A novel mechanism by which T cells contribute to host defense against microbial pathogens is release of the antimicrobial protein granulysin. We investigated the role of granulysin in human infectious disease using leprosy as a model. Granulysin-expressing T cells were detected in cutaneous leprosy lesions at a six-fold greater frequency in patients with the localized tuberculoid as compared with the disseminated lepromatous form of the disease. In contrast, perforin, a cytolytic molecule that colocalizes with granulysin in cytotoxic granules, was expressed at similar levels across the spectrum of disease. Within leprosy lesions, granulysin colocalized in CD4+ T cells and was expressed in CD4+ T-cell lines derived from skin lesions. These CD4+ T-cell lines lysed targets by the granule exocytosis pathway and reduced the viability of mycobacteria in infected targets. Given the broad antimicrobial spectrum of granulysin, these data provide evidence that T-cell release of granulysin contributes to host defense in human infectious disease.

Solar salterns are extreme hypersaline environments that are five to ten times saltier than seawater (150-300 g L(-1) salt concentration) and typically contain high numbers of halophiles adapted to tolerate such extreme hypersalinity. Thirty-five halophile cultures of both Bacteria and Archaea were isolated from the Exportadora de Sal saltworks in Guerrero Negro, Baja California, Mexico. 16S rRNA sequence analysis showed that these cultured isolates included members belonging to the Halorubrum, Haloarcula, Halomonas, Halovibrio, Salicola, and Salinibacter genera and what may represent a new archaeal genus. For the first time, metabolic substrate usage of halophile isolates was evaluated using the non-colorimetric BIOLOG Phenotype MicroArray plates. Unique carbon substrate usage profiles were observed, even for closely related Halorubrum species, with bacterial isolates using more substrates than archaeal cultures. Characterization of these isolates also included morphology and pigmentation analyses, as well as salinity tolerance over a range of 50-300 g L(-1) salt concentration. Salinity optima varied between 50 and 250 g L(-1) and doubling times varied between 1 and 12 h.

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Both the CD4−CD8− (double negative) and CD4−CD8+ T cell lineages have been shown to contain T cells which recognize microbial lipid and glycolipid Ags in the context of human CD1 molecules. To determine whether T cells expressing the CD4 coreceptor could recognize Ag in the context of CD1, we derived CD4+ T cell lines from the lesions of leprosy patients. We identified three CD4+ Mycobacterium leprae-reactive, CD1-restricted T cell lines: two CD1b restricted and one CD1c restricted. These T cell lines recognize mycobacterial Ags, one of which has not been previously described for CD1-restricted T cells. The response of CD4+ CD1-restricted T cells, unlike MHC class II-restricted T cells, was not inhibited by anti-CD4 mAb, suggesting that the CD4 coreceptor does not impact positive or negative selection of CD1-restricted T cells. The CD4+ CD1-restricted T cell lines produced IFN-γ and GM-CSF, the Th1 pattern of cytokines required for cell-mediated immunity against intracellular pathogens, but no detectable IL-4. The existence of CD4+ CD1-restricted T cells that produce a Th1 cytokine pattern suggests a contributory role in immunity to mycobacterial infection.

Mono Lake is a meromictic, hypersaline, soda lake that harbors a diverse and abundant microbial community. A previous report documented the high viral abundance in Mono Lake, and pulsed-field gel electrophoresis analysis of viral DNA from lake water samples showed a diverse population based on a broad range of viral genome sizes. To better understand the ecology of bacteriophages and their hosts in this unique environment, water samples were collected between February 2001 and July 2004 for isolation of bacteriophages by using four indigenous bacterial hosts. Plaque assay results showed a differential seasonal expression of cultured bacteriophages. To reveal the diversity of uncultured bacteriophages, viral DNA from lake water samples was used to construct clone libraries. Sequence analysis of viral clones revealed homology to viral as well as bacterial proteins. Furthermore, dot blot DNA hybridization analyses showed that the uncultured viruses are more prevalent during most seasons, whereas the viral isolates (Aphi and phi2) were less prevalent, confirming the belief that uncultured viruses represent the dominant members of the community, whereas cultured isolates represent the minority species.