A 22-kb DNA locus of Legionella pneumophila is described that contains 18 genes, 16 of which are required for macrophage killing (icm genes). In this paper two previously described icm loci were linked by the discovery of five genes located between the two loci. Four of the newly described genes are required for macrophage killing (icmMLKE) and one is dispensable. The 16 icm genes appeared to be organized as six individual genes (icmR, icmQ, icmG, icmC, icmD, and icmF), and four operons (icmTS, icmPO, icmMLKE, and icmJB). Four icm genes (icmP, icmO, icmL, and icmE) show significant sequence similarity to plasmid genes involved in conjugation, whereas the other icm genes were found not to bear any sequence similarity to database entries. We found that L. pneumophila can mediate plasmid DNA transfer at a frequency of 10 ؊3 to 10 ؊4 per donor. Strains containing null mutations in two icm genes (icmT and icmR) showed a severe reduction in conjugation frequency and macrophage killing. Strains containing an insertion in four other icm genes (icmF, icmE, icmC, and dotA) were shown to have a less severe defect in conjugation. Mutations in the other 11 icm genes had no effect on conjugation frequency. We currently do not know whether conjugation itself plays a role in macrophage killing. It is possible either that small plasmids can take advantage of an existing secretion system to be mobilized or that DNA transfer is required for human macrophage killing by L. pneumophila.Legionella pneumophila, the causative agent of Legionnaires' disease, is a facultative intracellular pathogen with a broad host range. The bacteria are able to infect, multiply within, and kill human macrophages, as well as free-living amoebae (1, 2). When inside host cells, L. pneumophila are found within a specialized phagosome that does not fuse with lysosomes (3). The bacteria multiply within the specialized phagosome, until the cell eventually lyses, releasing bacteria that can start new rounds of infection.Several years ago, a collection of 55 L. pneumophila mutants defective for macrophage killing were isolated from a large (n ϭ 4,500) pool of Tn903dIIlacZ insertions, and classified into 16 DNA hybridization groups (4). One of these groups (group 1), which contains 10 of the insertion mutants, was previously characterized as the icmA-dotA region (5, 6). More recently, five additional DNA hybridization groups were characterized as two separate regions (ref. 7; M.P. and H.A.S., unpublished results). One of the regions (6.5 kb), was shown to contain nine insertion mutations located on a single DNA hybridization group (group 3), that contains six icm genes (7). The second region (11 kb) was shown to contain 18 insertion mutations located on four contiguous DNA hybridization groups (groups 2, 6, 4, and 17), which contain an additional six icm genes (M.P. and H.A.S., unpublished results).The aim of this study was to complete the characterization of the additional DNA hybridization groups. We found that the two regions described above are conne...

Previously, a collection of mutants of Legionella pneumophila that had lost the ability to multiply within and kill human macrophages was generated by Tn903dIIlacZ transposon mutagenesis and classified into DNA hybridization groups. A subset of these mutants was complemented by a plasmid, pMW100, containing a 13.5-kb genomic DNA insert. This plasmid restored the ability to multiply within and produce cytopathic effects on human macrophages to members of DNA hybridization groups II, IV, VI, and XVII. A region of the genomic insert of pMW100 was sequenced, and eight potential genes were identified and named icmE,icmG, icmC, icmD, icmJ,icmB, icmF, and tphA. None of the genes encode potential protein products with significant homology to previously characterized proteins, except for tphA, whose product has significant homology to a family of metabolite/H+ symport proteins from gram-negative bacteria. The positions of the Tn903dIIlacZ insertions within the genes were determined by nucleotide sequencing. No Tn903dIIlacZ insertions mapped toicmG, icmJ, or tphA; therefore, these loci were mutated to test whether they were required for macrophage killing. Complementation analysis was used to evaluate the roles of the potential gene products and provide information on the organization of transcriptional units within the region. The results indicate that all identified open reading frames excepttphA are required for killing of human macrophages.

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OBJECTIVES/GOALS: CTSA Program hubs provide a wide range of research support services (funding, training, consultations, etc.) to individuals and teams. The CTSA Program hub at Columbia University seeks to identify best practices across CTSA hubs in how they facilitate researchers to identify, navigate, and access services at complex academic medical centers. METHODS/STUDY POPULATION: o A landscape analysis across CTSA Program hub websites was conducted during December 2021-February 2022, with the goal of assessing the availability of research navigation services and the ease of accessing and requesting research support services at each hub. Websites of 66 CTSA hubs were accessed and browsed for the following: 1) if a research navigation or concierge service was available; 2) how to request and apply to use common services such as pilot funding, biostatistics, clinical research services; 3) if there was a contact form and/or email address for general inquiries. Binary coding (1=Yes, 2=No) was used to track and summarize if these features were available, and then further classification and observations were noted into the full data set. RESULTS/ANTICIPATED RESULTS: The landscape analysis determined that 68% of CTSA hubs offer a form of research navigation including consultative models (personalized guidance, studios) and web-based models (self-service web portals, graphics, toolkits). Consultative models could be classified into three levels of support ranging from general information sharing to providing scientific expertise to convening more intensive studio sessions. 92% of CTSA hubs have at least 1 system in place for researchers to request services with a majority of hubs using a mix of tools and systems. In addition, 36% of hubs have additional general contact forms and 75% have general email addresses to assist researchers in obtaining more information. DISCUSSION/SIGNIFICANCE: There is a relative lack of data and information on the effectiveness of different research navigation models across the CTSA network, and barriers for researchers to identify services remain (Elworth et al). Our team is planning additional evaluations including interviews with leaders at other CTSA hubs and researchers and trainees at Columbia.