Microbial hitchhiking: how Streptomyces spores are transported by motile soil bacteria

Microbial Biotechnolog

Regulation of the chemotaxis histidine kinase CheA: a structural perspective

Microbial Biotechnolog

Atypical chemoreceptor arrays accommodate high membrane curvature

The prokaryotic chemotaxis system is arguably the best-understood signaling pathway in biology. In all previously described species, chemoreceptors organize into a hexagonal (P6 symmetry) extended array. Here, we report an alternative symmetry (P2) of the chemotaxis apparatus that emerges from a strict linear organization of the histidine kinase CheA in Treponema denticola cells, which possesses arrays with the highest native curvature investigated thus far. Using cryo-ET, we reveal that Td chemoreceptor arrays assume an unusual arrangement of the supra-molecular protein assembly that has likely evolved to accommodate the high membrane curvature. The arrays have several atypical features, such as an extended dimerization domain of CheA and a variant CheW-CheR-like fusion protein that is critical for maintaining an ordered chemosensory apparatus. Furthermore, the previously characterized Td oxygen sensor ODP influences CheA ordering. These results suggest a greater diversity of the chemotaxis signaling system than previously thought

A new class of protein sensor links spirochete pleomorphism, persistence, and chemotaxis

Microbial Biotechnolog

Influence of Exposure History on the Immunology and Development of Resistance to Human Schistosomiasis Mansoni

Schistosomiasis is a parasitic blood fluke infection of 200 million people worldwide. We have shown that humans can acquire immunity to reinfection after repeated exposures and cures with the drug praziquantel. The increase in resistance to reinfection was associated with an increase in schistosome-specific IgE. The ability to develop resistance and the rate at which resistance was acquired varied greatly in two cohorts of men within close geographic proximity and with similar occupational exposures to schistosomes. These differences are likely attributable to differences in history of exposure to Schistosoma mansoni infection and immunologic status at baseline, with those acquiring immunity faster having lifelong S. mansoni exposure and immunologic evidence of chronic S. mansoni infection. As many conflicting results have been reported in the literature regarding immunologic parameters associated with the development of resistance to schistosome infection, exposure history and prior immune status should be considered in the design of future immuno-epidemiologic studies

Regulatory and Activated T Cells in Human Schistosoma haematobium Infections

Acquired immunity against helminths is characterised by a complex interplay between the effector Th1 and Th2 immune responses and it slowly manifests with age as a result of cumulative exposure to parasite antigens. Data from experimental models suggest that immunity is also influenced by regulatory T cells (Treg), but as yet studies on Treg in human schistosome infections are limited

Reduced T Regulatory Cell Response during Acute Plasmodium falciparum Infection in Malian Children Co-Infected with Schistosoma haematobium

Regulatory T cells (Tregs) suppress host immune responses and participate in immune homeostasis. In co-infection, secondary parasite infections may disrupt the immunologic responses induced by a pre-existing parasitic infection. We previously demonstrated that schistosomiasis-positive (SP) Malian children, aged 4-8 years, are protected against the acquisition of malaria compared to matched schistosomiasis-negative (SN) children.To determine if Tregs contribute to this protection, we performed immunologic and Treg depletion in vitro studies using PBMC acquired from children with and without S. haematobium infection followed longitudinally for the acquisition of malaria. Levels of Tregs were lower in children with dual infections compared to children with malaria alone (0.49 versus 1.37%, respectively, P = 0.004) but were similar months later, during a period with negligible malaria transmission. The increased levels of Tregs in SN subjects were associated with suppressed serum Th1 cytokine levels, as well as elevated parasitemia compared to co-infected counterparts.These results suggest that lower levels of Tregs in helminth-infected children correlate with altered circulating cytokine and parasitologic results which may play a partial role in mediating protection against falciparum malaria

Intermicrobial hitchhiking: how nonmotile microbes leverage communal motility

Microbial Biotechnolog

The effect of intercropping Sclerocarya birrea (A. Rich.) Hochst., millet and corn in the presence of arbuscular mycorrhizal fungi

Sclerocarya birrea (A. Rich.) Hochst. (marula) is native to Africa occurring in the semi-arid, deciduous savannas of much of sub-Saharan Africa. It has multiple uses, including the fruits, kernels, oil, bark,wood and leaves which make it a key species to support the development of rural enterprises. Enhancing positive interactions between marula and other crops is key to successful introduction ofmarula into the farming systems in the arid and semiarid areas of Africa. The objective of the study was to determine the influence of various combinations of marula, Pennisetum glaucum (L.) R. Br. (millet)and Zea mays (corn) with one another when inoculated with arbuscular mycorrhizal (AM) fungi. A threechambered acrylic root boxes were used. One outer chamber contained seedlings of S. birrea while theother contained millet or corn or bare soil. The central chamber was either inoculated with an AM fungus (Gigaspora margarita Baker and Hall) or uninoculated. Inoculation in the presence of the twocrops enhanced both biomass production and height growth of marula seedlings. Both hyphal density and number of spores in marula compartments were increased under intercropping system comparedto marula monoculture. The study demonstrated that intercropping marula with millet or corn could help in the propagation of AM fungi spores in the soil which would enhance marula establishmentespecially in soil with low phosphorous and moisture scarcity