Breaking down walls to live in harmony

Some of the proteins and enzymes that allow bacteria to enter living fungal cells and cause rice seedling blight have been identified

Characterization of Burkholderia rhizoxinica and B. endofungorum Isolated from Clinical Specimens

Eight isolates submitted to CDC from 1989 to 2006 from clinical specimens were initially identified as members of the genus Burkholderia based on preliminary cellular fatty acid analysis and/or 16S rRNA gene sequencing. With the recent descriptions of the new species B. rhizoxinica and B. endofungorum, which are considered endosymbiotic bacteria in Rhizopus microsporus fungi, we now identify seven of these clinical isolates as B. rhizoxinica and one as B. endofungorum based on biochemical testing, 16s rRNA, and DNA-DNA hybridization results. We also further characterize these isolates by assessing toxin production and/or by multiple locus sequence typing

Thrombocytopenia-associated mutations in Ser/Thr kinase MASTL deregulate actin cytoskeleton dynamics in platelets

MASTL, a Ser/Thr kinase that inhibits PP2A-B55 complexes during mitosis, is mutated in autosomal dominant thrombocytopenia. However, the connections between the cell cycle machinery and this human disease remain unexplored. We report here that, whereas Mastl ablation in megakaryocytes prevented proper maturation of these cells, mice carrying the thrombocytopenia-associated mutation developed thrombocytopenia as a consequence of aberrant activation and survival of platelets. Activation of mutant platelets was characterized by hyper-stabilized pseudopods mimicking the effect of PP2A inhibition and actin polymerization defects. These aberrations were accompanied by abnormal hyper-phosphorylation of multiple components of the actin cytoskeleton and were rescued both in vitro and in vivo by inhibiting upstream kinases such as PKA, PKC, or AMPK. These data reveal an unexpected role of Mastl in actin cytoskeleton dynamics in postmitotic cells, and suggest that the thrombocytopenia-associated mutation in MASTL is a pathogenic dominant mutation that mimics decreased PP2A activity resulting in altered phosphorylation of cytoskeletal regulatory pathways.We thank Peter Storz (Mayo Clinic; Jacksonville, FL) for sharin g reagents and Sheila Rueda for her support with the management of the mouse colony. B.H. and R.S.-M. were supported by the Juan de la Cierva Programme from the Spanish M inistry of Economy and Competitiveness (MINECO). M.T. was supported by Foundation La Caixa. A.E.B. was supported by the Programa de Empleo Juvenil, Comunidad de M adrid. M.A.-F. received a young investigator g rant from MINECO (SAF2014-60442- JIN; co-financed by FEDER funds). P.G.dF. was supported by Fundació la Marató de TV3 (project 080121 and project 20153031). J.M. was supported by the Ramon y Cajal programme (MINECO; RYC-2012-10651). M.M. lab. is supported by grants from the MINE CO (SAF2015- 69920-R), Programa iLUNG from the Comunidad de Madrid (B2017/BM D-3884), and Worldwide Cancer Research (15-0278). CNIO is a Severo Ochoa Cen ter of Excellence (MINECO awards SEV-2015-0510)S

Antifungal Activity of Chitosan against Postharvest Fungi of Tropical and Subtropical Fruits

In the present chapter, results about the efficacy of chitosan (Chi) on sporulation, mycelial growth, germination, as well as quality parameters on fruits are shown. The results demonstrate that chitosan can control various phytopathogen isolates from diverse fruits. The pathogens in the genera Colletotrichum, Fusarium, and Rhizopus are involved in important postharvest disease losses throughout the world. In Nayarit, producers had reported high postharvest losses not only at field but also during the commercial chain with their products, besides the resistance of several pathogens to fungicides, which traditionally are applied for controlling diseases. In this sense, the aim of this research group is focused on the research of alternative and effective methods for controlling postharvest diseases. In vivo results are promising due to a good control in important tropical fruits like banana, avocado, mango, and jackfruit. An enhancement in the chitosan antimicrobial activity is reported with the combination with GRAS substances, as well as the use of nanotechnology. Chitosan can be an environment-friendly alternative to the use of chemical fungicides for controlling postharvest diseases in fruits

Evolution of an endofungal Lifestyle: Deductions from the Burkholderia rhizoxinica Genome

<p>Abstract</p> <p>Background</p> <p><it>Burkholderia rhizoxinica </it>is an intracellular symbiont of the phytopathogenic zygomycete <it>Rhizopus microsporus</it>, the causative agent of rice seedling blight. The endosymbiont produces the antimitotic macrolide rhizoxin for its host. It is vertically transmitted within vegetative spores and is essential for spore formation of the fungus. To shed light on the evolution and genetic potential of this model organism, we analysed the whole genome of <it>B. rhizoxinica </it>HKI 0454 - a type strain of endofungal <it>Burkholderia </it>species.</p> <p>Results</p> <p>The genome consists of a structurally conserved chromosome and two plasmids. Compared to free-living <it>Burkholderia </it>species, the genome is smaller in size and harbors less transcriptional regulator genes. Instead, we observed accumulation of transposons over the genome. Prediction of primary metabolic pathways and transporters suggests that endosymbionts consume host metabolites like citrate, but might deliver some amino acids and cofactors to the host. The rhizoxin biosynthesis gene cluster shows evolutionary traces of horizontal gene transfer. Furthermore, we analysed gene clusters coding for nonribosomal peptide synthetases (NRPS). Notably, <it>B. rhizoxinica </it>lacks common genes which are dedicated to quorum sensing systems, but is equipped with a large number of virulence-related factors and putative type III effectors.</p> <p>Conclusions</p> <p><it>B. rhizoxinica </it>is the first endofungal bacterium, whose genome has been sequenced. Here, we present models of evolution, metabolism and tools for host-symbiont interaction of the endofungal bacterium deduced from whole genome analyses. Genome size and structure suggest that <it>B. rhizoxinica </it>is in an early phase of adaptation to the intracellular lifestyle (genome in transition). By analysis of tranporters and metabolic pathways we predict how metabolites might be exchanged between the symbiont and its host. Gene clusters for biosynthesis of secondary metabolites represent novel targets for genomic mining of cryptic natural products. <it>In silico </it>analyses of virulence-associated genes, secreted proteins and effectors might inspire future studies on molecular mechanisms underlying bacterial-fungal interaction.</p

Alternative Eco-Friendly Methods in the Control of Post-Harvest Decay of Tropical and Subtropical Fruits

The effectiveness on several fruits by the application of alternative methods against fungi is summarized in the present chapter. Several investigations have reported the efficacy of these technologies for controlling fungal infections. Currently, high post-harvest loses have been reported due to several factors such as inefficient management, lack of training for farmers, and problems with appropriate conditions for storage of fruits and vegetables. Even now, in many countries, post-harvest disease control is led by the application of chemical fungicides. However, in this time, awareness about fungi resistance, environmental, and health issues has led to the research of eco-friendly and effective alternatives for disease management. The pathogen establishment on fruits can be affected by the application of GRAS compounds like chitosan, essential oils, salts, among others; besides, their efficacy can be enhanced by their combination with other technologies like ultrasound. Thus, the applications of these alternatives are suitable approaches for post-harvest management of fruits

Exploring the evolutionary ecology of fungal endophytes in agricultural systems: using functional traits to reveal mechanisms in community processes

All plants, including crop species, harbor a community of fungal endophyte species, yet we know little about the biotic factors that are important in endophyte community assembly. We suggest that the most direct route to understanding the mechanisms underlying community assembly is through the study of functional trait variation in the host and its fungal consortium. We review studies on crop endophytes that investigate plant and fungal traits likely to be important in endophyte community processes. We focus on approaches that could speed detection of general trends in endophyte community assembly: (i) use of the ‘assembly rules’ concept to identify specific mechanisms that influence endophyte community dynamics, (ii) measurement of functional trait variation in plants and fungi to better understand endophyte community processes and plant–fungal interactions, and (iii) investigation of microbe–microbe interactions, and fungal traits that mediate them. This approach is well suited for research in agricultural systems, where pair-wise host–fungus interactions and mechanisms of fungal–fungal competition have frequently been described. Areas for consideration include the possibility that human manipulation of crop phenotype and deployment of fungal biocontrol species can significantly influence endophyte community assembly. Evaluation of endophyte assembly rules may help to fine-tune crop management strategies

Cryptic Polyketide Synthase Genes in Non-Pathogenic Clostridium SPP

Modular type I polyketide synthases (PKS) produce a vast array of bacterial metabolites with highly diverse biological functions. Notably, all known polyketides were isolated from aerobic bacteria, and yet no example has been reported for strict anaerobes. In this study we explored the diversity and distribution of PKS genes in the genus Clostridium. In addition to comparative genomic analyses combined with predictions of modular type I polyketide synthase (PKS) gene clusters in sequenced genomes of Clostridium spp., a representative selection of other species inhabiting a variety of ecological niches was investigated by PCR screening for PKS genes. Our data reveal that all studied pathogenic Clostridium spp. are devoid of putative PKS genes. In stark contrast, cryptic PKS genes are widespread in genomes of non-pathogenic Clostridium species. According to phylogenetic analyses, the Clostridium PKS genes have unusual and diverse origins. However, reverse transcription quantitative PCR demonstrates that these genes are silent under standard cultivation conditions, explaining why the related metabolites have been overlooked until now. This study presents clostridia as a putative source for novel bioactive polyketides