Conserved features and major differences in the outer membrane protein composition of chlamydiae

Abstract

SummaryChlamydiae are a highly successful group of obligate intracellular bacteria infecting a variety of eukaryotic hosts. Outer membrane proteins involved in attachment to and uptake into host cells, and cross-linking of these proteins via disulfide bonds are key features of the biphasic chlamydial developmental cycle. In this study, we used a consensus approach to predict outer membrane proteins in the genomes of members of three chlamydial families. By analysing outer membrane protein fractions of purified chlamydiae with highly sensitive mass spectrometry, we show that the protein composition differs strongly between these organisms. Large numbers of major outer membrane protein-like proteins are present at high abundance in the outer membrane of Simkania negevensis and Waddlia chondrophila, whereas yet uncharacterized putative porins dominate in Parachlamydia acanthamoebae. Simkania represents the first case of a chlamydia completely lacking stabilizing cysteinerich proteins in its outer membrane. In agreement with this, and in contrast to Parachlamydia and Waddlia, the cellular integrity of Simkania is not impaired by conditions that reduce disulfide bonds of these proteins. The observed differences in the protein composition of the outer membrane among members of divergent chlamydial families suggest different stabilities of these organisms in the environment, probably due to adaption to different niches or transmission routes.

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

“…jjStrain 2032/99 does not have a plasmid. # (Aistleitner, 2015;Birkelund et al, 2009;Frandi et al, 2014;Jacquier et al, 2014;Kebbi-Beghdadi et al, 2015;Liechti et al, 2014;Pilhofer et al, 2014Pilhofer et al, , 2013. **Putative Pom encoded in the genome, but not isolated at the membrane.…”

“…MOMP (ompA) represents 60% of the surface proteins, at least in purified EBs and serves as a porin (Bavoil et al, 1984). Aistleitner et al have recently studied the structure of S. negevensis outer membrane (Aistleitner et al, 2015). Using a computerized proteomic approach, 65 OMPs were identified as major components of the S. negevensis EB's membrane.…”

“…Some authors suggested that they may replace the peptidoglycan layer present in the periplasm of other Gram-negative bacteria (Everett & Hatch, 1995;Sun et al, 2007). No homologs of OmcA and OmcB were identified in S. negevensis genome and none of the identified MOMP-like proteins could serve this function as their content in cysteine was extremely low (Aistleitner et al, 2015). Such differences may result in a more flexible envelope and a lack of surface proteins regulated by the redox state.…”

Permissivity of insect cells to Waddlia chondrophila, Estrella lausannensis and Parachlamydia acanthamoebae

“…E. lausannensis, whose pathogenic potential is currently under investigation, was first isolated from an environmental water sample and is also able to grow at different temperatures in protozoa, fishes and mammalian cells [14,24,30]. Strikingly, these two organisms that display such a broad host range, both encode an extended family of OmpA proteins with beta-barrel structure that were recently shown to be dominant in the outer membrane of W. chondrophila and to play a role in adhesion of this bacteria to its host [1,7,8,26,29]. In addition, Simkania negevensis, another Chlamydia-related bacteria that also possess a large family of 37 MOMP-like proteins in its outer membrane similarly displays a wide host range [1,27].…”

Waddlia: An emerging pathogen and a model organism to study the biology of chlamydiae

“…These differences may be associated with different tissue tropism and divergent pathogenetic mechanisms. Moreover, the protein composition of the outer membrane exhibits important variations among members of the Chlamydiales order suggesting adaptation to different ecological niches [38]. The subset of proteins implicated in adhesion and penetration in the host cell, which is crucial for virulence among members of the Chlamydiales order, was also found to be different in W. chondrophila with a predominance of diverse OmpA proteins and a single Pmp-like protein, contrarily to Chlamydia spp.…”