ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
(from Greek, syn: together, bios: livelihood) A mutually beneficial relationship in which members of different SPECIES live together at the same time. (Were it not at the same time the relationship would be better described as RECIPROCAL ALTRUISM.) The benefiting partners could live directly one on another (ectoparasitism); or one species could live within the other (endoparasitism). It is contrasted with the life of a PARASITE: parasitism involves one species living off another, to its own exclusive benefit, though without necessarily (in the short term at least) being detrimental to the host. (A better contrast for symbiosis might be the more specific form, MUTUAL PARASITISM, in which two species live off each other to the long-term detriment of both.) A related term is COMMENSAL (from Latin, con: together, mensa: table— commensal literally means sharing a table). Commensalism is where two species share an environment, but without necessarily bringing either harm or benefit to each other: foxes and badgers are often commensal.
Composition and Diversity of Human Oral Microbiome
Chaminda Jayampath Seneviratne in Microbial Biofilms, 2017
The human microbiome, in general, exhibits a phenomenon known as commensalism in which microbes coexist based on a mutually beneficial relationship. The commensal organisms reside at various anatomical locations in the body according to the conditions which favour their growth and proliferation. Although there are ample opportunities for the exchange of bacteria, each site maintains its own microbial profile. Despite their ubiquitous presence in the body, they remain confined to their inherent location because of the presence of physical and immunomodulatory barriers, thereby maintaining the sterility of underlying tissues and human health [98]. Thus a state of equilibrium exists among microorganisms by means of mutualism, commensalism and parasitism for their coexistence. These interactions maintain the balance and stability of the microbial community. However, perturbations in this balance results in microbial shifts leading to disease states.
Ethics of Research with Non-Human Animals
Howard Winet in Ethics for Bioengineering Scientists, 2021
It is not unusual for animal species within a given ecosystem to use one another for survival. Predator-prey relationships are, of course, non-cooperative at the individual level. Being devoured is of no benefit to the meal (unless the meal is a parasite and the host is part of its life cycle). But at the ecosystem level, predators keep herbivores from over-reproducing and devouring so many plants that there are none left to eat. Parasites that weaken prey also help keep down their numbers. If a parasite is too virulent, however, it kills all its hosts and dooms itself. Cooperative relationships such as symbiosis, where both species benefit, and commensalism, where one benefits and the other doesn’t but is not harmed, have also contributed to species survival for millions of years. A number of ant species use aphids like cows, milking them for sap that only the aphids can extract from trees. Remora fish attach themselves to sharks for a free ride to their host’s feeding leftovers.
Gut Bacteroides species in health and disease
Published in Gut Microbes, 2021
Hassan Zafar, Milton H. Saier
As the colon of the gastrointestinal tract (GIT) of mammals has the availability of diverse nutrient sources (derived from the host diet), this makes it a predilection site for numerous microbes.5 Members of the genus Bacteroides are potential colonizers of the colon and account for a major fraction of the gut bacteriome.6 These Gram-negative obligate anaerobes play multiple roles in the human gut bacteriome and are major players in sustaining the microbial food web of the gut.7 As proven commensals, mutualists, and beneficial organisms, they not only play the role of “Providers” for the host and other microbes residing close to them, but also assist the host by providing numerous health benefits. Nevertheless, some species of Bacteroides may play dual beneficial and pathogenic roles based on their locations in the host, often being beneficial in the gut but opportunistic pathogens in other body locations. Common sites of Bacteroides infections and possible disease conditions are illustrated in Figure 1. In this review we analyze the roles of Bacteroides species as beneficial organisms, gut competitors, and opportunistic pathogens. Also, recent relevant Bacteroides research findings will be evaluated.
Enteric bacteria induce IFNγ and Granzyme B from human colonic Group 1 Innate Lymphoid Cells
Published in Gut Microbes, 2020
Moriah J. Castleman, Stephanie M. Dillon, Christine Purba, Andrew C. Cogswell, Martin McCarter, Edward Barker, Cara Wilson
An intriguing observation in our data is that of the bacteria tested in this study enteric Gram-negative, but not Gram-positive bacteria-induced IFNγ production from NK cells and ILC1s. Although more work is needed to determine the mechanisms underlying this Gram-negative versus Gram-positive dichotomy, it is tempting to speculate that certain enteric commensal bacteria are inherently more pro-inflammatory. This is in keeping with the characterization of some commensal bacteria as “pathobionts,” which are commensals with the propensity to induce pathological conditions in certain situations, but are otherwise symbionts.46 Here, two of the Gram-negative commensals tested (P. stercorea and A. junii) reside within genera of bacteria that are reported to contain pathobionts,47,48 and thus members of these genera may induce inflammation in the setting of epithelial barrier damage. Interestingly, we have previously shown that these exact species can also induce IL-22 production by human colonic ILC3s,49 which is a cytokine with a role in epithelial barrier maintenance and regulation of intestinal health. However, it is important to note that while we did investigate the effect of four commensal bacteria representing four different phyla on the induction of cytokine production by Group 1 ILCs, we acknowledge that there are a multitude of different bacterial species in the human gut and therefore we cannot conclude that all bacteria would elicit similar responses in Group 1 ILCs.
Modeling spatial interaction networks of the gut microbiota
Published in Gut Microbes, 2022
Xiaocang Cao, Ang Dong, Guangbo Kang, Xiaoli Wang, Liyun Duan, Huixing Hou, Tianming Zhao, Shuang Wu, Xinjuan Liu, He Huang, Rongling Wu
More remarkably, the second-layer network of M3 produces structural and organizational changes from HC to UC groups (Figure 6). Lactobacillus coryniformis is a dominant leader that positively impact many other species in the HC group, but it turns to exert strong negative impacts on the same species in the UC group. Lactococcus piscium that coexists peacefully with its partners in HC guts becomes aggressive toward Firmicutes oral and phylum sp. Oral in UC guts. M4 and M6 are filled of commensalism in both HC and UC networks, but the strength of commensalism notably differs between two types of networks. Stronger commensalism exerted by particular species is observed in UC than HC groups. Taken together, multilayer microbial interaction networks provide a detailed roadmap of how each microbial species interacts with every other species through cooperation or competition to determine the change of guts from healthy to unhealthy states.
Related Knowledge Centers
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