Strains Of Xanthomonas Campestris Research Articles

Screening of Local Wild Xanthomonas Species for Xanthan Production on Crude Glycerol-based Medium

In this study, the effect of cultivation time on xanthan biosynthesis by different Xanthomonas campestris and Xanthomonas euvesicatoria strains, isolated from crucifers and pepper leaves, respectively, was examined. Xanthan was produced by submerged cultivation on crude glycerol-based medium at a laboratory level under aerobic conditions at 30 °C and 150 rpm for 168 h and 240 h. Bioprocess efficacy was estimated based on the xanthan concentration in media at the end of bioprocess and its average molecular weight. According to the obtained results, Xanthomonas strains have statistically significant effect on xanthan concentration in cultivation media when biosynthesis is performed by X. euvesicatoria strains, and cultivation time has significant effect on this parameter only when bioprocess is performed by X.campestris strains. The combination of Xanthomonas strains and cultivation time has a statistically significant effect on xanthan concentration in medium for both groups of isolates. The obtained results show that all applied Xanthomonas strains and cultivation time as well as their combination have statistically significant effect on average molecular weight of xanthan produced in applied experimental conditions. It is found that X. euvesicatoria strains produce higher amount of xanthan in a shorter period of time (168 h) when compared to the X.campestris strains. Xanthan of higher average molecular weight was produced when cultivation of both groups of isolates was performed for 240 h in applied experimental conditions. Results obtained in this research suggest that X. euvesicatoria strains have the greatest potential for application in biotechnological production of xanthan on crude glycerol-based medium.

Chemical Profile, Elemental Composition, and Antimicrobial Activity of Plants of the Teucrium (Lamiaceae) Genus Growing in Moldova

Teucrium L. is a widely distributed genus often used for the treatment of digestive disorders and respiratory problems. The aim of the present study was to determine the chemical composition of essential oils and elemental content of the plant species Teucrium polium, Teucrium hircanicum, Teucrium botrys, Teucrium chamaedrys, Teucrium flavum, Teucrium orientale, and Teucrium scordium of Moldovan origin, as well as to evaluate the antimicrobial activity of their extracts. The composition of essential oils was determined using gas chromatography–mass spectrometry (GC–MS), and neutron activation analysis (NAA) was used to assess the elemental composition of plants. Antimicrobial tests were performed in vitro on the Bacillus subtilis, Pseudomonas fluorescens, Xanthomonas campestris, Erwinia amylovora, Erwinia carotovora, and Candida utilis strains using the double-dilution method. GC–MS allowed the identification of 59 components of the analyzed essential oils, and showed that the analyzed species belong to four different chemotypes. Using NAA, 18 major and minor elements, the contents of which fell within the value ranges reported for other medicinal herbs of this genus, were identified. The hydroalcoholic extracts from Teucrium spp. exhibited in vitro antibacterial and antifungal activity at 0.03–0.06% and 0.015–0.03%, respectively. The extracts from Teucrium spp. exhibited high antibacterial and antifungal activity, enabling their application for medical purposes.

Two Flagellar mutants of Xanthomonas campestris are characterized by enhanced xanthan production and higher xanthan viscosity

Xanthomonas campestris strains are used world-wide for the production of the industrially important exopolysaccharide xanthan. The high industrial relevance of xanthan can be explained by its extraordinary qualities as rheological control agent in aqueous systems and by its stabilizing properties in suspensions and emulsions. The phytopathogen Xanthomonas campestris is a motile bacterium with one polar flagellum. The flagellum is a cost intensive structure, in terms of energy and building block consumption. Based on the assumption that inhibition of the flagellar biosynthesis and related proton driven motility might be beneficial for the xanthan production in Xcc, two genes (fliC and fliM) were mutated to inhibit the motility. Both mutants Xcc JBL007 fliC– and Xcc JBL007 fliM– showed an increased xanthan production. Remarkably, the produced xanthan from both mutants showed enhanced rheological properties. While the chemical composition of the produced xanthan of the initial and both mutant strains did not change, notable differences in persistence length could be measured via atomic force microscopy. Results presented in this study demonstrate the possibility to further improve the xanthan production by Xcc through rational strain design.

Safety and efficacy of an additive consisting of xanthan gum produced by Xanthomonas campestris strains ■■■■■, ■■■■■ for all animal species (Biopolymer International)

Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on xanthan gum as a feed additive for all animal species. Xanthan gum is manufactured using different production strains belonging to the X. campestris species. The identity of the strains producing xanthan gum was not unambiguously established, data on antimicrobial susceptibility were incomplete, and it was not possible to exclude the presence in the additive of viable cells/DNA of the production strains. Consequently, no conclusions could be drawn on the safety of the X. campestris strains ■■■■■. Considering the above and in the absence of adequate information on the additive under assessment, the FEEDAP Panel cannot conclude on the safety of xanthan gum produced by the X. campestris strains ■■■■■ for the target species, the consumer, the user and the environment. Xanthan gum is considered as an efficacious stabiliser and thickener in feedingstuffs for all animal species at the proposed conditions of use.

In Vitro Antimicrobial Activity of Cinnabarin on Xanthomonas campestris Isolated from Bean Crops of Puebla, Mexico

Phaseolus vulgaris is the most legume cultivated in the world; in Mexico, it is considered the second most important crop after corn. The aim of this research was to determine the characteristics of Xanthomonas campestris strain “Xcf1-APJR” isolated from the leaves of bean crops, and determine the antimicrobial activity of cinnabarin on this strain. Bacterial cultures were obtained from leaves with necrotic leaf spot symptoms of bean plant variety “Flor de Mayo M38” in Puebla, Mexico. The antimicrobial activity of cinnabarin was tested at 7, 14 and 21 days on X. campestris pv. campestris. The Xcf1-APJR strain showed 100% identity with X. campestris pv. campestris as a causal agent of necrotic leaf spot. Treatment with a potato dextrose medium with a dehydrated sugar cane (PDA+C) showed a higher orange pigmentation than the other treatments after 7, 14 and 21 days of incubation and a higher concentration of cinnabarin (54.33 InU/g) with in vitro antimicrobial activity against X. campestris pv. campestris.

Bactericidal Activity of Larrea tridentata Hydroalcoholic Extract against Phytopathogenic Bacteria

Due to the emergence of bacterial resistance in phytopathogenic microorganisms, it is necessary to search for new treatment alternatives for these pathogens. Natural extracts are a potential source of bioactive compounds that can act against such bacterial strains. The antibacterial activity of Larrea tridentata against bacteria with public health importance has been documented; however, few reports cover pathogens associated with the agricultural sector. The aim of the present study was to evaluate the antibacterial activity of Larrea tridentata hydroalcoholic extract (LTHE) and fractions against phytopathogenic bacteria. LTHE was obtained by the maceration technique and then subjected to bipartition using solvents of different polarities. Clavibacter michiganensis sbsp. michiganensis, Pseudomonas syringae, and Xanthomonas campestris strains were used, and their antibiotic sensitivity was determined. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of LTHE and its fractions (aqueous: LTAq-F; organic: LTEtOAc-F) were determined. LTHE and its organic fraction showed bactericidal activity against the three bacteria, showing better activity against X. campestris, exhibiting an MIC of 0.39 mg/mL and an MBC of 0.78 mg/mL. The results show that LTHE and its organic fraction have bactericidal activity in vitro against Clavibacter michiganensis sbsp. michiganensis, Pseudomonas syringae, and Xanthomonas campestris.

Optimisation of xanthan production on glycerol-based medium using response surface methodology

Xanthan is one of the most important biopolymers characterised by a high commercial value. Since the availability of essential nutrients influences its biosynthesis, the aim of this study was the optimisation of carbon, organic and inorganic nitrogen content in glycerol-based medium employing response surface methodology. The cultivation of strain Xanthomonas campestris ATCC 13951 was carried out under appropriate conditions on media with glycerol, peptone and ammonium-nitrate formulated according to Box-Behnken design (33), while the desirability function approach was used for determination of optimal nutrient levels. The final model predicts that the maximal amount of xanthan (12.95 g/L) is produced when the initial contents of glycerol, peptone and ammonium-nitrate in the medium are 32.96 g/L, 0.55 g/L and 0.73 g/L, respectively. To minimize the residual nutrient content and therefore the costs of effluent processing, additional optimisation was performed. In order to validate the optimisation model developed and examine the bioprocess success with crude glycerol as the sole carbon source, additional experiments were performed. The results represent reliable information for further investigations.

New Antimicrobial Phenyl Alkenoic Acids Isolated from an Oil Palm Rhizosphere-Associated Actinomycete, Streptomyces palmae CMU-AB204T.

Basal stem rot (BSR), or Ganoderma rot disease, is the most serious disease associated with the oil palm plant of Southeast Asian countries. A basidiomycetous fungus, Ganoderma boninense, is the causative microbe of this disease. To control BSR in oil palm plantations, biological control agents are gaining attention as a major alternative to chemical fungicides. In the course of searching for effective actinomycetes as potential biological control agents for BSR, Streptomyces palmae CMU-AB204T was isolated from oil palm rhizosphere soil collected on the campus of Chiang Mai University. The culture broth of this strain showed significant antimicrobial activities against several bacteria and phytopathogenic fungi including G. boninense. Antifungal and antibacterial compounds were isolated by antimicrobial activity-guided purification using chromatographic methods. Their structures were elucidated by spectroscopic techniques, including Nuclear Magnetic Resonance (NMR), Mass Spectrometry (MS), Ultraviolet (UV), and Infrared (IR) analyses. The current study isolated new phenyl alkenoic acids 1–6 and three known compounds, anguinomycin A (7), leptomycin A (8), and actinopyrone A (9) as antimicrobial agents. Compounds 1 and 2 displayed broad antifungal activity, though they did not show antibacterial activity. Compounds 3 and 4 revealed a strong antibacterial activity against both Gram-positive and Gram-negative bacteria including the phytopathogenic strain Xanthomonas campestris pv. oryzae. Compounds 7–9 displayed antifungal activity against Ganoderma. Thus, the antifungal compounds obtained in this study may play a role in protecting oil palm plants from Ganoderma infection with the strain S. palmae CMU-AB204T.

Potencijal različitih Xanthomonas campestris sojeva za biosintezu ksantana na otpadnom glicerolu iz proizvodnje biodizela

A rapid expansion of the biodiesel industry has created various ecological issues relative to crude glycerol disposal. Xanthan biosynthesis is considered one of the sustainable solutions for minimizing the adverse effects of waste crude glycerol on the environment. The initial phase of xanthan production on crude glycerol entails the screening of producing microorganism. Therefore, the purpose of this study is to examine the possibility of xanthan production on a crude glycerol-based medium using different Xanthomonas campestris strains. The bioprocesses performed were assessed according to the rheology of the media considered, amounts of xanthan produced and conversion degrees of the most important nutrients present. The pseudoplastic behavior of all the media considered, the amounts of xanthan produced (5.22-7.67 g/L) and the degrees of crude glycerol, total nitrogen and phosphorus conversion (34.44-57.61 %, 23.04-30.35 % and 18.20-22.28 %, respectively) suggest that crude glycerol, after additional bioprocess optimization, can be a suitable raw material for the industrial production of xanthan.

Proizvodnja biobaktericida za kontrolu crne truleži kupusnjača - uticaj izvora azota

The aim of this study was to examine the effects of variation of organic (yeast extract, soybean flour and peptone) and inorganic nitrogen sources (NaNO2, KNO3 and (NH4)2HPO4) in medium for biobactericides production by Bacillus subtilis ATCC 6633. The antibacterial activity of samples against the reference strain Xanthomonas campestris ATCC 13951 and different Xanthomonas strains isolated from cabbage, kale and cauliflower was determined in vitro by discdiffusion method. Following statistical analysis, it was concluded that both nitrogen sources have statistically significant effect on biobactericides production under applied conditions whereby the influence of inorganic nitrogen is more pronounced. The results of Duncan's test suggested that the highest biosynthesis of antibacterial compounds was achieved in both media, with or without yeast extract, when NaNO2 was used as an inorganic nitrogen source. The results from this study can be used in further research to improve biobactericides production by the reference B. subtilis strain.

Rapid Colorimetric Detection of Bacterial Species through the Capture of Gold Nanoparticles by Chimeric Phages.

Rapid, inexpensive, and sensitive detection of bacterial pathogens is an important goal for several aspects of human health and safety. We present a simple strategy for detecting a variety of bacterial species based on the interaction between bacterial cells and the viruses that infect them (phages). We engineer phage M13 to display the receptor-binding protein from a phage that naturally targets the desired bacteria. Thiolation of the engineered phages allows the binding of gold nanoparticles, which aggregate on the phages and act as a signal amplifier, resulting in a visible color change due to alteration of surface plasmon resonance properties. We demonstrate the detection of two strains of Escherichia coli, the human pathogens Pseudomonas aeruginosa and Vibrio cholerae, and two strains of the plant pathogen Xanthomonas campestris. The assay can detect ∼100 cells with no cross-reactivity found among the Gram-negative bacterial species tested here. The assay can be performed in less than an hour and is robust to different media, including seawater and human serum. This strategy combines highly evolved biological materials with the optical properties of gold nanoparticles to achieve the simple, sensitive, and specific detection of bacterial species.

Uticaj izvora ugljenika na proizvodnju ksantana sojevima Xanthomonas spp. izolovanih sa listova paprike

Xanthan is the most important microbial exopolysaccharide used in different branches of food and non-food industry. Due to high consumption of glucose and sucrose, usually utilized carbon sources in many bioprocesses, the most prominent research in xanthan production is related to the isolation of new xanthan producing strains capable to metabolize other carbon sources and to produce xanthan with characteristics appropriate for usage in food industry. The aim of this study was to examine the effect of variation of carbon sources in cultivation media on xanthan production by reference strain Xanthomonas campestris ATCC 13951 and five Xanthomonas strains isolated from infected pepper leaves. Bioprocess efficacy was estimated based on the quantity and quality of biosynthesized xanthan. The obtained results show that both, the selection of the carbon source and selection of producing strain have a statistically significant effect on bioprocess efficacy whereby the influence of carbon sources on the analyzed parameters is more pronounced. It was confirmed that Xanthomonas strains responsible for the production of a large amount of xanthan are not suitable for biosynthesis of good-quality biopolymer. Taking into account all results it can be concluded that the greatest potential in biotechnological xanthan production has strain PFNS PL4 and glucose or starch containing media which is the basis for further research.

Effect of essential oil from Zataria multiflora on local strains of Xanthomonas campestris : An efficient antimicrobial agent for decontamination of seeds of Brassica oleracea var. capitata

Abstract In this study, the effect of the essential oil of Zataria multiflora was examined against the local strains of Xanthomonas campestris isolated from the soil. The pathogenicity of the bacteria was confirmed using seedlings on culture media under sterile conditions. The minimum inhibitory and bactericidal concentrations of Zataria multiflora essential oil and two main components (thymol and carvacrol) were evaluated by the microdilution method in microtiter plates. The morphology of the surface of the seeds and characteristics of the grooves were studied by scanning electron microscopy. Hermetic effect of the essential oil and antimicrobial activity of the solvent on X. campestris were evaluated. Minimum inhibitory and bactericidal concentrations of Zataria multiflora essential oil were 231.8 and 463.5 μg/mL, respectively. The viability of X. campestris in Yeast Malt Broth was reduced by 100% in the presence of Zataria multiflora essential oil (231.8 μg/mL), while, the seeds contaminated with the same count of X. campestris were disinfected at higher concentration of Zataria multiflora essential oil (463.5 μg/mL). Killing of X. campestris cells adhered to the seeds with uneven surface and deep grooves required greater concentrations of the essential oil. The impregnation of the seeds in the essential oil at 463.5 μg/mL showed that a 2-h exposure period causes the least possible damage to the seedlings and is sufficient to prevent the occurrence of the disease caused by X. campestris in Brassica oleracea.

High production of xanthan gum by a glycerol-tolerant strain Xanthomonas campestris WXLB-006

ABSTRACTThe superior properties of xanthan gum make it an industrial aginomoto used in many industries, especially in oil recovery. In the present work, xanthan production from glycerol by a mutant strain Xanthomonas campestris WXLB-006 reached as high as 17.8 g/L in flask culture. With the adoption of pH control, varied aeration and agitation, and varied glycerol feeding strategy, xanthan production reached 33.9 g/L in a 7-L fermenter and fermentation time decreased to 60 hr. Instead of difficultly and costly purifying glycerol, this research provides a very good case for glycerol utilization. At the same time, this is the first report on a high glycerol-tolerant strain for microbial polysaccharide production and 33.9 g/L is the highest production of xanthan gum produced from glycerol so far.

Use of Response Surface Methodology Analysis for Xanthan Biopolymer Production by Xanthomonas campestris: Focus on Agitation Rate, Carbon Source and Temperature

The current study is an attempt to contribute for efficient and cost-effective substrates for xanthan gum production. In this context, the sugar cane molasses wastes can be used as a cheap substrate for xanthan gum production. Xanthan biopolymer production by a novel Xanthomonas campestris strain IBRC-M 10644 was optimized with statistical approaches. Based on the results of Response Surface Methodology (RSM) with Central Composite Design (CCD) technique, a second-order polynomial model was developed and evaluated the effects of variables on the maximum xanthan production. Agitation rate (X1: 200-500 rpm), sugar cane molasses concentration (X2: 30-90 g/L) and operation temperature (X3: 25-35 °C) were the factors investigated. The optimal conditions for maximum yield of xanthan production were derived from agitation rate 500 rpm, carbon source concentration 65 g/L and operation temperature 30°C. Under these conditions, xanthan and biomass production were found to be 16.03 g/L and 1.37 g/L, respectively. Our results signify that the sugar cane molasses can be used as a cheap substrate for xanthan biopolymer production.

Characterization of xanthan gum produced from glycerol by a mutant strain Xanthomonas campestris CCTCC M2015714

Xanthan gum was produced by a mutant strain X. campestris CCTCC M2015714 with glycerol as the sole carbon source. The monosaccharide composition and molar ratio of xanthan gum produced from glycerol are glucose: mannose: glucuronic acid=2.0:1.65:1.0. Meanwhile, chemical structure of xanthan gum produced from glycerol is similar to that of the commercial xanthan through FT-IR and NMR. Remarkably, the molecular weight of xanthan gum produced using our method (3.0±0.14×106Da) is about half that of the commercial one (5.8±0.25×106Da), and the consistency index (K) of which is less than 1/10 that of the commercial xanthan. This work paves the way for xanthan production from glycerol and is useful for studying the structure/application of xanthan gum.

Compatible and incompatible pathogen–plant interactions differentially affect plant volatile emissions and the attraction of parasitoid wasps

Summary The effects of multiple insect attacks on herbivore‐induced plant volatiles and carnivorous arthropods are increasingly studied. Phytopathogens also represent an important threat to plants, and plant defence strategies against pathogens and insects are strongly interconnected, yet the potential impact of pathogens on insect‐induced volatiles has been largely overlooked, and degree of pathogenicity is rarely considered. We investigated how pathogen challenge, with virulent and avirulent strains of Xanthomonas campestris either alone or with simultaneous Pieris brassicae caterpillar herbivory, affected the volatile emissions of Brassica nigra plants. The impact of these volatiles on the foraging behaviour of Cotesia glomerata parasitoids wasps was then assessed. Pathogens themselves induced volatiles that were highly attractive to parasitoids, and enhanced the attractiveness of host‐infested plant volatiles. Chemical analyses revealed that virulent and avirulent strains differentially induced plant volatiles, with primarily sesquiterpene, homoterpene and green leaf volatile compounds contributing to the differences. Strong similarities were found in the blends induced by the virulent strain and caterpillar herbivory. Challenge by either virulent or avirulent pathogens has a significant impact on plant chemistry and its interactions with other community members, demonstrating the importance of integrating pathogen‐ and insect‐based research to broaden our knowledge of plant defences under conditions of increasing complexity. A lay summary is available for this article.

Identification of a small molecule signaling factor that regulates the biosynthesis of the antifungal polycyclic tetramate macrolactam HSAF in Lysobacter enzymogenes.

Lysobacter species are emerging as new sources of antibiotics. The regulation of these antibiotics is not well understood. Here, we identified a small molecule metabolite (LeDSF3) that regulates the biosynthesis of the antifungal antibiotic heat-stable antifungal factor (HSAF), a polycyclic tetramate macrolactam with a structure and mode of action distinct from the existing antifungal drugs. LeDSF3 was isolated from the culture broth of Lysobacter enzymogenes, and its chemical structure was established by NMR and MS. The purified compound induced green fluorescence in a reporter strain of Xanthomonas campestris, which contained a gfp gene under the control of a diffusible signaling factor (DSF)-inducible promoter. Exogenous addition of LeDSF3 in L. enzymogenes cultures significantly increased the HSAF yield, the transcription of HSAF biosynthetic genes, and the antifungal activity of the organism. The LeDSF3-regulated HSAF production is dependent on the two-component regulatory system RpfC/RpfG. Moreover, LeDSF3 upregulated the expression of the global regulator cAMP receptor-like protein (Clp). The disruption of clp led to no HSAF production. Together, the results show that LeDSF3 is a fatty acid-derived, diffusible signaling factor positively regulating HSAF biosynthesis and that the signaling is mediated by the RfpC/RpfG-Clp pathway. These findings may facilitate the antibiotic production through applied genetics and molecular biotechnology in Lysobacter, a group of ubiquitous yet underexplored microorganisms.

Involvement of proline oxidase (PutA) in programmed cell death of Xanthomonas.

Xanthomonas campestris strains have been reported to undergo programmed cell death (PCD) in a protein rich medium. Protein hydrolysates used in media such as nutrient broth comprise of casein digest with abundance of proline and glutamate. In the current study, X. campestris pv. campestris (Xcc) cells displayed PCD when grown in PCD inducing medium (PIM) containing casein tryptic digest. This PCD was also observed in PCD non-inducing carbohydrate rich medium (PNIM) fortified with either proline or proline along with glutamate. Surprisingly, no PCD was noticed in PNIM fortified with glutamate alone. Differential role of proline or glutamate in inducing PCD in Xcc cells growing in PNIM was studied. It was found that an intermediate product of this oxidation was involved in initiation of PCD. Proline oxidase also called as proline utilization A (PutA), catalyzes the two step oxidation of proline to glutamate. Interestingly, higher PutA activity was noticed in cells growing in PIM, and PCD was found to be inhibited by tetrahydro-2-furoic acid, a competitive inhibitor of this enzyme. Further, PCD was abolished in Xcc ΔputA strain generated using a pKNOCK suicide plasmid, and restored in Xcc ΔputA strain carrying functional PutA in a plasmid vector. Xanthomonas cells growing in PIM also displayed increased generation of ROS, as well as cell filamentation (a probable indication of SOS response). These filamented cells also displayed enhanced caspase-3-like activity during in situ labeling using a fluorescent tagged caspase-3 inhibitor (FITC-DEVD-FMK). The extent of PCD associated markers such as DNA damage, phosphatidylserine externalization and membrane depolarization were found to be significantly enhanced in wild type cells, but drastically reduced in Xcc ΔputA cells. These findings thus establish the role of PutA mediated proline oxidation in regulating death in stressed Xanthomonas cells.

Biological control of bacterial spot on peach by nonpathogenic Xanthomonas campestris strains AZ98101 and AZ98106

A suspension of nonpathogenic Xanthomonas campestris (nXc) strain AZ98101 or AZ98106 was sprayed on peach trees in biological control tests against bacterial spot caused by Xanthomonas arboricola pv. pruni. Treatment with each strain reduced the number of leaves with spots. Meta-analysis of the results from seven field trials showed an integrated risk ratio (the ratio of leaf spot incidence on inoculated leaves to incidence on control leaves) of 0.46 by treatment with AZ98101 and 0.54 by AZ98106, indicating that leaf spot incidence was significantly reduced by each strain. Each also significantly reduced the incidence of fruit spot. The risk ratio with AZ98101 was significantly lower than that with AZ98106. The population of AZ98101R-1, a rifampicin-resistant mutant of AZ98101, was 6.3 × 103 CFU/g (fresh mass) on leaves and 8.0 × 103 CFU/g on fruit at 12 days after inoculation, but was undetectable (<102 CFU/g) by 24 days. This is the first report that nXc strains AZ98101 and AZ98106 effectively control bacterial spot on peach.