The effects of spaceflight on the infectious disease process have only been studied at the level of the host immune response and indicate a blunting of the immune mechanism in humans and animals. Accordingly, it is necessary to assess potential changes in microbial virulence associated with spaceflight which may impact the probability of in-flight infectious disease. In this study, we investigated the effect of altered gravitational vectors on Salmonella virulence in mice. Salmonella enterica serovar Typhimurium grown under modeled microgravity (MMG) were more virulent and were recovered in higher numbers from the murine spleen and liver following oral infection compared to organisms grown under normal gravity. Furthermore, MMG-grown salmonellae were more resistant to acid stress and macrophage killing and exhibited significant differences in protein synthesis than did normal-gravity-grown cells. Our results indicate that the environment created by simulated microgravity represents a novel environmental regulatory factor of Salmonella virulence.

Cells of Candida albicans WO-1 spontaneously switch between a white and opaque CFU, and this phase transition involves a dramatic change in cellular phenotype. By using a differential hybridization screen, an opaque-specific cDNA, Opla, which represents the transcript of a gene regulated by that it represents the transcript of an acid protease gene of C. albicans, a member of the pepsinogen family. MATERIALS AND METHODSGrowth and development. Cells from C. albicans WO-1 were stored on agar slants in capped tubes. For experimental purposes, cells from a storage slant were clonally plated on agar containing the nutrient composition of Lee's medium (27) supplemented with 70 ,ug of arginine per ml and 0.1 ,M ZnSO4 (7), which we will refer to as modified Lee's medium. Cells from white and opaque colonies were independently diluted into 25 ml of liquid modified Lee's medium, and cultures were rotated at 200 rpm at 25°C as previously described (7,46). The method of pH-regulated dimorphism (11,42)

Candida spp. carriage and strain relatedness were assessed in 52 healthy women at 17 anatomical locations by using an isolation procedure which assesses carriage intensity and by using a computer-assisted DNA fingerprinting system which computes genetic similarity between strains on the basis of the patterns of Southern blots probed with the moderately repetitive sequence Ca3. Candida spp. were cultured from 73% of the test individuals, most frequently from the oral (56%), vulvovaginal (40%), and anorectal (24%) regions. Half of the test individuals with Candida spp. carried the organism simultaneously in more than one of the three general areas of carriage. Isolates from different body locations of the same individual were either completely unrelated, identical, or highly similar but nonidentical. In 11 cases in which Candida spp. were simultaneously isolated from the oral cavity and vaginal canal, seven pairs of isolates were genetically unrelated and four pairs were similar but nonidentical. In the latter cases, the isolate pairs each appear to have arisen by genetic divergence from a single progenitor. A comparison of the genetic relatedness of isolates from different individuals further uncovered a single strain which was vaginospecific in the Iowa City, Iowa area and reduced genetic diversity among vulvovaginal strains compared with those isolated from other body locations. These results suggest that strains adapt to different anatomical locations and, conversely, that in a healthy individual there is anatomical selection of vaginotropic, anotropic, and orotropic strains of Candida spp.

DNA microarrays provide a global view of the physiological state of the cell by parallel analysis of the expression levels of all the genes in an organism. The effects of four bactericidal agents on the expression pattern of Escherichia coli MG1655 were assessed. Compounds were chosen on the basis of their different mechanisms of action and included inhibitors of DNA replication and recombination, translation, transcription and cell wall biosynthesis. The addition of rifampin resulted in increased expression of the target, rpoB, as well as several genes involved in nucleotide salvage and purine biosynthesis. The addition of ampicillin resulted in overall changes in gene expression that showed some similarity to changes induced by rifampin. The addition of the antibiotics kanamycin or norfloxacin resulted in the induction of unique gene expression signatures: a heat shock response to kanamycin and an SOS response to norfloxacin. Several genes of unknown function showed expression profiles similar to the genes associated with the SOS or the heat shock response. Thus, these profiles define families of genes with similar expression phenotypes that can be tested for related function.

Several different DNA fragments containing nonribosomal repetitive sequences have been isolated from the genome of Aspergiflus fumigatus and tested as potential DNA fingerprinting probes. Eight of these clones generate 19 or more bands when hybridized to EcoRI-digested DNA of a reference strain in Southern blots, and they fall into four families. Individual clones from two families were tested and were found to generate complex Southern blot hybridization patterns which are stable within a single strain over many generations, which vary among unrelated strains, and which are amenable to computer-assisted analyses involving large numbers of strains in epidemiological studies. Clones from three of the families clustered a majority of test strains in a similar fashion in individual dendrograms based on similarity coefficients computed from band positions in Southern blot hybridization patterns. These clones therefore fulfill the major requisites for effective DNA fingerprinting probes.