Heavy oil exposure increases viral production in natural marine bacterial populations

This study examined whether heavy oil (HO) increases viral production and how that change may affect the marine bacterial community. The addition of a relatively low concentration (10 μg/mL) of HO to seawater resulted in the highest degree of viral lysis. Although the composition of the bacterial community did not change upon the viral lysis in terms of the taxa present, the relative abundance of the γ-Proteobacteria family Alteromonadaceae decreased (by 10 %) after the HO exposure, implying that the selective lysis by viruses and induced prophages may be responsible for changes in the composition of the bacterial community.     

The structure and transformation of the nanomineral schwertmannite: a synthetic analog representative of field samples

The phase transformation of schwertmannite, an iron oxyhydroxide sulfate nanomineral synthesized at room temperature and at 75 °C using H₂O₂ to drive the precipitation of schwertmannite from ferrous sulfate (Regenspurg et al. in Geochim Cosmochim Acta 68:1185–1197, 2004), was studied using high-resolution transmission electron microscopy. The results of this study suggest that schwertmannite synthesized using this method should not be described as a single phase with a repeating unit cell, but as a polyphasic nanomineral with crystalline areas spanning less than a few nanometers in diameter, within a characteristic ‘pin-cushion’-like amorphous matrix. The difference in synthesis temperature affected the density of the needles on the schwertmannite surface. The needles on the higher-temperature schwertmannite displayed a dendritic morphology, whereas the needles on the room-temperature schwertmannite were more closely packed. Visible lattice fringes in the schwertmannite samples are consistent with the powder X-ray diffraction (XRD) pattern taken on the bulk schwertmannite and also matched d-spacings for goethite, indicating a close structural relationship between schwertmannite and goethite. The incomplete transformation from schwertmannite to goethite over 24 h at 75 °C was tracked using XRD and TEM. TEM images suggest that the sample collected after 24 h consists of aggregates of goethite nanocrystals. Comparing the synthetic schwertmannite in this study to a study on schwertmannite produced at 85 °C, which used ferric sulfate, reveals that synthesis conditions can result in significant differences in needle crystal structure. The bulk powder XRD patterns for the schwertmannite produced using these two samples were indistinguishable from one another. Future studies using synthetic schwertmannite should account for these differences when determining schwertmannite’s structure, reactivity, and capacity to take up elements like arsenic. The schwertmannite synthesized by the Regenspurg et al. method produces a mineral that is consistent with the structure and morphology of natural schwertmannite observed in our previous study using XRD and TEM, making this an ideal synthetic method for laboratory-based mineralogical and geochemical studies that intend to be environmentally relevant.