Samba virus: a novel mimivirus from a giant rain forest, the Brazilian Amazon

Abstract

BackgroundThe identification of novel giant viruses from the nucleocytoplasmic large DNA viruses group and their virophages has increased in the last decade and has helped to shed light on viral evolution. This study describe the discovery, isolation and characterization of Samba virus (SMBV), a novel giant virus belonging to the Mimivirus genus, which was isolated from the Negro River in the Brazilian Amazon. We also report the isolation of an SMBV-associated virophage named Rio Negro (RNV), which is the first Mimivirus virophage to be isolated in the Americas.Methods/resultsBased on a phylogenetic analysis, SMBV belongs to group A of the putative Megavirales order, possibly a new virus related to Acanthamoeba polyphaga mimivirus (APMV). SMBV is the largest virus isolated in Brazil, with an average particle diameter about 574 nm. The SMBV genome contains 938 ORFs, of which nine are ORFans. The 1,213.6 kb SMBV genome is one of the largest genome of any group A Mimivirus described to date. Electron microscopy showed RNV particle accumulation near SMBV and APMV factories resulting in the production of defective SMBV and APMV particles and decreasing the infectivity of these two viruses by several logs.ConclusionThis discovery expands our knowledge of Mimiviridae evolution and ecology.

Oysters as hot spots for mimivirus isolation

“…Sequences were aligned with previously published sequences from GenBank using ClustalW and MEGA software version 4.1 (Arizona State University, Phoenix, AZ, USA) (http:// www.megasoftware.net). The optimal nucleotide sequence alignment of a fragment of the mimivirus helicase gene revealed a high similarity (98.2-100 %) among our isolates and mimiviruses belonging to group A, including APMV, mamavirus, sambavirus and others [3,5,8]. However, some samples contained polymorphic sites in the helicase gene ( Fig.…”

“…A total of three blind passages were performed, and samples showing a cytopathic effect were collected, titrated using the TCID 50 method and analyzed by transmission electron microscopy (TEM) and qPCR [10]. Also, to characterize those isolates biologically, representative viral samples from each studied area were used to make one-step-growth curves and analyzed by polyacrylamide gel electrophoresis (PAGE) [3].…”

Mimivirus Fibrils Are Important for Viral Attachment to the Microbial World by a Diverse Glycoside Interaction Repertoire

“…For transmission electron microscopy (TEM) analyses, the samples were prepared as described previously (15). Briefly, Acanthamoeba castellanii cells infected with viruses treated with enzymes at a multiplicity of infection (MOI) of 10 for 1 h were fixed with 2.5% glutaraldehyde in 0.1 M phosphate buffer.…”

Provirophages in the Bigelowiella genome bear testimony to past encounters with giant viruses

“…The coinfection of host cells by NCLDVs and virophages has been shown to limit the production of NCLDV particles, accompanied by greater survival of the eukaryotic host (1,5,6,8,16). At the community level, these parasitic relationships result in complex interplays between virophages, NCLDVs, and eukaryotic hosts.…”

“…In analogy to the term bacteriophage it was called a virophage, but this designation has been challenged (3). Three additional virophages infecting members of the Mimiviridae, e.g., Sputnik 2, Rio Negro, and Zamilon, were subsequently reported (4)(5)(6). Virophages that prey on giant viruses that infect heterotrophic nanoflagellates and microalgae have also been discovered, including Organic Lake virophage 1 [OLV1 (7)], Mavirus (8), and a virophage of the Phaeocystis globosa virus (PgVV) (9), yet the classification of the latter as a virophage sensu stricto is uncertain.…”