Abstract. Histoplasma capsulatum was isolated from gut, lung, liver, and spleen of 17 of 208 captured bats belonging to 6 different genera and species. Three of the 17 infected bats were from the State of Guerrero and 14 were from the State of Morelos. All were adult bats: 6 males (1 Pteronotus parnellii, 2 Natalus stramineus, 2 Artibeus hirsutus, and 1 Leptonycteris nivalis) and 11 females (1 Myotis californicus, 1 Mormoops megalophylla, 8 A. hirsutus, and 1 L. nivalis). High rates of bat infection with H. capsulatum were found in the monitored sites of the State of Morelos. Histoplasma infection of N. stramineus, A. hirsutus, and L. nivalis should be considered as the first records in the world. The fungus isolated from infected bats was identified by its typical mycelial-phase morphology and by its yeast-phase conversion. Exoantigen production confirmed the fungal identification by the presence of specific precipitation lines in double immunodiffusion assays using human immune serum. Histopathologic studies showed intracellular yeast-like cells compatible with H. capsulatum yeast-phase in tissues of several bats, especially in pulmonary (intra-alveolar and septal) macrophages, with none or minimal tissue reaction. In contrast to past reports, present data support a high risk of bat infection with H. capsulatum in Mexican cave environments.Bat guano and bird droppings have been shown to be the most common sources of the pathogenic fungus Histoplasma capsulatum var. capsulatum Darling, 1906, the causative agent of the deep mycosis histoplasmosis, which has a worldwide distribution.1 The fungus is found either in confined spaces where bat guano is abundant or in open spaces such as public parks and home yards, where bird droppings are frequently found. Excreta from these animals are rich in nutrients necessary for fungal growth and together with soil and environmental conditions, humidity and temperature, constitute the ecologic niche of this microorganism. [1][2][3][4] Bats are among the few infected mammals that contribute to the maintenance of this fungus in natural foci, in addition to some gregarious birds such as starlings, black birds, chickens, oil birds, and pigeons. Aguirre-Pequeño in 1959 5 and González-Ochoa in 1963, 6 defined the habitat of bats related to the isolation of H. capsulatum in Mexico, and the latter tested experimental infection of Desmodus rotundus in the laboratory without success. Fungal infection of Myotis californicus and Mormoops megalophylla is considered the first record in the world, whereas P. parnellii infection is new for Mexico. Although the environmental factors promoting H. capsulatum growth in shared ecologic niches have long been known, the circumstances that favor bat infection have been poorly studied. This paper presents data that might contribute to the understanding of the conditions that foster bat infection with this fungus. MATERIALS AND METHODSBats capture sites. Bat specimens were captured from 11 different sites located in 2 states in Mexico: Guerrero and M...

The Arc two-component system, comprising the ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous genes in response to the respiratory conditions of growth. Under anoxic growth conditions, ArcB autophosphorylates and transphosphorylates ArcA, which in turn represses or activates its target operons. Under aerobic growth conditions, phosphorylated ArcA (ArcA-P) dephosphorylates and its transcriptional regulation is released. The dephosphorylation of ArcA-P has been shown to occur, at least in vitro, via an ArcA Asp54 -P 3 ArcB His717 -P 3 ArcB Asp576 -P 3 P i reverse phosphorelay. In this study, the physiological significance of this pathway was assessed. The results demonstrate that the receiver and phosphotransfer domains of the tripartite sensor kinase ArcB are necessary and sufficient for efficient ArcA-P dephosphorylation in vivo.

The Arc two-component system, comprising the ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous genes in response to the respiratory conditions of growth. ArcB is a tripartite histidine kinase whose activity is regulated by the oxidation of two cytosol-located redox-active cysteine residues that participate in intermolecular disulfide bond formation. Here we show that ArcB autophosphorylates through an intramolecular reaction which diverges from the usually envisaged intermolecular autophosphorylation of homodimeric histidine kinases.

Three isolates of Histoplasma capsulatum were identified from mice lung, liver, and spleen inoculated with soil samples of the X hotel's ornamental potted plants that had been fertilized with organic material known as compost. The presence of H. capsulatum in the original compost was detected using the dot-enzyme-linked immunosorbent assay. Nested-PCR, using a specific protein Hcp100 coding gene sequence, confirmed the fungal identification associated with an unusual histoplasmosis outbreak in Acapulco. Although, diversity between the H. capsulatum isolate from the hotel and some clinical isolates from Guerrero (positive controls) was observed using random amplification of polymorphic DNA based-PCR, sequence analyses of H-anti and ole fragment genes revealed a high homology (92-99%) between them.

The Arc (anoxic redox control) two-component system of , comprising ArcA as the response regulator and ArcB as the sensor histidine kinase, modulates the expression of numerous genes in response to respiratory growth conditions. Under reducing growth conditions, ArcB autophosphorylates at the expense of ATP, and transphosphorylates ArcA via a His → Asp → His → Asp phosphorelay, whereas under oxidizing growth conditions, ArcB catalyzes the dephosphorylation of ArcA-P by a reverse Asp → His → Asp → P phosphorelay. However, the exact phosphoryl group transfer routes and the molecular mechanisms determining their directions are unclear. Here, we show that, during signal propagation, the His → Asp and Asp → His phosphoryl group transfers within ArcB dimers occur intra- and intermolecularly, respectively. Moreover, we report that, during signal decay, the phosphoryl group transfer from His to Asp takes place intramolecularly. In conclusion, we present a mechanism that dictates the direction of the phosphoryl group transfer within ArcB dimers and that enables the discrimination of the kinase and phosphatase activities of ArcB.