Christine Citti

French National Institute for Agriculture, Food, and Environment (INRAE) | INRAE · Interactions Hôtes-Agents Pathogènes (IHAP)

Unlabelled: Horizontal gene transfer (HGT) is a main driving force of bacterial evolution and innovation. This phenomenon was long thought to be marginal in mycoplasmas, a large group of self-replicating bacteria characterized by minute genomes as a result of successive gene losses during evolution. Recent comparative genomic analyses challenged t...

The class Mollicutes (trivial name "mycoplasma") is composed of wall-less bacteria with reduced genomes whose evolution was long thought to be only driven by gene losses. Recent evidences of massive horizontal gene transfer (HGT) within and across species provided a new frame to understand the successful adaptation of these minimal bacteria to a br...

Horizontal Gene Transfer was long thought to be marginal in Mycoplasma a large group of wall-less bacteria often portrayed as minimal cells because of their reduced genomes (ca. 0.5 to 2.0 Mb) and their limited metabolic pathways. This view was recently challenged by the discovery of conjugative exchanges of large chromosomal fragments that equally...

Bacteria of the Mycoplasma genus are characterized by the lack of a cell-wall, the use of UGA as tryptophan codon instead of a universal stop, and their simplified metabolic pathways. Most of these features are due to the small-size and limited-content of their genomes (580–1840 Kbp; 482–2050 CDS). Yet, the Mycoplasma genus encompasses over 200 spe...

DNA methylations play an important role in the biology of bacteria. Often associated with restriction modification (RM) systems, they are important drivers of bacterial evolution interfering in horizontal gene transfer events by providing a defence against foreign DNA invasion or by favouring genetic transfer through production of recombinogenic DN...

Mycoplasma bovis est aujourd’hui reconnu comme un agent pathogène responsable de pertes économiques majeures pour la filière bovine à l’échelle mondiale. Les signes cliniques liés à cette infection sont variés. Si les infections respiratoires dominent en Europe, les États-Unis sont principalement confrontés à des cas de mammites. Nos connaissances...

Horizontal gene transfer was long thought to be marginal in Mollicutes, but the capacity of some of these wall-less bacteria to exchange large chromosomal regions has been recently documented. Mycoplasma chromosomal transfer (MCT) is an unconventional mechanism that relies on the presence of a functional integrative conjugative element (ICE) in at...

Background Mycoplasma agalactiae, causing agent of contagious agalactia, infects domestic small ruminants such as sheep and goats but also wild Caprinae. M. agalactiae is highly contagious and transmitted through oral, respiratory, and mammary routes spreading rapidly in an infected herd. Results In an outbreak of contagious agalactia in a mixed h...

Horizontal gene transfer was long thought to be marginal in Mollicutes , but the capacity of some of these wall-less bacteria to exchange large chromosomal regions has been recently documented. Mycoplasma chromosomal transfer (MCT) is an unconventional mechanism that relies on the presence of a functional integrative conjugative element (ICE) in at...

DNA methylation plays an important role in the biology of bacteria. Often associated with restriction-modification (RM) systems, they also provide a defence against foreign DNA. Little is known regarding the methylome of the mycoplasma genus, which encompasses several pathogenic species with small genomes. Here, single molecule real-time (SMRT) and...

Respiratory infections in domestic animals are a major issue for veterinary and livestock industry. Pathogens in the respiratory tract share their habitat with a myriad of commensal microorganisms. Increasing evidence points towards a respiratory pathobiome concept, integrating the dysbiotic bacterial communities, the host and the environment in a...

In Mycoplasma agalactiae, two simultaneous processes of DNA transfer have been described that require direct cell-to-cell contact and are similar to conjugation. One involves the self-transmission of an integrative conjugative element (ICE) while the second concerns the horizontal transfer of large and small fragments of chromosomal DNA. Here, we d...

Mycoplasma bovis is an important bovine pathogen causing pneumonia, mastitis, and arthritis and is responsible for major economic losses worldwide. In the absence of an efficient vaccine, control of M. bovis infections mainly relies on antimicrobial treatments, but resistance is reported in an increasing number of countries. To address the situatio...

Mycoplasmas are host-restricted prokaryotes with a nearly minimal genome. To overcome their metabolic limitations, these wall-less bacteria establish intimate interactions with epithelial cells at mucosal surfaces. The alarming rate of antimicrobial resistance among pathogenic species is of particular concern in the medical and veterinary fields. T...

Molecules contributing to microbial cytoadhesion are important virulence factors. In Mycoplasma bovis, a minimal bacterium but an important cattle pathogen, binding to host cells is emerging as a complex process involving a broad range of surface-exposed structures. Here, a new cytoadhesin of M. bovis was identified by producing a collection of ind...

Microbial access to host nutrients is a key factor of the host-pathogen interplay. With their nearly minimal genome, wall-less bacteria of the class Mollicutes have limited metabolic capacities and largely depend on host nutrients for their survival. Despite these limitations, host-restricted mycoplasmas are widely distributed in nature and many sp...

Integrative and conjugative elements (ICEs) are modular mobile genetic elements that can disseminate through excision, circularization, and transfer. Mycoplasma ICEs have recently been found distributed among some mycoplasma species and there is accumulating evidence that they play a pivotal role in horizontal gene transfers. The occurrence of ICEs...

The capacity of Mycoplasmas to engage in horizontal gene transfers has recently been highlighted. Despite their small genome, some of these wall-less bacteria are able to exchange multiple, large portions of their chromosome via a conjugative mechanism that does not conform to canonical Hfr/oriT models. To understand the exact features underlying m...

Mycoplasma hominis is an opportunistic human pathogen associated with genital and neonatal infections. Until this study, the lack of a reliable transformation method for the genetic manipulation of M. hominis hindered the investigation of the pathogenicity and the peculiar arginine-based metabolism of this bacterium. A genomic analysis of 20 differ...

Mycoplasma bovis is an important pathogen of cattle causing bovine mycoplasmosis. Clinical manifestations are numerous, but pneumonia, mastitis, and arthritis cases are mainly reported. Currently, no efficient vaccine is available and antibiotic treatments are not always satisfactory. The design of new, efficient prophylactic and therapeutic approa...

Mycoplasma wenyonii, a hemoplasma infecting cattle, was never detected in France. In 2014, evocative inclusions were observed in erythrocytes from cattle presenting milk drops, anemia, and edema in Brittany (France). A survey was then initiated to investigate the epidemiological situation and correlate mycoplasma detection with clinical signs. For...

L’ambition de l’Atelier de Réflexion Prospective sur l’élevage a été de repenser la place, les rôles de l’élevage et en quoi il doit se transformer pour contribuer pleinement au développement de systèmes agri-alimentaires plus durables ainsi que d’identifier des thématiques de recherches interdisciplinaires permettant d’explorer des fronts de scien...

The discovery of integrative conjugative elements (ICEs) in wall-less mycoplasmas and the demonstration of their role in massive gene flows within and across species have shed new light on the evolution of these minimal bacteria. Of these, the ICE of the ruminant pathogen Mycoplasma agalactiae (ICEA) represents a prototype and belongs to a new clad...

The discovery of integrative conjugative elements (ICEs) in wall-less mycoplasmas and the demonstration of their role in massive gene flows within and across species has shed new light on the evolution of these minimal bacteria. Of these, ICEA of the ruminant pathogen Mycoplasma agalactiae represents a prototype and belongs to a new clade of the Mu...

Despite very small genomes, mycoplasmas retain large multigene families encoding variable antigens whose exact role in pathogenesis needs to be proven. To understand their in vivo significance, we used Mycoplasma agalactiae as a model exhibiting high-frequency variations of a family of immunodominant Vpma lipoproteins via Xer1-mediated site-specifi...

VpmaW and VpmaX are highly immunogenic and evoke a strong antibody reaction during natural sheep infections. (A) Expression of MBP (Maltose Binding Protein)-Vpma fusion proteins [13] as observed on Coomassie blue-stained reducing SDS-polyacrylamide gel. Z1 and Z2 correspond to two different (regions) VpmaZ-MBP fusion proteins. (B) Immunostaining wi...

Representative colony immunoblots of M. agalactiae reisolates obtained from right udder halves of sheep MS 9. All colonies were negative for immunostaining using VpmaY- and VpmaU-specific α-Y and α-U antisera, respectively, and appeared pink with the non-specific Ponceau S counterstaining. (PDF)

Representative colony immunoblots of M. agalactiae reisolates obtained from the mesenterial lymph node of sheep MS 6. Colonies were positive only when immunostained with VpmaW-specific antisera (α-W) and were negative with all the other five Vpma specific pAbs (α-U, α-Y, α-Z, α-X and α-V) and were counterstained in pink using the non-specific prote...

Representative colony immunoblots of M. agalactiae reisolates obtained from right udder halves of sheep MS 8. Many colonies were positive when immunostained with α-U pAb and were completely negative with α-Y and α-Z, whereas singular positive colonies were observed with α-W, α-X and α-V antisera. Negative colonies were counterstained in pink using...

Oligonucleotide sequences used in this study. (DOCX)

Relatively few virulence genes have been identified in pathogenic mycoplasmas, so we used signature-tagged mutagenesis to identify mutants of the avian pathogen Mycoplasma gallisepticum with reduced capacity to persist in vivo and compared the virulence of selected mutants in experimentally infected chickens. Four mutants had insertions in one of t...

Importance: Many if not all bacteria are able to secrete polysaccharides, either attached to the cell-surface or exported unbound into the extracellular environment. Both types of polysaccharides can play a role in the bacterial-hosts interactions. Mycoplasmas are no exception despite their poor overall metabolic capacity. We showed here thatM. ag...

Mycoplasma bovis is a cause of pneumonia, mastitis, arthritis and otitis media in cattle throughout the world. However, despite its clinical significance, there is a paucity of tools to genetically manipulate it, impeding our capacity to further explore the molecular basis of its virulence. To address this limitation, we developed a series of homol...

Comparative genomics have revealed massive Horizontal Gene Transfer (HGT) in between Mycoplasma species sharing common ruminant hosts. Further results pointed towards an integrative conjugative element (ICE) as an important contributor of HGT in the small ruminant pathogen Mycoplasma agalactiae. To estimate the prevalence of ICEs in ruminant mycopl...

Mycoplasmas of the Mycoplasma mycoides cluster are all ruminant pathogens. Mycoplasma mycoides subsp. mycoides is responsible for contagious bovine pleuropneumonia and is known to produce capsular polysaccharide (CPS) and exopolysaccharide (EPS). Previous studies have strongly suggested a role for Mycoplasma mycoides subsp. mycoides polysaccharides...

Mollicutes is a class of parasitic bacteria that have evolved from a common Firmicutes ancestor mostly by massive genome reduction. With genomes under 1 Mbp in size, most Mollicutes species retain the capacity to replicate and grow autonomously. The major goal of this work was to identify the minimal set of proteins that can sustain ribosome biogen...

Mechanisms underlying pathogenic processes in mycoplasma infections are poorly understood, mainly because of limited sequence similarities with classical, bacterial virulence factors. Recently, large-scale transposon mutagenesis in the ruminant pathogen Mycoplasma agalactiae identified the NIF locus, including nifS and nifU, as essential for mycopl...

The concept of pathogenesis has evolved considerably over recent years, and the scenario "a microbe + virulence factors = disease" is probably far from reality in a number of cases. Actual pathogens have extremely broad biological diversity and are found in all major groups of microorganisms (viruses, bacteria, fungi, protozoa…). Their pathogenicit...

While transposon mutagenesis has been successfully used for Mycoplasma spp. to disrupt and determine non-essential genes, previous attempts with Ureaplasma spp. have been unsuccessful. Using a polyethylene glycol-transformation enhancing protocol, we were able to transform three separate serovars of Ureaplasma parvum with a Tn4001-based mini-transp...

Mollicutes are a class of simple bacteria characterized by the lack of a bacterial cell wall and their very small genomes (580 kb to 2200 kb). This phylogenetically coherent group contains a broad range of different plant and animal pathogens making it an ideal model for understanding gene function, gene regulation and the evolution of virulence fa...

Motivation Among challenges that hamper reaping the benefits of genome assembly are both unfinished assemblies and the ensuing experimental costs. First, numerous software solutions for genome de novo assembly are available, each having its advantages and drawbacks, without clear guidelines as to how to choose among them. Second, these solutions pr...

Horizontal gene transfer (HGT) is a major force of microbial evolution but was long thought to be marginal in mycoplasmas. In silico detection of exchanged regions and of loci encoding putative Integrative Conjugative Elements (ICE) in several mycoplasma genomes challenged this view, raising the prospect of these simple bacteria being able to conju...

We report here the draft genome sequences of Mycoplasma auris and Mycoplasma yeatsii, two species commonly isolated from the external ear canal of Caprinae.

Mycoplasma putrefaciens is one of the etiologic agents of contagious agalactia in goats. We report herein the complete genome sequence of Mycoplasma putrefaciens strain 9231.

We report here the draft genome sequences of Mycoplasma alkalescens, Mycoplasma arginini, and Mycoplasma bovigenitalium. These three species are regularly isolated from bovine clinical specimens, although their role in disease is unclear.

There is limited understanding of the molecular basis of virulence in the important avian pathogen Mycoplasma gallisepticum. To define genes that may be involved in colonisation of chickens, a collection of mutants of the virulent Ap3AS strain of M. gallisepticum were generated by signature-tagged transposon mutagenesis. The collection included mut...

Mycoplasma gallisepticum is an important avian pathogen that commonly induces chronic respiratory disease in chicken. To better understand the mycoplasma factors involved in host colonization, chickens were infected via aerosol with two hemadsorption-negative (HA−) mutants, mHAD3 and RCL2, that were derived from a low passage of the pathogenic stra...

Commonly known as mycoplasmas, bacteria of the class Mollicutes include the smallest and simplest life forms capable of self replication outside of a host. Yet, this minimalism hides major human and animal pathogens whose prevalence and occurrence have long been underestimated. Owing to advances in sequencing methods, large data sets have become av...

The evolution of mycoplasmas from a common ancestor with Firmicutes has been characterized not only by genome down-sizing but also by horizontal gene transfer between mycoplasma species sharing a common host. The mechanisms of these gene transfers remain unclear because our knowledge of the mycoplasma mobile genetic elements is limited. In particul...

Figure S2. Detection of pMyBK1 ssDNA intermediates by Southern blot hybridization. Total DNA from Mycoplasma yeatsii type strain GIH TS (lane 1-2) was analyzed on a 0.8% agarose gel (A) with (+) or without (-) prior S1 nuclease treatment. Southern blot (B) was performed with digoxigenin-labeled pMyBK1 probe under non-denaturing conditions. M, DNA l...

Table S1. Additional file 5.

Table S2. History of mycoplasma strains and plasmid screening.

Table S3. Pairwise nucleic sequence identities between mycoplasma plasmids. Global alignments of the full-length nucleic sequence of mycoplasma plasmids were accomplished using a Needleman–Wunsch algorithm implemented in the Needleall program (Needleman & Wunsch, 1970). Identity percents are indicated. Rep group refers to Rep phylogeny (see Figure...

Figure S1. Nucleotide sequences of the predicted ctRNA coding strands. The counter-transcripts were first identified by analogy with those of pMV158 or its derivative pLS1. These ctRNA overlap the rep gene start and have a length of only a few tens of nucleotides. Using the consensus sequence TTGACA – (N17) –TG-N-TATAAT for the promoter, putative p...

Figure S3. Expression of spiralin in Mcc using pMyBK1 derivatives. Whole cell dot immunoblot of 12 Mcc transformants harboring the spiralin expression vector pCM-K3-spi (a) or the empty vector pCM-K3 (b). Mycoplasma cells were applied to a nitrocellulose membrane and probed with rabbit anti-spiralin antibodies and anti-rabbit IgG peroxidase conjuga...

Mycoplasma mycoides subsp. mycoides "Small Colony" (MmmSC) is responsible for contagious bovine pleuropneumonia (CBPP) in bovidae, a notifiable disease to the World Organization for Animal Health (OIE). Although its origin is not documented, the disease was known in Europe in 1773. It reached nearly world-wide distribution in the 19(th) century thr...

Input file for BEAST analysis. Xml file generated by the BEAUTi software. This file contains all sequence data as well as informations needed by the BEAST software to perform a Bayesian evolutionary analysis such as site model, clock models, priors, operators and MCMC chain length. (XML)

Haplotype network of Mycoplasma mycoides subsp. mycoides “Small Colony” (MmmSC) sequences obtained using statistical parsimony. The cladogram was obtained with TCS from the alignment of the 139 nucleotides corresponding to the MmmSC polymorphic sites of 62 concatenated core genes. Strains KH3J and PG1T were not connected to this network because the...