A giant virus infecting green algae encodes key fermentation genes

Abstract

The family Mimiviridae contains uncommonly large viruses, many of which were isolated using a free-living amoeba as a host. Although the genomes of these and other mimivirids that infect marine heterokont and haptophyte protists have now been sequenced, there has yet to be a genomic investigation of a mimivirid that infects a member of the Viridiplantae lineage (green algae and land plants). Here we characterize the 668-kilobase complete genome of TetV-1, a mimivirid that infects the cosmopolitan green alga Tetraselmis (Chlorodendrophyceae). The analysis revealed genes not previously seen in viruses, such as the mannitol metabolism enzyme mannitol 1-phosphate dehydrogenase, the saccharide degradation enzyme alpha-galactosidase, and the key fermentation genes pyruvate formate-lyase and pyruvate formate-lyase activating enzyme. The TetV genome is the largest sequenced to date for a virus that infects a photosynthetic organism, and its genes reveal unprecedented mechanisms by which viruses manipulate their host's metabolism.

Chromulinavorax destructans, a pathogenic TM6 bacterium with an unusual replication strategy targeting protist mitochondrion

“…Sampling Samples were collected from 11 freshwater locations in southern British Columbia, Canada (49°49'4"N, 123° 7'46"W; 49°42'5"N, 123° 8'47"W; 49°37'34"N, 123°12'27"W; 49° 6'12"N, 122° 4'38"W; 49° 5'22"N, 122° 7'1"W; 49°18'10"N, 122°42'9"W; 49° 8'27"N; 123° 3'16"W; 49°13'21"N, 123°12'43"W; 49°13'13"N, 123°12'41"W; 49°14'52"N, 123°13'59"W; 49°15'58"N, 123°15'34"W. See Chapter 2). To concentrate pathogens, 20 liter water samples were prefiltered with a GF-A filter (Millipore, Bedford, MA, USA; nominal pore size 1.1 μm) over a 0.8-μm pore-size PES membrane (Sterlitech, Kent, WA, USA) [16]. Filtrates from all locations were pooled and concentrated using a 30kDa MW cut-off tangential flow ultrafiltration cartridge (Millipore, Bedford, MA, USA) [17].…”

Giant mimiviruses escape many canonical criteria of the virus definition

“…The mobilome represents all types of mobile genetic elements, which are key players of genetic evolution: it comprises [1] Mimivirus First microorganism with a capsid and no ribosome 2004 [41] Mimivirus genome Largest viral genome and gene repertoire Translation components Hypothesis that giant viruses might represent a fourth domain of life 2008 [42] Marseillevirus Giant viruses of amoebae are diverse 2009 [25] Sputnik virophage First virus of virus (of mimivirus) 2012 [34] Pro-virophages and transpovirons Expansion of the mimivirus mobilome 2013 [37] Pandoraviruses Giant viruses devoid of capsids and capsid-encoding genes 2012 [101] Senegalvirus First giant virus of amoebae isolated from a human 2013 [82] Mimivirus LBA111 First mimivirus isolated from a human, a patient suffering from pneumonia 2013 [59] Zamilon virophage Some mimiviruses can resist virophages 2015 [38] Faustovirus Giant viruses can infect amoebae other than Acanthamoeba spp. (Vermamoeba vermiformis) 2016 [60] Mimiviruses, Zamilon virophage Mimiviruses can defend themselves against virophages through integration of short DNA fragments of these virophages: the MIMIVIRE system 2018 [5] Tupanvirus Largest set of translation components in the virosphere 2018 [17] Tetraselmis virus 1 Genes encoding energy production (fermentation) enzymes in a mimivirus transposable elements, plasmids, introns and inteins, as well as viruses [34]. The mimivirus-specific mobilome corresponds to provirophages, transpovirons, inteins and introns.…”

“…Images were obtained with the Hitachi SU5000 instrument (Hitachi High-Technologies Corporation, Tokyo, Japan). [17]. Besides, some obligatory intracellular parasites, including the small bacterium Carsonella ruddii, are devoid of a complete ATP generation machinery [72].…”

An Optimized Metabarcoding Method for Mimiviridae

“…The first member of the Mimiviridae family is the amoeba-infecting giant mimivirus (Acanthamoeba polyphaga mimivirus) with a particle diameter of 750 nm and a large genome encoding over 1,000 genes [2,3]. While this first-discovered member of Mimiviridae infects amoeba, other members infect unicellular algae or heterotrophic protists other than amoeba [4][5][6]. The genome sizes of alga-infecting Mimiviridae are mostly from 370 kb to 560 kb, but larger genomes up to 668 kb have also been reported [5,7].…”

“…While this first-discovered member of Mimiviridae infects amoeba, other members infect unicellular algae or heterotrophic protists other than amoeba [4][5][6]. The genome sizes of alga-infecting Mimiviridae are mostly from 370 kb to 560 kb, but larger genomes up to 668 kb have also been reported [5,7]. Their virion sizes range from 140 nm to 310 nm [4,7].…”