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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

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

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

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

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

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

DÉTENTE. "New evidence in animals indicates that chronic virus infection can fundamentally alter innate immunity to nonviral pathogens. IFN-γ expression during herpesvirus latency can symbiotically protect the host from infection by the bacteria Listeria monocytogenes and Yersinia pestis, the causative agent of plague. Thus, the détente developed between herpesviruses and their hosts over tens of millions of years of coevolution may offer benefits to the host." http://www.sciencedirect.com/science/article/pii/S0092867409007831 View in LinkedIn

EUK VIRUSES. "Based on the current knowledge of bacterial and archaeal virus genomics, bacteriophages of the endosymbiont(s) played a much greater role in the origin of eukaryotic viruses than archaeal selfish elements." https://lnkd.in/dHhQ6QH View in LinkedIn

CHRONIC INFECTIONS. "The viral strategies...for the maintenance of chronic infection are balanced by the effects of the virus-specific immune response, thereby establishing a metastable equilibrium between host and pathogen. It is well established that there is a complex regulatory network that actively inhibits immune responses during chronic viral infections." http://www.sciencedirect.com/science/article/pii/S0092867409007831 View in LinkedIn

GENE FLUX. "The relationships between bacteriophage genes and those of eukaryotic viruses imply that the mitochondria and, possibly, other, transient endosymbionts also contributed many genes from their phage gene pool to the emerging eukaryotic viruses." https://lnkd.in/dHhQ6QH View in LinkedIn