Macroscopic biofilms in fracture-dominated sediment that anaerobically oxidize methane

Methane release from seafloor sediments is moderated, in part, by the anaerobic oxidation of methane (AOM) performed by consortia of archaea and bacteria. These consortia occur as isolated cells and aggregates within the sulfate-methane transition (SMT) of diffusion and seep-dominant environments. Here we report on a new SMT setting where the AOM consortium occurs as macroscopic pink to orange biofilms within subseafloor fractures. Biofilm samples recovered from the Indian and northeast Pacific Oceans had a cellular abundance of 10(7) to 10(8) cells cm(-3). This cell density is 2 to 3 orders of magnitude greater than that in the surrounding sediments. Sequencing of bacterial 16S rRNA genes indicated that the bacterial component is dominated by Deltaproteobacteria, candidate division WS3, and Chloroflexi, representing 46%, 15%, and 10% of clones, respectively. In addition, major archaeal taxa found in the biofilm were related to the ANME-1 clade, Thermoplasmatales, and Desulfurococcales, representing 73%, 11%, and 10% of archaeal clones, respectively. The sequences of all major taxa were similar to sequences previously reported from cold seep environments. PhyloChip microarray analysis detected all bacterial phyla identified by the clone library plus an additional 44 phyla. However, sequencing detected more archaea than the PhyloChip within the phyla of Methanosarcinales and Desulfurococcales. The stable carbon isotope composition of the biofilm from the SMT (-35 to -43‰) suggests that the production of the biofilm is associated with AOM. These biofilms are a novel, but apparently widespread, aggregation of cells represented by the ANME-1 clade that occur in methane-rich marine sediments.     

Production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from plant oil by engineered Ralstonia eutropha strains

The polyhydroxyalkanoate (PHA) copolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(HB-co-HHx)] has been shown to have potential to serve as a commercial bioplastic. Synthesis of P(HB-co-HHx) from plant oil has been demonstrated with recombinant Ralstonia eutropha strains expressing heterologous PHA synthases capable of incorporating HB and HHx into the polymer. With these strains, however, short-chain-length fatty acids had to be included in the medium to generate PHA with high HHx content. Our group has engineered two R. eutropha strains that accumulate high levels of P(HB-co-HHx) with significant HHx content directly from palm oil, one of the world's most abundant plant oils. The strains express a newly characterized PHA synthase gene from the bacterium Rhodococcus aetherivorans I24. Expression of an enoyl coenzyme A (enoyl-CoA) hydratase gene (phaJ) from Pseudomonas aeruginosa was shown to increase PHA accumulation. Furthermore, varying the activity of acetoacetyl-CoA reductase (encoded by phaB) altered the level of HHx in the polymer. The strains with the highest PHA titers utilized plasmids for recombinant gene expression, so an R. eutropha plasmid stability system was developed. In this system, the essential pyrroline-5-carboxylate reductase gene proC was deleted from strain genomes and expressed from a plasmid, making the plasmid necessary for growth in minimal media. This study resulted in two engineered strains for production of P(HB-co-HHx) from palm oil. In palm oil fermentations, one strain accumulated 71% of its cell dry weight as PHA with 17 mol% HHx, while the other strain accumulated 66% of its cell dry weight as PHA with 30 mol% HHx.     

A mathematical model for breath gas analysis of volatile organic compounds with special emphasis on acetone

Recommended standardized procedures for determining exhaled lower respiratory nitric oxide and nasal nitric oxide (NO) have been developed by task forces of the European Respiratory Society and the American Thoracic Society. These recommendations have paved the way for the measurement of nitric oxide to become a diagnostic tool for specific clinical applications. It would be desirable to develop similar guidelines for the sampling of other trace gases in exhaled breath, especially volatile organic compounds (VOCs) which may reflect ongoing metabolism. The concentrations of water-soluble, blood-borne substances in exhaled breath are influenced by: (i) breathing patterns affecting gas exchange in the conducting airways, (ii) the concentrations in the tracheo-bronchial lining fluid, (iii) the alveolar and systemic concentrations of the compound. The classical Farhi equation takes only the alveolar concentrations into account. Real-time measurements of acetone in end-tidal breath under an ergometer challenge show characteristics which cannot be explained within the Farhi setting. Here we develop a compartment model that reliably captures these profiles and is capable of relating breath to the systemic concentrations of acetone. By comparison with experimental data it is inferred that the major part of variability in breath acetone concentrations (e.g., in response to moderate exercise or altered breathing patterns) can be attributed to airway gas exchange, with minimal changes of the underlying blood and tissue concentrations. Moreover, the model illuminates the discrepancies between observed and theoretically predicted blood-breath ratios of acetone during resting conditions, i.e., in steady state. Particularly, the current formulation includes the classical Farhi and the Scheid series inhomogeneity model as special limiting cases and thus is expected to have general relevance for a wider range of blood-borne inert gases. The chief intention of the present modeling study is to provide mechanistic relationships for further investigating the exhalation kinetics of acetone and other water-soluble species. This quantitative approach is a first step towards new guidelines for breath gas analyses of volatile organic compounds, similar to those for nitric oxide.     

Angiotensinergic and noradrenergic neurons in the rat and human heart

Although the physiological and pharmacological evidences suggest a role for angiotensin II (Ang II) with the mammalian heart, the source and precise location of Ang II are unknown. To visualize and quantitate Ang II in atria, ventricular walls and interventricular septum of the rat and human heart and to explore the feasibility of local Ang II production and function, we investigated by different methods the expression of proteins involved in the generation and function of Ang II. We found mRNA of angiotensinogen (Ang-N), of angiotensin converting enzyme, of the angiotensin type receptors AT(1A) and AT? (AT(1B) not detected) as well as of cathepsin D in any part of the hearts. No renin mRNA was traceable. Ang-N mRNA was visualized by in situ hybridization in atrial ganglial neurons. Ang II and dopamine-β-hydroxylase (DβH) were either colocalized inside the same neuronal cell or the neurons were specialized for Ang II or DβH. Within these neurons, the vesicular acetylcholine transporter (VAChT) was neither colocalized with Ang II nor DβH, but VAChT-staining was found with synapses en passant encircle these neuronal cells. The fibers containing Ang II exhibited with blood vessels and with cardiomyocytes supposedly angiotensinergic synapses en passant. In rat heart, right atrial median Ang II concentration appeared higher than septal and ventricular Ang II. The distinct colocalization of neuronal Ang II with DβH in the heart may indicate that Ang II participates together with norepinephrine in the regulation of cardiac functions: produced as a cardiac neurotransmitter Ang II may have inotropic, chronotropic or dromotropic effects in atria and ventricles and contributes to blood pressure regulation.     

A new phenol oxidase produced during melanogenesis and encystment stage in the nitrogen-fixing soil bacterium Azotobacter chroococcum

Laccases are copper-containing phenol oxidases that are commonly found in many types of plant, insect, fungi and bacteria. Whilst phenol oxidases have been well characterized in fungal species, laccase-type enzymes originating from bacteria have been much less well defined. Bacteria belonging to the family Azotobacteraceae share many morphological characteristics with strains already known to exhibit polyphenol and phenol oxidase activity; and hence the aim of this work was to identify and characterize a novel laccase from the isolated strain Azotobacter chroococcum SBUG 1484 in an attempt to provide further understanding of the roles such enzymes play in physiological development. Laccase activity was clearly observed through oxidation of 2,6-dimethoxyphenol, other typical substrates including: methoxy-monophenols, ortho- and para-diphenols, 4-hydroxyindole, and the non-phenolic compound para-phenylenediamine. A. chroococcum SBUG 1484 showed production of a cell-associated phenol oxidase when grown under nitrogen-fixing conditions, and was also observed when cells enter the melanogenic and encystment stages of growth. Catechol which is structurally related to melanin compounds was also released from Azotobacter cells into the surrounding culture medium during nitrogen-fixing growth. From our results we propose that a membrane-bound laccase plays an important role in the formation of melanin, which was monitored to correlate with progression of A. chroococcum SBUG 1484 cells into the encystment stage of growth.     

Chronic stress in pregnant guinea pigs (<Emphasis Type="Italic">Cavia aperea f. porcellus</Emphasis>) attenuates long-term stress hormone levels and body weight gain,but not reproductive output

Stress, when extreme or chronic, can have a negative impact on health and survival of mammals. This is especially true for females during reproduction when self-maintenance and investment in offspring simultaneously challenge energy turnover. Therefore, we investigated the effects of repeated stress during early- and mid-gestation on the maternal stress axis, body weight gain and reproductive output. Female guinea pigs (Cavia aperea f. porcellus, n = 14) were either stressed (treatment: exposure to strobe light in an unfamiliar environment on gestational day -7, 0, 7, 14, 21, 28, 35, 42) or left completely undisturbed (control) throughout pregnancy. Females of both groups received the same respective diets, and reproductive parameters were evaluated upon parturition. Additionally, hormonal data were obtained from blood and feces. The stress exposure induced a significant increase in plasma cortisol concentrations during the afternoon. In contrast to this short-term response in plasma cortisol concentrations, we found no significant differences in the levels of cortisol metabolites in feces collected after stress exposure between groups and even significantly decreased levels of fecal cortisol metabolites on non-stress days over time in treatment females. Among treatment females, gain in body weight was attenuated over gestation and body weight was lower compared to control females during lactation, especially in cases of large litter sizes. No differences could be seen in the reproductive parameters. We conclude that repeated stress exposure with strobe light during early- and mid-gestation results in a down-regulation of the hypothalamic–pituitary–adrenal axis and lower weight gain in treatment females, but has no effect on reproductive output.     

Tropospheric 14CO2 at Wellington, New Zealand: the world??s longest record

Measurements of near-sea-level tropospheric ??¹⁴CO₂ have been made at Wellington, New Zealand since December 1954; these measurements comprise the longest such record available. The ??¹⁴C rose from ?10?? in 1955 peaking at 695?? in 1965 as a result of ??bomb ¹⁴C?? production, before falling thereafter to the present day (2005) value of 73??. The ??¹⁴C peak occurred about 1?year later in the southern hemisphere than in the northern hemisphere. The post-1965 fall is due to the transfer of ¹⁴C-enriched CO₂ to the biospheric and oceanic pools together with ongoing release of ¹⁴C-free CO₂ from fossil fuel combustion, during an era without major atmospheric nuclear-weapon tests. Time series analysis of the data using Loess decomposition and filtering indicates an approximately exponential decline in excess ??¹⁴CO₂ over 1967?C2005 with an e-folding time of 18?years. The seasonal cycle from 1954 until 1980 had a maximum in the late (austral) summer, a minimum in winter, with peak-to-trough amplitude that peaked at 20?? in 1966. For the period 1980?C1989, a new seasonal cycle emerged, with a maximum in winter and a minimum in late summer/early autumn and peak-to-trough amplitude of 3.5??, transitioning to a new seasonal structure after about 1990.     

Chloroflexi bacteria are more diverse, abundant, and similar in high than in low microbial abundance sponges

Some marine sponges harbor dense and phylogenetically complex microbial communities [high microbial abundance (HMA) sponges] whereas others contain only few and less diverse microorganisms [low microbial abundance (LMA) sponges]. We focused on the phylum Chloroflexi that frequently occurs in sponges to investigate the different associations with three HMA and three LMA sponges from New Zealand. By applying a range of microscopical and molecular techniques a clear dichotomy between HMA and LMA sponges was observed: Chloroflexi bacteria were more abundant and diverse in HMA than in LMA sponges. Moreover, different HMA sponges contain similar Chloroflexi communities whereas LMA sponges harbor different and more variable communities which partly resemble Chloroflexi seawater communities. A comprehensive phylogenetic analysis of our own and publicly available sponge-derived Chloroflexi 16S rRNA gene sequences (>?780 sequences) revealed the enormous diversity of this phylum within sponges including 29 sponge-specific and sponge-coral clusters (SSC/SCC) as well as a 'supercluster' consisting of >?250 sponge-derived and a single nonsponge-derived 16S rRNA gene sequence. Interestingly, the majority of sequences obtained from HMA sponges, but only a few from LMA sponges, fell into SSC/SCC clusters. This indicates a much more specific association of Chloroflexi bacteria with HMA sponges and suggests an ecologically important role for these prominent bacteria.     

Inhibition of glutamine synthesis induces glutamate dehydrogenase-dependent ammonia fixation into alanine in co-cultures of astrocytes and neurons

It has been previously demonstrated that ammonia exposure of neurons and astrocytes in co-culture leads to net synthesis not only of glutamine but also of alanine. The latter process involves the concerted action of glutamate dehydrogenase (GDH) and alanine aminotransferase (ALAT). In the present study it was investigated if the glutamine synthetase (GS) inhibitor methionine sulfoximine (MSO) would enhance alanine synthesis by blocking the GS-dependent ammonia scavenging process. Hence, co-cultures of neurons and astrocytes were incubated for 2.5 h with [U-¹³C]glucose to monitor de novo synthesis of alanine and glutamine in the absence and presence of 5.0 mM NH₄Cl and 10 mM MSO. Ammonia exposure led to increased incorporation of label but not to a significant increase in the amount of these amino acids. However, in the presence of MSO, glutamine synthesis was blocked and synthesis of alanine increased leading to an elevated content intra- as well as extracellularly of this amino acid. Treatment with MSO led to a dramatic decrease in glutamine content and increased the intracellular contents of glutamate and aspartate. The large increase in alanine during exposure to MSO underlines the importance of the GDH and ALAT biosynthetic pathway for ammonia fixation, and it points to the use of a GS inhibitor to ameliorate the brain toxicity and edema induced by hyperammonemia, events likely related to glutamine synthesis.     

A large-scale study on subjective perception of discomfort during 7 and 1.5 T MRI examinations

A study on subjective perception has been carried out in order to gain further insight into subjective discomfort and sensations experienced during 7 T magnetic resonance imaging (MRI). This study provides information about subjective acceptance, which is essential if 7 T MRI is to become a clinical diagnostic tool. Of 573 subjects who underwent 7 T MRI, 166 were also examined at 1.5 T, providing a means of discriminating field‐dependent discomfort. All subjects judged sources of discomfort and physiological sensations on an 11‐point scale (0 = no side effects, 10 = intolerable side effects) and scores were analyzed separately for exam phases, with and without table movement at each field strength. Results revealed that 7 T MRI was, in general, judged more uncomfortable than 1.5 T; however, most subjects rated the effects as being non‐critical (mean scores between 0.5 and 3.5). Significant differences were detected regarding vertigo and sweating between subjects positioned “head‐first” and “feet‐first” at 7 T (worse in “head‐first”) and between 7 and 1.5 T (worse at 7 T), with the effects being more pronounced in the moving compared to the stationary table position. The most unpleasant factor at 7 T was the extensive examination duration, while potentially field‐dependent sensations were rated less bothersome. In summary, our study indicates that although certain sensations increase at 7 T compared to 1.5 T, they are unlikely to hinder the use of 7 T MRI as a clinical diagnostic tool. Bioelectromagnetics. Bioelectromagnetics 32:610–619, 2011. © 2011 Wiley Periodicals, Inc.