PLD expression is uncommon among other bacterial pathogens and these PLDs are exclusively of the HKD superfamily. However, most of the pathogens that do express PLD have obligate or facultative intracellular lifestyles and expression of this enzyme is thought to be involved in disease pathogenesis [31–35]. Specifically in Neisseria gonorrhoeae and Rickettsia spp., PLDs are required for invasion of host cells [32, 35]. This work characterizes the effects of A. haemolyticum Cell Cycle inhibitor PLD on host cells, with an aim to elucidating the role of this toxic enzyme in disease pathogenesis. We report that PLD is required for optimal adhesion to host cells, via remodeling

of lipid rafts. Furthermore, PLD expressed inside host cells is directly toxic, leading to cell death via necrosis. These findings provide the first conclusive evidence that PLD may be required for A. haemolyticum disease pathogenesis. Results Analysis of the pld gene region A draft genome sequence of A. haemolyticum ATCC9345 was determined (B.H. Jost and S.J. Billington, unpublished

data), and this data was used to identify sequences flanking the pld gene (GenBank Accession Number L16583). The pld gene was found in a region resembling a 1.9-kb genomic island of lower %G + C than the rest of the A. haemolyticum genome (53.1%). This region consists of pld (47.2% G + C), and orf489 (50.3% G + C) which lacks a signal sequence and is of unknown Selleckchem GSK621 function (Figure 1). 43-bp downstream Depsipeptide cell line of pld and 17-bp upstream of orf489 is a stem-loop structure with a ΔG = -20.8 kcal/mol, which may act as a transcriptional terminator or attenuator. There does not appear to be any BAY 11-7082 mw direct or indirect repeats flanking this region. The pld region is flanked upstream by three tRNA genes and gluRS, encoding a glutamyl-tRNA synthetase (EC 6.1.1.17), and downstream by dcp, encoding a peptidyl-dipeptidase (EC 3.4.15.5), which is divergently transcribed

compared to pld (Figure 1). The %G + C of the surrounding housekeeping genes (Figure 1) more closely resembles the %G + C of the A. haemolyticum genome. Figure 1 Map of the pld gene region. The open arrows indicate genes and the direction of transcription. Triangles below the sequence indicate the location of stem-loop structures, with the ΔG (kcal/mol) shown inside the triangle. Gene names are given above or below the arrows and the number below the name indicates the %G + C of the gene. A bar indicating 1-kb is shown on the right. Given the variation in %G + C of the pld gene and the presence of adjacent tRNA genes, which often act as sites of foreign gene insertion [36], it is possible that the A. haemolyticum pld gene was acquired by horizontal gene transfer. It would appear that orf489 is also part of the transferred DNA, and while it is not translationally coupled to pld, its transcription may be linked to that of pld despite the presence of a transcriptional terminator/attenuator between the two genes.