The Waddlia Genome: A Window into Chlamydial Biology

Abstract

Growing evidence suggests that a novel member of the Chlamydiales order, Waddlia chondrophila, is a potential agent of miscarriage in humans and abortion in ruminants. Due to the lack of genetic tools to manipulate chlamydia, genomic analysis is proving to be the most incisive tool in stimulating investigations into the biology of these obligate intracellular bacteria. 454/Roche and Solexa/Illumina technologies were thus used to sequence and assemble de novo the full genome of the first representative of the Waddliaceae family, W. chondrophila. The bacteria possesses a 2′116′312bp chromosome and a 15′593 bp low-copy number plasmid that might integrate into the bacterial chromosome. The Waddlia genome displays numerous repeated sequences indicating different genome dynamics from classical chlamydia which almost completely lack repetitive elements. Moreover, W. chondrophila exhibits many virulence factors also present in classical chlamydia, including a functional type III secretion system, but also a large complement of specific factors for resistance to host or environmental stresses. Large families of outer membrane proteins were identified indicating that these highly immunogenic proteins are not Chlamydiaceae specific and might have been present in their last common ancestor. Enhanced metabolic capability for the synthesis of nucleotides, amino acids, lipids and other co-factors suggests that the common ancestor of the modern Chlamydiales may have been less dependent on their eukaryotic host. The fine-detailed analysis of biosynthetic pathways brings us closer to possibly developing a synthetic medium to grow W. chondrophila, a critical step in the development of genetic tools. As a whole, the availability of the W. chondrophila genome opens new possibilities in Chlamydiales research, providing new insights into the evolution of members of the order Chlamydiales and the biology of the Waddliaceae.

Simkania negevensis, an insight into the biology and clinical importance of a novel member of the Chlamydiales order

“…Indeed, Simkaniaceae share an 86-87% homology in the 16S rRNA encoding gene sequence with Rhabdochlamydiaceae (Kostanjsek et al, 2004) and only 82% homology with Chlamydiaceae (Kahane et al, 1995). Comparative analysis of the full genome sequences showed more than 400 conserved core genes preserved in all Chlamydiales members (Bertelli et al, 2010;Collingro et al, 2011;Pillonel et al, 2015). Among them, 20 are highly informative taxonomically and should be preferentially used to assign new strains at species level (Pillonel et al, 2015).…”

“…Thus, it is suspected that these chlamydial operons encode a conjugative DNA transfer system. Corsaro, 2009 14 Santelli, 2008 15 Bertelli, 2010 Figure 1. Evolutionary relationships of Simkaniaceae.…”

“…¶ (Horn et al, 2004). § (Bertelli et al, 2010;Carlson et al, 2008;Collingro et al, 2011;Horn et al, 2004;Stephens et al, 1998). jjStrain 2032/99 does not have a plasmid.…”

“…§ § (Collingro et al, 2011;Rusconi & Greub, 2013). jjjj (Bertelli et al, 2010;Carlson et al, 2006;Collingro et al, 2011;Horn et al, 2004;Knab et al, 2011;Omsland et al, 2014).…”

“…S. negevensis encodes a type III secretion system (T3SS) (Collingro et al, 2011). Hsia et al first suggested the existence of a type III secretion system in Chlamydia (Hsia et al, 1997), which was likely present in the Chlamydiales common ancestor given its presence in every genome sequenced so far (Bertelli et al, , 2010Greub et al, 2009;Horn et al, 2004;Hovis et al, 2013;Stephens et al, 1998), as summarized in Table 1. The T3SS appears as a needle inserted in the inner and outer membranes of the bacterium, which protrudes into the cytoplasm of the cell through the inclusion membrane (Pilhofer et al, 2013).…”