Facets of diazotrophy in the oxygen minimum zone waters off Peru

Nitrogen fixation, the biological reduction of dinitrogen gas (N₂) to ammonium (NH₄⁺), is quantitatively the most important external source of new nitrogen (N) to the open ocean. Classically, the ecological niche of oceanic N₂ fixers (diazotrophs) is ascribed to tropical oligotrophic surface waters, often depleted in fixed N, with a diazotrophic community dominated by cyanobacteria. Although this applies for large areas of the ocean, biogeochemical models and phylogenetic studies suggest that the oceanic diazotrophic niche may be much broader than previously considered, resulting in major implications for the global N-budget. Here, we report on the composition, distribution and abundance of nifH, the functional gene marker for N₂ fixation. Our results show the presence of eight clades of diazotrophs in the oxygen minimum zone (OMZ) off Peru. Although proteobacterial clades dominated overall, two clusters affiliated to spirochaeta and archaea were identified. N₂ fixation was detected within OMZ waters and was stimulated by the addition of organic carbon sources supporting the view that non-phototrophic diazotrophs were actively fixing dinitrogen. The observed co-occurrence of key functional genes for N₂ fixation, nitrification, anammox and denitrification suggests that a close spatial coupling of N-input and N-loss processes exists in the OMZ off Peru. The wide distribution of diazotrophs throughout the water column adds to the emerging view that the habitat of marine diazotrophs can be extended to low oxygen/high nitrate areas. Furthermore, our statistical analysis suggests that NO₂⁻ and PO₄³⁻ are the major factors affecting diazotrophic distribution throughout the OMZ. In view of the predicted increase in ocean deoxygenation resulting from global warming, our findings indicate that the importance of OMZs as niches for N₂ fixation may increase in the future.     

Bacterial formation of struvite

We studied the formation of exocellular precipitates of struvite (Mg NH₄PO4.6H₂O) by 96 kinds of calcite‐pro‐ducing bacterial strains isolated from soil. We also studied the influence of calcium ions on struvite precipitation. The number of strains producing struvite was 20. Only four consistently formed large amounts. These results seem to indicate that the bacterial precipitation of struvite is not a general phenomenon. The strains studied were taxonomically identified, and no relationship was found between the production of struvite and the taxonomic identity of such strains. Calcium, supplied as Ca acetate in the culture medium, appeared to inhibit the biological precipitation of struvite.     

Ontogenetic and spatiotemporal variability in anchoveta Engraulis ringens diet off Peru

In this study, historical data available since 1954 were used to get new insight to ontogenetic and spatiotemporal variability in Peruvian anchovy or anchoveta Engraulis ringens diet. Whatever the period, E. ringens foraged mainly on macrozooplankton and the importance of euphausiids in E. ringens diet appears directly related to euphausiids abundance. This bottom‐up effect is also observed at smaller scale because the euphausiids fraction increased with E. ringens total length and euphausiids accessibility. Selecting the largest prey, the euphausiids, provides an energetic advantage for E. ringens in its ecosystem where oxygen depletion imposes strong metabolic constraints on pelagic fishes. This study illustrates the plasticity of E. ringens that allows it to cope with its highly variable environment.     

Bacterial shape: growing off this mortal coil

Members of the actin-like MreB family of proteins localize as a helical filament in bacteria and are important for determining cylindrical cell shape. Recent results show that new cell wall biosynthesis occurs along a helical track dependent on one of these actin homologs, providing new insights into bacterial cell growth, division and shape.     

Spatial Pattern of a Free-Living Marine Nematode Community off the Coast of Peru

The numerical abundance and biomass of free-living marine nematodes from sandy sediment off the coast of Peru (water depth 40 m) was similar to that reported from other areas. Dispersion chi-square analysis indicated that three species were aggregated, while the remaining species were randomly distributed throughout the samples. The most reasonable hypothesis is that variation in size of individual pore spaces is the mechanism controlling the distribution of the aggregated species.     

Cephalopod remains from the stomachs of Sperm whales caught off Peru and Chile

One thousand cephalopod lower beaks from random samples of the stomach contents of four Sperm whales caught off Peru and Chile are identified and/or described. Non-random samples of stomach contents from 10 whales were also examined. The size of the lower beaks is used to estimate the mean and the total weight of the cephalopods of each taxon identified. The three most numerous species are Histioteuthis sp. i (50%), Chiroteuthis sp. A (16%) and Octopoteuthis sp. (9%) while the greatest weight of flesh is contributed by Histioteuthis sp. A₁ (56%), Dosidicus gigas (32%) and Vampyroteuthis infemalis (3%). Lower rostral length frequency distributions are compared with those that have been constructed for other regions. Antarctic species of cephalopods represented by beaks show that two female and one male whale probably moved north from much further south immediately prior to being shot off Peru in November, December and February.     

Synapse formation: astrocytes spout off

Trillions of synapses form as the brain develops. This intimate contact between two neurons has now been shown to be facilitated by thrombospondins - large extracellular matrix proteins secreted by astrocytes.     

Giant Hydrogen Sulfide Plume in the Oxygen Minimum Zone off Peru Supports Chemolithoautotrophy

In Eastern Boundary Upwelling Systems nutrient-rich waters are transported to the ocean surface, fuelling high photoautotrophic primary production. Subsequent heterotrophic decomposition of the produced biomass increases the oxygen-depletion at intermediate water depths, which can result in the formation of oxygen minimum zones (OMZ). OMZs can sporadically accumulate hydrogen sulfide (H₂S), which is toxic to most multicellular organisms and has been implicated in massive fish kills. During a cruise to the OMZ off Peru in January 2009 we found a sulfidic plume in continental shelf waters, covering an area >5500 km², which contained ∼2.2×10⁴ tons of H₂S. This was the first time that H₂S was measured in the Peruvian OMZ and with ∼440 km³ the largest plume ever reported for oceanic waters. We assessed the phylogenetic and functional diversity of the inhabiting microbial community by high-throughput sequencing of DNA and RNA, while its metabolic activity was determined with rate measurements of carbon fixation and nitrogen transformation processes. The waters were dominated by several distinct γ-, δ- and ε-proteobacterial taxa associated with either sulfur oxidation or sulfate reduction. Our results suggest that these chemolithoautotrophic bacteria utilized several oxidants (oxygen, nitrate, nitrite, nitric oxide and nitrous oxide) to detoxify the sulfidic waters well below the oxic surface. The chemolithoautotrophic activity at our sampling site led to high rates of dark carbon fixation. Assuming that these chemolithoautotrophic rates were maintained throughout the sulfidic waters, they could be representing as much as ∼30% of the photoautotrophic carbon fixation.Postulated changes such as eutrophication and global warming, which lead to an expansion and intensification of OMZs, might also increase the frequency of sulfidic waters. We suggest that the chemolithoautotrophically fixed carbon may be involved in a negative feedback loop that could fuel further sulfate reduction and potentially stabilize the sulfidic OMZ waters.     

Bacterial biofilm formation under microgravity conditions

Although biofilm formation is widely documented on Earth, it has not been demonstrated in the absence of gravity. To explore this possibility, Pseudomonas aeruginosa, suspended in sterile buffer, was flown in a commercial payload on space shuttle flight STS-95. During earth orbit, biofilm formation was induced by exposing the bacteria to sterile media through a 0.2-microm (pore size) polycarbonate membrane. Examination of these membranes by confocal microscopy revealed biofilms to be present and that these biofilms could persist in spite of vigorous agitation. These results represent the first report of biofilm formation under microgravity conditions.     

Six new species of marine Tubificidae (Oligochaeta) from the continental shelf off Peru

Six species of marine tubifieids are described from the continental shelf off Peru. Two of them are members of the gutless genus Olavius Erséus, 1984 (subfamily Phallodrilinae). Olavius bullatus sp.n. possesses 2 pairs of large penial setae in voluminous copulatory sacs, tiny atria, and spermathecal pores in line with dorsal setae. Olavius crassitunicatus sp.n. is characterized by small atria with thin muscular layer, spermathecae with short ducts, opening dorso-laterally, and lack of penial setae. Four species arc members of the subfamily Limnodriloidinae. Limnodriloides busilicus sp.n. belongs to the appendiculatus-group (sensu Erséus). It is discriminated by somatic setae with subdental ligaments, and its voluminous elongate prostatic pads. Limnodriloides clavellatus sp.n. is distinguished from its congeners by a peculiar bulge in the cavity of each atrial ampulla, and spermatozeugmata imbedded in the walls of the spermathecae. Tectidrilus intermixtus sp.n. is similar to T. bori (Righi & Kanner, 1979); it is distinguished from the latter by having trisetal bundles in segment V or V-VI and by lacking copulatory glands. Marcusaedrilus peruanus sp.n. is characterized by nongranulated atrial ducts and bipartite spermathecae.     

Bacterial cell division: regulating Z-ring formation

The earliest stage of cell division in bacteria is the formation of a Z ring, composed of a polymer of the FtsZ protein, at the division site. Z rings appear to be synthesized in a bi‐directional manner from a nucleation site (NS) located on the inside of the cytoplasmic membrane. It is the utilization of a NS specifically at the site of septum formation that determines where and when division will occur. However, a Z ring can be made to form at positions other than at the division site. How does a cell regulate utilization of a NS at the correct location and at the right time? In rod‐shaped bacteria such as Escherichia coli and Bacillus subtilis, two factors involved in this regulation are the Min system and nucleoid occlusion. It is suggested that in B. subtilis, the main role of the Min proteins is to inhibit division at the nucleoid‐free cell poles. In E. coli it is currently not clear whether the Min system can direct a Z ring to the division site at mid‐cell or whether its main role is to ensure that division inhibition occurs away from mid‐cell, a role analogous to that in B. subtilis. While the nucleoid negatively influences Z‐ring formation in its vicinity in these rod‐shaped organisms, the exact relationship between nucleoid occlusion and the ability to form a mid‐cell Z ring is unresolved. Recent evidence suggests that in B. subtilis and Caulobacter crescentus, utilization of the NS at the division site is intimately linked to the progress of a round of chromosome replication and this may form the basis of achieving co‐ordination between chromosome replication and cell division.     

Distribution, abundance and behaviour of Buller's, Chatham Island and Salvin's Albatrosses off Chile and Peru

During 15 cruises between 1980 and 1995, we studied three species of albatross that nest in New Zealand but occur as non‐breeders along the Pacific coast of South America: Buller's Thalassarche bulleri, Chatham Island T. eremita, and Salvin's Albatross T. salvini. We logged 547 h of observation, surveying 7638 km² of ocean surface, and recorded 86, 27, and 475 individuals, respectively, of the three species. Chatham Island and Salvin's Albatrosses occurred throughout the Humboldt Current, but habitats differed. Buller's and Salvin's Albatrosses preferred the continental slope, while Chatham Island Albatrosses frequented mostly pelagic waters. On a latitudinal basis, Salvin's Albatross distribution was skewed northward in the austral autumn and southward in spring; Chatham Island Albatross occurred southward during autumn, but was everywhere scarce in spring; and Buller's Albatross occurred almost exclusively in the south (30°S to 40°S) in both seasons. Upwelling and wind speed were positively correlated with densities of Buller's and Salvin's Albatrosses. Densities of Chatham Island Albatrosses also were positively correlated with wind speed, but they occurred further offshore in more stratified waters (with less mixing/upwelling) than did the other two. Pelagic population estimates for the Humboldt Current system, analysed using generalized additive models, peaked at 26 700 individuals for Buller's Albatross (95% confidence interval (CI) 13 100–37 100); 6790 for Chatham Island Albatross (CI 3900–11 100); and 133 100 for Salvin's Albatross (CI 82 800–183 600). Based on adult:subadult ratios observed in the study area, our best estimates for the number of wintering adults were 9100, 5800 and 114 400 birds, respectively, or 20%, 73% and 75% of the numbers estimated (44 500, 8000 and 153 300 birds) for the breeding populations at respective colonies. If we subtract from the autumn count the number of adult‐plumaged birds seen in spring (assumed to be non‐breeders), then respective percentages were 0%, 73% and 65%. Foraging locations and attraction by these birds to commercial fishing operations makes them susceptible to mortality as a result of the recent development of a long‐line fishery on the continental slope of Chile.     

Tubular phosphatic microproblematica from the Early Ordovician of China

Fenhsiangia zhangwentangi gen. et sp. nov., is named for an animal represented by a phosphatic tube-like exoskeleton with the internal walls ornamented by stellate-based rounded tubercles. As vertebrates are the only animals known to possess stellate tubercles of phosphatic material in the dermal skeleton, yet our remains do not show any morphological or histological similarity to primitive fish bone, we suggest that Fenhsiangia was an ancestral protovertebrate, possibly an ascidian or related form. A second form, here referred to as Fenhsiangia sp. differs in that the tubercles are flat-topped or concave, and the external walls are deeply pitted with lines of small pustules bordering the depressions. The Upper Cambrian and Ordovician could have been a time of great diversity and radiation for protovertebrates. with the evolution of the first true vertebrates resulting from this radiation. □ Ordovician, China, phosphatic microproblematica, protovertebrate.     

Structural,photoluminescence and dielectric investigations of phosphatic shale

In the current study, the structural and spectroscopic properties of phosphatic shale samples obtained from the Atomic Minerals Directorate for Exploration and Research were probed for potential use as a phosphor material. X‐ray diffraction and Raman and Fourier transform infrared spectroscopy revealed that the beneficiated phosphatic shale samples were primarily monophasic consisting of fluorapatite [Ca₅(PO₄)₃F, (FAP)] with minor traces of haematite (α‐Fe₂O₃) and calcite (CaCO₃). Energy dispersive X‐ray fluorescence revealed the presence of U, Eu, Dy and Tb in the FAP matrix substituted at Ca(I) and Ca(II) sites of FAP. A reduced optical direct band gap of 4.46 eV was calculated from the Tauc plot. Photoluminescence spectral studies revealed multicolour emissions (red, yellow, green and blue) on ultraviolet light excitation that were attributed to luminescence spectra from rare earth ions Eu³⁺, Tb³⁺, U⁴⁺ and U⁶⁺ in the FAP matrix. The overall emissions for the rare earth and actinide‐doped FAP were obtained in the cool white region and the corresponding Commission Internationale de l’Eclairage chromaticity coordinates were calculated to be (0.274, 0.317). The corresponding colour correlated temperature obtained was 9342 K. Furthermore, phosphatic shale had a high room temperature dielectric constant of 11 at a frequency of 1 kHz that demonstrated its suitability for use in biological sensors. The study showed that natural phosphatic shale could be a potential material for optical, biological and dielectric applications.     

Bacterial aggregates formation after addition of glucose in Lake Baikal water

For determining the process of bacterial aggregation, glucose was added into water from Lake Baikal which had been stored for seven months. In the presence of a higher concentration of glucose, the abundance of single bacteria and aggregates were higher, but the biovolumes of both bacteria were similar. Theses results mean that both free-living and aggregated bacteria have similar maximum sizes and that aggregates are forming with available organic materials. With available organic materials, the biovolume of aggregates becomes larger.     

Bacterial lipopolysaccharide induces osteoclast formation in RAW 264.7 macrophage cells

Lipopolysaccharide (LPS) is a potent bone resorbing factor. The effect of LPS on osteoclast formation was examined by using murine RAW 264.7 macrophage cells. LPS-induced the formation of multinucleated giant cells (MGC) in RAW 264.7 cells 3 days after the exposure. MGCs were positive for tartrate-resistant acid phosphatase (TRAP) activity. Further, MGC formed resorption pits on calcium-phosphate thin film that is a substrate for osteoclasts. Therefore, LPS was suggested to induce osteoclast formation in RAW 264.7 cells. LPS-induced osteoclast formation was abolished by anti-tumor necrosis factor (TNF)-alpha antibody, but not antibodies to macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor (NF)-kappaB ligand (RANKL). TNF-alpha might play a critical role in LPS-induced osteoclast formation in RAW 264.7 cells. Inhibitors of NF-kappaB and stress activated protein kinase (SAPK/JNK) prevented the LPS-induced osteoclast formation. The detailed mechanism of LPS-induced osteoclast formation is discussed.