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Molecular Plant Pathology Apr 2020LuxR-type regulators regulate many bacterial processes and play important roles in bacterial motility and virulence. Acidovorax citrulli is a seedborne bacterial...
LuxR-type regulators regulate many bacterial processes and play important roles in bacterial motility and virulence. Acidovorax citrulli is a seedborne bacterial pathogen responsible for bacterial fruit blotch, which causes great losses in melon and watermelon worldwide. We identified a LuxR-type, nonquorum sensing-related regulator, AcrR, in the group II strain Aac-5 of A. citrulli. We found that the acrR mutant lost twitching and swimming motilities, and flagellar formation. It also showed reduced virulence, but increased biofilm formation and growth ability. Transcriptomic analysis revealed that 394 genes were differentially expressed in the acrR mutant of A. citrulli, including 33 genes involved in flagellar assembly. Our results suggest that AcrR may act as a global regulator affecting multiple important biological functions of A. citrulli.
Topics: Bacterial Proteins; Biofilms; Citrullus; Comamonadaceae; Cucurbitaceae; Plant Diseases; Virulence
PubMed: 31943660
DOI: 10.1111/mpp.12910 -
Microbiology Spectrum Sep 2021Fe(II)-oxidizing microorganisms and Fe(III)-reducing microorganisms, which drive the biogeochemical Fe cycle on the Earth's surface, are phylogenetically and...
Fe(II)-oxidizing microorganisms and Fe(III)-reducing microorganisms, which drive the biogeochemical Fe cycle on the Earth's surface, are phylogenetically and ecologically diverse. However, no single organism capable of aerobic Fe(II) oxidation and anaerobic Fe(III) reduction at circumneutral pH have been reported so far. Here, we report a novel neutrophilic Fe(II)-oxidizing bacterium, strain MIZ03, isolated from an iron-rich wetland in Japan. Our cultivation experiments demonstrate that MIZ03 represents a much more versatile metabolism for energy acquisition than previously recognized in the genus . MIZ03 can grow chemolithoautotrophically at circumneutral pH by oxidation of Fe(II), H, or thiosulfate as the sole electron donor under (micro)aerobic conditions (i.e., using O as the sole electron acceptor). In addition, it can reduce Fe(III) or nitrate under anaerobic conditions. Thus, this is the first report demonstrating the presence of a single bacterium capable of both Fe(II) oxidation and Fe(III) reduction at circumneutral pH. The observed physiology was consistent with its 4.9-Mbp complete genome encoding key genes for iron oxidation/reduction ( and ), for nitrate reduction (), for thiosulfate oxidation (), and for carbon fixation via the Calvin cycle. Our metagenomic survey suggests that there are more members capable of Fe(II) oxidation and Fe(III) reduction. Such bifunctional may have an ecological advantage in suboxic/anoxic environments at circumneutral pH by recycling of Fe as the electron donor and acceptor. The biogeochemical cycle of iron (Fe) via reactions of oxidation, reduction, precipitation, and dissolution is involved in the cycle of other ecologically relevant elements, such as C, N, P, S, As, Co, Ni, and Pb. The Fe cycle on the Earth's surface is driven by a variety of Fe(II)-oxidizing microorganisms and Fe(III)-reducing microorganisms. Here, we discovered a novel bacterium, sp. strain MIZ03, capable of both Fe(II) oxidation and Fe(III) reduction at circumneutral pH, and we report its physiological characteristics and complete genome sequence. The unexpected capability of this bacterium provides novel insights into the Fe cycle in the environment. Moreover, this bacterium will help to better understand the molecular mechanisms of microbial Fe redox cycling as a model organism.
Topics: Aerobiosis; Chemoautotrophic Growth; Comamonadaceae; Ferric Compounds; Ferrous Compounds; Genome, Bacterial; Hydrogen; Hydrogen-Ion Concentration; Japan; Oxidation-Reduction; Phylogeny; Wetlands
PubMed: 34431720
DOI: 10.1128/Spectrum.00161-21 -
Molecular Plant-microbe Interactions :... Oct 2023In recent years subsp. was identified as a major cause of bacterial etiolation and decline (BED) in turfgrasses and has become a growing economical concern for the...
In recent years subsp. was identified as a major cause of bacterial etiolation and decline (BED) in turfgrasses and has become a growing economical concern for the turfgrass industry. The symptoms of BED resemble those of "bakanae," or foolish seedling disease, of rice (), in which the gibberellins produced by the infecting fungus, , contribute to the symptom development. Additionally, an operon coding for the enzymes necessary for bacterial gibberellin production was recently characterized in plant-pathogenic bacteria belonging to the γ-proteobacteria. We therefore investigated whether this gibberellin operon might be present in subsp. . A homolog of the operon has been identified in two turfgrass-infecting subsp. phylogenetic groups but not in closely related phylogenetic groups or strains infecting other plants. Moreover, even within these two phylogenetic groups, the operon presence is not uniform. For that reason, the functionality of the operon was examined in one strain of each turfgrass-infecting phylogenetic group ( subsp. strains KL3 and MD5). All nine operon genes were functionally characterized through heterologous expression in and enzymatic activities were analyzed by liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry. All enzymes were functional in both investigated strains, thus demonstrating the ability of phytopathogenic β-proteobacteria to produce biologically active GA. This additional gibberellin produced by subsp. could disrupt phytohormonal balance and be a leading factor contributing to the pathogenicity on turf grasses. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Topics: Gibberellins; Phylogeny; Poaceae; Comamonadaceae; Plants
PubMed: 37227226
DOI: 10.1094/MPMI-02-23-0017-R -
Molecular Plant Pathology Oct 2012Acidovorax citrulli is the causal agent of bacterial fruit blotch (BFB) of cucurbit plants. In recent years, the disease has spread to many parts of the world, mainly...
UNLABELLED
Acidovorax citrulli is the causal agent of bacterial fruit blotch (BFB) of cucurbit plants. In recent years, the disease has spread to many parts of the world, mainly via the inadvertent distribution of contaminated commercial seeds. Because of the costly lawsuits filed by growers against seed companies and the lack of efficient management methods, BFB represents a serious threat to the cucurbit industry, and primarily to watermelons and melons. Despite the economic importance of the disease, little is known about the basic aspects of A. citrulli pathogenesis. Nevertheless, the release of the genome of one A. citrulli strain, as well as the optimization of molecular manipulation and inoculation methods, has prompted basic studies and allowed advances towards an understanding of A. citrulli pathogenicity. In this article, we summarize the current knowledge about this important pathogen, with emphasis on its epidemiology and the factors involved in its pathogenicity and virulence.
TAXONOMY
Bacteria; Betaproteobacteria; order Burkholderiales; family C omamonadaceae; genus Acidovorax; species citrulli.
MICROBIOLOGICAL PROPERTIES
Gram-negative, strictly aerobic, rod-shaped; average dimensions of 0.5 μm × 1.7 μm; motile by means of an ~5.0-μm-long polar flagellum; colonies on King's medium B are round, smooth, transparent and nonpigmented; optimal temperatures for growth around 27-30 °C; induces a hypersensitive response on nonhost tobacco and tomato leaves.
HOST RANGE
Acidovorax citrulli strains are pathogenic to various species of the Cucurbitaceae family, including watermelon, melon, squash, pumpkin and cucumber. Significant economic losses have been reported in watermelon and melon.
DISEASE SYMPTOMS
Watermelon and melon seedlings and fruits are highly susceptible to A. citrulli. Typical seedling symptoms include water-soaked lesions on cotyledons that are often adjacent to the veins and later become necrotic, lesions on the hypocotyl, and seedling collapse and death. On watermelon fruits, symptoms begin as small, irregular, water-soaked lesions which later extend through the rind, turn brown and crack. On melon fruits, symptoms are characterized by small, often sunken rind lesions and internal fruit decay. Symptoms on the leaves of mature plants are difficult to diagnose because they are often inconspicuous or similar to those caused by other biotic or abiotic stresses. When they occur, leaf lesions can spread along the midrib and main veins. Lesions appear dark-brown to black on watermelon and light to reddish-brown on melon.
USEFUL WEBSITES
Bacterial fruit blotch of cucurbits at APSnet, http://www.apsnet.org/edcenter/intropp/lessons/prokaryotes/Pages/BacterialBlotch.aspx; bacterial fruit blotch guide from ASTA, http://www.amseed.com/pdfs/DiseaseGuide-BFB-English.pdf; Acidovorax citrulli AAC00-1 genome at JGI, http://genome.jgi-psf.org/aciav/aciav.info.html.
Topics: Comamonadaceae; Crops, Agricultural; Cucurbitaceae; Internationality
PubMed: 22738439
DOI: 10.1111/j.1364-3703.2012.00810.x -
Applied and Environmental Microbiology Dec 2015Bacterial oxidation of arsenite [As(III)] is a well-studied and important biogeochemical pathway that directly influences the mobility and toxicity of arsenic in the...
Bacterial oxidation of arsenite [As(III)] is a well-studied and important biogeochemical pathway that directly influences the mobility and toxicity of arsenic in the environment. In contrast, little is known about microbiological oxidation of the chemically similar anion antimonite [Sb(III)]. In this study, two bacterial strains, designated IDSBO-1 and IDSBO-4, which grow on tartrate compounds and oxidize Sb(III) using either oxygen or nitrate, respectively, as a terminal electron acceptor, were isolated from contaminated mine sediments. Both isolates belonged to the Comamonadaceae family and were 99% similar to previously described species. We identify these novel strains as Hydrogenophaga taeniospiralis strain IDSBO-1 and Variovorax paradoxus strain IDSBO-4. Both strains possess a gene with homology to the aioA gene, which encodes an As(III)-oxidase, and both oxidize As(III) aerobically, but only IDSBO-4 oxidized Sb(III) in the presence of air, while strain IDSBO-1 could achieve this via nitrate respiration. Our results suggest that expression of aioA is not induced by Sb(III) but may be involved in Sb(III) oxidation along with an Sb(III)-specific pathway. Phylogenetic analysis of proteins encoded by the aioA genes revealed a close sequence similarity (90%) among the two isolates and other known As(III)-oxidizing bacteria, particularly Acidovorax sp. strain NO1. Both isolates were capable of chemolithoautotrophic growth using As(III) as a primary electron donor, and strain IDSBO-4 exhibited incorporation of radiolabeled [(14)C]bicarbonate while oxidizing Sb(III) from Sb(III)-tartrate, suggesting possible Sb(III)-dependent autotrophy. Enrichment cultures produced the Sb(V) oxide mineral mopungite and lesser amounts of Sb(III)-bearing senarmontite as precipitates.
Topics: Antimony; Autotrophic Processes; Base Sequence; Chemoautotrophic Growth; Comamonadaceae; DNA, Bacterial; Geologic Sediments; Idaho; Mining; Molecular Sequence Data; Nitrates; Oxidation-Reduction; Oxidoreductases; Oxygen; Phylogeny; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Soil Microbiology; Water Microbiology
PubMed: 26431974
DOI: 10.1128/AEM.01970-15 -
Classifying Interactions in a Synthetic Bacterial Community Is Hindered by Inhibitory Growth Medium.MSystems Oct 2022Predicting the fate of a microbial community and its member species relies on understanding the nature of their interactions. However, designing simple assays that...
Predicting the fate of a microbial community and its member species relies on understanding the nature of their interactions. However, designing simple assays that distinguish between interaction types can be challenging. Here, we performed spent medium assays based on the predictions of a mathematical model to decipher the interactions among four bacterial species: Agrobacterium tumefaciens, Comamonas testosteroni, Microbacterium saperdae, and Ochrobactrum anthropi. While most experimental results matched model predictions, the behavior of did not: its lag phase was reduced in the pure spent media of A. tumefaciens and but prolonged again when we replenished our growth medium. Further experiments showed that the growth medium actually delayed the growth of , leading us to suspect that A. tumefaciens and could alleviate this inhibitory effect. There was, however, no evidence supporting such "cross-detoxification," and instead, we identified metabolites secreted by A. tumefaciens and that were then consumed or "cross-fed" by , shortening its lag phase. Our results highlight that even simple, defined growth media can have inhibitory effects on some species and that such negative effects need to be included in our models. Based on this, we present new guidelines to correctly distinguish between different interaction types such as cross-detoxification and cross-feeding. Communities of microbes colonize virtually every place on earth. Ultimately, we strive to predict and control how these communities behave, for example, if they reside in our guts and make us sick. But precise control is impossible unless we can identify exactly how their member species interact with one another. To find a systematic way to measure interactions, we started very simply with a small community of four bacterial species and carefully designed experiments based on a mathematical model. This first attempt accurately mapped out interactions for all species except one. By digging deeper, we understood that our method failed for that species as it was suffering in the growth medium that we chose. A revised model that considered that growth media can be harmful could then make more accurate predictions. What we have learned with these four species can now be applied to decipher interactions in larger communities.
Topics: Bacteria; Comamonas testosteroni; Models, Theoretical; Microbiota; Actinomycetales
PubMed: 36197097
DOI: 10.1128/msystems.00239-22 -
Applied and Environmental Microbiology Oct 2015Di- and trichloroisocyanuric acids are widely used as water disinfection agents, but cyanuric acid accumulates with repeated additions and must be removed to maintain...
Di- and trichloroisocyanuric acids are widely used as water disinfection agents, but cyanuric acid accumulates with repeated additions and must be removed to maintain free hypochlorite for disinfection. This study describes the development of methods for using a cyanuric acid-degrading enzyme contained within nonliving cells that were encapsulated within a porous silica matrix. Initially, three different bacterial cyanuric acid hydrolases were compared: TrzD from Acidovorax citrulli strain 12227, AtzD from Pseudomonas sp. strain ADP, and CAH from Moorella thermoacetica ATCC 39073. Each enzyme was expressed recombinantly in Escherichia coli and tested for cyanuric acid hydrolase activity using freely suspended or encapsulated cell formats. Cyanuric acid hydrolase activities differed by only a 2-fold range when comparing across the different enzymes with a given format. A practical water filtration system is most likely to be used with nonviable cells, and all cells were rendered nonviable by heat treatment at 70°C for 1 h. Only the CAH enzyme from the thermophile M. thermoacetica retained significant activity under those conditions, and so it was tested in a flowthrough system simulating a bioreactive pool filter. Starting with a cyanuric acid concentration of 10,000 μM, more than 70% of the cyanuric acid was degraded in 24 h, it was completely removed in 72 h, and a respike of 10,000 μM cyanuric acid a week later showed identical biodegradation kinetics. An experiment conducted with water obtained from municipal swimming pools showed the efficacy of the process, although cyanuric acid degradation rates decreased by 50% in the presence of 4.5 ppm hypochlorite. In total, these experiments demonstrated significant robustness of cyanuric acid hydrolase and the silica bead materials in remediation.
Topics: Bacterial Proteins; Biodegradation, Environmental; Comamonadaceae; Hydrolases; Moorella; Pseudomonas; Triazines; Water Pollutants, Chemical; Water Purification
PubMed: 26187963
DOI: 10.1128/AEM.02175-15 -
Phytopathology Jan 2017Bacterial fruit blotch of cucurbits (BFB) is caused by the gram-negative bacterium Acidovorax citrulli, whose populations can be distinguished into two genetically...
Bacterial fruit blotch of cucurbits (BFB) is caused by the gram-negative bacterium Acidovorax citrulli, whose populations can be distinguished into two genetically distinct groups, I and II. Based on visual assessment of BFB severity on cucurbit seedlings and fruit after inoculation under greenhouse conditions, group I A. citrulli strains have been reported to be moderately to highly virulent on several cucurbit hosts, whereas group II strains have exhibited high virulence on watermelon but low virulence on other cucurbits. Additionally, group I strains are recovered from a range of cucurbit hosts, while group II strains are predominantly found on watermelon. The goal of this research was to develop tools to characterize and rapidly distinguish group I and II A. citrulli strains. We first sought to determine whether quantification of A. citrulli colonization of cucurbit seedling tissue reflects the differences between group I and II strains established by visual assessment of BFB symptom severity. Spray inoculation of melon seedlings with cell suspensions containing approximately 1 × 10 CFU/ml resulted in significantly higher (P = 0.01) population growth of M6 (group I; mean area under population growth curve [AUPGC] = 43.73) than that of AAC00-1 (group II; mean AUPGC = 39.33) by 10 days after inoculation. We also investigated the natural spread of bacterial cells and the resulting BFB incidence on watermelon and melon seedlings exposed to three group I and three group II A. citrulli strains under mist chamber conditions. After 5 days of exposure, the mean BFB incidence on melon seedlings exposed to representative group II A. citrulli strains was significantly lower (25 and 3.98% in experiments 1 and 2, respectively) than on melon seedlings exposed to representative group I strains (94.44 and 76.11% in experiments 1 and 2, respectively), and on watermelon seedlings exposed to representative group I and II strains (70 to 93.33%). Finally, we developed a polymerase chain reaction assay based on the putative type III secretion effector gene, Aave_2166, to rapidly distinguish group I and II A. citrulli strains. This assay will be important for future epidemiological studies on BFB.
Topics: Bacterial Proteins; Base Sequence; Citrullus; Comamonadaceae; Cucurbitaceae; DNA Primers; Fruit; Plant Diseases; Polymerase Chain Reaction; Seedlings; Virulence
PubMed: 27618192
DOI: 10.1094/PHYTO-06-16-0245-R -
Frontiers in Cellular and Infection... 2023is a seed-borne bacterial pathogen that causes bacterial fruit blotch in cucurbits and severely affects the production of cucumbers and watermelons globally. In this...
is a seed-borne bacterial pathogen that causes bacterial fruit blotch in cucurbits and severely affects the production of cucumbers and watermelons globally. In this study, we investigated the effects of di-(2-ethylhexyl) phthalate (DEHP) on the growth, metabolism, and virulence of . Bacterial population was not affected by DEHP exposure; moreover, significant changes were not observed in lipid peroxidation, membrane permeability, and nucleic acid leakage. However, palmitoleic acid content was increased in the cell membrane of DEHP-exposed . Further, DEHP exposure increased the activity of TCA cycle-related enzymes, including α-ketoglutarate dehydrogenase and succinyl-CoA synthetase, along with increase in the content of glutamate, succinate, fumarate, and malate in TCA cycle. Additionally, total 270 genes were differentially expressed by the treatment, of which 28 genes were upregulated and 242 genes, including those related to translation, flagellum-dependent cell motility, and flagellum assembly, were downregulated. Regarding virulence traits, swimming activity was decreased in DEHP-exposed ; however, biofilm formation was not affected in assay. Moreover, relative expression of pathogenicity genes, including and , were decreased in DEHP-exposed compared to that of unexposed . Therefore, these results suggest that DEHP accumulation in soil could potentially influence the metabolism and virulence traits of .
Topics: Virulence; Diethylhexyl Phthalate; Comamonadaceae
PubMed: 37692166
DOI: 10.3389/fcimb.2023.1228713 -
Scientific Reports Feb 2018Springtails are important members of the soil fauna and play a key role in plant litter decomposition, for example through stimulation of the microbial activity....
Springtails are important members of the soil fauna and play a key role in plant litter decomposition, for example through stimulation of the microbial activity. However, their interaction with soil microorganisms remains poorly understood and it is unclear which microorganisms are associated to the springtail (endo) microbiota. Therefore, we assessed the structure of the microbiota of the springtail Orchesella cincta (L.) using 16S rRNA gene amplicon sequencing. Individuals were sampled across sites in the field and the microbiota and in particular the endomicrobiota were investigated. The microbiota was dominated by the families of Rickettsiaceae, Enterobacteriaceae and Comamonadaceae and at the genus level the most abundant genera included Rickettsia, Chryseobacterium, Pseudomonas, and Stenotrophomonas. Microbial communities were distinct for the interior of the springtails for measures of community diversity and exhibited structure according to collection sites. Functional analysis of the springtail bacterial community suggests that abundant members of the microbiota may be associated with metabolism including decomposition processes. Together these results add to the understanding of the microbiota of springtails and interaction with soil microorganisms including their putative functional roles.
Topics: Animals; Arthropods; Biodiversity; Chryseobacterium; Comamonadaceae; DNA, Bacterial; Enterobacteriaceae; Microbiota; Pseudomonas; RNA, Ribosomal, 16S; Rickettsiaceae; Sequence Analysis, DNA; Soil Microbiology; Stenotrophomonas
PubMed: 29410494
DOI: 10.1038/s41598-018-20967-0