Month: September 2022

BLURRED BOUNDARY. "Taken together, these findings for the Buchnera–aphid symbiosis point to extensive genomic and metabolic integration of symbiotic partners and blur the distinction between symbiont and organelle." https://lnkd.in/dcBwzRs View in LinkedIn

REPRESSING IMMUNITY. "Accommodation of symbionts may require that hosts suppress or modify immune responses, potentially elevating risk of pathogen invasion. In aphids, many genes underlying responses to Gram-negative bacteria have been eliminated, including the immune deficiency signaling pathway (IMD), peptidoglycan receptor proteins, and antimicrobial peptides." https://lnkd.in/dcBwzRs View in LinkedIn

DRASTIC MEASURES. "A well-documented force affecting heritable symbionts is genetic drift leading to the fixation of neutral or deleterious mutations that cause gene inactivation, gene loss, or inefficiency of gene products. The basis for elevated genetic drift is the drastic shift in population genetic structure that occurs when a free-living microorganism adopts an obligate symbiotic lifestyle." https://lnkd.in/dcBwzRs View in LinkedIn

GENETIC STREAMLINING. "Symbiont genome decay affects genes in all functional categories. The first obligate symbiont genome sequenced, that of Buchnera of the pea aphid, was most notable for the fact that it had undergone extensive gene loss and contained no novel genes yet did retain genes for biosynthesis of essential amino acids needed by hosts." https://lnkd.in/dcBwzRs View in LinkedIn

OUTSOURCING COLLABORATION. "With more genome sequencing, it became apparent that Buchnera genomes in different aphid lineages continue to undergo irreversible gene loss, over long and short time scales. Similar ongoing gene loss is evident in every obligate symbiont clade for which multiple genomes have been sequenced." https://lnkd.in/dcBwzRs View in LinkedIn

OBLIGATE SYMBIONTS. "Many show far more extreme genome reduction than does Buchnera. Indeed, symbiont genomes have repeatedly evolved to be the very smallest genomes known in cellular organisms (aside from organelles), with total gene counts often

OPPOSING FORCES. "We have argued that symbionts are prone to evolve in directions detrimental to hosts, due both to genetic drift in clonal symbiont populations and to selection favoring selfish traits. An implication is that hosts are continually selected to compensate." https://lnkd.in/dcBwzRs View in LinkedIn

ONE WAY STREET. "Once a host lineage has proceeded down the irreversible path into obligate symbiosis, it seems that there is little opportunity to exit. In a few cases, such as the leafhopper subfamily Typhlocybinae, symbionts may have been lost in connection with dietary shifts: e.g., phloem sap to parenchyma. More often, the only escape from degenerate partners seems to be to supplement or replace them with new symbionts." https://lnkd.in/dcBwzRs View in LinkedIn

TRADING UP. "Numerous clear examples of an ancient obligate symbiont being joined or replaced by a newer one are evident, including several in the sap-feeding insects of suborder Auchenorrhyncha. A likely driver for adding a new symbiont is the degradation of functions in an ancient one: A new symbiont can replace or supplement functions that are lost or inefficient in the older partner." https://lnkd.in/dcBwzRs View in LinkedIn

"THE STERILE WOMB PARADIGM is an enduring premise in biology that human infants are born sterile. Recent studies suggest that infants incorporate an initial microbiome before birth and receive copious supplementation of maternal microbes through birth and breastfeeding. Moreover, evidence for microbial maternal transmission is increasingly widespread across animals." https://lnkd.in/ds5gpCY View in LinkedIn