There have been multiple conflicting reports about the biocompatibility and antimicrobial activity of graphene oxide. To address this, we conducted a study to characterize the antimicrobial properties of graphene oxide (GO) and its biocompatibility with mammalian cells. When GO was added to a bacterial culture at 25 μg/mL, the results showed that bacteria grew faster and to a higher optical density than cultures without GO. Scanning electron microscopy indicated that bacteria formed dense biofilms in the presence of GO. This was shown by a large mass of aggregated cells and extracellular polymeric material. Bacterial growth on filters coated with 25 and 75 μg of GO grew 2 and 3 times better than on filters without GO. Closer analysis showed that bacteria were able to attach and proliferate preferentially in areas containing the highest GO levels. Graphene oxide films failed to produce growth inhibition zones around them, indicating a lack of antibacterial properties. Also, bacteria were able to grow on GO films to 9.5 × 10(9) cells from an initial inoculation of 1.0 × 10(6), indicating that it also lacks bacteriostatic activity. Thus, silver-coated GO films were able to produce clearing zones and cell death. Also, graphene oxide was shown to greatly enhance the attachment and proliferation of mammalian cells. This study conclusively demonstrates that graphene oxide does not have intrinsic antibacterial, bacteriostatic, and cytotoxic properties in both bacteria and mammalian cells. Furthermore, graphene oxide acts as a general enhancer of cellular growth by increasing cell attachment and proliferation.

A pyrene-degrading bacterial consortium was obtained from deep-sea sediments of the Pacific Ocean. The consortium degraded many kinds of polycyclic aromatic hydrocarbons (PAHs), including naphthalene, phenanthrene, pyrene, acenaphthene, fluorene, anthracene, fluoranthene, 2-methylnaphthalene and 2,6-dimethylnaphthalene, but it did not grow with chrysene and benzo[alpha]pyrene. With methods of plate cultivation and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), 72 bacteria belonging to 22 genera were detected from this consortium. Among the detected bacteria, the following genera frequently occurred: Flavobacterium, Cycloclasticus, Novosphingobium, Halomonas, Achromobacter, Roseovarius and Alcanivorax. The first two genera showed the strongest bands in denaturing gradient gel electrophoresis (DGGE) profiles and appeared in all PAH treatments. By now, only one isolate designated P1 was confirmed to be a pyrene degrader. It was identified to be Cycloclasticus spirillensus (100%). Although P1 can degrade pyrene independently, other bacteria, such as Novosphingobium sp. (Band 14), Halomonas sp. (Band 16) and an unidentified bacterium (Band 35), were involved in pyrene degradation in some way; they persist in the consortium in the test of dilution to extinction if only the consortium was motivated with pyrene. However, the secondary most important member Flavobacterium sp. evaded from the community at high dilutions. As a key member of the consortium, P1 distinguished itself by both cell morphology and carbon source range among the isolates of this genus. Based on intermediate analyses of pyrene degradation, P1 was supposed to take an upper pathway different from that previously reported. Together with the results of obtained genes from P1 homology with those responsible for naphthalene degradation, its degradation to pyrene is supposed to adopt another set of genes unique to presently detected. Summarily, an efficient pyrene-degrading consortium was obtained from the Pacific Ocean sediment, in which Cycloclasticus bacterium played a key role. This is the first report to exploit the diversity of pyrene-degrading bacteria in oceanic environments.

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A taxonomic study was carried out on a novel bacterial strain, designated W11-5 T , which was isolated from a pyrene-degrading consortium enriched from deep-sea sediment of the Pacific Ocean. The isolate was Gram-reaction-negative and oxidase-and catalase-positive. Growth was observed in 0.5-12 % (w/v) NaCl and at 10-42 6C. On the basis of 16S rRNA gene sequence analysis, strain W11-5 T was shown to belong to the genus Alcanivorax with a close relation to A. dieselolei B-5 T (93.9 % 16S rRNA sequence similarity), A. balearicus MACL04 T (93.1 %), A. hongdengensis A-11-3 T (93.1 %), A. borkumensis SK2 T (93.0 %), A. venustensis ISO4 T (93.0 %) and A. jadensis T9 T (92.9 %). Similarities between the gyrB gene sequences of W11-5 T and other species of the genus Alcanivorax were between 76.8 and 80.8 %. The principal fatty acids were C 12 : 0 3-OH (8.0 %), C 16 : 0 (29.1 %) and C 18 : 1 v7c (27.4 %). The G+C content of the chromosomal DNA was 60.8 mol%. Based on its morphology, physiology and fatty acid composition as well as the results of 16S rRNA and gyrB gene sequence analyses, strain W11-5 T (5MCCC 1A00474 T 5CCTCC AB 208236 T 5LMG 25514 T ) represents a novel species of the genus Alcanivorax, for which the name Alcanivorax pacificus sp. nov. is proposed.

An aerobic, Gram-negative, ovoid to rod-shaped bacterial isolate, strain 81-2 T , was isolated from