The authors have no acknowledgements to make.

1. Sample Collection
<ol>
	<li>Collect 70 samples from different environments and regions. In this case, use the following: 5 dirty water samples from the village of Saint Pierre de Meyzoargues (France), 15 samples from the lake in Parc Bor&#233;ly in Marseille (France); 15 sea water samples with sediment from the rocky inlets at Samena in Marseille (France), 25 river water samples from the Alps (France), and finally, 10 samples from sewage in La Ciotat (France).</li>
	<li>Vortex samples for homogenization before inoculating, for one minute at room temperature without any treatment.</li>
</ol>
2. Isolation Procedure
<ol>
	<li>Host Preparation for Blind Culture Procedures and Sample Inoculation
	<ol>
		<li>Use V. vermiformis (strain CDC19) as a cell support for the co-culture.</li>
		<li>Maintain the amoebae at 28 &#176;C, in a 75 cm2 cell culture flask with 30 ml of protease-peptone-yeast extract-glucose medium (PYG). Please check PYG composition in Table 1. 
		Note: After 48 hr, amoebae are quantified by a normal count using counting slides (e.g., Kovaslides).</li>
		<li>Harvest cells at a concentration of 5 x 105 to 106 cell/ml, and pellet amoebae by centrifugation at 720 x g for 10 min.</li>
		<li>Remove the supernatant by aspiration, and re-suspend the amoebae pellet in 30 ml of sterile Page&#39;s amoebal saline (PAS) Table 1. Repeat this rinsing procedure.</li>
		<li>Re-suspend amoebae in 30 ml of starvation medium with an antibiotic and antifungal mixture at a concentration of approximately 106 amoeba/ml. The starvation medium is a survival medium for the amoeba, enabling it to stay alive without encystment or multiplication. Check composition in Table 1. 
		Note: The antimicrobial agent mix contained 10 &#181;g/ml vancomycin, 10 &#181;g/ml imipenem, 20 &#181;g/ml ciprofloxacin, 20 &#181;g/ml doxycycline, and 20 &#181;g/ml voriconazole. This mix served to reduce the bacterial and fungal contamination that can decrease or alter viral multiplication.</li>
		<li>Directly inoculate 25 &#181;l of each sample onto the 200 &#181;l amoeba monolayer in a 96-well plate flat bottom favoring the amoeba adherence and incubate at 30 &#176;C in a humid environment (a humid environment consists of placing a wet compress inside the bag containing the plate in order to avoid evaporation). This is the primo-culture. Leave two wells of amoebae without any sample inoculation; this acts as the negative control. Incubate this primo-culture for three days.</li>
		<li>Three days after the first inoculation, sub-culture the primo-culture plate on fresh amoebae as described above without any microscopic observation. Incubate the new plate for three days under the same conditions as the primo-culture.</li>
		<li>Perform the final culture after these three days of incubation the same way as for the primo- and sub-culture. Incubate the final culture for two days. Then proceed to detection.</li>
	</ol>
	</li>
	<li>Detection of Lysis by Automated Flow Cytometry 
	Note: Blind culture coupled with flow cytometry differs from the previous standard system of isolation. It is more sensitive, precise and automated. For detection purposes, we applied a new technique developed to detect lysis at the highest speed and without microscopic observation. This technique is advantageous for screening samples and has better sensitivity than older techniques.7-9
	<ol>
		<li>Use the 96-well plate of the final co-culture to detect lysis.</li>
		<li>Turn on the cytometer and run a clean and rinse cycle in order to obtain lower background noise according to manufacturer&#39;s protocol.</li>
		<li>Launch the High Throughput Sampler (HTS) combined with flow cytometer to automatically load samples from the 96-well plate and perform a completely automated acquisition within 40 min according to manufacturer&#39;s protocol.</li>
		<li>Set up the HTS as follows: sample volume 150 &#181;l, mixing volume 50 &#181;l, mixing speed 180, number of mixes 5, washing volume between each sample 400 &#181;l, flow rate 2.5 &#181;l/sec, number of recorded events 10,000.</li>
		<li>Assess the negative control wells of the final co-culture micro-plate first in order to gate the amoeba population and to determine the percentage of these cell hosts according to their physical characteristics. Be sure to have a homogeneous amoeba population and a second population of a lower events corresponding to debris and noise. 
		Note: This gating procedure distinguishes subcellular debris and clumps from single cells by size, estimated by forward scatter. It is therefore important to accurately determine the percentage of each population using the best possible gating procedure. These percentages may vary, especially if many types of protozoa are used, so it is important always to have a negative control, which can be used as the reference population for the rest of the samples.</li>
		<li>Start the gating by clicking acquire sample.</li>
		<li>Record the number of events not less than 10,000 events.</li>
		<li>Localize the amoeba population of interest using the arrow. This is how to define the gates.</li>
		<li>After gating, let the HTS spot or locate the plate by clicking &#39;Home&#39;, then run the entire plate automatically. Perform data acquisition and analysis according to the size and structure parameters (respectively, FSC (forward scatter) and SSC (side scatter)). 
		Note: Detecting the loss of the amoeba-gated population signals the presence of a pathogenic agent responsible for amoeba lysis. Protozoa lysis associated with virus infection is detected with an arbitrarily designed threshold of 50% lysis of the amoeba population gated by the analyzer and compared to the same non-infected population used as a reliable negative control.</li>
	</ol>
	</li>
</ol>
3. Characterization of the New Isolates after Lysis Detection
<ol>
	<li>Preliminary Staining to Reveal the Presence of Giant Viruses
	<ol>
		<li>After lysis detection by flow cytometry, pipette the lysed co-cultures to suspend the remaining amoebae. Then directly cytocentrifuge 50 &#181;l of the suspension at 800 x g for 10 min.</li>
		<li>After centrifugation, fix the slides with a pure methanol solution. Stain the slides using a commercial rapid staining of Eosin/blue Azur and DAPI staining and observe under a light microscope at 1,000X magnification in order to check for the presence of virus factories.
		<ol>
			<li>For rapid staining, plunge the slides into the first eosin solution (4 sec repeated three times) then pass directly to plunge slides into the second fixing solution containing blue Azur for 6 sec, and finally rinse the slides for 45 sec with a phosphate buffer solution pH 7.2. Leave the slides to dry at room temperature, then proceed to observation.</li>
			<li>For DAPI staining, deposit 15 &#181;l of the DAPI commercial stock solution onto the fixed dry slide. Protect from light then proceed to observation.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Electron Microscopy
	<ol>
		<li>After the first identification on the slides, assess the presence of the giant virus through electron microscopy observation of supernatant cultures.</li>
		<li>Deposit 5 &#181;l of the positive sample onto the glow-discharged grid. Wait for approximately 20 min at room temperature.</li>
		<li>Dry the grid carefully and deposit on it a small drop of 1% ammonium molybdate for 10 sec. Leave the grid to dry for 5 min.</li>
		<li>Proceed to electron microscopy at 200 keV.</li>
		<li>Place the grid on the holder; introduce the holder into the microscope. Check the vacuum overview by clicking on the corresponding icon. Close valves and begin observation at a spot size 5, and magnification of x 25,000.</li>
		<li>Measure the giant virus using ImageJ or directly on the microscope using the measure tool of the microscope located on the acquisition screen. 
		Note: Classify the sample into the Faustovirus group with a capsid size of approximately 200 nm.</li>
	</ol>
	</li>
	<li>Molecular Biology 
	Note: Following this identification, molecular biology tests were crucial for the confirmation in order to distinguish Faustovirus from Marseillevirus, which has the same capsid size and appearance under electron microscopy, although they do not have the same host specificity. The Marseillevirus cannot grow on Vermamoeba, the Faustovirus is specific to Vermamoeba and all attempts to grow it on other amoeba such as Acanthamoeba have failed to date. The design and application of the specific primer/probe systems listed in the works of Reteno et al. enabled a more precise preliminary classification of the newly isolated viruses through amplification and sequencing of the viral genes.
	<ol>
		<li>Extract DNA from the positive culture samples using an automated extraction system according to the manufacturer&#39;s protocol.</li>
		<li>Perform Real-time PCR using a thermocycler as described in Reteno et al.19</li>
		<li>Sequence using the same primers that were used for amplification. Use the primers targeting DNA-directed RNA polymerase subunit 1 gene: Fstv_S2F 5&#39;-CCA GGA CAT GAT GGT CAC ATA G-3&#39; (forward) and Fstv_S2R 5&#39;-TTG CAC CTC CGC AGT TAA A-3&#39; (reverse) with the Fstv_S2P FAM-TATGCTCCAATGGCCTTCAACGACA-TAMRA probe.</li>
	</ol>
	</li>
</ol>
4. Virus Production, Purification and Genome Sequencing
<ol>
	<li>Subculture the single virus amoeba culture for end-point dilution cloning.</li>
	<li>For the production: prepare 20 flasks containing 30 ml of PYG, 10 ml of Vermamoeba vermiformis and 5 ml of the isolated virus already transferred from wells to small flasks.</li>
	<li>Incubate at 30 &#176;C until complete lysis of the amoeba. Observe every day by inverted optical microscopy until all amoeba are lysed.</li>
	<li>After complete lysis, pool all flasks into one recipient. Filter with a 0.45 &#181;m filter to eliminate debris.</li>
	<li>Start the purification by ultracentrifugation at 89,800 x g for 75 min. Make sure to calibrate the weight of the tubes before starting centrifugation.</li>
	<li>After centrifugation, remove the supernatant from each tube by aspiration and re-suspend the pellet in PAS with the same volume used for calibration, before repeating centrifugation.</li>
	<li>As above, remove the supernatant and re-suspend all the pellets in 1 ml of phosphate buffered saline (PBS).</li>
	<li>Purify the virus that is produced, using 25% sucrose (27.5 g of sucrose in 100 ml of PBS, filtered on a 0.22 &#181;m filter).
	<ol>
		<li>Use 8 ml of sucrose and 2 ml of the viral suspension. Centrifuge at 89,800 x g for 1 hr 15 min. Re-suspend the pellet in 1 ml of PBS. Store at -80 &#176;C.</li>
	</ol>
	</li>
</ol>

<ol><li>Raoult, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+1.2-megabase+genome+sequence+of+Mimivirus%5BTitle%5D)+AND+%22Science%22%5BJournal%5D)">The 1.2-megabase genome sequence of Mimivirus.</a> Science. 306 (5700), 1344-1350 (2004).</li>
<li>Claverie, J. -M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Giant+viruses+in+the+oceans%3A+the+4th+Algal+Virus+Workshop%5BTitle%5D)+AND+%22Virol+J%22%5BJournal%5D)">Giant viruses in the oceans: the 4th Algal Virus Workshop.</a> Virol J. 2, 52-52 (2004).</li>
<li>Monier, A. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Marine+mimivirus+relatives+are+probably+large+algal+viruses%5BTitle%5D)+AND+%22Audio%2C+Transactions+of+the+IRE+Professional+Group+on%22%5BJournal%5D)">Marine mimivirus relatives are probably large algal viruses.</a> Audio, Transactions of the IRE Professional Group on. 5, 12-12 (2007).</li>
<li>Monier, A., Claverie, J. M., Ogata, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Taxonomic+distribution+of+large+DNA+viruses+in+the+sea%5BTitle%5D)+AND+%22Genome+Biol%22%5BJournal%5D)">Taxonomic distribution of large DNA viruses in the sea.</a> Genome Biol. , (2008).</li>
<li>Claverie, J. -M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mimivirus+and+Mimiviridae%3A+Giant+viruses+with+an+increasing+number+of+potential+hosts%2C+including+corals+and+sponges%5BTitle%5D)+AND+%22J+Invertebr+Pathol%22%5BJournal%5D)">Mimivirus and Mimiviridae: Giant viruses with an increasing number of potential hosts, including corals and sponges.</a> J Invertebr Pathol. 101 (3), 9-9 (2009).</li>
<li>Colson, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Evidence+of+the+megavirome+in+humans%5BTitle%5D)+AND+%22J+Clin+Virol%22%5BJournal%5D)">Evidence of the megavirome in humans.</a> J Clin Virol. 57 (3), 191-200 (2013).</li>
<li>La Scola, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tentative+characterization+of+new+environmental+giant+viruses+by+MALDI-TOF+mass+spectrometry%5BTitle%5D)+AND+%22Intervirology%22%5BJournal%5D)">Tentative characterization of new environmental giant viruses by MALDI-TOF mass spectrometry.</a> Intervirology. 53 (5), 344-353 (2010).</li>
<li>Boughalmi, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((High-throughput+isolation+of+giant+viruses+of+the+Mimiviridae+and+Marseilleviridae+families+in+the+Tunisian+environment%5BTitle%5D)+AND+%22Environ+Microbiol%22%5BJournal%5D)">High-throughput isolation of giant viruses of the Mimiviridae and Marseilleviridae families in the Tunisian environment.</a> Environ Microbiol. , (2012).</li>
<li>Pagnier, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+decade+of+improvements+in+mimiviridae+and+marseilleviridae+isolation+from+amoeba%5BTitle%5D)+AND+%22Intervirology%22%5BJournal%5D)">A decade of improvements in mimiviridae and marseilleviridae isolation from amoeba.</a> Intervirology. 56 (6), 354-363 (2012).</li>
<li>Philippe, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Pandoraviruses%3A+Amoeba+Viruses+with+Genomes+Up+to+2.5+Mb+Reaching+That+of+Parasitic+Eukaryotes%5BTitle%5D)+AND+%22Science%22%5BJournal%5D)">Pandoraviruses: Amoeba Viruses with Genomes Up to 2.5 Mb Reaching That of Parasitic Eukaryotes.</a> Science. 341 (6143), 281-286 (2013).</li>
<li>Legendre, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Thirty-thousand-year-old+distant+relative+of+giant+icosahedral+DNA+viruses+with+a+pandoravirus+morphology%5BTitle%5D)+AND+%22PNAS%22%5BJournal%5D)">Thirty-thousand-year-old distant relative of giant icosahedral DNA viruses with a pandoravirus morphology.</a> PNAS. , (2014).</li>
<li>Saadi, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((First+Isolation+of+Mimivirus+in+a+Patient+With+Pneumonia%5BTitle%5D)+AND+%22Clin+Infect+Dis%22%5BJournal%5D)">First Isolation of Mimivirus in a Patient With Pneumonia.</a> Clin Infect Dis. , (2013).</li>
<li>Saadi, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Shan+virus%3A+a+new+mimivirus+isolated+from+the+stool+of+a+Tunisian+patient+with+pneumonia%5BTitle%5D)+AND+%22Intervirology%22%5BJournal%5D)">Shan virus: a new mimivirus isolated from the stool of a Tunisian patient with pneumonia.</a> Intervirology. 56 (6), 424-429 (2013).</li>
<li>Claverie, J. -M., Abergel, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mimivirus%3A+the+emerging+paradox+of+quasi-autonomous+viruses%5BTitle%5D)+AND+%22Trends+Genet+%3A+TIG%22%5BJournal%5D)">Mimivirus: the emerging paradox of quasi-autonomous viruses.</a> Trends Genet : TIG. 26 (10), 431-437 (2010).</li>
<li>Colson, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Viruses+with+more+than+1%2C000+genes%3A+Mamavirus%2C+a+new+Acanthamoeba+polyphaga+mimivirus+strain%2C+and+reannotation+of+Mimivirus+genes%5BTitle%5D)+AND+%22Genome+Biol+Evol%22%5BJournal%5D)">Viruses with more than 1,000 genes: Mamavirus, a new Acanthamoeba polyphaga mimivirus strain, and reannotation of Mimivirus genes.</a> Genome Biol Evol. 3 (0), 737-742 (2010).</li>
<li>Claverie, J. -M., Abergel, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Open+questions+about+giant+viruses%5BTitle%5D)+AND+%22Adv+Virus+Res%22%5BJournal%5D)">Open questions about giant viruses.</a> Adv Virus Res. 85, 25-56 (2013).</li>
<li>Fischer, M. G. M., Allen, M. J. M., Wilson, W. H. W., Suttle, C. A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Giant+virus+with+a+remarkable+complement+of+genes+infects+marine+zooplankton%5BTitle%5D)+AND+%22PNAS%22%5BJournal%5D)">Giant virus with a remarkable complement of genes infects marine zooplankton.</a> PNAS. 107 (45), 19508-19513 (2010).</li>
<li>Van Etten, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Another+really%2C+really+big+virus%5BTitle%5D)+AND+%22Viruses%22%5BJournal%5D)">Another really, really big virus.</a> Viruses. 3 (1), 32-46 (2011).</li>
<li>Reteno, D. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Faustovirus%2C+an+asfarvirus-related+new+lineage+of+giant+viruses+infecting+amoebae%5BTitle%5D)+AND+%22J.Virol%22%5BJournal%5D)">Faustovirus, an asfarvirus-related new lineage of giant viruses infecting amoebae.</a> J.Virol. , (2015).</li>
<li>Coşkun, K. A., Ozçelik, S., Tutar, L., Elaldı, N., Tutar, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Isolation+and+identification+of+free-living+amoebae+from+tap+water+in+Sivas%2C+Turkey%5BTitle%5D)+AND+%22Biomed+res+Int%22%5BJournal%5D)">Isolation and identification of free-living amoebae from tap water in Sivas, Turkey.</a> Biomed res Int. 2013, 675145(2013).</li>
<li>Bradbury, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Free-living+amoebae+recovered+from+human+stool+samples+in+Strongyloides+agar+culture%5BTitle%5D)+AND+%22J+Clin+microbiol%22%5BJournal%5D)">Free-living amoebae recovered from human stool samples in Strongyloides agar culture.</a> J Clin microbiol. 52 (2), 699-700 (2014).</li>
<li>Pagnier, I., Valles, C., Raoult, D., La Scola, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Isolation+of+Vermamoeba+vermiformis+and+associated+bacteria+in+hospital+water%5BTitle%5D)+AND+%22Microb+Pathog%22%5BJournal%5D)">Isolation of Vermamoeba vermiformis and associated bacteria in hospital water.</a> Microb Pathog. 80, 14-20 (2015).</li>
<li>Ogata, H., Toyoda, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Remarkable+sequence+similarity+between+the+dinoflagellate-infecting+marine+girus+and+the+terrestrial+pathogen+African+swine+fever+virus%5BTitle%5D)+AND+%22Virol+J%22%5BJournal%5D)">Remarkable sequence similarity between the dinoflagellate-infecting marine girus and the terrestrial pathogen African swine fever virus.</a> Virol J. 6, 178-178 (2008).</li>
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</ol>

The authors declare that they have no competing financial interests.

The possibility that Faustovirus could be the first member of a new Megavirales family close to ASFV was first suggested by Reteno et al.,19 but some differences can still be distinguished. It appears unclear whether Faustovirus should join the Asfarviridae family or whether it should instead form a new putative viral family. This issue will require further investigation, in particular a more comprehensive characterization of its morphology, host range, replication cycle and gene repertoire. More Faus...

The discovery of giant viruses, especially those belonging to the Megavirales order, completely changed the world of viruses in terms of particle size and genome complexity. Viruses were previously thought to be small entities, and the Mimivirus appeared to break all the rules.1 Metagenomic data suggests the ubiquity of giant viruses not only in the environment, 2-5 but also in humans.6 Therefore, there is still a need to search for these viruses on a large scale. The diversity of these giant viruses was assessed by sampling not only a variety of aquatic environments and their associated sediments worldwide,7-11 but also by screening a variety of human samples12,13 and environmental samples.7,9 The Acanthamoeba polyphaga mimivirus was isolated by co-culture using phagocytic protists, primarily Acanthamoeba spp.14-16 An entire collection of giant viruses were then also isolated from this specified protist host, which made the scientific community restrict its research and isolation procedure for Acanthamoeba spp. Clearly this reliance on a single host species has resulted in a large fraction of viruses being overlooked. The fact that the giant virus, CroV, was isolated with the highly motile marine protozoa Cafeteria roenbergensis,17,18 demonstrates the need to use a wider range of protozoa in order to discover new lineages or families of giant viruses. Reteno et al. managed to select other protozoa as cell hosts which had never previously been used, and isolated the new Asfar-related lineage of giant viruses (the newly named Faustovirus).19
In an attempt to isolate new Faustovirus genotypes in order to expand the members of this viral lineage, we modified our isolation procedures and used them to screen environmental samples capable of harvesting new Faustoviruses. We then described the entire protocol to characterize the new isolates. We assessed Vermamoeba vermiformis, the most common free-living protist found in human environments,20-22 which is already used in the isolation of the first Faustovirus prototype E12.19 This protist is currently still host-specific for Faustovirus. We knew that none of the known giant viruses was pathogenic for this amoeba, because no attempts to grow other giant viruses in our lab showed amoeba lysis or viral growth. For this reason, we believe that V. vermiformis is the best and most unique cell support known to isolate new Faustoviruses.

<table><tbody><tr><td>LSR FORTESSA cytometer&amp;nbsp;</td><td>BD Biosciences</td><td>France&amp;nbsp;</td><td>649225B4</td></tr><tr><td>TECNAI G2 F20</td><td>FEI</td><td>Germany&amp;nbsp;</td><td>5027/11</td></tr><tr><td>Optical inverted microscope</td><td>leica&amp;nbsp;</td><td>France</td><td>72643</td></tr><tr><td>DNA extraction</td><td>Qiagen EZ1 Advanced XL Extraction Robot</td><td>France&amp;nbsp;</td><td>L106A0452</td></tr><tr><td>PCR Cycler CFX96</td><td>Bio rad</td><td>France</td><td>785BR06298</td></tr><tr><td>PYG medium, PAS, Starvation medium</td><td>In house laboratory production&amp;nbsp;</td><td>Marseille URMITE</td><td>x</td></tr><tr><td>Amoeba strain CDC-19</td><td>ATCC</td><td>France</td><td>50237</td></tr><tr><td>Plates</td><td>Cellstar</td><td>France</td><td>655180</td></tr><tr><td>PCR materials, primers.&amp;nbsp;</td><td>eurogentec</td><td>France</td><td>Primers cited in manuscript</td></tr><tr><td>glasstic slide 10 with grids</td><td>Kova&amp;nbsp;</td><td>USA</td><td>H899871441F</td></tr><tr><td>Eosin/blue Azur-Hemacolor stain</td><td>Merck milipore&amp;nbsp;</td><td>France</td><td>111955,6,57,109468</td></tr><tr><td>Vacuum driven filters</td><td>Thermo scientific</td><td>France</td><td>BPV4550 / 20170115</td></tr><tr><td>Phosphate-Buffered Saline</td><td>Thermo Fisher scientific&amp;nbsp;</td><td>France&amp;nbsp;</td><td>10010-023</td></tr><tr><td>DAPI stain</td><td>Life Technologies&amp;nbsp;</td><td>France&amp;nbsp;</td><td>D1306</td></tr><tr><td>cytospin 4 cytocentrifuge</td><td>Thermo Fisher scientific</td><td>France</td><td>10522013JT184-31</td></tr><tr><td>Single cytology tunnel</td><td>Biomedical polymers inc.</td><td>France</td><td>BMP-cyto-S50</td></tr><tr><td>Carbon grids&amp;nbsp;</td><td>Euromedex</td><td>France&amp;nbsp;</td><td>FCF400NI</td></tr><tr><td>Ammonium molibdate</td><td>VWR internationanl&amp;nbsp;</td><td>France&amp;nbsp;</td><td>21276185</td></tr><tr><td>Flasks&amp;nbsp;</td><td>SARSTEDT</td><td>Germany</td><td>833911</td></tr><tr><td>0.22 &amp;mu;m filters&amp;nbsp;</td><td>Milex millipor&amp;nbsp;</td><td>France</td><td>SE2M229104</td></tr><tr><td>Ultracentrifuge Sorval WX 80</td><td>Thermo scientific</td><td>France</td><td>9102448</td></tr><tr><td>Rapid-flow filters</td><td>Nalgene</td><td>France</td><td>450-0020</td></tr></tbody></table>

a rapid strategy for the isolation of new faustoviruses from environmental samples using vermamoeba vermiformis

The isolation of giant viruses is of great interest in this new era of virology, especially since these giant viruses are related to protists. Giant viruses may be potentially pathogenic for many species of protists. They belong to the recently described order of Megavirales. The new lineage Faustovirus that has been isolated from sewage samples is distantly related to the mammalian pathogen African swine fever virus. This virus is also specific to its amoebal host, Vermamoeba vermiformis, a protist common in health care water systems. It is crucial to continue isolating new Faustovirus genotypes in order to enlarge its genotype collection and study its pan-genome. We developed new strategies for the isolation of additional strains by improving the use of antibiotic and antifungal combinations in order to avoid bacterial and fungal contaminations of the amoeba co-culture and favoring the virus multiplication. We also implemented a new starvation medium to maintain V. vermiformis in optimal conditions for viruses co-culture. Finally, we used flow cytometry rather than microscopic observation, which is time-consuming, to detect the cytopathogenic effect. We obtained two isolates from sewage samples, proving the efficiency of this method and thus widening the collection of Faustoviruses, to better understand their environment, host specificity and genetic content.

The system studied in this manuscript validated its proof of concept by isolating two new Faustoviruses. Of the 70 samples tested, two episodes of lysis were detected, in contrast to our reliable negative controls. The negative control for lysis contained an 86% amoeba population. By contrast, the positive samples (ST1 for Saint Pierre de Meyzoargues), and (LC9 for the La Ciotat Sample 9) showed a dramatic decline in gated amoebae; more than 60% of amoebae were lysed with the highest perc...

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A Rapid Strategy for the Isolation of New Faustoviruses from Environmental Samples Using Vermamoeba vermiformis

We describe here the latest advances in viral isolation for the characterization of new genotypes of Faustovirus, a new asfarvirus-related lineage of giant viruses. This protocol can be applied to the high throughput isolation of viruses, especially giant viruses infecting amoeba.

A Rapid Strategy for the Isolation of New Faustoviruses from Environmental Samples Using Vermamoeba vermiformis

The isolation of giant viruses is of great interest in this new era of virology, especially since these giant viruses are related to protists. Giant ...

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Research

JoVE Journal

Immunology and Infection

7.6K Views.  Aix Marseille University. We describe here the latest advances in viral isolation for the characterization of new genotypes of Faustovirus, a new asfarvirus-related lineage of giant viruses. This protocol can be applied to the high throughput isolation of viruses, especially giant viruses infecting amoeba. 

Video: A Rapid Strategy for the Isolation of New Faustoviruses from Environmental Samples Using Vermamoeba vermiformis

EPA Method 1615. Measurement of Enterovirus and Norovirus Occurrence in Water by Culture and RT-qPCR. I. Collection of Virus Samples

EPA Method 1615 was developed with a goal of providing a standard method for measuring enteroviruses and noroviruses in environmental and drinking waters. The standardized sampling component of the method concentrates viruses that may be present in water by passage of a minimum specified volume of water through an electropositive cartridge filter. The minimum specified volumes for surface and finished/ground water are 300 L and 1,500 L, respectively. A major method limitation is the tendency for the filters to clog before meeting the sample volume requirement. Studies using two different, but equivalent, cartridge filter options showed that filter clogging was a problem with 10% of the samples with one of the filter types compared to 6% with the other filter type. Clogging tends to increase with turbidity, but cannot be predicted based on turbidity measurements only. From a cost standpoint one of the filter options is preferable over the other, but the water quality and experience with the water system to be sampled should be taken into consideration in making filter selections.

EPA Method 1615 uses an electropositive filter to concentrate enteroviruses and noroviruses in environmental and drinking waters. This manuscript describes the procedure for collecting samples for Method 1615 analyses.

EPA Method 1615 was developed with a goal of providing a standard method for measuring enteroviruses and noroviruses in environmental and drinking waters. ...

Environment

Estimating Virus Production Rates in Aquatic Systems

Viruses are pervasive components of marine and freshwater systems, and are known to be significant agents of microbial mortality. Developing quantitative estimates of this process is critical as we can then develop better models of microbial community structure and function as well as advance our understanding of how viruses work to alter aquatic biogeochemical cycles. The virus reduction technique allows researchers to estimate the rate at which virus particles are released from the endemic microbial community. In brief, the abundance of free (extracellular) viruses is reduced in a sample while the microbial community is maintained at near ambient concentration. The microbial community is then incubated in the absence of free viruses and the rate at which viruses reoccur in the sample (through the lysis of already infected members of the community) can be quantified by epifluorescence microscopy or, in the case of specific viruses, quantitative PCR. These rates can then be used to estimate the rate of microbial mortality due to virus-mediated cell lysis.

The turnover rate of viruses in marine and freshwater systems can be estimated by a reduction and reoccurrence technique. The data allow researchers to infer rates of virus-mediated microbial mortality in aquatic systems.

Viruses are pervasive components of marine and freshwater systems, and are known to be significant agents of microbial mortality. Developing quantitative ...

Cost-effective Method for Microbial Source Tracking Using Specific Human and Animal Viruses

Microbial contamination of the environment represents a significant health risk. Classical bacterial fecal indicators have shown to have significant limitations, viruses are more resistant to many inactivation processes and standard fecal indicators do not inform on the source of contamination. The development of cost-effective methods for the concentration of viruses from water and molecular assays facilitates the applicability of viruses as indicators of fecal contamination and as microbial source tracking (MST) tools. Adenoviruses and polyomaviruses are DNA viruses infecting specific vertebrate species including humans and are persistently excreted in feces and/or urine in all geographical areas studied. In previous studies, we suggested the quantification of human adenoviruses (HAdV) and JC polyomaviruses (JCPyV) by quantitative PCR (qPCR) as an index of human fecal contamination. Recently, we have developed qPCR assays for the specific quantification of porcine adenoviruses (PAdV) and bovine polyomaviruses (BPyV) as animal fecal markers of contamination with sensitivities of 1-10 genome copies per test tube. In this study, we present the procedure to be followed to identify the source of contamination in water samples using these tools. As example of representative results, analysis of viruses in ground water presenting high levels of nitrates is shown.
Detection of viruses in low or moderately polluted waters requires the concentration of the viruses from at least several liters of water into a much smaller volume, a procedure that usually includes two concentration steps in series. This somewhat cumbersome procedure and the variability observed in viral recoveries significantly hamper the simultaneous processing of a large number of water samples.
In order to eliminate the bottleneck caused by the two-step procedures we have applied a one-step protocol developed in previous studies and applicable to a diversity of water matrices. The procedure includes: acidification of ten-liter water samples, flocculation by skimmed milk, gravity sedimentation of the flocculated materials, collection of the precipitate and centrifugation, resuspension of the precipitate in 10 ml phosphate buffer. The viral concentrate is used for the extraction of viral nucleic acids and the specific adenoviruses and polyomaviruses of interest are quantified by qPCR. High number of samples may be simultaneously analyzed using this low-cost concentration method.
The procedure has been applied to the analysis of bathing waters, seawater and river water and in this study, we present results analyzing groundwater samples. This high-throughput quantitative method is reliable, straightforward, and cost-effective.

The study describes a cost-effective method for the identification of the source of fecal/urine contamination or contamination by nitrates in water using qPCR for the specific quantification of human/porcine/bovine DNA viruses, adenoviruses and polyomaviruses, proposed as MST tools.

Microbial contamination of the environment represents a significant health risk. Classical bacterial fecal indicators have shown to have significant ...

Isolation and Genome Analysis of Single Virions using 'Single Virus Genomics'

Whole genome amplification and sequencing of single microbial cells enables genomic characterization without the need of cultivation 1-3. Viruses, which are ubiquitous and the most numerous entities on our planet 4 and important in all environments 5, have yet to be revealed via similar approaches. Here we describe an approach for isolating and characterizing the genomes of single virions called 'Single Virus Genomics' (SVG). SVG utilizes flow cytometry to isolate individual viruses and whole genome amplification to obtain high molecular weight genomic DNA (gDNA) that can be used in subsequent sequencing reactions.

Single Virus Genomics (SVG) is a method to isolate and amplify the genomes of single virons. Viral suspensions of a mixed assemblage are sorted using flow cytometry onto a microscope slide with discrete wells containing agarose, thereby capturing the virion and reducing genome shearing during downstream processing. Whole genome amplification is achieved using multiple displacement amplification (MDA) resulting in genomic material that is suitable for sequencing.

Whole genome amplification and sequencing of single microbial cells enables genomic characterization without the need of cultivation 1-3. Viruses, which ...

Mass Isolation and In Vitro Cultivation of Intramolluscan Stages of the Human Blood Fluke Schistosoma Mansoni

Human blood flukes, Schistosoma spp., have a complex life cycle that involves asexual and sexual developmental phases within a snail intermediate and mammalian final host, respectively. The ability to isolate and sustain the different life cycle stages under in vitro culture conditions has greatly facilitated investigations of the cellular, biochemical and molecular mechanisms regulating parasite growth, development and host interactions. Transmission of schistosomiasis requires asexual reproduction and development of multiple larval stages within the snail host; from the infective miracidium, through primary and secondary sporocysts, to the final cercarial stage that is infective to humans. In this paper we present a step-by-step protocol for mass hatching and isolation of Schistosoma mansoni miracidia from eggs obtained from livers of infected mice, and their subsequent introduction into in vitro culture. It is anticipated that the detailed protocol will encourage new researchers to engage in and broaden this important field of schistosome research.

Mass Isolation and In Vitro Cultivation of Intramolluscan Stages of the Human Blood Fluke Schistosoma Mansoni

This article describes a protocol for the large-scale axenic isolation and collection of free-swimming miracidia of the human blood fluke Schistosoma mansoni and their subsequent processing for introduction into in vitro culture.

Human blood flukes, Schistosoma spp., have a complex life cycle that involves asexual and sexual developmental phases within a snail intermediate and ...

Developmental Biology

Discovery of New Intracellular Pathogens by Amoebal Coculture and Amoebal Enrichment Approaches

Intracellular pathogens such as legionella, mycobacteria and Chlamydia-like organisms are difficult to isolate because they often grow poorly or not at all on selective media that are usually used to cultivate bacteria. For this reason, many of these pathogens were discovered only recently or following important outbreaks. These pathogens are often associated with amoebae, which serve as host-cell and allow the survival and growth of the bacteria. We intend here to provide a demonstration of two techniques that allow isolation and characterization of intracellular pathogens present in clinical or environmental samples: the amoebal coculture and the amoebal enrichment. Amoebal coculture allows recovery of intracellular bacteria by inoculating the investigated sample onto an amoebal lawn that can be infected and lysed by the intracellular bacteria present in the sample. Amoebal enrichment allows recovery of amoebae present in a clinical or environmental sample. This can lead to discovery of new amoebal species but also of new intracellular bacteria growing specifically in these amoebae. Together, these two techniques help to discover new intracellular bacteria able to grow in amoebae. Because of their ability to infect amoebae and resist phagocytosis, these intracellular bacteria might also escape phagocytosis by macrophages and thus, be pathogenic for higher eukaryotes.

Amoebal coculture is a cell culture system using adherent amoebae to selectively grow intracellular pathogens able to resist phagocytic cells such as amoebae and macrophages. It thus represents a key tool to discover new infectious agents. Amoebal enrichment allows discovery of new amoebal species and of their specific intracellular bacteria.

Intracellular pathogens such as legionella, mycobacteria and Chlamydia-like organisms are difficult to isolate because they often grow poorly or not at ...

Rapid Isolation of Wild Nematodes by Baermann Funnel

Beyond being robust experimental model organisms, Caenorhabditis elegans and its relatives are also real animals that live in nature. Studies of wild nematodes in their natural environments are valuable for understanding many aspects of biology, including the selective regimes in which distinctive genomic and phenotypic characters evolve, the genetic basis for complex trait variation, and the natural genetic diversity fundamental to all animal populations. This manuscript describes a simple and efficient method for extracting nematodes from their natural substrates, including rotting fruits, flowers, fungi, leaf litter, and soil. The Baermann funnel method, a classical nematology technique, selectively isolates active nematodes from their substrates. Because it recovers nearly all active worms from the sample, the Baermann funnel technique allows for the recovery of rare and slow-growing genotypes that co-occur with abundant and fast-growing genotypes, which might be missed in extraction methods that involve multiple generations of reproduction. The technique is also well suited to addressing metagenetic, population-genetic, and ecological questions. It captures the entire population in a sample simultaneously, allowing an unbiased view of the natural distribution of ages, sexes, and genotypes. The protocol allows for deployment at scale in the field, rapidly converting substrates into worm plates, and the authors have validated it through fieldwork on multiple continents.

This protocol outlines a method for efficiently extracting live nematodes from natural substrates in the field.

Beyond being robust experimental model organisms, Caenorhabditis elegans and its relatives are also real animals that live in nature. Studies of wild ...

Genetics

Concentration of Virus Particles from Environmental Water and Wastewater Samples Using Skimmed Milk Flocculation and Ultrafiltration

Water and wastewater-based epidemiology have emerged as alternative methods to monitor and predict the course of outbreaks in communities.&#160;The recovery of microbial fractions, including viruses, bacteria, and microeukaryotes from wastewater and environmental water samples&#160;is one of the challenging steps in these approaches. In this study, we focused on the recovery efficiency of sequential ultrafiltration and skimmed milk flocculation (SMF) methods using Armored RNA as a test virus, which is also used as a control by some other studies. Prefiltration with 0.45 &#181;m and 0.2 &#181;m membrane disc filters were applied to eliminate solid particles before ultrafiltration to prevent the clogging of ultrafiltration devices. Test samples, processed with the sequential ultrafiltration method, were centrifuged at two different speeds. An increased speed resulted in lower recovery and positivity rates of Armored RNA.&#160;On the other hand, SMF resulted in relatively consistent recovery and positivity rates of Armored RNA. Additional tests conducted with environmental water samples demonstrated the utility of SMF to concentrate other microbial fractions. The partitioning of viruses into solid particles might have an impact on the overall recovery rates, considering the prefiltration step applied before the ultrafiltration of wastewater samples. SMF with prefiltration performed better when applied to environmental water samples&#160;due to lower solid concentrations in the samples and thus lower partitioning rates to solids. In the present study, the idea of using a sequential ultrafiltration method arose from the necessity to decrease the final volume of the viral concentrates during the COVID-19 pandemic, when the supply of the commonly used ultrafiltration devices was limited, and there was a need for the development of alternative viral concentration methods.

Virus concentration from environmental water and wastewater samples is a challenging task, carried out primarily for the identification and quantification of viruses. While several virus concentration methods have been developed and tested, we demonstrate here the effectiveness of ultrafiltration and skimmed milk flocculation for RNA viruses with different sample types.

Water and wastewater-based epidemiology have emerged as alternative methods to monitor and predict the course of outbreaks in communities.&#160;The ...

VirWaTest, A Point-of-Use Method for the Detection of Viruses in Water Samples

Viruses excreted by humans and animals may contaminate water sources and pose a risk to human health when this water is used for drinking, food irrigation, washing, etc. The classical fecal bacteria indicator does not always check for the presence of viral pathogens so the detection of viral pathogens and viral indicators is relevant in order to adopt measures of risk mitigation, especially in humanitarian scenarios and in areas where water-borne viral outbreaks are frequent.
At present, several commercial tests allowing the quantification of fecal indicator bacteria (FIB) are available for testing at the point of use. However, such commercial tests are not available for the detection of viruses. The detection of viruses in environmental water samples requires concentrating several liters into smaller volumes. Moreover, once concentrated, the detection of viruses relies on methods such as nucleic acid extraction and molecular detection (e.g., polymerase chain reaction [PCR]-based assays) of the viral genomes.
The method described here allows the concentration of viruses from 10 L water samples, as well as the extraction of viral nucleic acids at the point of use, with simple and portable equipment. This allows the testing of water samples at the point of use for several viruses and is useful in humanitarian scenarios, as well as at any context where an equipped laboratory is not available. Alternatively, the method allows concentrating viruses present in water samples and the shipping of the concentrate to a laboratory at room temperature for further analysis.

Here we present VirWaTest, which is a simple, affordable and portable method for the concentration and detection of viruses from water samples at the point of use.

Viruses excreted by humans and animals may contaminate water sources and pose a risk to human health when this water is used for drinking, food ...

Single Cell Micro-aspiration as an Alternative Strategy to Fluorescence-activated Cell Sorting for Giant Virus Mixture Separation

During the amoeba co-culture process, more than one virus may be isolated in a single well. We previously solved this issue by end point dilution and/or fluorescence activated cell sorting (FACS) applied to the viral population. However, when the viruses in the mixture have similar morphologic properties and one of the viruses multiplies slowly, the presence of two viruses is discovered at the stage of genome assembly and the viruses cannot be separated for further characterization. To solve this problem, we developed a single cell micro-aspiration procedure that allows for separation and cloning of highly similar viruses. In the present work, we present how this alternative strategy allowed us to separate the small viral subpopulations of Clandestinovirus ST1 and Usurpativirus LCD7, giant viruses that grow slowly and do not lead to amoebal lysis compared to the lytic and fast-growing Faustovirus. Purity control was assessed by specific gene amplification and viruses were produced for further characterization.

Here, we describe a single cell micro-aspiration method for the separation of infected amoebae. In order to separate viral subpopulations in Vermamoeba vermiformis infected by Faustoviruses and unknown giant viruses, we developed the protocol detailed below and demonstrated its ability to separate two low-abundance novel giant viruses.

During the amoeba co-culture process, more than one virus may be isolated in a single well. We previously solved this issue by end point dilution and/or ...

A Rapid Strategy for the Isolation of New Faustoviruses from Environmental Samples Using Vermamoeba vermiformis

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