To determine the effects of three PGPRs on plant growth, yield, and quality of tomato under simulated seawater irrigation, a two consecutive seasons’ field experiment was conducted in Yancheng Teachers University plot from April to June and August to October, 2011. The results showed that Erwinia persicinus RA2 containing ACC deaminase exhibited the best ability compared with Bacillus pumilus WP8 and Pseudomonas putida RBP1 which had no ACC deaminase activity to enhance marketable yields of fresh and dried fruits in tomato under simulated seawater irrigation especially under HS condition. B. pumilus WP8 had significant effects on improving tomato fruit quality under the conditions of irrigating with 1.0% NaCl solution (MS) and with 2.0% NaCl solution (HS). Na+ contents were generally accumulated much more in tomato plant mid-shoot leaves than in fruits whatever the salt concentration. More sodium accumulation in leaves of E. persicinus RA2 and B. pumilus WP8 treatments under HS condition were found than in control. E. persicinus RA2 and B. pumilus WP8 can promote tomato growth, improve fruit quality more firmly than P. putida RBP1 during two consecutive seasons. Our study suggested that E. persicinus RA2 and B. pumilus WP8 are considered to be promising PGPR strains which are suited for application in salt marsh planting, ACC deaminase activity was not unique index on screening for PGPRs with the aim of salt stress tolerance, and plant growth promoting activities may be relevant to different growth indices and different stress conditions.
A bacterial strain named CB4, with highly effective glyphosate degradation capability, was isolated from soil after enrichment. On the basis of the Biolog omniLog identification system (Biolog) and 16S ribosomal RNA (rRNA) gene sequencing methods, strain CB4 was identified as Bacillus cereus. Further experiments were carried out to optimize the growth of strain CB4 and the glyphosate degradation activity by high performance liquid chromatography (HPLC). The optimal conditions were found as follows: initial pH 6.0, incubation temperature 35°C, glyphosate concentration 6 g L−1, inoculation amount 5% and incubation time 5 days. Under the optimal conditions, stain CB4 utilized 94.47% of glyphosate. This is the first report on B. cereus with a capacity to utilize herbicide glyphosate, and it can degrade glyphosate concentrations up to 12 g L−1. Metabolization of glyphosate by strain B. cereus CB4 was studied. Results indicated that two concurrent pathways were capable of degrading glyphosate to AMPA, glyoxylate, sarcosine, glycine and formaldehyde as products. Glyphosate breakdown in B. cereus CB4 was achieved by the C-P lyase activity and the glyphosate oxidoreductase activity.
In fish sauce production, microorganisms are associated with the fermentation process; however, the sequential changes in the bacterial communities have never been examined throughout the period of fermentation. In this study, we determined the bacterial floras in a fish sauce mash over 8 months, using three different culture media and 16S rRNA gene clone library analysis. During the first 4 weeks, viable counts of non-halophilic and halophilic bacteria decreased and were dominated by Staphylococcus species. Between 4 and 6 weeks, halophilic and highly halophilic bacterial counts markedly increased from 107 to 108 cfu/g, and the predominant species changed to Tetragenococcus halophilus. The occurrence of T. halophilus was associated with an increase of lactic acid and a reduction of pH values. In contrast, non-halophilic bacterial counts decreased to 106 cfu/g by 6 weeks with Bacillus subtilis as the dominant isolate. Clone library analysis revealed that the dominant bacterial group also changed from Staphylococcus spp. to T. halophilus, and the changes were consistent with those of the floras of halophilic and highly halophilic isolates. This is the first report describing a combination approach of culture and clone library methods for the analysis of bacterial communities in fish sauce mash.
A tributyltin (TBT) resistance gene was isolated from the TBT-resistant marine origin bacterium Pseudomonas aeruginosa 25W. This gene was identical to PA0320 deposited in the P. aeruginosa PAO1 database (http://www.pseudomonas.com). The deduced amino acid sequence of PA0320 appears to be homologous to the YgiW proteins of Escherichia coli and Salmonella enterica. The deletion mutant of PA0320 showed a reduction of growth rate in the presence of TBT. A susceptibility test to cadmium, mercury, hydrogen peroxide and acidic pH in the deletion mutant showed an increasing susceptibility to them. PA0320 plays a certain role in stress tolerance against TBT as well as in stressors producing reactive oxygen species.
The manipulation of microbes within oil reservoirs has been the subject of a number of studies. The aims of these studies have included alteration of oil characteristics, improvement in recovery of oil and suppression of microbes that produce H2S. Understanding microbial communities and their microbial responses is important in predicting the outcome of these studies. Palm oil waste is an abundant waste product, particularly in Asia, and we sought to examine its usefulness for altering microbial communities in oil reservoirs. Data from the present study demonstrated that after amendment with a palm oil analogue (POA), oil reservoir microflora produced methane and nitrogen gas along with a net consumption of CO2. The addition stimulated a novel taxon in the family Deferribacteraceae. Amendment with POA also affected the methanogen community by stimulating the growth of Methanothermobacter, Methanoculleus and Methanocalculus spp. Overall the study indicated that POA addition allowed the development of a consortium that was able to convert CO2 into CH4 in a process powered by an abundant waste product.
The aim of this study was the development of an efficient method to identify the prebiotics-assimilating-bacteria in gut microbiota using DNA-stable isotope probing (DNA-SIP) technology. For efficient probing of microbiota with stable isotopes, a small-scale repeated batch culture using a low-carbon-source-containing medium was developed. Fecal samples from cattle were inoculated and [U-13C]-fructose was applied to the culture after 24 h stabilization. Organic acid production, pH value of the period and the total diversity of microorganisms of the culture were successfully maintained during the chasing period. DNA samples were extracted from the culture and were subjected to isopycnic centrifugation and fractionation in order to separate fructose fermenters from non-fermenters. T-RFLP (Terminal Restriction Fragment Length Polymorphism) and the modified T-RFLP of each fraction suggested that Streptococcus bovis was the most dominant fructose fermenter in this culture. In addition, we improved the modified T-RFLP method and successfully identified Lactobacillus vitulinus and Megasphaella eldenii as minor fructose-fermenters and several species of Clostridium cluster IV as non-fermenters. From these results we concluded that the methods shown here provide a means for assessing the importance of individual prebiotics on gut microbiota.
The Gram-negative, aerobic, non-motile, non-spore forming, and rod-shaped bacterium designated as THG-T17T was isolated from the soil of a ginseng field of Pocheon in Korea, and its taxonomic position was investigated by using a polyphasic approach. The growth of strain THG-T17T occurred at 4−40°C and pH 4.0−9.0 with 1−2% (w/v) NaCl on nutrient agar. Strain THG-T17T displayed β-glucosidase activity that was responsible for its ability to transform ginsenoside Rb1 (one of the dominant ginsenosides of ginseng) to compound F2 via gypenoside XVII. On the basis of 16S rRNA gene sequence similarity, strain THG-T17T was shown to belong to the genus Pedobacter and was related to Pedobacter soli 15−51T (98.8%), Pedobacter sandarakinus DS-27T (98.0%) and Pedobacter terrae DS-57T (98.1%). The G+C content of the genomic DNA was 42.4 mol%. The DNA-DNA relatedness values between strain THG-T17T and its phylogenetically closest neighbors were below 14%. Phenotypic and chemotaxonomic data, especially analysis of cellular fatty acid, supported the affiliation of strain THG-T17T to the genus Pedobacter. The results of genotyping and biochemical tests showed strain THG-T17T to be differentiated genotypically and phenotypically from the recognized species of the genus Pedobacter. Therefore, the novel isolate represents a novel species, for which the name Pedobacter kyungheensis sp. nov. is proposed, with the type strain THG-T17T (=KACC 16221T = LMG 26577T).
The development of Lactobacillus plantarum to be used in starter cultures in the food industry has been limited because of the lack of a food-grade cloning vector for the bacterium. In this study, the plasmid pFLP1 was constructed by joining 2 DNA fragments derived from food-approved organisms. The 5.2-kb BamHI/KpnI DNA fragment of pRV566 containing the theta-type replicon of Lactobacillus sakei was ligated to the BamHI/KpnI DNA fragment of a 2.9-kb lactococcal cadmium resistance determinant amplified from pND918. The 8.1-kb newly constructed plasmid could transform L. plantarum N014, a bacteriocin-producing bacteria originally isolated from nham, a traditional Thai fermented sausage. The resulting transformant, L. plantarum N014-FLP, and its parent strain were shown to be very similar in growth rate and bacteriocin activity. In addition, the plasmid was very stable in its host bacteria under nonselective pressure for 100 generations in MRS medium and for 5 days in a nham model. These results suggest that pFLP1 is a potential food-grade cloning vector for L. plantarum.