scoping review methods was conducted, including an electronic database search, hand-searching of journals, and citation tracking. Descriptive and thematic analyses of the articles were performed. Thirty articles were identified through the literature search. Themes that emerged related to opportunities were professional and personal development, independence and autonomy, client-centeredness, and new occupational therapy perspective. Themes that emerged related to challenges were defining a professional role, lack of structure and support, and high level of responsibility. Future directions centered on recommendations for future students and establishing roles within sites. Students benefited from the self-directed nature and client-centered practice in their role-emerging fieldwork placements, while the challenging environment contributed to their overall development. Students recognized a need for occupational therapy services in the wider community and saw role-emerging settings as legitimate career opportunities. Future research is encouraged to explore peer models, student-initiated roleemerging fieldwork placements, and postgraduate experiences. Comments The authors report that they have no conflicts of interest to disclose.