Phenotypic and Molecular-Phylogenetic Analyses Reveal Distinct Features of Crown Gall-Associated Xanthomonas Strains.

In summer 2019, widespread occurrence of crown gall disease caused by Agrobacterium spp. was observed on commercially grown ornamental plants in southern Iran. Beside agrobacteria, pale yellow-pigmented Gram-negative strains resembling the members of Xanthomonas were also associated with crown gall tissues on weeping fig (Ficus benjamina) and Amaranthus sp. plants. The purpose of the present study was to characterize the crown gall-associated Xanthomonas strains using plant inoculation assays, molecular-phylogenetic analyses, and comparative genomics approaches. Pathogenicity tests showed that the Xanthomonas strains did not induce disease symptoms on their host of isolation. However, the strains induced hypersensitive reaction on tobacco, geranium, melon, squash, and tomato leaves via leaf infiltration. Multilocus sequence analysis suggested that the strains belong to clade IA of Xanthomonas, phylogenetically close to Xanthomonas translucens, X. theicola, and X. hyacinthi. Average nucleotide identity and digital DNA-DNA hybridization values between the whole-genome sequences of the strains isolated in this study and reference Xanthomonas strains are far below the accepted thresholds for the definition of prokaryotic species, signifying that these strains could be defined as two new species within clade IA of Xanthomonas. Comparative genomics showed that the strains isolated from crown gall tissues are genetically distinct from X. translucens, as almost all the type III secretion system genes and type III effectors are lacking in the former group. The data obtained in this study provide novel insight into the breadth of genetic diversity of crown gall-associated bacteria and pave the way for research on gall-associated Xanthomonas-plant interactions. IMPORTANCE Tumorigenic agrobacteria-members of the bacterial family Rhizobiaceae-cause crown gall and hairy root diseases on a broad range of plant species. These bacteria are responsible for economic losses in nurseries of important fruit trees and ornamental plants. The microclimate of crown gall and their accompanying microorganisms has rarely been studied for the microbial diversity and population dynamics of gall-associated bacteria. Here, we employed a series of biochemical tests, pathogenicity assays, and molecular-phylogenetic analyses, supplemented with comparative genomics, to elucidate the biological features, taxonomic position, and genomic repertories of five crown gall-associated Xanthomonas strains isolated from weeping fig and Amaranthus sp. plants in Iran. The strains investigated in this study induced hypersensitive reactions (HR) on geranium, melon, squash, tobacco, and tomato leaves, while they were nonpathogenic on their host of isolation. Phylogenetic analyses and whole-genome-sequence-based average nucleotide identity (ANI)/digital DNA-DNA hybridization (dDDH) calculations suggested that the Xanthomonas strains isolated from crown gall tissues belong to two taxonomically unique clades closely related to the clade IA species of the genus, i.e., X. translucens, X. hyacinthi, and X. theicola.

Selection of rhizobacteria isolates with bioherbicide potential against Palmer amaranth (Amarathus palmeri S. Wats.).

Crop yield and quality are affected by the presence of weeds such as Palmer amaranth. Chemical control is the most commonly used method to eradicate weeds, due to its quickness and efficacy. However, the inappropriate use of chemical herbicides can lead to resistant weed biotypes, as well as problems related to environmental pollution and human health hazards. One ecological alternative to combat weeds is the use of deleterious rhizobacteria (DRB). We evaluated the potential bioherbicidal effect in 15 DRB isolates from the rhizosphere of Palmer amaranth, both in vitro and in greenhouse tests. Isolates TR10 and TR18 inhibited seed germination in vitro, whereas the TR25 and TR36 isolates showed the potential to inhibit Palmer amaranth plant development in growth room assays without affecting maize and common bean germination and growth. These four isolates were molecularly identified as either Pseudomonas sp. (TR10 and TR36), Enterobacter sp. (TR18), or Bacillus sp. (TR25). In addition, the production of volatiles and diffusible metabolites were identified as possible mechanisms of germination arrestment and plant development inhibition. This study suggests the bioherbicide potential of some indigenous rhizobacteria against Palmer amaranth.

Lactobacillus plantarum and molasses alter dynamic chemical composition, microbial community, and aerobic stability of mixed (amaranth and rice straw) silage.

BACKGROUND: The objective was to determine how molasses and Lactobacillus plantarum affect chemical composition, fermentation quality, aerobic stability, and the microbial community of an ensiled mixture of amaranth (Amaranthus hypochondriaus, AF) and rice straw. Treatments were control (C, no addition), L. plantarum (L; 2 × 105 cfu g-1 fresh weight), molasses (M; 40 g kg-1 fresh matter), and their combination (LM). All treatments were ensiled for 1, 3, 5, 7, and 30 days. RESULTS: All additives improved fermentation quality with greater lactic acid (LA), acetic acid, and lower pH than C silage over the ensiling period. The LM silage combination optimized fermentability, manifested as greater LA contents and a more rapid pH reduction during the first 7 days of ensiling than L or M silages. After 30 days of ensiling, inoculant L. plantarum increased Lactobacillus abundance and reduced bacterial diversity and Enterobacteriaceae abundance compared with silage treated with molasses. Molasses addition reduced the relative concentration of structural carbohydrates (neutral and acid detergent fiber, and hemicellulose) after 30 days of ensiling. Finally, there was spoilage after 2 days and 4 days of aerobic exposure in C and LM silages respectively, whereas L silage had not spoiled after 4 days. CONCLUSIONS: Although the combination of L. plantarum and molasses further optimized fermentation characteristics, L silage had better aerobic stability. © 2021 Society of Chemical Industry.

910 metagenome-assembled genomes from the phytobiomes of three urban-farmed leafy Asian greens.

The genome sequences of many microbial species from the phytobiomes of several leafy Asian greens remain unknown. Here, we address this gap by reconstructing 910 prokaryotic draft genomes from 24 leaf, 65 root, 12 soil, and 6 compost metagenomes from the seedling and adult developmental stages of three leafy Asian greens - Brassica rapa var. parachinensis, Brassica oleracea var. alboglabra and Amaranthus spp. - grown in a commercial, soil-based urban farm. Of these, 128 are near-complete (>90% completeness, <5% redundancy), 540 are substantially complete (≥70% completeness, <10%, redundancy), while the rest have a completeness ≥50% and redundancy <10%. The draft genomes together span 292 bacterial and 3 archaeal species, a subset of which are from underrepresented genus-level lineages in public databases. We expect our dataset to facilitate a wide range of comparative studies that seek to understand the different functional aspects of vegetable crop phytobiomes and for devising new strategies for microbial cultivation in the future.

Enhancement of γ-aminobutyric acid (GABA) production by Lactobacillus brevis CRL 2013 based on carbohydrate fermentation.

Gamma aminobutyric acid (GABA) is a non-protein amino acid that is widely distributed in nature and its physiological importance goes beyond its role as an inhibitory neurotransmitter of the central nervous system in mammals. Since microbial fermentation is one of the most promising methods to obtain GABA, the production of this metabolite by several strains of lactic acid bacteria isolated from quinoa and amaranth sourdoughs was investigated. Lactobacillus brevis CRL 2013 produced the highest GABA levels, reaching 265 mM when optimal culture conditions were set up. The fermentative profile showed that CRL 2013 was able to catabolize carbohydrates through the phosphoketolase pathway yielding variable amounts of lactic acid, acetate and ethanol, which depended on the type of carbon source available and the presence of external electron acceptors such as fructose. Enhanced growth parameters and low GABA synthesis were associated to pentose fermentation. This impairment on GABA production machinery was partially overpassed by the addition of ethanol to the culture media. These results support the potential use of L. brevis CRL 2013 as a starter culture for the manufacture of GABA-enriched functional foods and provide further insights to the understanding of the GAD system regulation in lactic acid bacteria.

Fermentation of pseudocereals quinoa, canihua, and amaranth to improve mineral accessibility through degradation of phytate.

BACKGROUND: Pseudocereals are nutrient-rich grains with high mineral content but also phytate content. Phytate is a mineral absorption inhibitor. The study's aim was to evaluate phytate degradation during spontaneous fermentation and during Lactobacillus plantarum 299v® fermentation of quinoa, canihua, and amaranth grains and flours. It also aimed to evaluate the accessibility of iron, zinc, and calcium and to estimate their bioavailability before and after the fermentation of flours with starter culture. Lactic acid, pH, phytate, and mineral content were analyzed during fermentation. RESULTS: Higher phytate degradation was found during the fermentation of flours (64-93%) than during that of grains (12-51%). Results suggest that phytate degradation was mainly due to endogenous phytase activity in different pseudocereals rather than the phytase produced by added microorganisms. The addition of Lactobacillus plantarum 299v® resulted in a higher level of lactic acid (76.8-82.4 g kg-1 DM) during fermentation, and a relatively quicker reduction in pH to 4 than in spontaneous fermentation. Mineral accessibility was increased (1.7-4.6-fold) and phytate : mineral molar ratios were reduced (1.5-4.2-fold) in agreement with phytate degradation (1.8-4.2-fold) in fermented flours. The reduced molar ratios were still above the threshold value for the improved estimated mineral bioavailability of mainly iron. CONCLUSION: Fermentation proved to be effective for degrading phytate in pseudocereal flours, but less so in grains. Fermentation with Lactobacillus plantarum 299v® improved mineral accessibility and estimated bioavailability in flours. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Applying ß-cyclodextrin to amaranth inoculated with white-rot fungus for more efficient remediation of soil co-contaminated with Cd and BDE-209.

A pot experiment was conducted to investigate the effect of a series of ß-cyclodextrin (ß-CD) concentrations on bioremediation of soil co-contaminated with Cd and BDE-209 using amaranth and the white-rot fungus Phanerochaete chrysosporium, with BDE-209 degrading ability. Results showed that the white-rot fungus was beneficial to the growth of amaranth, Cd uptake and BDE-209 degradation. Addition of ß-CD further increased biomass of both shoots and roots, shoot Cd concentrations and contents, chlorophyll concentrations and soil manganese peroxidase (MnP) activities. Furthermore, well-organized mesophyll cells were observed in ß-CD treatments, implying that the combination of white-rot fungus and ß-CD can alleviate the stresses of Cd and BDE-209 to mesophyll cells. The BDE-209 degradation rate was positively correlated to ß-CD concentration and MnP activity in soil. Our results also revealed that RF+ß0.8 treatment possessed the greatest Cd removal efficiency due to its well-configured mesophyll cells and the highest shoot biomass, chlorophyll concentration, and shoot Cd concentration. Considering simultaneous removal of Cd and BDE-209 from soil, using 0.8% ß-CD to amaranth inoculated with white-rot fungus is a promising way forward for the phytoremediation of soil co-contaminated with Cd and BDE-209. A high percentage of mono-BDE was detected in inoculated amaranth, suggesting that BDE-209 was debrominated into low brominated PBDEs by the fungus in soil, which were then absorbed and further debrominated into mono-BDE in the plant.

Amaranth seeds (Amaranthus palmeri L.) as novel feedstock for biodiesel production by oleaginous yeast.

The potential of lipid accumulation by oleaginous yeast Cryptococcus vishniaccii grown on amaranth seed aqueous extract (AAE) media was assessed. Maximum cell biomass productivity of 104 mg/L/h, lipid productivity of 54 mg/L/h, and lipid content of 52.31% were recorded on AAE when carbon to nitrogen (C:N) ratio increased from 134 to 147 after removal of ammonia nitrogen. The lipid droplet (LD) size (2.32 ± 0.38 µm) was visualized by fluorescence microscopy using Nile red stain indicating maximum accumulated triacylglycerol (TAG) at C:N 147. Fatty acid methyl ester (FAME) profile obtained after transesterification of extracted lipid revealed the presence of palmitic acid (16:0), palmitoleic acid (16:1), stearic acid (18:0), oleic acid (18:1), and linoleic acid (18:2). Data showed the presence of high monounsaturated fatty acid (MUFA) content (68.17%) depicting improved winter operating conditions of biodiesel. Various quality parameters of biodiesel were evaluated and compared to the American and European biodiesel standards specifications. Based on the lipid productivity, distribution of fatty acids, and evaluated properties obtained; the lipid accumulation by C. vishniaccii utilizing amaranth seeds as substrate could serve as a feasible feedstock for biodiesel production.

Biodiversity and technological potential of lactic acid bacteria isolated from spontaneously fermented amaranth sourdough.

UNLABELLED: Spontaneous fermented sourdoughs prepared from amaranth flour were investigated for the presence of autochthonous lactic acid bacteria (LAB) predominating microbiota. The doughs were fermented with daily backslopping on a laboratory scale at 30°C for 10 days. LAB counts ranged from 2·60 to 8·54 log CFU g(-1) with a pH declined from 6·2 to 3·8 throughout fermentation. The combined use of randomly amplified polymorphic DNA (RAPD)-PCR analysis and sequence analysis of 16S rRNA was applied for LAB intraspecies differentiation and taxonomic identification, respectively. Enterococcus, Pediococcus and Lactobacillus species were present in amaranth sourdoughs (AS). After the first refreshment step, Lactobacillus plantarum dominated AS until the end of fermentation. In coincidence, when DGGE analysis was performed, the occurrence of a progressive change in bacterial communities allowed the selection of Lact. plantarum as a dominant species. Moreover, technological, functional and safety characteristics of representative RAPD-biotypes were investigated. Lact. plantarum CRL1898 was selected as a potential candidate for gluten-free amaranth sourdough starter. SIGNIFICANCE AND IMPACT OF THE STUDY: Nowadays, there is an increasing interest in ancient noncereal gluten-free (GF) crops such as amaranth, due to their reported nutritional and health benefits. However, the use of these grains is still limited to traditional foods and bread making processes that are not yet well standardized. Results on the dynamics of autochthonous lactic acid bacteria (LAB) microbiota during laboratory spontaneous amaranth sourdoughs (AS) fermentation will contribute to overcome challenges for GF-fermented products development. In addition, knowledge about LAB diversity involving Enterococcus, Pediococcus and Lactobacillus species, with Lactobacillus plantarum predominating during AS fermentation, and their technological and functional properties provides the basis for the selection of autochthonous strains as starters cultures for novel gluten-free bakery products with enhanced nutritional, sensory and/or safety quality.

Effects of ensiling treatments on lactic acid production and supplementary methane formation of maize and amaranth--an advanced green biorefining approach.

A green biorefinery enables the material and energetic use of biomass via lactic acid and methane production. Different ensiling techniques were applied to maize and amaranth with the aim to increase the amount of lactic acid in the silage. In addition the methane formation potential of the ensiled samples and the remaining solid residues after separating the organic juice were assessed. Treating maize with homofermentative lactic acid bacteria in combination with carbonated lime increased the amount of lactic acid about 91.9%. For amaranth no additional lactic acid production was obtained by treating the raw material. Specific methane yields for the solid residues of amaranth were significantly lower in comparison to the corresponding silages. The most promising treatment resulted in a production of 127.9±4.1 g kg(-1) DM lactic acid and a specific methane yield for the solid residue of 349.5±6.6 lN kg(-1) ODM.

Treatment of Amaranthus cruentus with chemical and biological inducers of resistance has contrasting effects on fitness and protection against compatible Gram positive and Gram negative bacterial pathogens.

Amaranthus cruentus (Ac) plants were treated with the synthetic systemic acquired resistance (SAR) inducer benzothiadiazole (BTH), methyl jasmonate (MeJA) and the incompatible pathogen, Pseudomonas syringae pv. syringae (Pss), under greenhouse conditions. The treatments induced a set of marker genes in the absence of pathogen infection: BTH and Pss similarly induced genes coding for pathogenesis-related and antioxidant proteins, whereas MeJA induced the arginase, LOX2 and amarandin 1 genes. BTH and Pss were effective when tested against the Gram negative pathogen Ps pv. tabaci (Pst), which was found to have a compatible interaction with grain amaranth. The resistance response appeared to be salicylic acid-independent. However, resistance against Clavibacter michiganensis subsp. michiganensis (Cmm), a Gram positive tomato pathogen also found to infect Ac, was only conferred by Pss, while BTH increased susceptibility. Conversely, MeJA was ineffective against both pathogens. Induced resistance against Pst correlated with the rapid and sustained stimulation of the above genes, including the AhPAL2 gene, which were expressed both locally and distally. The lack of protection against Cmm provided by BTH, coincided with a generalized down-regulation of defense gene expression and chitinase activity. On the other hand, Pss-treated Ac plants showed augmented expression levels of an anti-microbial peptide gene and, surprisingly, of AhACCO, an ethylene biosynthetic gene associated with susceptibility to Cmm in tomato, its main host. Pss treatment had no effect on productivity, but compromised growth, whereas MeJA reduced yield and harvest index. Conversely, BTH treatments led to smaller plants, but produced significantly increased yields. These results suggest essential differences in the mechanisms employed by biological and chemical agents to induce SAR in Ac against bacterial pathogens having different infection strategies. This may determine the outcome of a particular plant-pathogen interaction, leading to resistance or susceptibility, as in Cmm-challenged Ac plants previously induced with Pss or BTH, respectively.

The ecological roles of Bacillus thuringiensis within phyllosphere environments.

Bacillus thuringiensis (Bt) is one of the most used bio-control agents to control plant insects, but little is known about its effect on the microbial population and communities on plant leaves. With the culture dependent method, it has been observed that the dynamics of Bt within the phyllosphere varied dependent on both the doses of Bt sprayed on the leaves and the plant species, however, Bt's population size kept stable at about 1000 cfu g(-1) after 15 d since inoculation. By comparing the bacterial abundances and community structures within the phyllosphere of three plant species, we confirmed that Bt at the doses of 1.5×10(7) and 1.5×10(9) cfu mL(-1) respectively did not significantly influence the natural bacterial population size on the leaf surfaces based on culture dependent assay. However, based on culture independent denaturing gradient gel electrophoresis (DGGE), Shannon-Wiener index (H') and Unweighted Pair Group Method with Arithmetic Mean (UPGMA) analysis, Bt has a significant influence on the bacterial communities within the phyllosphere of amaranth and cotton, but not rice. These results indicate that Bt exhibits different behaviors and ecological roles on the microbial diversity within the phyllosphere, and its environmental safety has to be concerned and evaluated in the future.

Burkholderia ambifaria and B. caribensis promote growth and increase yield in grain amaranth (Amaranthus cruentus and A. hypochondriacus) by improving plant nitrogen uptake.

Grain amaranth is an emerging crop that produces seeds having high quality protein with balanced amino-acid content. However, production is restricted by agronomic limitations that result in yields that are lower than those normally produced by cereals. In this work, the use of five different rhizobacteria were explored as a strategy to promote growth and yields in Amaranthus hypochondriacus cv. Nutrisol and A. cruentus cv. Candil, two commercially important grain amaranth cultivars. The plants were grown in a rich substrate, high in organic matter, nitrogen (N), and phosphorus (P) and under greenhouse conditions. Burkholderia ambifaria Mex-5 and B. caribensis XV proved to be the most efficient strains and significantly promoted growth in both grain amaranth species tested. Increased grain yield and harvest index occurred in combination with chemical fertilization when tested in A. cruentus. Growth-promotion and improved yields correlated with increased N content in all tissues examined. Positive effects on growth also occurred in A. cruentus plants grown in a poor soil, even after N and P fertilization. No correlation between non-structural carbohydrate levels in roots of inoculated plants and growth promotion was observed. Conversely, gene expression assays performed at 3-, 5- and 7-weeks after seed inoculation in plants inoculated with B. caribensis XV identified a tissue-specific induction of several genes involved in photosynthesis, sugar- and N- metabolism and transport. It is concluded that strains of Burkholderia effectively promote growth and increase seed yields in grain amaranth. Growth promotion was particularly noticeable in plants grown in an infertile soil but also occurred in a well fertilized rich substrate. The positive effects observed may be attributed to a bio-fertilization effect that led to increased N levels in roots and shoots. The latter effect correlated with the differential induction of several genes involved in carbon and N metabolism and transport.

Recombinant amaranth cystatin (AhCPI) inhibits the growth of phytopathogenic fungi.

Phytocystatins are cysteine proteinase inhibitors from plants implicated in defense mechanisms against insects and plant pathogens. We have previously characterized an amaranth cystatin cDNA and analyzed its response to different kinds of abiotic stress [37]. In order to characterize amaranth cystatin, the coding sequence was expressed in Escherichia coli using the pQE-2 vector. Recombinant cystatin was predominantly found in the soluble fraction of the cell extract. Large amounts (266 mgL(-1)) of pure recombinant protein were obtained by affinity chromatography in a single step of purification. The amaranth cystatin with a pI 6.8 and an apparent 28 kDa molecular mass inhibited papain (E.C.3.4.22.2) (Ki 115 nM), ficin (E.C.3.4.22.3) (Ki 325 nM) and cathepsin L (E.C.3.4.22.15) (Ki 12.7 nM) but not stem bromelain (E.C.3.4.22.32), and cathepsin B (E.C.3.4.22.1) activities, in colorimetric assays. Furthermore, it was able to arrest the fungal growth of Fusarium oxysporum, Sclerotium cepivorum and Rhyzoctonia solani. It was further demonstrated that recombinant AhCPI is a weak inhibitor of the endogenous cysteine proteinase activities in the fungal mycelium. These findings contribute to a better understanding of the amaranth cystatin activity and encourage further studies of this protein.

Isolation, molecular characterization and growth-promotion activities of a cold tolerant bacterium Pseudomonas sp. NARs9 (MTCC9002) from the Indian Himalayas.

A bacterium that grows and expresses plant growth promotion traits at 4 degrees C was isolated from the rhizospheric soil of Amaranth, cultivated at a high altitude location in the North Western Indian Himalayas. The isolate was Gram negative and the cells appeared as rods (2.91 x 0.71 microm in size). It grew at temperatures ranging from 4 to 30 degrees C, with a growth optimum at 28 degrees C. It exhibited tolerance to a wide pH range (5-10; optimum 8.0) and salt concentrations up to 6% (wt/vol). Although it was sensitive to Rifampicin (R 20 microg mi-1), Gentamicin (G 3 microg mi-1), and Streptomycin (S 5 microg mi-1), it showed resistance to higher concentrations of Ampicillin (A 500 microg mi-1), Penicillin (P 300 microg mi-1), Polymixin B sulphate (Pb 100 microg mi-1) and Chloramphenicol (C 200 microg mi-1). The 16S rRNA sequence analysis revealed maximum identity with Pseudomonas lurida. The bacterium produced indole Acetic Acid (IAA) and solubilizes phosphate at 4, 15 and 28 degrees C. It also retained its ability to produce rhamnolipids and siderophores at 15 degrees C. Seed bacterization with the isolate enhanced the germination, shoot and root lengths of thirty-day-old wheat seedlings by 19.2, 30.0 & 22.9% respectively, as compared to the un-inoculated controls.

Evaluation of lactic acid bacteria for sourdough fermentation of amaranth.

Spontaneous fermented sourdoughs prepared from five amaranth flours were investigated for the presence of lactic acid bacteria predominating the autochthonous microbiota and thus may be suitable as starter cultures. The doughs were fermented with daily back-slopping on a laboratory scale at 30 degrees C for 10 days. Each day, pH-values and total titratable acidity degrees were determined and samples were analyzed for lactic acid bacteria and yeasts by cultural methods. The identity of the strains was tracked with randomly amplified polymorphic DNA-PCR during fermentation. Taxonomic identity of the strains was revealed by sequence analysis of 16S rDNA. Sugar and organic acid profiles of fermented doughs were determined with HPLC. The strains Lactobacillus plantarum RTa12, L. sakei RTa14, and Pediococcus pentosaceus RTa11 were selected and applied as starters in laboratory scale fermentations. All strains were predominant in repeated experiments, both as single strains and in combination, regardless of the amaranth flour used. The competitiveness of the strains L. plantarum RTa12 and P. pentosaceus RTa11 was characterized in further growth experiments. Both strains facilitated fast declines of pH-values, overgrew the autochthonous microbiota, and allowed stable fermentation characteristics at different temperatures. Thus, the characterized strains may be considered as candidates for amaranth sourdough starter cultures.

Combined effects of chitosan and MAP to improve the microbial quality of amaranth homemade fresh pasta.

In this work a study on the combined effects of chitosan and modified atmosphere packaging (MAP) to improve the microbiological quality of amaranth-based homemade fresh pasta is presented. In particular, two different chitosan concentrations were combined to three different MAP conditions and tested against the following spoilage microorganisms: mesophilic bacteria, Staphylococcus spp., yeasts, moulds and total coliforms. Their viable cell concentrations were monitored for about 2 months at 4 degrees C. Results suggest that there is a combined effect between MAP and chitosan in delaying the microbial quality loss of pasta during storage. Moreover, it was also found that among the tested MAP conditions, the combination of 30:70 N2:CO2 is the most efficient, promoting an extension of the microbial acceptability limit beyond two months.

Use of natural compounds to improve the microbial stability of Amaranth-based homemade fresh pasta.

A study on the use of natural antimicrobial compounds to improve the microbiological stability of refrigerated amaranth-based homemade fresh pasta is presented in this work. In particular, the antimicrobial activity of thymol, lemon extract, chitosan and grapefruit seed extract (GFSE) has been tested against mesophilic and psychrotrophic bacteria, total coliforms, Staphylococcus spp., yeasts and moulds. A sensory analysis on both fresh and cooked pasta was also run. Results suggest that chitosan and GFSE strongly increase the microbial acceptability limit of the investigated spoilage microorganisms, being the former the most effective. Thymol efficiently reduces the growth of mesophilic bacteria, psychrotrophic bacteria and Staphylococcus spp., whereas it does not affect, substantially, the growth cycle of total coliforms. Lemon extract is the less effective in preventing microbial growth. In fact, it is able to delay only total mesophilic and psychrotrophic bacterial evolution. From a sensorial point of view no significant differences were recorded between the control samples and all the types of loaded amaranth-based pasta.

Isolation, molecular characterization and growth-promotion activities of a cold tolerant bacterium Pseudomonas sp. NARs9 (MTCC9002) from the Indian Himalayas

A bacterium that grows and expresses plant growth promotion traits at 4°C was isolated from the rhizospheric soil of Amaranth, cultivated at a high altitude location in the North Western Indian Himalayas. The isolate was Gram negative and the cells appeared as rods (2.91 x 0.71 μm in size). It grew at temperatures ranging from 4 to 30°C, with a growth optimum at 28°C. It exhibited tolerance to a wide pH range (5-10; optimum 8.0) and salt concentrations up to 6 percent (wt/vol). Although it was sensitive to Rifampicin (R 20 μg mi-1), Gentamicin (G 3 μg mi-1), and Streptomycin (S 5 μg mi-1), it showed resistance to higher concentrations of Ampicillin (A 500 μg mi-1), Penicillin (P 300 μg mi-1), Polymixin B sulphate (Pb 100 μg mi-1) and Chloramphenicol (C 200 μg mi-1). The 16S rRNA sequence analysis revealed maximum identity with Pseudomonas lurida. The bacterium produced indole Acetic Acid (IAA) and solubilizes phosphate at 4, 15 and 28°C. It also retained its ability to produce rhamnolipids and siderophores at 15°C. Seed bacterization with the isolate enhanced the germination, shoot and root lengths of thirty-day-old wheat seedlings by 19.2, 30.0 & 22.9 percent respectively, as compared to the un-inoculated controls.

Screening for soil streptomycetes from North Jordan that can produce herbicidal compounds.

A total of 231 different soil Streptomyces isolates were recovered from 16 different locations in North Jordan. They were assessed for their phytotoxic activity on seeds of cucumber (Cucumis sativus L.) and ryegrass (Lolium perenne L.) placed adjacent to a 2 cm wide Streptomyces culture strips grown at 28C degrees for 3 weeks on starch casein nitrate (SCN) agar. Phytotoxicity was ascertained on the basis of suppressed seed germination, discoloration of the root tip, reduced root and the shoot growth and eventual death of the root. Twenty one of the isolates exhibited adverse effect against growth of germinated cucumber seeds, germination and growth of ryegrass seeds. Using filter paper bioassay method, culture filtrate from the SCN broth of the isolate R9; identified as Streptomyces aburaviensis, significantly inhibited seed germination, radicle and shoot growth ofryegrass, reduced radicle and shoot growth of cucumber and suppressed the shoot growth of milk thistle (Silybum marianum L.). Also, culture filtrate from the glucose-peptone-molasses (GPM) broth diluted (1:1) with sterilized distilled water caused complete inhibition of seed germination of redroot pigweed (Amaranthus retroflexus L.). Dichloromethane extracted fraction of S. aburaviensis (strain R9) culture filtrate from GPM broth completely inhibited seed germination of ryegrass when applied at doses of 3 and 5 mg of dry weight, and the seedling growth of cucumber and milk thistle was severely reduced by the same doses.