Microbial Interactions with Humans and Animals

Each animal or human body is a complex macrocosm comprised of multiple interconnected ecological systems of different body sites, including numerous body surfaces which are highly populated by microorganisms. Each region differs from the others and thus, creating a selective environment where certain microorganisms are favored more than others. These residents participate in commensal, parasitic and mutualistic relationships with their hosts. The microorganisms that establish more or less permanent residence but do not produce disease under normal conditions are members of the normal microbiota. Others are called the transient microbiota which may be present for several days, weeks or months and then disappear. Within the gastrointestinal system, animals have established relationships with microbes that appear to benefit both in many cases. Normal microbiota are not only found in gastrointestinal system, but also localized in skin, eyes, upper respiratory system and urogenital system of mammals. Digestive symbioses are most common among insects feeding on wood or other lignified plant materials. The symbiotic relationship in gut of termite is completely mutual and is beneficial for the host termite, its gut protists and their associated prokaryotes. Nematophagus fungi are an important group of soil microorganisms that can suppress the populations of plant-parasitic and animal-parasitic nematodes. The pathogenic mechanisms of nematophagous fungi are diverse. The present review enlightens the microbial interactions in four sections. First two sections discuss microbial interactions with gastrointestinal system and other body sites of mammals. Other two sections include microbial interactions with nematodes and termites.