Klebsiella pneumoniae KE-1 degrades endosulfan without formation of the toxic metabolite,endosulfan sulfate

For bioremediation of toxic endosulfan, endosulfan degradation bacteria, which do not form toxic endosulfan sulfate, were isolated from various soil samples using endosulfan as sole carbon and energy source. Among the 40 isolated bacteria, strain KE-1, which was identified as Klebsiella pneumoniae by physiological and 16S rDNA sequence analysis, showed superior endosulfan degradation activity. Analysis of culture pH, growth, free sulfate and endosulfan and its metabolites demonstrated that KE-1 biologically degrades 8.72 microg endosulfan ml(-1) day(-1) when incubated with 93.9 microg ml(-1) endosulfan for 10 days without formation of toxic endosulfan sulfate. Our results suggest that K. pneumoniae KE-1 degraded endosulfan by a non-oxidative pathway and that strain KE-1 has potential as a biocatalyst for endosulfan bioremediation.     

Implication of two glutathione S-transferases in the optimal metabolism of m-toluate by Sphingomonas yanoikuyae B1

A putative glutathione S-transferase (GST) gene (bphK) was identified in the meta-cleavage operon for the degradation of m-toluate by Sphingomonas yanoikuyae B1. Disruption of bphK resulted in the loss of GST activity against 1-chloro-2,4-dinitrobenzene and a much increased lag time of the mutant strain MB3 (bphK::Km) following subculture into m-toluate medium. In contrast, an increased lag time was not observed when MB3 was grown on biphenyl or m-xylene and MB3 showed normal growth on m-toluate when complemented with a subclone containing the bphK gene only. Furthermore, an additional GST activity was detected in MB3. The induction timing of this second GST activity coincided with the beginning of the exponential growth phase of MB3 on m-toluate, reached maximal activity within three hours, and then dropped sharply to the basal level. Thus, it is apparent that BphK and/or the second GST are necessary for optimal growth of B1 on m-toluate. This revised version was published online in June 2006 with corrections to the Cover Date.     

Green fluorescent protein as a marker for monitoring a pentachlorophenol degrader Sphingomonas chlorophenolica ATCC39723

Sphingomonas chlorophenolica ATCC39723 was successfully labeled with the gfp (green fluorescent protein) gene inserted into the pcpB gene by homologous recombination. As the gfp recombinant was easily distinguished from other indigenous organisms, the population of gfp recombinant was monitored after being released into the soil microcosms. Their population density dropped from 10(8) to 10(6) (cfu/ml) in the non-sterilized soil microcosms during the first 6 days. Moreover, the gfp recombinant was not detected even at lower dilution rates after a certain time period. The recombinant, however, survived for at least 28 days in the sterilized soil microcosms. Although the gfp recombinant did not degrade pentachlorophenol (PCP), this experiment showed the possibility of using gfp as a monitoring reporter system for S. chlorophenolica ATCC39723 and potentially other species of Sphingomonas.     

Specific biodegradation of polychlorinated biphenyls (PCBs) facilitated by plant terpenoids

The aim of this study was to examine how plant terpenoids, as natural growth substrates or inducers, would affect the biodegradation of PCB congeners. Various PCB degraders that could grow on biphenyl and several terpenoids were tested for their PCB degradation capabilities. Degradation activities of the PCB congeners, 4,4′-dichlorobiphenyl (4,4′-DCBp) and 2,2′-dichlorobiphenyl (2,2′-DCBp), were initially monitored through a resting cell assay technique that could detect their degradation products. The PCB degraders,Pseudomonas sp. P166 andRhodococcus sp. T104, were found to grow on both biphenyl and terpenoids ((S)-(−) limonene,p-cymene and α-terpinene) whereasArthrobacter sp. B1B could not grow on the terpenoids as a sole carbon source. The B1B strain grown on biphenyl exhibited good degradation activity for 4,4′-DCBp and 2,2′-DCBp, while the activity of strains P166 and T104 was about 25% that of the B1B strain, respectively. Concomitant GC analysis, however, demonstrated that strain T104, grown on (S)-(−) limonene,p-cymene and α-terpinene, could degrade 4,4′-DCBp up to 30%, equivalent to 50% of the biphenyl induction level. Moreover, strain T104 grown on (S)-(−) limonene, could also degrade 2,2′-DCBp up to 30%. This indicates that terpenoids, widely distributed in nature, could be utilized as both growth and/or inducer substrate(s) for PCB biodegradation in the environment.     

Rapid and sensitive detection by PCR of mpcI gene in the rhizosphere

Abstract: A simple and sensitive detection system, using polymerase chain reaction (PCR) and a soil microcosm, was developed to detect a bacterial catabolic gene in the rhizosphere. The inoculated population of Alcaligenes eutrophus JMP134, a phenol and 2,4-dichlorophenoxy acetic acid utilizer, was readily detected by this technique, which permitted taking of samples from specific locations of root (including rhizosphere) and soil. The number of JMP134 viable cells (10²–10³ cells), typically picked up by the nitrocellulose filter strip method, yielded sufficient amount of the target DNA to be detected by PCR. Primers encoding metapyrocatechase I (MPC I; catechol 2,3-dioxygenase) enabled the discrimination of at least five viable cells of JMP134 among the indigenous microorganisms inhabiting bush bean roots. This simplified PCR detection procedure facilitated monitoring of the specific degradative gene in the rhizosphere in only 5 h.     

Visualizing the infection process of Xanthomonas campestris in cabbage using green fluorescent protein

The plant pathogen, Xanthomonas campestris NRRL B-1459 was chromosomally tagged with gfp, and the transformant, which was subjected to Southern hybridization showed the presence of gfp in the chromosome. The virulence-related gene of the transformant was not affected by the insertion of gfp. After inoculation into cabbage plants, the infection process was visually studied in planta. Using a fluorescence microscope, the migration and distribution of gfp-labelled bacteria was visualized in real time. As the gfp-labelled cells were easily visualized from the beginning of infection, we observed a time delay of 2 days between distribution of the Xanthomonas cells in cabbage plant and the appearance of visible necrosis.     

Second-line Helicobacter pylori eradication: a randomized comparison of 1-week or 2-week bismuth-containing quadruple therapy

Objectives: The increasing levels of bacterial antibiotic resistance have increased the need to evaluate the second‐line treatments for Helicobacter pylori. Bismuth‐based quadruple therapy is recommended as a second‐line treatment, but the optimal duration of this treatment is still debatable. We prospectively analyzed the eradication rate of H. pylori according to the duration of the second‐line bismuth‐based quadruple therapy. Methods: One hundred and ninety‐nine patients who failed at H. pylori eradication were prospectively randomized to receive pantoprazole 40 mg twice daily, metronidazole 500 mg thrice daily, and bismuth subcitrate 300 mg and tetracycline 500 mg four times daily for 7 days (PBMT7) or for 14 days (PBMT14). The post‐treatment H. pylori status was determined by the ¹³C‐urea breath test. The eradication rates, drug compliance, and side effects of each group were evaluated. Results: The intention‐to‐treat (ITT) eradication rates were 81.6% (95% CI 73.9–89.3%, 80/98) in the PBMT7 arm and 85.1% (95% CI 78.2–92.0%, 86/101) in the PBMT14 arm (p = .028, noninferiority test), while the per‐protocol (PP) eradication rates were 89.6% (95% CI 83.2–96.0%, 78/87) and 96.2% (95% CI 92.0–100.0% 77/80) (p = .015, noninferiority test), respectively. The compliance was 88.8% (87/98) and 79.2% (80/101) in the PBMT7 and PBMT14 groups, respectively. (p = .066) The number of patients having severe side effects was 15.3% (15/98) and 21.8% (22/101) in the PBMT7 and PBMT14 groups, respectively, which was similar between both groups. (p = .243). Conclusions: Although PBMT7 was not inferior to PBMT14 statistically, PBMT could not demonstrate enough ITT/PP eradication rate. Therefore, it could be better to extend the duration of treatment for 2 weeks for the second‐line treatment of H. pylori in Korea.