Switching by parasites to novel hosts has profound effects on ecological and evolutionary disease dynamics. Switching requires that parasites are able to establish contact with novel hosts and to overcome host defenses. For most host-parasite associations, it is unclear as to what specific mechanisms prevent infection of novel hosts. Here, we show that parasitic fungal species in the genus Esco...

A basic tenet of ecology is that negative feedback on abundance plays an important part in the coexistence of species within guilds. Mutualistic interactions generate positive feedbacks on abundance and therefore are not thought to contribute to the maintenance of diversity. Here, I report evidence of negative feedback on plant growth through changes in the composition of their mutualistic fung...

The arbuscular mycorrhizal fungi (AMF) are important symbionts of land plants, which are known for their tremendous positive effects on terrestrial ecosystems, their peculiar cellular features, and their very old evolutionary history. To date, no sexual stage or apparatus have ever been observed in these organisms; a remarkable absence for a eukaryotic lineage. For this reason, AMF have long be...

Understanding the relative evolutionary importance of parasites to different host taxa is problematic because the expression of disease and resistance are often confounded by factors such as host age and condition. The antibiotic-producing metapleural glands of ants are a potentially useful exception to this rule because they are a key first-line defense that are fixed in size in adults. Here w...

Arbuscular mycorrhizal fungi (AMF) can form complex networks in the soil that connect different host plants. Previous studies have focused on the effects of these networks on individual hosts and host communities. However, very little is known about how different host species affect the success of the fungal network itself. Given the potentially strong selection pressure against hosts that inve...

The isolation, structural elucidation and biological activities of oligosporon (1), oligosporol A (2) and oligosporol B (3), three new antibiotics from cultures of the predacious deuteromycete, Arthrobotrys oligospora, are reported. The structures were elucidated by means of high resolution mass and high field N M R spectroscopy. The compounds exhibited weak antimicro­ bial, cytotoxic and hemol...

Microplot experiments were conducted to evaluate the effects of inoculum level and time of application of Paecilomyces lilacinus on the protection of tomato against MeIoidogyne incognita. The best protection against M. incognita was attained with 10 and 20 g of fungus-infested wheat kernels per microplot which resulted in a threefold and fourfold increase in tomato yield, respectively, compared...

The ancient mutualism between fungus-growing ants and the fungi they cultivate for food is a textbook example of symbiosis. Fungus-growing ants' ability to cultivate fungi depends on protection of the garden from the aggressive microbes associated with the substrate added to the garden as well as from the specialized virulent garden parasite Escovopsis. We examined ants' ability to remove alien...

The symbiosis between fungus-growing ants and the fungi they cultivate for food has been shaped by 50 million years of coevolution. Phylogenetic analyses indicate that this long coevolutionary history includes a third symbiont lineage: specialized microfungal parasites of the ants' fungus gardens. At ancient levels, the phylogenies of the three symbionts are perfectly congruent, revealing that ...

corneal ulcer is a major cause of blindness throughout the world. when the cornea is injured by foreign particles, there are chances of infection by the organism and development of ulcer. bacterial infection in the cornea is invariably an alteration of the defense mechanism of the outer eye. it is essential to determine the local etiology within a given region when planning a corneal ulcer mana...