Project description:Anthropogenic nutrient inputs alter soil biodiversity; however, it remains largely unknown whether changes in soil microeukaryotes (fungi and protists) are primarily driven by direct effects, such as modifications in soil properties, or by indirect effects, such as plant diversity loss. To disentangle these mechanisms, we investigated the long-term effects (11 years) of fertilization and manipulated plant diversity (1, 2, or 4 plant species) on soil microeukaryote communities in a temperate grassland experiment using long-amplicon rRNA sequencing. Our results indicate that fertilization generally had a stronger influence on microeukaryote communities than plant species richness. Fertilization altered the community composition of fungi and protists, increased OTU richness by 20.8% and 52.7%, respectively, and shifted community dominance from fungi to protists. Regarding plant diversity, we observed an effect exclusively on the protist community. Changes were primarily explained by increased plant biomass (driven by both fertilization and plant diversity) and by higher soil phosphorus and lower soil pH levels (driven exclusively by fertilization). Regarding life strategies, we observed synergistic treatment effects: fertilization primarily enhanced fungal saprophytes (only richness), fungal animal pathogens, and protist consumers, whereas plant diversity affected phototrophic protists (reduction) and protist animal pathogens (enhancement). Notably, fertilization and plant diversity decline together led to a cumulative increase in fungal plant pathogens. In conclusion, we highlight that fertilisation alone has a significant effect on soil microeukaryotes, while the additional decline in plant diversity affects different soil groups that are not directly affected by fertilisation. This synergistic pattern indicates that fertilization can influence the entire microeukaryote community through direct and indirect mechanisms, with a cumulative enhancement on certain groups, such as plant pathogens.
Project description:Temperate bacteriophages play a pivotal role in the biology of their bacterial host. Of particular interest are bacteriophages infecting enterohemorrhagic E. coli (EHEC) due to their significant contribution in the pathogenicity of these pathogens, most notably by encoding the key virulence factor of this pathogen, the Shiga toxin. To better understand the role of EHEC phages on the functionality of its host, we isolated eight temperate phages from clinical EHEC isolates and characterized their genomic composition, morphology and receptor targeting. Morphological analysis identified one long-tailed member from the Siphoviridae family, targeting the OmpC receptor for host recognition, while the other seven phages are short-tailed (Podoviridae) and target the essential BamA protein. Genomic characterization revealed significant variation between the long- and short-tailed phages. Five of the eight isolated phages encode the potent Shiga toxin. Comparative analysis displays the typical lambdoid mosaicism, indicative of horizontal gene transfer driving evolution. These findings provide insights into the genetic and morphologic diversity and receptor specificity of EHEC phages, highlighting their role in evolution and pathogenicity of clinical EHEC strains
Project description:Plant pathogens require lethal virulence factors, susceptible hosts, and optimal environmental conditions for disease establishment. High soil salinity, exacerbated by climate change, significantly impacts agro-biological ecosystems. However, the overall interactions between plant pathogens and salt stress are not fully characterized or understood. This study examines the effects of salt stress on representative plant pathogens: Burkholderia gladioli, Pectobacterium carotovorum subsp. carotovorum, and Ralstonia solanacearum. Using pan-genome-based comparative transcriptomics, we analyzed the comprehensive alterations within the biological systems of plant pathogens when treated with 200 mM NaCl. Our results highlight the differential responses between salt-sensitive and salt-tolerant pathogens to salt stress.
Project description:Rapidly growing antibiotic resistance among gastrointestinal pathogens, and the ability of antibiotics to induce the virulence of these pathogens makes it increasingly difficult to rely on antibiotics to treat gastrointestinal infections. The probiotic E. coli strain Nissle 1917 (EcN) is the active component of the pharmaceutical preparation Mutaflor® and has been successfully used in the treatment of gastrointestinal disorders. Gut bacteriophages are dominant players in maintaining the microbial homeostasis in the gut, however, their interaction with incoming probiotic bacteria remains to be at conception. The presence of bacteriophages in the gut makes it inevitable for any probiotic bacteria to be phage resistant, in order to survive and successfully colonize the gut. This study addresses the phage resistance of EcN, specifically against lytic T4 phage infection. From various experiments we could show that i) EcN is resistant towards T4 phage infection, ii) EcN’s K5 polysaccharide capsule plays a crucial role in T4 phage resistance and iii) EcN’s lipopolysaccharide (LPS) inactivates T4 phages and notably, treatment with the antibiotic polymyxin B which neutralizes the LPS destroyed the phage inactivation ability of isolated LPS from EcN. Our results further indicate that N-acetylglucosamine at the distal end of O6 antigen in EcN’s LPS could be the interacting partner with T4 phages. From our findings, we have reported for the first time, the role of EcN’s K5 capsule and LPS in its defense against T4 phages. In addition, by inactivating the T4 phages, EcN also protects E. coli K-12 strains from phage infection in tri-culture experiments. The combination of the identified properties is not found in other tested commensal E. coli strains. Furthermore, our research highlights phage resistance as an additional safety feature of EcN, a clinically successful probiotic E. coli strain.
Project description:Phages have emerged as prime suspects in the adaptation of pathogens to new hosts and the emergence of new pathogens or epidemic clones. Here we describe the genomic features of two related prophages (Ab105-1Ø and Ab105-2Ø) present in the ST-2 epidemic clone of Acinetobacter baumannii clinical strain Ab105_GEIH-2010 and not present in genetically related Ab155_GEIH-2000 strain isolated 10 years before. The Quasicore genome of Ab105-1Ø and Ab105-2Ø prophages revealed genes that promote bacterial-host fitness. The results of microarray analysis under stress conditions, SOS response activation revealed 5% and 30% of genes expressed by Ab105-1Ø and Ab105-2Ø prophages (which produce bacterial lysis) in the first case and underexpression of these genes from prophages in the second case. Hence, the QS system plays a major role in the evolution of phages in their natural hosts and environments. Interestingly, in host-virus interactions, RT-PCR showed several mechanisms of overexpression of the SOS response in relation to phage defence mechanisms: i) SAM or AdoMet-MTase (methyltransferases) and MazG protein (pyrophosphohydrolase) associated with phage defence in response to bacterial attack; ii) eukaryotic-like protein kinase (glutamate 5-kinase) associated with prevention of secondary infection by the same or a closely related virus. Overexpression of secretory virulence factors such as oxidoreductase (DsbA-like), anfo-nitrogenase and chromosome segregation proteins were also observed. In conclusion, study of the co-evolution of phages (virus) and bacteria may be essential in the search for means of combatting multi-resistant epidemic clones.
Project description:Retrons are bacterial genetic elements that encode a reverse transcriptase and, in combination with toxic effector proteins, can serve as antiphage defense systems. However, the mechanisms of action of most retron effectors, and how phages evade retrons, are not well understood. Here, we show that some phages can evade retrons and other defense systems by producing specific tRNAs. We find that expression of retron-Eco7 effector proteins (PtuA and PtuB) leads to degradation of tRNA-Tyr and abortive infection. The genomes of T5 phages that evade retron-Eco7 include a tRNA-rich region, including a highly expressed tRNA-Tyr gene, which confers protection against retron-Eco7. Furthermore, we show that other phages (T1, T7) can use a similar strategy, expressing a tRNA-Lys, to counteract a tRNA anticodon defense system (PrrC170).
Project description:Phages have emerged as prime suspects in the adaptation of pathogens to new hosts and the emergence of new pathogens or epidemic clones. Here we describe the genomic features of “swarms” of three related prophages (Ab105-1ϕ, Ab105-2ϕ and Ab105-3ϕ) present in the ST-2 epidemic clone of Acinetobacter baumannii clinical strain Ab105 GEIH-2010 and not present in genetically related Ab155 GEIH-2000 strain isolated 10 years before. The “Quasicore genome” of Ab105-1ϕ, Ab105-2ϕ and Ab105-3ϕ prophages revealed genes that promote bacterial-host fitness. The results of microarray analysis under stress conditions, SOS response and Quorum Sensing (QS) activation revealed 42% and 21% of genes expressed by Ab105-2ϕ and Ab105-3ϕ prophages (which produce bacterial lysis) in the first case and underexpression of these genes from prophages in the second case. Hence, the QS system plays a major role in the evolution of phages in their natural hosts and environments. Interestingly, in host-virus interactions, RT-PCR showed several mechanisms of overexpression of the SOS response in relation to phage defence mechanisms: i) SAM or AdoMet-MTase (methyltransferases) and MazG protein (pyrophosphohydrolase) associated with phage defence in response to bacterial attack; ii) eukaryotic-like protein kinase (glutamate 5-kinase) associated with prevention of secondary infection by the same or a closely related virus. Overexpression of secretory virulence factors such as oxidoreductase (DsbA-like), anfo-nitrogenase and chromosome segregation proteins were also observed. Moreover, under iron-deficient growth, there was an overexpression by RT-PCR of the a new interesting cluster of genes located following a “Moron” organization in the Ab105-3ϕ prophage being associated with iron uptake systems (Xanthine dehydrogenase gene cluster, Anthranilate operon, ABC transporter and TonB dependent receptor). In conclusion, study of the co-evolution of phages (virus) and bacteria may be essential in the search for means of combatting multi-resistant epidemic clones. Two parental clinical strains of A. baumannii (90% identity, indicated by PFGE, and ST2, indicated by Multilocus Sequence Typing, MLST) isolated in the same Intensive Care Unit (ICU) of a Spanish hospital, in 2000 and 2010, during the “I Multicenter Study GEIH-REIPI-Ab-2000” (Ab155 GEIH-2000) and “II Multicenter Study GEIH-REIPI-Ab-2010” (Ab105 GEIH-2010), respectively. Three replicates from RNA of the AB105 GEIH-2010 strain x 2 conditions (SOS response by Mitomycin C) and (Quorum Sensing activation by AHLs mixture).