Early expression of the type III secretion system ofParachlamydia acanthamoebaeduring a replicative cycle within its natural host cellAcanthamoeba castellanii

Abstract

The type three secretion system (T3SS) operons of Chlamydiales bacteria are distributed in different clusters along their chromosomes and are conserved at both the level of sequence and genetic organization. A complete characterization of the temporal expression of multiple T3SS components at the transcriptional and protein levels has been performed in Parachlamydia acanthamoebae, replicating in its natural host cell Acanthamoeba castellanii. The T3SS components were classified in four different temporal clusters depending on their pattern of expression during the early, mid- and late phases of the infectious cycle. The putative T3SS transcription units predicted in Parachlamydia are similar to those described in Chlamydia trachomatis, suggesting that T3SS units of transcriptional expression are highly conserved among Chlamydiales bacteria. The maximal expression and activation of the T3SS of Parachlamydia occurred during the early to mid-phase of the infectious cycle corresponding to a critical phase during which the intracellular bacterium has (1) to evade and/or block the lytic pathway of the amoeba, (2) to differentiate from elementary bodies (EBs) to reticulate bodies (RBs), and (3) to modulate the maturation of its vacuole to create a replicative niche able to sustain efficient bacterial growth.

Importance of amoebae as a tool to isolate amoeba‐resisting microorganisms and for their ecology and evolution: the Chlamydia paradigm

“…It can detect five DNA copies of any member of the Chlamydiales order, exhibits a high specificity for bacteria of this order and does not amplify DNA of any other bacterial clade (Lienard et al ., 2011b). This new PCR may fill the gap generally left when using conventional eubacterial PCR. Because of particular features of their extracellular membrane (Rusconi and Greub, ; Rusconi et al ., ), chlamydial elementary bodies are highly resistant to classical bacterial lysis protocols thus hampering DNA extraction (Croxatto et al ., ). An alternate extraction protocol has thus been set up (Croxatto et al ., ) that includes a 2 h proteinase K digestion step ensuring complete bacterial membrane lysis and consequently efficient DNA extraction. Chlamydiales bacteria are obligate intracellular organisms strictly dependent of an eukaryotic host for multiplication.…”

“…This new PCR may fill the gap generally left when using conventional eubacterial PCR. Because of particular features of their extracellular membrane (Rusconi and Greub, ; Rusconi et al ., ), chlamydial elementary bodies are highly resistant to classical bacterial lysis protocols thus hampering DNA extraction (Croxatto et al ., ). An alternate extraction protocol has thus been set up (Croxatto et al ., ) that includes a 2 h proteinase K digestion step ensuring complete bacterial membrane lysis and consequently efficient DNA extraction. Chlamydiales bacteria are obligate intracellular organisms strictly dependent of an eukaryotic host for multiplication. As discussed above, amoebal co‐culture is a very good tool to recover these fastidious organisms, but one possible limitation of this approach is the restricted host range observed for some microbial species (Birtles et al ., ; Horn et al ., ; Michel et al ., 2004; 2005; Coulon et al ., ; Corsaro et al ., 2013b).…”

“…Because of particular features of their extracellular membrane (Rusconi and Greub, ; Rusconi et al ., ), chlamydial elementary bodies are highly resistant to classical bacterial lysis protocols thus hampering DNA extraction (Croxatto et al ., ). An alternate extraction protocol has thus been set up (Croxatto et al ., ) that includes a 2 h proteinase K digestion step ensuring complete bacterial membrane lysis and consequently efficient DNA extraction.…”

Identification of genes required for Mycobacterium abscessus growth in vivo with a prominent role of the ESX-4 locus

“…Although the specialization in parasitism seems most advanced with Mycobacterium tuberculosis, the etiologic agent of tuberculosis, specific host-oriented adaptation processes also exist for several nontuberculous bacteria (NTM) (1,2). Environmental amoebae represent a natural unicellular eukaryotic host and reservoir for many pathogenic bacteria, such as Legionella, Chlamydia, and Pseudomonas (3)(4)(5)(6) and probably also for selected mycobacterial species that can survive within amoebae (7). For example, Mycobacterium marinum, a close relative of M. tuberculosis, contains different sets of virulence determinants that are tailored for specific hosts (8).…”

Benefits of Genomic Insights and CRISPR-Cas Signatures to Monitor Potential Pathogens across Drinking Water Production and Distribution Systems

“…For Parachlamydia , known VFs included: negative regulator of the T3SS, SctW; protein kinase, Pkn5; translocated actin-recruiting phosphoprotein, tarp ; inclusion membrane proteins IncA to IncG; translocator protein, CopB; modulation of host cell apoptosis, CADD; and Mip (Greub, 2009 ; Betts-Hampikian and Fields, 2010 ; Collingro et al, 2011 ; Croxatto et al, 2013 ). Furthermore, genes coding for nucleotide transporters that import host cell ATP in exchange for ADP ( ntt ) were part of the complex involving in bacteria-host interaction, but were generally not considered as VFs (Schmitz-Esser et al, 2004 ; Haferkamp et al, 2006 ).…”