title: Proteomic analysis of an unculturable bacterial endosymbiont (Blochmannia) reveals high abundance of chaperonins and biosynthetic enzymes.
abstract: Many insect groups have coevolved with bacterial endosymbionts that live within specialized host cells. As a salient example, ants in the tribe Camponotini rely on Blochmannia, an intracellular bacterial mutualist that synthesizes amino acids and recycles nitrogen for the host. We performed a shotgun, label-free, LC/MS/MS quantitative proteomic analysis to investigate the proteome of Blochmannia associated with Camponotus chromaiodes. We identified more than 330 Blochmannia proteins, or 54% coverage of the predicted proteome, as well as 244 Camponotus proteins. Using the average intensity of the top 3 "best flier" peptides along with spiking of a surrogate standard at a known concentration, we estimated the concentration (fmol/μg) of those proteins with confident identification. The estimated dynamic range of Blochmannia protein abundance spanned 3 orders of magnitude and covered diverse functional categories, with particularly high representation of metabolism, information transfer, and chaperones. GroEL, the most abundant protein, totaled 6% of Blochmannia protein abundance. Biosynthesis of essential amino acids, fatty acids, and nucleotides, and sulfate assimilation had disproportionately high coverage in the proteome, further supporting a nutritional role of the symbiosis. This first quantitative proteomic analysis of an ant endosymbiont illustrates a promising approach to study the functional basis of intimate symbioses.
authors.affiliation: Institute for Genome Sciences and Policy, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Yongliang
authors.initials: Y
authors.lastname: Fan
authors.forename: J Will
authors.initials: JW
authors.lastname: Thompson
authors.forename: Laura G
authors.initials: LG
authors.lastname: Dubois
authors.forename: M Arthur
authors.initials: MA
authors.lastname: Moseley
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Wernegreen
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001000:Ants / Q000378:metabolism / Q000382:microbiology; D001426:Bacterial Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002853:Chromatography, Liquid; D004755:Enterobacteriaceae / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D056384:Group I Chaperonins / Q000302:isolation & purification* / Q000378:metabolism; D019476:Insect Proteins / Q000302:isolation & purification* / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D040901:Proteomics; D013431:Sulfates / Q000378:metabolism; D013559:Symbiosis / Q000502:physiology; D053719:Tandem Mass Spectrometry
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D005227:Fatty Acids; D019476:Insect Proteins; D009711:Nucleotides; D013431:Sulfates; D056384:Group I Chaperonins