Month: September 2022

"DEEP GENOME REDUCTION, with the smallest sequenced genome of only 2.9 Mb, is also observed in Microsporidia, the eukaryotic intracellular parasites that appear to be highly derived fungi. The most extreme genome reduction among eukaryotes is observed in nucleomorphs which are remnants of algal endosymbionts present in cryptophytes and chlorarachniophytes and retain only a few hundred genes." https://lnkd.in/egqWFZp View in LinkedIn

COMMENSALS. "Beyond parasites and symbionts, reductive evolution was observed in several groups of organisms that evolved a commensal life style. One of the best-characterized cases involves the Lactobacillales, a group of Gram-positive bacteria that is extremely common in a variety of animal- and plant-associated habitats...substantial gene loss, from ∼3,000 genes in the common ancestor of Bacilli to ∼1,300–1,800 genes in various Lactobacilli species." https://lnkd.in/egqWFZp View in LinkedIn

REDUCTION CONSTRAINTS. "The evolution of the genomes of parasites, symbionts and commensals is not a one-way path of reduction. On the contrary, the reduction ratchet is constrained by the advantages of retaining certain metabolic pathways that complement the host metabolism." https://lnkd.in/egqWFZp View in LinkedIn

SECONDARY GAINS. "The reductive trend is countered by proliferation of genes involved in parasite-host interaction such as, for example, ankyrin repeat proteins that act as secreted virulence factors." https://lnkd.in/egqWFZp View in LinkedIn

ANCIENT REDUCTIONS. "The most compelling evidence of the dominance of genome reduction and simplification was obtained through the reconstruction of the genomic evolution of archaea that almost exclusively are free-living organisms." https://lnkd.in/egqWFZp View in LinkedIn

EUKARYOTE GENES. "The reconstructions consistently indicate that ancestral eukaryotes including...the founders of each supergroup were intron-rich forms, with intron densities higher than those in the genes of most extant eukaryotes and probably only slightly lower than those in the modern organisms with the most complex gene structures, such as mammals." https://lnkd.in/egqWFZp View in LinkedIn

BIG TICKET REDUCTIONS. "The mitochondria, the ubiquitous energy-transforming organelles of eukaryotes, and the chloroplasts, the organelles responsible for the eukaryotic photosynthesis, are the ultimate realizations of bacterial reductive evolution." Massive gene loses. https://lnkd.in/egqWFZp View in LinkedIn

MASSIVE JUMP IN EUKARYOTES. "The complexity of the emerging chimeric organism drastically increases, both at the genomic and at the phenotypic level, and it has been argued that such complexification would not have been attainable if not for the endosymbiosis." https://lnkd.in/egqWFZp View in LinkedIn

MASS TRANSFER. "Hundreds of genes, in the case of the mitochondrion, and even thousands in the case of the chloroplast, were not lost but rather transferred from the endosymbiont genome to the nuclear genome of the host." https://lnkd.in/egqWFZp View in LinkedIn

SO ENDS our review of evolutionary genomic simplification. Simple organisms are generally regarded as lesser in the Victorian tree of life. Even viruses, that many think are not living. But evolution shows that in many cases, simpler systems with outsourced genes may in fact be more advanced. And often much older. And smaller systems can in fact be a greater complexity. It takes a lot to be simple. View in LinkedIn