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Culture-independent techniques, denaturing gradient gel electrophoresis (DGGE) analysis, and random cloning of 16S rRNA gene sequences amplified from community DNA were used to determine the diversity of microbial communities in gas industry pipelines. Samples obtained from natural gas pipelines were used directly for DNA extraction, inoculated into sulfate-reducing bacterium medium, or used to inoculate a reactor that simulated a natural gas pipeline environment. The variable V2-V3 (average size, 384 bp) and V3-V6 (average size, 648 bp) regions of bacterial and archaeal 16S rRNA genes, respectively, were amplified from genomic DNA isolated from nine natural gas pipeline samples and analyzed. A total of 106 bacterial 16S rDNA sequences were derived from DGGE bands, and these formed three major clusters: beta and gamma subdivisions of Proteobacteria and gram-positive bacteria. The most frequently encountered bacterial species was Comamonas denitrificans, which was not previously reported to be associated with microbial communities found in gas pipelines or with microbially influenced corrosion. The 31 archaeal 16S rDNA sequences obtained in this study were all related to those of methanogens and phylogenetically fall into three clusters: order I, Methanobacteriales; order III, Methanomicrobiales; and order IV, Methanosarcinales. Further microbial ecology studies are needed to better understand the relationship among bacterial and archaeal groups and the involvement of these groups in the process of microbially influenced corrosion in order to develop improved ways of monitoring and controlling microbially influenced corrosion.Corrosion is a leading cause of pipe failure and is a main component of the operating and maintenance costs of gas industry pipelines (3,10,18,23,30,31,(42)(43)(44)54). Quantifying the cost of corrosion generally, and more specifically the cost associated with microbial corrosion, in the gas industry is not easily done and is controversial. Pipeline corrosion was estimated in 1996 to cost the gas industry about $840 million/year (10), and in 2001 it was estimated that the annual cost of all forms of corrosion to the oil and gas industries was $13.4 billion, of which microbially influenced corrosion accounted for about $2 billion (31). While it is well recognized that chemical and microbial mechanisms both contribute to corrosion, it is uncertain what the relative contribution of microbial activity to overall pipe corrosion is. It has been estimated that 40% of all internal pipeline corrosion in the gas industry can be attributed to microbial corrosion (23, 44), but data are needed to confirm or revise this estimate. Basic research to increase our understanding of the microbial species involved in microbial corrosion and their interactions with metal surfaces and with other microorganisms will be the basis for the development of new approaches for the detection, monitoring, and control of microbial corrosion. A thorough knowledge of the causes of microbially influenced corrosion and an effici...

Growth assays reveal that Rhodococcus rhodochrous IGTSS uses a wide range of organosulphur compounds as the sole source of sulphur, yet none of the compounds serve as carbon sources. Compounds that are utilized include thiophenes, sulphides, disulphides, mercaptans, sulphoxides, and sulphones. A convenient spectrophotometric assay (Gibbs assay), based on the chromogenic reaction of 2,6-dichloroquinone-4-chloroimide with aromatic hydroxyl groups, was developed and used in conjunction with GC/MS analyses to examine the kinetics of dibenzothiophene metabolism by axenic and mixed cell cultures of Rhodococcus rhodochrous IGTSS. The desulphurization trait is expressed at increasing levels during the exponential phase of growth and then declines in stationary-phase cells. Mixtures of streptomycin-resistant Rhodococcus rhodochrous IGTSS and Enterobacter cloacae (an organism incapable of cleaving carbon-sulphur bonds in relevant test compounds) were prepared in ratios that varied over six orders of magnitude. Growth studies revealed that E. cloacae was able to gain access to sulphur liberated from organosulphur compounds by IGTSS ; however, cell-to-cell contact appears to be required. These experiments also indicate that the desulphurization activity, on a per cell basis, is higher in mixed cultures than in axenic cultures.

The first benzoxazine incorporating cyanate ester group in its structure has been synthesized. The polymerization process investigated by differential scanning calometry (DSC) exhibits two clearly separated exotherm maxima, corresponding to cyanate ester trimerization and benzoxazine, respectively. The nature of each exotherm is studied by Fourier transform infrared spectroscopy (FT-IR). The activation energies for cyanate ester trimerization and benzoxazine ring-opening polymerization are determined by both Kissinger's and Ozawa's methods. Furthermore, both exothermic temperatures observed are lower than those of the published values of benzoxazine and dicyanate ester blends. Thermal properties such as glass transition temperature and char yield are studied by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Those properties are found to be outstanding compared to the reported properties of general benzoxazine resins and polymerized blends of benzoxazine and dicyanate ester, offering a polymeric matrix for composite satisfying many requirements for such a material.

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