Transcriptional study of genes involved in the passage from teliospore to hyphae stage in the fungus Thecaphora frezii, the causal agent of peanut smut

Peanuts (Arachis hypogaea L.) are among the most important leguminous crops in Argentina. During the growing season, they are frequently attacked by fungal diseases, including Thecaphora frezii. The spores of T. frezii are structures that confer resistance to this phytopathogen. The transition from teliospore to hypha is a characteristic process of some fungi, which is essential for completing their life cycle. Using the transcriptomes of teliospores and hyphae of T. frezii, we aimed to identify genes that were differentially expressed during this transition, and we found 134 up-regulated and 66 down-regulated genes, which would participate in different cellular processes such as: (a) cell cycle and DNA processing; (b) cell fate; (c) rescue, defense and cellular virulence; (d) detoxification by CYP450; (e) energy; (f) nutrient interaction and nutritional adaptation; (g) metabolism; (g) proteins with binding functions or cofactor requirements; (h) stress, cell differentiation and biogenesis of cell components; and (i) transport, cell communication and transcription. The identification of genes in T. frezii and their expression levels during different stages of differentiation could contribute to our understanding of the biological mechanisms in this fungus.

Changes of lipids composition in different ontogenetic stages of Thecaphora frezii: expression of key enzymes for lipid biosynthetic pathways

AIMS

It is known that Thecaphora frezii produces peanut smut that generates numerous economic losses. For this reason, it is a priority to search for control strategies. In this sense, we investigated the lipid profile of this pathogen, as possible antifungal targets, regarding polar lipid composition, fatty acid profile, and transcriptional regulation of genes involved in each stage of the development.

METHOD AND RESULTS

Lipids from T. frezii teliospores, basidiospores, and hyphae were analyzed by HPLC/CAD and CG/FID. We found differences in the unsaturation levels as well as in the long-chain fatty acids along the stages. Phosphatidylcholine was the main component in the three development stages, followed by cardiolipins. Phosphatidylinositol, phosphatidylethanolamine, and lyso-phosphatidylethanolamine were found in similar amounts in all stages. Although ergosterol was not detected, we found two unsaponifiable lipids. In addition, we found transcripts that encode 28 enzymes involved in the biosynthesis of three lipids by RNA-Seq.

CONCLUSIONS

Thecaphora frezii shows changes in the composition of membrane lipids in different ontogenetic stages as well as in the expression of transcripts for enzymes involved in lipid biosynthesis.

Pseudomonas putida group species as reservoirs of mobilizable Tn402-like class 1 integrons carrying blaVIM-2 metallo-β-lactamase genes

The Pseudomonas putida group (P. putida G) is composed of at least 21 species associated with a wide range of environments, including the clinical setting. Here, we characterized 13 carbapenem-resistant P. putida G clinical isolates bearing class 1 integrons/transposons (class 1 In/Tn) carrying bla_VIM-2 metallo-β-lactamase gene cassettes obtained from hospitals of Argentina. Multilocus sequencing (MLSA) and phylogenetic analyses based on 16S rDNA, gyrB and rpoD sequences distinguished 7 species among them. bla_VIM-2 was found in three different cassette arrays: In41 (bla_VIM-2-aacA4), In899 (only bla_VIM-2), and In528 (dfrB1-aacA4-bla_VIM-2). In41 and In899 were associated with complete tniABQC transposition modules and IRi/IRt boundaries characteristic of the Tn5053/Tn402 transposons, which were designated Tn6335 and Tn6336, respectively. The class 1 In/Tn element carrying In528, however, exhibited a defective tni module bearing only the tniC (transposase) gene, associated with a complete IS6100 bounded with two oppositely-oriented IRt end regions. In some P. putida G isolates including P. asiatica, P. juntendi, P. putida G/II, and P. putida G/V, Tn6335/Tn6336 were carried by pLD209-type conjugative plasmids capable of self-mobilization to P. aeruginosa or Escherichia coli. In other isolates of P. asiatica, P. putida G/II, and P. monteiliieilii, however, these bla_VIM-2-containing class 1 In/Tn elements were found inserted into the res regions preceding the tnpR (resolvase) gene of particular Tn21 subgroup members of Tn3 transposons. The overall results reinforce the notion of P. putida G members as bla_VIM-2 reservoirs, and shed light on the mechanisms of dissemination of carbapenem resistance genes to other pathogenic bacteria in the clinical setting.

[Pseudomonas aeruginosa: a multicenter study in 136 hospitals in Spain]

A cooperative group of 136 Spanish hospitals identified 1014 isolates of P. aeruginosa in one week. It was estimated that Spanish microbiology laboratories identified 168 P. aeruginosa isolates per 100,000 inhabitants population and year (25 isolates for every 1,000 hospital admissions/year). P. aeruginosa was recovered in 5.3% of all the samples with bacterial isolates. Seventy-five percent of samples containing P. aeruginosa came from the lower respiratory tract, wound exudates, abscesses and urine. The three most common serotypes present in Spain were found to be 0:1, 0:4 and 0:11 and constituted more than 50% of all isolates. The antimicrobials active against more than 85% of all the isolates included: ceftazidime (85.2%), piperacillin-tazobactam (92.8%), imipenem (86.2%), meropenem (92.2%) amikacin (91.4%) and tobramycin (91.2%). The study showed a high rate of resistance to ciprofloxacin (22.7%) and gentamicin (31.1%). Of the 529 patients who underwent clinical follow-up, 25.5% showed P. aeruginosa colonization and the remaining 74.5% had clinical infections. We estimated an incidence rate of 88.4 patients infected with P. aeruginosa per 100,000 inhabitants and year (13.8 cases per 1000 hospital admissions and year). Overall, 42% were community acquired. The overall mortality in this study was 15%, and mortality attributable to P. aeruginosa infections was 5%. After logistical regression analysis, the two independent predictors of mortality were the presence of a rapidly fatal underlying condition and the presence of bacteremia. In Spain, P. aeruginosa is much more than a cause of severe nosocomial infections in immunocompromised patients.