title: Mimivirus Fibrils Are Important for Viral Attachment to the Microbial World by a Diverse Glycoside Interaction Repertoire.
abstract: Acanthamoeba polyphaga mimivirus (APMV) is a giant virus from the Mimiviridae family. It has many unusual features, such as a pseudoicosahedral capsid that presents a starfish shape in one of its vertices, through which the ∼ 1.2-Mb double-stranded DNA is released. It also has a dense glycoprotein fibril layer covering the capsid that has not yet been functionally characterized. Here, we verified that although these structures are not essential for viral replication, they are truly necessary for viral adhesion to amoebae, its natural host. In the absence of fibrils, APMV had a significantly lower level of attachment to the Acanthamoeba castellanii surface. This adhesion is mediated by glycans, specifically, mannose and N-acetylglucosamine (a monomer of chitin and peptidoglycan), both of which are largely distributed in nature as structural components of several organisms. Indeed, APMV was able to attach to different organisms, such as Gram-positive bacteria, fungi, and arthropods, but not to Gram-negative bacteria. This prompted us to predict that (i) arthropods, mainly insects, might act as mimivirus dispersers and (ii) by attaching to other microorganisms, APMV could be ingested by amoebae, leading to the successful production of viral progeny. To date, this mechanism has never been described in the virosphere.
  
  
  OBJECTIVE
  APMV is a giant virus that is both genetically and structurally complex. Its size is similar to that of small bacteria, and it replicates inside amoebae. The viral capsid is covered by a dense glycoprotein fibril layer, but its function has remained unknown, until now. We found that the fibrils are not essential for mimivirus replication but that they are truly necessary for viral adhesion to the cell surface. This interaction is mediated by glycans, mainly N-acetylglucosamine. We also verified that APMV is able to attach to bacteria, fungi, and arthropods. This indicates that insects might act as mimivirus dispersers and that adhesion to other microorganisms could facilitate viral ingestion by amoebae, a mechanism never before described in the virosphere.
authors.affiliation: Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Rodrigo Araújo Lima
authors.initials: RA
authors.lastname: Rodrigues
authors.affiliation: Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Ludmila Karen
authors.initials: LK
authors.lastname: dos Santos Silva
authors.affiliation: Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Fábio Pio
authors.initials: FP
authors.lastname: Dornas
authors.affiliation: Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Danilo Bretas
authors.initials: DB
authors.lastname: de Oliveira
authors.affiliation: Laboratório de Micologia, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Thais Furtado Ferreira
authors.initials: TF
authors.lastname: Magalhães
authors.affiliation: Laboratório de Micologia, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Daniel Assis
authors.initials: DA
authors.lastname: Santos
authors.affiliation: Faculdade de Farmácia, Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Adriana Oliveira
authors.initials: AO
authors.lastname: Costa
authors.affiliation: Laboratório de Microbiologia Oral e Anaeróbios, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Luiz
authors.initials: L
authors.lastname: de Macêdo Farias
authors.affiliation: Laboratório de Microbiologia Oral e Anaeróbios, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Paula Prazeres
authors.initials: PP
authors.lastname: Magalhães
authors.affiliation: Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Cláudio Antônio
authors.initials: CA
authors.lastname: Bonjardim
authors.affiliation: Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Erna Geessien
authors.initials: EG
authors.lastname: Kroon
authors.affiliation: URMITE CNRS UMR 6236-IRD 3R198, Aix Marseille Université, Marseille, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: La Scola
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Departamento de Virologia-Centro de Ciências da Saúde, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ, Brazil.
authors.forename: Juliana Reis
authors.initials: JR
authors.lastname: Cortines
authors.affiliation: Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas (ICB), Universidade Federal de Minas Gerais, Brasil (UFMG), Belo Horizonte, Minas Gerais, Brazil jonatas.abrahao@gmail.com.
authors.forename: Jônatas Santos
authors.initials: JS
authors.lastname: Abrahão
mesh_terms: D000048:Acanthamoeba / Q000502:physiology / Q000648:ultrastructure / Q000821:virology*; D000117:Acetylglucosamine / Q000378:metabolism; D000704:Analysis of Variance; D006023:Glycoproteins / Q000378:metabolism*; D008358:Mannose / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D056686:Mimiviridae / Q000502:physiology*; D013045:Species Specificity; D014764:Viral Proteins / Q000378:metabolism*; D053585:Virus Attachment; D014779:Virus Replication / Q000502:physiology
chemical_list: D006023:Glycoproteins; D014764:Viral Proteins; D008358:Mannose; D000117:Acetylglucosamine