Contaminants in sediments are less available than their concentrations might imply, but measures of this availability have been generally lacking. Sediments ingested by benthic animals can be expected to undergo a unique chemical environment controlled by the digestive chemistry of the organism. We measured solubilization of sedimentary contaminantsCu, Pb, and polycyclic aromatic hydrocarbons (PAH)by digestive fluids extracted from marine invertebrates. Bioavailability of these contaminants, thus measured, is a small fraction of total contaminant loadingtypically 1−10%. The amounts of metals solubilized by digestive fluids were orders of magnitude greater than would be predicted from water−solid partitioning with clean seawater, although they correlated well with solubilization by seawater. Digestive fluids from two different animal species solubilized different amounts of metals, indicating that bioavailability varies among species even under constant mode of uptake. High concentrations of solubilizing agents, such as amino acids for metals and surfactants for PAH, in the digestive fluids can explain the enhanced solubilization. This biomimetic approach to contaminant measurement provides the basis for more accurate mechanistic and routine assessments of environmental impact.

Several fullerene-based nanomaterials generate reactive oxygen species that can damage cells. In this study, we investigated the effect of buckminsterfullerene (C60) introduced as colloidal aggregates in water (nC60) on bacterial membrane lipid composition and phase behavior. Pseudomonas putida (Gram-negative) and Bacillus subtilis (Gram-positive) responded to nC60 by altering membrane lipid composition, phase transition temperature, and membrane fluidity. P. putida decreased its levels of unsaturated fatty acids and increased the proportions of cyclopropane fatty acids in the presence of nC60, possibly to protect the bacterial membrane from oxidative stress. Fourier transform infrared spectroscopy measurement of intact bacterial cells showed slightly increased phase transition temperatures (Tm) and increased membrane fluidity for cells grown in the presence of high, growth-inhibiting concentrations (0.5 mg L(-1)) of nC60. B. subtilis responded to a low dose of nC6o (0.01 mg L(-1)) by significantly increasing the levels of iso- and anteiso-branched fatty acids (from 5.8 to 31.5% and 12.9 to 32.3% of total fatty acids, respectively) and to a high, growth-inhibiting concentration of nC60 (0.75 mg L-1) by increasing synthesis of monounsaturated fatty acids. In contrast to P. putida, B. subtilis response was a decrease in Tm and an increase in membrane fluidity. These findings represent the first demonstrated physiological adaptation response of bacteria to a manufactured nanomaterial, and they showthat response inlipid composition and membrane phase behavior depends on both the nC60 concentration and the cell wall morphology.

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A magnetotactic bacterium, designated strain MV-1T, was isolated from sulfide-rich sediments in a salt marsh near Boston, MA, USA. Cells of strain MV-1T were Gram-negative, and vibrioid to helicoid in morphology. Cells were motile by means of a single polar flagellum. The cells appeared to display a transitional state between axial and polar magnetotaxis: cells swam in both directions, but generally had longer excursions in one direction than the other. Cells possessed a single chain of magnetosomes containing truncated hexaoctahedral crystals of magnetite, positioned along the long axis of the cell. Strain MV-1T was a microaerophile that was also capable of anaerobic growth on some nitrogen oxides. Salinities greater than 10 % seawater were required for growth. Strain MV-1T exhibited chemolithoautotrophic growth on thiosulfate and sulfide with oxygen as the terminal electron acceptor (microaerobic growth) and on thiosulfate using nitrous oxide (N2O) as the terminal electron acceptor (anaerobic growth). Chemo-organoautotrophic and methylotrophic growth was supported by formate under microaerobic conditions. Autotrophic growth occurred via the Calvin–Benson–Bassham cycle. Chemo-organoheterotrophic growth was supported by various organic acids and amino acids, under microaerobic and anaerobic conditions. Optimal growth occurred at pH 7.0 and 26–28 °C. The genome of strain MV-1T consisted of a single, circular chromosome, about 3.7 Mb in size, with a G+C content of 52.9–53.5 mol%.Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain MV-1T belongs to the family Rhodospirillaceae within the Alphaproteobacteria , but is not closely related to the genus Magnetospirillum . The name Magnetovibrio blakemorei gen. nov., sp. nov. is proposed for strain MV-1T. The type strain of Magnetovibrio blakemorei is MV-1T ( = ATCC BAA-1436T  = DSM 18854T).

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Particle-attached (PA) and free-living (FL) microorganisms play significant but different roles in mineralization of organic matter (OM) in the ocean. Currently, little is known about PA and FL microbial communities in bathyal and abyssal pelagic waters, and understanding of their diversity and distribution in the water column and their interactions with environmental factors in the trench area is limited. We investigated for the first time the variations of abundance and diversities of the PA and FL bacterial communities in the epi-, bathy-, and abyssopelagic zones of the New Britain Trench (NBT). The PA communities showed decreasing species richness but increasing relative abundance with depth, suggesting the increasing ecological significance of the PA bacteria in the deep ocean. The abundance and diversity of PA and FL bacterial communities in the NBT water column appeared to be shaped by different sets of environment factors, which might be related to different micro-niches of the two communities. Analysis on species distribution suggested that the differences between PA and FL bacteria communities mainly resulted from the different relative abundance of the “shared taxa” in the two types of communities. These findings provide valuable information for understanding the relative ecological roles of the PA and FL bacterial communities and their interactions with environmental factors in different pelagic zones along the vertical profile of the NBT water column.