Finished Genome of the Fungal Wheat Pathogen Mycosphaerella graminicola Reveals Dispensome Structure, Chromosome Plasticity, and Stealth Pathogenesis.

The plant-pathogenic fungus Mycosphaerella graminicola (asexual stage: Septoria tritici) causes septoria tritici blotch, a disease that greatly reduces the yield and quality of wheat. This disease is economically important in most wheat-growing areas worldwide and threatens global food production. Control of the disease has been hampered by a limited understanding of the genetic and biochemical bases of pathogenicity, including mechanisms of infection and of resistance in the host. Unlike most other plant pathogens, M. graminicola has a long latent period during which it evades host defenses. Although this type of stealth pathogenicity occurs commonly in Mycosphaerella and other Dothideomycetes, the largest class of plant-pathogenic fungi, its genetic basis is not known. To address this problem, the genome of M. graminicolawas sequenced completely. The finished genome contains 21 chromosomes, eight of which could be lost with no visible effect on the fungus and thus are dispensable. This eight-chromosome dispensome is dynamic in field and progeny isolates, is different from the core genome in gene and repeat content, and appears to have originated by ancient horizontal transfer from an unknown donor. Synteny plots of the M. graminicola chromosomes versus those of the only other sequenced Dothideomycete, Stagonospora nodorum, revealed conservation of gene content but not order or orientation, suggesting a high rate of intra-chromosomal rearrangement in one or both species. This observed “mesosynteny” is very different from synteny seen between other organisms. A surprising feature of the M. graminicolagenome compared to other sequenced plant pathogens was that it contained very few genes for enzymes that break down plant cell walls, which was more similar to endophytes than to pathogens. The stealth pathogenesis of M. graminicola probably involves degradation of proteins rather than carbohydrates to evade host defenses during the biotrophic stage of infection and may have evolved from endophytic ancestors

Tannerella forsythia, a periodontal pathogen entering the genomic era

Several questions need to be addressed to evaluate whether Tannerella forsythia is to be considered a periodontal pathogen. T. forsythia has been detected in periodontal health and disease, so could it be a pathogen? The species was not detected in many studies despite finding other putative pathogens, so could it be important in pathogenicity? The challenges of working with T. forsythia include its fastidious and anaerobic growth requirements for cultural detection. Thus, studies associating T. forsythia with periodontal and other oral infections have used noncultural approaches (immunoassays and DNA-based assays) in addition to cultural approaches. We feel the timing of this review represents an interesting transition period in our understanding of the relationships of species with infection. Information from the recently released full genome sequence data of T. forsythia will provide new approaches and tools that can be directed to assess pathogenicity. Furthermore, molecular assessment of gene expression will provide a new understanding of the pathogenical potential of the species, and its effect on the host. T. forsythia, was described in reviews focusing on periodontal pathogens associated with herpesvirus detection (200), species for which genome projects were underway (41), members of polybacterial periodontal pathogenic consortium (91), and participants in periodontal microbial ecology (202). We will describe the history, taxonomy, and characteristics of T. forsythia, and related species or phylotypes in the genus Tannerella. To assess the pathogenic potential of T. forsythia, we first describe species associations with periodontal and other infections, including animal models, as has been the traditional approach arising from Koch’s postulates (203). Criteria for pathogenicity were expanded to incorporate sequence- derived information (58), and again more recently to include molecular signatures of pathogens and disease (170). We used sequence and genome-derived information, in addition to biofilm, pathogenic mediators, and host responses, to further explore the pathogenic potential of T. forsythia

13 | Chèvre – Columnatien

Publié avec le concours du Centre national du livre (CNL) et sur recommandation du Conseil international de la philosophie et des sciences humaines (UNESCO). Ce volume, à l'origine publié par Edisud, est désormais diffusé par les Editions Peeters sous l'Isbn : 978-2-85744-696-5

Reasons for Outpatient Referrals from Generalists to Specialists

OBJECTIVE: To determine the relative importance of medical and nonmedical factors influencing generalists’ decisions to refer, and of the factors that might avert unnecessary referrals. DESIGN: Prospective survey of all referrals from generalists to subspecialists over a 5-month period. SETTING: University hospital outpatient clinics. PARTICIPANTS: Fifty-seven staff physicians in general internal medicine, family medicine, dermatology, orthopedics, gastroenterology, and rheumatology. MEASUREMENTS AND MAIN RESULTS: For each referral, the generalist rated a number of medical and nonmedical reasons for referral, as well as factors that may have helped avert the referral; the specialist seeing the patient then rated the appropriateness, timeliness, and complexity of the referral. Both physicians rated the potential avoidability of the referral by telephone consultation. Generalists were influenced by a combination of both medical and nonmedical reasons for 76% of the referrals, by only medical reasons in 20%, and by only nonmedical reasons in 3%. In 33% of all referrals, generalists felt that training in simple procedures or communication with a generalist or specialist colleague would have allowed them to avoid referral. Specialists felt that the vast majority of referrals were timely (as opposed to premature or delayed) and of average complexity. Although specialists rated most referrals as appropriate, 30% were rated as possibly appropriate or inappropriate. Generalists and specialists failed to agree on the avoidability of 34% of referrals. CONCLUSIONS: Generalists made most referrals for a combination of medical and nonmedical reasons, and many referrals were considered avoidable. Increasing procedural training for generalists and enhancing informal channels of communication between generalists and subspecialists might result in more appropriate referrals at lower cost