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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 -
Plants (Basel, Switzerland) Apr 2023Nanomaterials are increasingly being used for crop growth, especially as a new paradigm for plant disease management. Among the other nanomaterials, silver nanoparticles...
Nanomaterials are increasingly being used for crop growth, especially as a new paradigm for plant disease management. Among the other nanomaterials, silver nanoparticles (AgNPs) draw a great deal of attention because of their unique features and multiple usages. Rapid expansion in nanotechnology and utilization of AgNPs in a large range of areas resulted in the substantial release of these nanoparticles into the soil and water environment, causing concern for the safety of ecosystems and phytosanitary. In an attempt to find an effective control measure for sweet potato soft rot disease, the pathogen was exposed to AgNPs, the cell-free culture supernatant (CFCS) of alone, and both in combination. AgNPs were synthesized using CFCS of strain A3. The green synthesized AgNPs exhibited a characteristic surface plasmon resonance peak at 410-420 nm. Electron microscopy and X-ray diffraction spectroscopy determined the nanocrystalline nature and 20-100 nm diameters of AgNPs. Release of metal Ag ion from biosynthesized AgNPs increases with time. AgNPs and CFCS of alone exhibited antibacterial activity against the growth, biofilm formation, swimming motility, and virulence of strain A3. The antibacterial activities elevated with the elevation in AgNPs and CFCS concentration. Similar antibacterial activities against were obtained with AgNPs at 50 µg·mL, 50% CFCS alone, and the combination of AgNPs at 12 µg·mL and 12% CFCS of . In planta experiments indicated that all the treatments reduced infection and increased plant growth. These findings suggest that AgNPs along with CFCS of can be applied to minimize this bacterial disease by controlling pathogen-contaminated sweet potato tuber with minimum Ag nano-pollutant in the environment.
PubMed: 37176882
DOI: 10.3390/plants12091817 -
Frontiers in Microbiology 2023For a coherent response to environmental changes, bacterial evolution has formed a complex transcriptional regulatory system comprising classical DNA binding proteins...
For a coherent response to environmental changes, bacterial evolution has formed a complex transcriptional regulatory system comprising classical DNA binding proteins sigma factors and modulation of DNA topology. In this study, we investigate replication-induced gene copy numbers - a regulatory concept that is unlike the others not based on modulation of promoter activity but on replication dynamics. We show that a large fraction of genes are predominantly affected by transient copy numbers and identify cellular functions and central pathways governed by this mechanism in . Furthermore, we show quantitatively that the previously observed spatio-temporal expression pattern between different growth phases mainly emerges from transient chromosomal copy numbers. We extend the analysis to the plant pathogen and the biotechnologically relevant organism . The analysis reveals a connection between growth phase dependent gene expression and evolutionary gene migration in these species. A further extension to the bacterial kingdom indicates that chromosome evolution is governed by growth rate related transient copy numbers.
PubMed: 37152747
DOI: 10.3389/fmicb.2023.1119878 -
Molecules (Basel, Switzerland) Mar 2023Essential oils (EOs) obtained by hydro-distillation from different parts of twigs (EOT), leaves (EOL), and fruits (EOF) of Hook. f. were screened for their chemical...
Essential oils (EOs) obtained by hydro-distillation from different parts of twigs (EOT), leaves (EOL), and fruits (EOF) of Hook. f. were screened for their chemical composition, insecticidal, repellence, and antibacterial properties. Based on GC and GC/MS analysis, 23 constituents were identified across the twigs, leaves, and fruits, with 23, 23, and 21 components, respectively. The primary significant class was oxygenated monoterpenes (82.2-95.5%). The main components were 1,8-cineole (65.6-86.1%), α-terpinyl acetate (2.5-7.6%), o-cymene (3.3-7.5%), and α-terpineol (3.3-3.5%). All three EOs exhibited moderate antibacterial activities. EOL was found to have higher antibacterial activity against all tested strains except (CFBP 8199), for which EOT showed more potency. Globally, (CFBP 8199) was the most sensitive (MIC ≤ 2 mg/mL), while the most resistant bacteria were (CFBP 3855) and subsp. (CFBP 5387). Fumigant, contact toxicity, and repellent bioassays showed different potential depending on plant extracts, particularly EOT and EOL as moderate repellents and EOT as a medium toxicant.
Topics: Oils, Volatile; Eucalyptus; Myrtaceae; Plant Leaves; Insect Repellents; Anti-Bacterial Agents; Plant Oils
PubMed: 36985610
DOI: 10.3390/molecules28062638 -
Plant Disease Mar 2023(satin pothos or silver vine) is an evergreen climbing plant belonging to the Araceae family, subfamily Monstereae (Bown, 2000), which is also cultivated as a foliage...
(satin pothos or silver vine) is an evergreen climbing plant belonging to the Araceae family, subfamily Monstereae (Bown, 2000), which is also cultivated as a foliage ornamental (Masnira et al. 2019). In September of 2022, soft rot symptoms were observed on potted . plants grown in a greenhouse in Nantun District, Taichung, Taiwan, in which soft rot of another aroid (philodendron) has also been reported (Wu et al. 2023). The symptoms appeared on the petioles and most of them tended to extend to the leaf blades; the colors of leaf lesions ranged from dark brown to gray (Fig. S1). Some 70% of the plants in the greenhouse showed similar symptoms and losses were estimated to be 15-30%. Four symptomatic plants were sampled. Macerated tissues from rotting petioles were soaked in 10 mM MgCl and observed under a light microscope (Nikon, Japan) at 400 x magnification. Motile, rod-shaped bacteria were observed, and 1-2 loopfuls of undiluted sample suspension were streaked onto nutrient agar (NA; Gibco, USA). After culturing at 28°C for 1 day, all samples yielded round, creamy-white colonies (0.9 mm in diameter) and from each of the four samples a pure culture was obtained (Spi1-Spi4). All isolates exhibited oxidative and fermentative metabolism of glucose (Schaad et al. 2001). They caused pitting on crystal violet pectate agar, induced maceration on potato tuber and were tested positive for phosphatase activity and indigoidine production (Lee and Yu 2006; Schaad et al. 2001). Polymerase chain reaction tests using -specific primers 5A and 5B (Chao et al. 2006) amplified the expected amplicon (0.5 kb) in extracted DNA samples of all isolates. Identification of the strains was achieved by amplifying and sequencing fragments of the housekeeping genes , , , , and (Marrero et al. 2013); the lengths of the five gene fragments analyzed were 822, 762, 720, 672, and 450 bp, respectively (accession nos. OP985528-OP985532). The five sequences were concatenated for every isolate; the resulting 3,426 bp sequences were aligned with ClustalW and found to be identical. A maximum-likelihood analysis was conducted using the 3,426-bp sequences and those of known species' type strains. Spi1 to Spi4 clustered with . subsp. NCPPB 2976 and . subsp. CFBP 1269 (Fig. S2) with sequence identities of 98.4 and 98%, respectively. To fulfil Koch's Postulates, stab inoculations of the four isolates into the petioles of cutting propagated, 38-day-old . plants (3 plants per isolate) were conducted using sterile toothpicks. The amounts of bacteria used was approximately 10 cfu per toothpick; the bacterial loads were estimated by suspending the cells in 10 mM MgCl and spread-plating diluted suspensions on NA. Sterile toothpicks were used as control. All tested plants were sealed in plastic bags (containing wet paper towel) and kept in a growth chamber (28°C; 12-h photoperiod). After 1 day, all isolates induced soft rot symptoms resembling those observed under natural conditions in the greenhouse. Bacteria were re-isolated, and they all shared the same sequence with strains Spi1 to Spi4. This is the first report of . affected by . in Taiwan. Further investigation is needed to determine whether Spi1-Spi4 belong to . subsp. . has been found infecting different aroids (Lee and Chen 2021; Lin et al. 2012). The species has also been reported in Taiwan on poinsettia (Wei et al., 2019) and philodendron (Wu et al. 2023). Because these plants are often grown closely in the same facilities, growers should be wary of . 's spread among these plants. Reduction of environmental humidity and avoiding overhead irrigation may be effective in preventing the pathogen's transmission.
PubMed: 36947837
DOI: 10.1094/PDIS-12-22-2885-PDN -
Metallomics : Integrated Biometal... Mar 2023Bacteria secrete siderophores whose function is to acquire iron. In recent years, the siderophores of several Chryseobacterium species were shown to promote the health...
Bacteria secrete siderophores whose function is to acquire iron. In recent years, the siderophores of several Chryseobacterium species were shown to promote the health and growth of various plants such as tomato or rice. However, the chemical nature of Chryseobacterium siderophores remained unexplored despite great interest. In this work, we present the purification and structure elucidation by nuclear magnetic resonance (NMR) spectroscopy and tandem mass spectrometry (MS/MS) of chryseochelin A, a novel citrate-based siderophore secreted by three Chryseobacterium strains involved in plant protection. It contains the unusual building blocks 3-hydroxycadaverine and fumaric acid. Furthermore, the unstable structural isomer chryseochelin B and its stable derivative containing fatty acid chains, named chryseochelin C, were identified by mass spectrometric methods. The latter two incorporate an unusual ester connectivity to the citrate moiety showing similarities to achromobactin from the plant pathogen Dickeya dadantii. Finally, we show that chryseochelin A acts in a concentration-dependent manner against the plant-pathogenic Ralstonia solanacearum strain by reducing its access to iron. Thus, our study provides valuable knowledge about the siderophores of Chryseobacterium strains, which have great potential in various applications.
Topics: Siderophores; Citric Acid; Chryseobacterium; Tandem Mass Spectrometry; Iron; Citrates
PubMed: 36792066
DOI: 10.1093/mtomcs/mfad008 -
Phytopathology Mar 2023Nitrate metabolism plays an important role in bacterial physiology. During the interaction of plant-pathogenic bacteria with their hosts, bacteria face variable...
Nitrate metabolism plays an important role in bacterial physiology. During the interaction of plant-pathogenic bacteria with their hosts, bacteria face variable conditions with respect to nitrate availability. Perception mechanisms through the chemosensory pathway drive the entry and control the colonization of the plant host in phytopathogenic bacteria. In this work, the identification and characterization of the nitrate- and nitrite-sensing (NIT) domain-containing chemoreceptor of 3937 () allowed us to unveil the key role of nitrate sensing not only for the entry into the plant apoplast through wounds but also for infection success. We determined the specificity of this chemoreceptor to bind nitrate and nitrite, with a slight ligand preference for nitrate. Gene expression analysis showed that nitrate perception controls not only the expression of nitrate reductase genes involved in respiratory and assimilatory metabolic processes but also the expression of , , and , three well-known virulence determinants in .
Topics: Virulence; Nitrates; Solanum tuberosum; Nitrites; Plant Diseases; Enterobacteriaceae; Plants; Bacterial Proteins; Gene Expression Regulation, Bacterial
PubMed: 36399025
DOI: 10.1094/PHYTO-10-22-0367-R -
The Journal of Biological Chemistry Dec 2022Succination is the spontaneous reaction between the respiratory intermediate fumarate and cellular thiols that forms stable S-(2-succino)-adducts such as...
Succination is the spontaneous reaction between the respiratory intermediate fumarate and cellular thiols that forms stable S-(2-succino)-adducts such as S-(2-succino)cysteine (2SC). 2SC is a biomarker for conditions associated with elevated fumarate levels, including diabetes, obesity, and certain cancers, and succination likely contributes to disease progression. Bacillus subtilis has a yxe operon-encoded breakdown pathway for 2SC that involves three distinct enzymatic conversions. The first step is N-acetylation of 2SC by YxeL to form N-acetyl-2SC (2SNAC). YxeK catalyzes the oxygenation of 2SNAC, resulting in its breakdown to oxaloacetate and N-acetylcysteine, which is deacetylated by YxeP to give cysteine. The monooxygenase YxeK is key to the pathway but is rare, with close homologs occurring infrequently in prokaryote and fungal genomes. The existence of additional 2SC breakdown pathways was not known prior to this study. Here, we used comparative genomics to identify a S-(2-succino) lyase (2SL) that replaces yxeK in some yxe gene clusters. 2SL genes from Enterococcus italicus and Dickeya dadantii complement B. subtilis yxeK mutants. We also determined that recombinant 2SL enzymes efficiently break down 2SNAC into fumarate and N-acetylcysteine, can perform the reverse reaction, and have minor activity against 2SC and other small molecule thiols. The strong preferences both YxeK and 2SL enzymes have for 2SNAC indicate that 2SC acetylation is a conserved breakdown step. The identification of a second naturally occurring 2SC breakdown pathway underscores the importance of 2SC catabolism and defines a general strategy for 2SC breakdown involving acetylation, breakdown, and deacetylation.
Topics: Cysteine; Lyases; Acetylcysteine; Sulfhydryl Compounds; Fumarates
PubMed: 36309089
DOI: 10.1016/j.jbc.2022.102639 -
Mobile DNA Aug 2022ICEs are mobile genetic elements found integrated into bacterial chromosomes that can excise and be transferred to a new cell. They play an important role in horizontal...
BACKGROUND
ICEs are mobile genetic elements found integrated into bacterial chromosomes that can excise and be transferred to a new cell. They play an important role in horizontal gene transmission and carry accessory genes that may provide interesting phenotypes for the bacteria. Here, we seek to research the presence and the role of ICEs in 300 genomes of phytopathogenic bacteria with the greatest scientific and economic impact.
RESULTS
Seventy-eight ICEs (45 distinct elements) were identified and characterized in chromosomes of Agrobacterium tumefaciens, Dickeya dadantii, and D. solani, Pectobacterium carotovorum and P. atrosepticum, Pseudomonas syringae, Ralstonia solanacearum Species Complex, and Xanthomonas campestris. Intriguingly, the co-occurrence of four ICEs was observed in some P. syringae strains. Moreover, we identified 31 novel elements, carrying 396 accessory genes with potential influence on virulence and fitness, such as genes coding for functions related to T3SS, cell wall degradation and resistance to heavy metals. We also present the analysis of previously reported data on the expression of cargo genes related to the virulence of P. atrosepticum ICEs, which evidences the role of these genes in the infection process of tobacco plants.
CONCLUSIONS
Altogether, this paper has highlighted the potential of ICEs to affect the pathogenicity and lifestyle of these phytopathogens and direct the spread of significant putative virulence genes in phytopathogenic bacteria.
PubMed: 35962419
DOI: 10.1186/s13100-022-00275-1 -
Nucleic Acids Research Sep 2022DNA supercoiling is an essential mechanism of bacterial chromosome compaction, whose level is mainly regulated by topoisomerase I and DNA gyrase. Inhibiting either of...
DNA supercoiling is an essential mechanism of bacterial chromosome compaction, whose level is mainly regulated by topoisomerase I and DNA gyrase. Inhibiting either of these enzymes with antibiotics leads to global supercoiling modifications and subsequent changes in global gene expression. In previous studies, genes responding to DNA relaxation induced by DNA gyrase inhibition were categorised as 'supercoiling-sensitive'. Here, we studied the opposite variation of DNA supercoiling in the phytopathogen Dickeya dadantii using the non-marketed antibiotic seconeolitsine. We showed that the drug is active against topoisomerase I from this species, and analysed the first transcriptomic response of a Gram-negative bacterium to topoisomerase I inhibition. We find that the responding genes essentially differ from those observed after DNA relaxation, and further depend on the growth phase. We characterised these genes at the functional level, and also detected distinct patterns in terms of expression level, spatial and orientational organisation along the chromosome. Altogether, these results highlight that the supercoiling-sensitivity is a complex feature, which depends on the action of specific topoisomerases, on the physiological conditions, and on their genomic context. Based on previous in vitro expression data of several promoters, we propose a qualitative model of SC-dependent regulation that accounts for many of the contrasting transcriptomic features observed after DNA gyrase or topoisomerase I inhibition.
Topics: DNA Gyrase; DNA Topoisomerases, Type I; DNA, Superhelical; DNA, Bacterial; Enterobacteriaceae; Anti-Bacterial Agents
PubMed: 35950487
DOI: 10.1093/nar/gkac679