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Frontiers in Microbiology 2023Tailocins are nanomolecular machines with bactericidal activity. They are produced by bacteria to contribute to fitness in mixed communities, and hence, they play a...
Tailocins are nanomolecular machines with bactericidal activity. They are produced by bacteria to contribute to fitness in mixed communities, and hence, they play a critical role in their ecology in a variety of habitats. Here, we characterized the new tailocin produced by strain 3937, a well-characterized member of plant pathogenic Soft Rot (SRP). Tailocins induced in were 166 nm long tubes surrounded by contractive sheaths with baseplates having tail fibers at one end. A 22-kb genomic cluster involved in their synthesis and having high homology to the cluster coding for the tail of the Peduovirus P2 was identified. The tailocins, termed dickeyocins P2D1 (phage P2-like dickeyocin 1), were resistant to inactivation by pH (3.5-12), temperature (4-50°C), and elevated osmolarity (NaCl concentration: 0.01-1 M). P2D1 could kill a variety of different spp. but not any strain of spp. tested and were not toxic to .
PubMed: 38098664
DOI: 10.3389/fmicb.2023.1307349 -
Plant Disease Apr 2024Blackleg and soft rot are harmful diseases in potato (Solanum tuberosum) caused by Pectobacterium spp. and Dickeya spp. (Czajkowski et al. 2015). The occurrence of...
Blackleg and soft rot are harmful diseases in potato (Solanum tuberosum) caused by Pectobacterium spp. and Dickeya spp. (Czajkowski et al. 2015). The occurrence of potato blackleg was serious in potato-producing areas around Xiapu County in Fujian Province, China, in 2021 (6 ha) and 2022 (7 ha), with an incidence of approximately 5%, which reached nearly 23%. Three diseased plants were collected to isolate the pathogen. Single colonies from each sampled plant were isolated and streaked onto fresh plates. DNA from three colonies from different plants was PCR amplified with primer pair 27F/1492R (Lane 1991) for the 16S rRNA gene. Since the sequences were identical, we selected strain M2-3 for further analysis. The strain M2-3 was gram-negative, pectolytic on CVP, grew at 37°C and 5% NaCl. The bacterium was positive for phosphatase activity, erythromycin sensitivity, indole production, gelatin liquefaction, malonic utilization, and acid production from, melibiose, raffinose, and arabinose. The bacterium was negative for sucrose, α-methyl glucoside, sorbitol, trehalose, lactose, and sodium citrate (Fujimoto et al. 2018;),although sucrose and lactose did not provide the expected results, there are exception in all species. The genome of strain M2-3 was sequenced and deposited in the NCBI database under accession numbers: CP077422. An Average Nucleotide Identity (ANI) analysis showed that M2-3 clustered with other D. dadantii strains and has a 98.39% identity with D. dadantii strain DSM 18020 (CP023467). The housekeeping genes (recA, dnaX, acnA, gapA, icd, mdh, mtlD and pgi) were amplified with primer pairs designed previously(Fujimoto et al. 2018; Ma et al. 2007) and sequenced. A multilocus sequence analysis (MLSA) was performed by concatenating the 8 gene sequences and constructing a maximum likelihood phylogenetic tree using PhyloSuite version 1.2.1 (Zhang et al. 2020) and IQ-tree version 1.6.8 (Nguyen et al. 2015) software. Strain M2-3 was clustered together with Dickeya dadantii. For the pathogenicity test, three plants per treatment, totaling nine plants, were used. Bacterial suspensions (1×10^8 CFU/mL) were made in a 10mM PBS buffer. 10 μL of M2-3, D. dadantii type strain 18020 (positive control), and buffer (negative control) were injected into the plant stems near the base. Water stains appeared at the site of inoculation after 2 days and they gradually became black and rotten. The leaves became yellow and wilted, and the petiole base rotted within 5 days of inoculation completing the Koch postulate. According to average nucleotide identity and housekeeping gene sequence analysis, strain M2-3 was identified as Dickeya dadantii. Previous studies have reported several pathogens that cause potato blackleg in China, including P. atrosepticum, P. carotovorum, P. brasiliense, P. parmentieri, P. polaris, and P. punjabense (Li-ping et al. 2020; Wang et al. 2021). To the best of our knowledge, this study is the first to report potato blackleg disease caused by Dickeya dadantii in Fujian Province, China. This finding suggests that this pathogen may cause a threat to potato production in Fujian Province.
PubMed: 38687907
DOI: 10.1094/PDIS-04-23-0755-PDN -
Microbiology Spectrum Dec 2023Bacteria respond to environmental changes and adapt to host systems. The response regulator VfmH of the Vfm quorum sensing system regulates a crucial virulence factor,...
Bacteria respond to environmental changes and adapt to host systems. The response regulator VfmH of the Vfm quorum sensing system regulates a crucial virulence factor, pectate lyase (Pel), in . At high c-di-GMP concentrations, VfmH binds c-di-GMP, resulting in the loss of its activation property in the Pel and virulence regulation in . VfmH binds to c-di-GMP three conserved arginine residues, and mutations of these residues eliminate the c-di-GMP-related phenotypes of VfmH in Pel synthesis. Our data also show that VfmH interacts with CRP to regulate transcription, thus integrating cyclic AMP and c-di-GMP signaling pathways to control virulence in . We propose that VfmH is an important intermediate factor incorporating quorum sensing and nucleotide signaling pathways for the collective regulation of pathogenesis.
Topics: Bacterial Proteins; Enterobacteriaceae; Cyclic GMP; Gene Expression Regulation, Bacterial
PubMed: 37811940
DOI: 10.1128/spectrum.01537-23 -
Plant Disease Jul 2023Cariru (Talinum fruticosum) is a non-conventional food plant and a source of vitamins A, B2, B5, and C, calcium, phosphorus, and iron. It is an important crop for...
Cariru (Talinum fruticosum) is a non-conventional food plant and a source of vitamins A, B2, B5, and C, calcium, phosphorus, and iron. It is an important crop for producers of the Amazon region and it is used as a leafy green vegetable, similar to spinach, as well as for medicinal purposes. It is cultivated by producers in the states of Pará and Amazonas (Amorim et al. 2014). In February 2020, in gardens of approximately 1.0 and 0.18 ha in the municipality of Ananindeua (01° 34' 12" S - 48° 38' 11" W), Pará, Brazil, we observed approximately 10% of the plants exhibited soft rot symptoms, bacterial oozing, and stem pith disintegration. From cariru infected leaves, the bacteria were selectively isolated using healthy pepper fruit, as described by Moraes et al. (2017). Two strain (UFRADD17 and UFRADD18) were obtained and both showed white, small, "broken glass" colonies on CPG (peptone-casamino acid-glucose) medium when observed in a stereoscope under oblique lighting. Pathogenicity tests were performed on 20-day-old cariru seedlings by depositing 10 ul of the bacterial suspension (106 CFU/ml) onto a wound made on the leaf blade with an entomological pin. After inoculation, seedlings were incubated in a greenhouse for 48 h at 30 ± 2°C and 90 ± 2% RH. Plants treated similarly with sterile distilled water were used as a negative control. Symptoms of soft rot were observed between 12 and 24 h after inoculation. Seedlings used as negative control remained symptomless. Forty-eight hours after inoculation, we reisolated the pathogen and performed rep-PCR (REP, ERIC, and BOX-PCR) analyses (Gama et al. 2018) with the strains used for inoculation and those reisolated from the pathogenicity test to confirm the identity of the strains and to fulfill Koch's postulates. The two re-isolated strains showed the same REP, ERIC, and BOX-PCR profiles as the strains used for inoculation. In addition, there were no differences between the rep-PCR profiles of the isolates UFRADD17 and UFRADD18. These isolates were Gram-negative, grew at 37°C, and were positive for maceration in pepper fruit and potato tubers. Molecular identification of the isolate UFRADD18 was performed from sequencing fragments from the 16S rDNA region and dnaX, fusA, gyrA, and mdH housekeeping genes as previously described (Van der Wolf et al. 2014; Ma et al. 2007). Sequences were deposited in Genbank under accessions OP142347, OP191704, OP191705, OP191706, and OP191707. Blastn analysis showed 96.15% identity with the 16S rDNA region of accession KY231142.1 (400/416 bp), 99.5% identity with dnaX of accession KC844490.1 (396/398 bp), 99.86% identity with fusA of accession CP023467.1 (714/715 bp), 99.74% identity with gyrA of accession KC844598 (387/388 bp), and 99.10% identity with mdH of accession GQ891979.1 (563/560 bp) from the type strain of Dickeya dadantii. A phylogenetic analysis performed by Bayesian inference with the dnaX, fusA, gyrA, and mdH genes grouped the isolate UFRADD18 along with NCPPB898T, with a 1.00 posterior probability. To our knowledge, this is the first report of D. dadantii causing soft rot in cariru in the Brazilian territory. In addition, this report increases understanding of the host range of this bacterium, which is important for adopting management strategies based on the control of alternative hosts.
PubMed: 37408126
DOI: 10.1094/PDIS-02-23-0397-PDN -
Microbiology Spectrum Aug 2023Genome evolution, and more specifically gene duplication, is a key process shaping host-microorganism interaction. The conserved paralogs usually provide an advantage to...
Genome evolution, and more specifically gene duplication, is a key process shaping host-microorganism interaction. The conserved paralogs usually provide an advantage to the bacterium to thrive. If not, these genes become pseudogenes and disappear. Here, we show that during the emergence of the genus , the gene encoding the porin OmpF was duplicated. Our results show that the expression is deleterious to the virulence of , the agent causing soft rot disease. Interestingly, 2 is regulated while is constitutive but activated by the EnvZ-OmpR two-component system. , acidic pH triggers the system. The pH measured in four eudicotyledons increased from an initial pH of 5.5 to 7 within 8 h post-infection. Then, the pH decreased to 5.5 at 10 h post-infection and until full maceration of the plant tissue. Yet, the production of phenolic acids by the plant's defenses prevents the activation of the EnvZ-OmpR system to avoid the expression even though environmental conditions should trigger this system. We highlight that gene duplication in a pathogen is not automatically an advantage for the infectious process and that, there was a need for our model organism to adapt its genetic regulatory networks to conserve these duplicated genes. IMPORTANCE species cause various diseases in a wide range of crops and ornamental plants. Understanding the molecular program that allows the bacterium to colonize the plant is key to developing new pest control methods. Unlike other enterobacterial pathogens, , the causal agent of soft rot disease, does not require the EnvZ-OmpR system for virulence. Here, we showed that during the emergence of the genus , the gene encoding the porin OmpF was duplicated and that the expression of was deleterious for virulence. We revealed that while the EnvZ-OmpR system was activated by acidic pH and even though the pH was acidic when the plant is colonized, this system was repressed by phenolic acid (generated by the plant's defenses). These results provide a unique- biologically relevant-perspective on the consequence of gene duplication and the adaptive nature of regulatory networks to retain the duplicated gene.
PubMed: 37642428
DOI: 10.1128/spectrum.00833-23 -
Journal of Bacteriology Jul 2023The transcriptional regulator PecS is encoded by select bacterial pathogens. For instance, in the plant pathogen Dickeya dadantii, PecS controls a range of virulence...
The transcriptional regulator PecS is encoded by select bacterial pathogens. For instance, in the plant pathogen Dickeya dadantii, PecS controls a range of virulence genes, including pectinase genes and the divergently oriented gene , which encodes an efflux pump through which the antioxidant indigoidine is exported. In the plant pathogen (formerly named Agrobacterium tumefaciens), the locus is conserved. Using a strain of in which has been disrupted, we show here that PecS controls a range of phenotypes that are associated with bacterial fitness. PecS represses flagellar motility and chemotaxis, which are processes that are important for to reach plant wound sites. Biofilm formation and microaerobic survival are reduced in the disruption strain, whereas the production of acyl homoserine lactone (AHL) and resistance to reactive oxygen species (ROS) are increased when is disrupted. AHL production and resistance to ROS are expected to be particularly relevant in the host environment. We also show that PecS does not participate in the induction of genes. The inducing ligands for PecS, urate, and xanthine, may be found in the rhizosphere, and they accumulate within the plant host upon infection. Therefore, our data suggest that PecS mediates fitness during its transition from the rhizosphere to the host plant. PecS is a transcription factor that is conserved in several pathogenic bacteria, where it regulates virulence genes. The plant pathogen is important not only for its induction of crown galls in susceptible plants but also for its role as a tool in the genetic manipulation of host plants. We show here that PecS controls a range of phenotypes, which would confer the bacteria an advantage while transitioning from the rhizosphere to the host plant. This includes the production of signaling molecules, which are critical for the propagation of the tumor-inducing plasmid. A more complete understanding of the infection process may inform approaches by which to treat infections as well as to facilitate the transformation of recalcitrant plant species.
Topics: Transcription Factors; Reactive Oxygen Species; Gene Expression Regulation, Bacterial; Agrobacterium; Agrobacterium tumefaciens; Bacterial Proteins
PubMed: 37314346
DOI: 10.1128/jb.00478-22 -
Frontiers in Microbiology 2024The type VI secretion system (T6SS) assembles into a contractile nanomachine to inject effectors across bacterial membranes for secretion. The species complex is a...
The type VI secretion system (T6SS) assembles into a contractile nanomachine to inject effectors across bacterial membranes for secretion. The species complex is a group of soil inhabitants and phytopathogens that deploys T6SS as an antibacterial weapon against bacterial competitors at both inter-species and intra-species levels. The strain 1D1609 genome encodes one main T6SS gene cluster and four genes (i.e., ), each encoding a spike protein as an effector carrier. A previous study reported that associated gene 2, named encodes a His-Me finger nuclease toxin (also named HNH/ENDO VII nuclease), contributing to DNase-mediated antibacterial activity. However, the functions and roles of other putative effectors remain unknown. In this study, we identified associated gene 2 () that encodes another His-Me finger nuclease but with a distinct Serine Histidine Histidine (SHH) motif that differs from the AHH motif of V2a. We demonstrated that the ectopic expression of V2c caused growth inhibition, plasmid DNA degradation, and cell elongation in using DNAse activity assay and fluorescence microscopy. The cognate immunity protein, V3c, neutralizes the DNase activity and rescues the phenotypes of growth inhibition and cell elongation. Ectopic expression of V2c DNase-inactive variants retains the cell elongation phenotype, while V2a induces cell elongation in a DNase-mediated manner. We also showed that the amino acids of conserved SHH and HNH motifs are responsible for the V2c DNase activity and . Notably, V2c also mediated the DNA degradation and cell elongation of the target cell in the context of interbacterial competition. Importantly, V2a and V2c exhibit different capacities against different bacterial species and function synergistically to exert stronger antibacterial activity against the soft rot phytopathogen, .
PubMed: 38426053
DOI: 10.3389/fmicb.2024.1351590