Divergence and Mosaicism among Virulent Soil Phages of the Burkholderia cepacia Complex

Authors

Elizabeth J. Summer, Texas A&M University, College Station, Texas
Carlos F. Gonzalez, Texas A&M University, College Station, Texas
Morgan Bomer, Texas A&M University, College Station, Texas
Thomas Carlile, Texas A&M University, College Station, Texas
Addie Embry, Texas A&M University, College Station, Texas
Amalie M. Kucherka, Texas A&M University, College Station, Texas
Jonte Lee, Texas A&M University, College Station, Texas
Leslie Mebane, Texas A&M University, College Station, Texas
William C. Morrison, Texas A&M University, College Station, Texas
Louise Mark, National University of Ireland, Cork, Ireland
Maria D. King, Texas A&M University, College Station, Texas
John J. LiPuma, University of Michigan Medical School, Ann Arbor, Michigan
Anne K. Vidaver, University of Nebraska-LincolnFollow
Ry Young, Texas A & M University, College Station, TX

Document Type

Article

Date of this Version

1-1-2006

Comments

Published in JOURNAL OF BACTERIOLOGY, Jan. 2006, p. 255–268 Vol. 188, No. 1. Copyright © 2006, American Society for Microbiology. Used by permission.

Abstract

We have determined the genomic sequences of four virulent myophages, Bcep1, Bcep43, BcepB1A, and Bcep781, whose hosts are soil isolates of the Burkholderia cepacia complex. Despite temporal and spatial separations between initial isolations, three of the phages (Bcep1, Bcep43, and Bcep781, designated the Bcep781 group) exhibit 87% to 99% sequence identity to one another and most coding region differences are due to synonymous nucleotide substitutions, a hallmark of neutral genetic drift. Phage BcepB1A has a very different genome organization but is clearly a mosaic with respect to many of the genes of the Bcep781 group, as is a defective prophage element in Photorhabdus luminescens. Functions were assigned to 27 out of 71 predicted genes of Bcep1 despite extreme sequence divergence. Using a lambda repressor fusion technique, 10 Bcep781-encoded proteins were identified for their ability to support homotypic interactions. While head and tail morphogenesis genes have retained canonical gene order despite extreme sequence divergence, genes involved in DNA metabolism and host lysis are not organized as in other phages. This unusual genome arrangement may contribute to the ability of the Bcep781-like phages to maintain a unified genomic type. However, the Bcep781 group phages can also engage in lateral gene transfer events with otherwise unrelated phages, a process that contributes to the broader-scale genomic mosaicism prevalent among the tailed phages.