Isolation and characterization of Campylobacter jejuni subsp. jejuni from macaroni penguins (Eudyptes chrysolophus) in the subantarctic region.
(17/765)
On Bird Island, South Georgia, albatrosses (n = 140), penguins (n = 100), and fur seals (n = 206) were sampled for Campylobacter jejuni. C. jejuni subsp. jejuni was recovered from three macaroni penguins (Eudyptes chrysolophus). These isolates, the first reported for the subantarctic region, showed low genetic diversity and high similarity to Northern Hemisphere C. jejuni isolates, possibly suggesting recent introduction to the area. (+info)
A habitat for psychrophiles in deep Antarctic ice.
(18/765)
Microbes, some of which may be viable, have been found in ice cores drilled at Vostok Station at depths down to approximately 3,600 m, close to the surface of the huge subglacial Lake Vostok. Two types of ice have been found. The upper 3,500 m comprises glacial ice containing traces of nutrients of aeolian origin including sulfuric acid, nitric acid, methanosulfonic acid (MSA), formic acid, sea salts, and mineral grains. Ice below approximately 3,500 m comprises refrozen water from Lake Vostok, accreted to the bottom of the glacial ice. Nutrients in the accretion ice include salts and dissolved organic carbon. There is great interest in searching for living microbes and especially for new species in deepest Antarctic ice. I propose a habitat consisting of interconnected liquid veins along three-grain boundaries in ice in which psychrophilic bacteria can move and obtain energy and carbon from ions in solution. In the accretion ice, with an age of a few 10(4) years and a temperature a few degrees below freezing, the carbon and energy sources in the veins can maintain significant numbers of cells per cubic centimeter that are metabolizing but not multiplying. In the 4 x 10(5)-year-old colder glacial ice, at least 1 cell per cm(3) in acid veins can be maintained. With fluorescence microscopy tuned to detect NADH in live organisms, motile bacteria could be detected by direct scanning of the veins in ice samples. (+info)
Structural comparison of psychrophilic and mesophilic trypsins. Elucidating the molecular basis of cold-adaptation.
(19/765)
Structural rationalizations for differences in catalytic efficiency and stability between mesophilic and cold-adapted trypsins have been suggested from a detailed comparison of eight trypsin structures. Two trypsins, from Antarctic fish and Atlantic cod, have been constructed by homology modeling techniques and compared with six existing X-ray structures of both cold-adapted and mesophilic trypsins. The structural analysis focuses on the cold trypsin residue determinants found in a more extensive comparison of 27 trypsin sequences, and reveals a number of structural features unique to the cold-adapted trypsins. The increased substrate affinity of the psychrophilic trypsins is probably achieved by a lower electrostatic potential of the S1 binding pocket particularly arising from Glu221B, and from the lack of five hydrogen bonds adjacent to the catalytic triad. The reduced stability of the cold trypsins is expected to arise from reduced packing in two distinct core regions, fewer interdomain hydrogen bonds and from a destabilized C-terminal alpha-helix. The helices of the cold trypsins lack four hydrogen bonds and two salt-bridges, and they have poorer van der Waals packing interactions to the body of the molecule, compared to the mesophilic counterparts. (+info)
Alkaline phosphatase from the Antarctic strain TAB5. Properties and psychrophilic adaptations.
(20/765)
The gene encoding alkaline phosphatase (AP) from the psychrophilic strain TAB5 was cloned, and its nucleotide sequence was determined. A single open reading frame consisting of 1125 base pairs which encodes a polypeptide consisting of signal peptide of 22 amino acids and a mature protein of 353 amino acids was identified. The deduced protein sequence of AP exhibits a 38% identity to the AP III and AP IV sequences of Bacillus subtilis and conserves the typical sequence motifs of the core structure and active sites of APs from various sources. Based on the crystal structure of the mutated Escerichia coli AP D153H, a homology-based 3D model of the TAB5 AP was constructed on the basis of which various features of the enzyme amino-acid sequence can be interpreted in terms of potential psychrophilic adaptations. The AP gene was expressed in E. coli BL21(DE3) cells, the recombinant protein was isolated to homogeneity from the membrane fraction of the cells and its properties were examined. The purified TAB5 AP shows typical features of a cold enzyme: high catalytic activity at low temperature and a remarkable thermosensitivity. The use of this heat-labile enzyme, for dephosphorylation of nucleic acids, simplifies dephosphorylation protocols. (+info)
Antarctic sponges may host large populations of planktonic and benthic diatoms. After settling on the sponge, these diatoms enter its body through pinacocytes (1) and form, there, large mono- or pauci-specific assemblages. Yet the total amount of carbohydrates in the invaded sponge tissue is inversely correlated with that of chlorophyll-a. We suggest, therefore, that endobiont diatoms utilize the products of the metabolism of their host as an energy source. This is the first evidence indicating that an endobiotic autotrophic organism may parasitize its animal host. Moreover, this unusual symbiotic behavior could be a successful strategy that allows the diatom to survive in darkness. (+info)
Concentrations of myoglobin and myoglobin mRNA in heart ventricles from Antarctic fishes.
(22/765)
We used a combined immunochemical and molecular approach to ascertain the presence and concentrations of both the intracellular oxygen-binding hemoprotein myoglobin (Mb) and its messenger RNA (mRNA) in 13 of 15 known species of Antarctic channichthyid icefishes. Mb protein is present in the hearts of eight species of icefishes: Chionodraco rastrospinosus, Chionodraco hamatus, Chionodraco myersi, Chaenodraco wilsoni, Pseudochaenichthys georgianus, Cryodraco antarcticus, Chionobathyscus dewitti and Neopagetopsis ionah. Five icefish species lack detectable Mb protein: Chaenocephalus aceratus, Pagetopsis macropterus, Pagetopsis maculatus, Champsocephalus gunnari and Dacodraco hunteri. Mb concentrations range from 0.44+/-0.02 to 0.71+/-0.08 mg Mb g(-)(1 )wet mass in heart ventricle of species expressing the protein. A Mb-mRNA-specific cDNA probe was used to quantify mRNA in five Mb-expressing icefishes. Mb mRNA was found in low but detectable amounts in Champsocephalus gunnari, one of the species lacking detectable Mb. Mb mRNA concentrations in heart ventricle from Mb-expressing species ranged from 0.78+/-0.02 to 16.22+/-2.17 pg Mb mRNA microg(-)(1 )total RNA). Mb protein and Mb mRNA are absent from the oxidative skeletal muscle of all icefishes. Steady-state concentrations of Mb protein do not parallel steady-state concentrations of Mb mRNA within and among icefishes, indicating that the concentration of Mb protein is not determined by the size of its mRNA pool. (+info)
The interplay among cardiac ultrastructure, metabolism and the expression of oxygen-binding proteins in Antarctic fishes.
(23/765)
We examined heart ventricle from three species of Antarctic fishes that vary in their expression of oxygen-binding proteins to investigate how some of these fishes maintain cardiac function despite the loss of hemoglobin (Hb) and/or myoglobin (Mb). We quantified ultrastructural features and enzymatic indices of metabolic capacity in cardiac muscle from Gobionotothen gibberifrons, which expresses both Hb and Mb, Chionodraco rastrospinosus, which lacks Hb but expresses Mb, and Chaenocephalus aceratus, which lacks both Hb and Mb. The most striking difference in cellular architecture of the heart among these species is the percentage of cell volume occupied by mitochondria, V(v)(mit,f), which is greatest in Chaenocephalus aceratus (36.53+/-2.07), intermediate in Chionodraco rastrospinosus (20.10+/-0.74) and lowest in G. gibberifrons (15.87+/-0.74). There are also differences in mitochondrial morphologies among the three species. The surface area of inner mitochondrial membrane per volume of mitochondria, S(v)(imm, mit), varies inversely with mitochondrial volume density so that S(v)(imm,mit) is greatest in G. gibberifrons (29.63+/-1.62 microm(-)(1)), lower in Chionodraco rastrospinosus (21.52+/-0.69 microm(-)(1)) and smallest in Chaenocephalus aceratus (20.04+/-0.79 microm(-)(1)). The surface area of mitochondrial cristae per gram of tissue, however, is greater in Chaenocephalus aceratus than in G. gibberifrons and Chionodraco rastrospinosus, whose surface areas are similar. Despite significant ultrastructural differences, oxidative capacities, estimated from measurements of maximal activities per gram of tissue of enzymes from aerobic metabolic pathways, are similar among the three species. The combination of ultrastructural and enzymatic data indicates that there are differences in the density of electron transport chain proteins within the inner mitochondrial membrane; proteins are less densely packed within the cristae of hearts from Chaenocephalus aceratus than in the other two species. High mitochondrial densities within hearts from species that lack oxygen-binding proteins may help maintain oxygen flux by decreasing the diffusion distance between the ventricular lumen and mitochondrial membrane. Also, high mitochondrial densities result in a high intracellular lipid content, which may enhance oxygen diffusion because of the higher solubility of oxygen in lipid compared with cytoplasm. These results indicate that features of cardiac myocyte architecture in species lacking oxygen-binding proteins may maintain oxygen flux, ensuring that aerobic metabolic capacity is not diminished and that cardiac function is maintained. (+info)
Haemolymph Mg(2+) regulation in decapod crustaceans: physiological correlates and ecological consequences in polar areas.
(24/765)
Reptant decapod crustaceans are almost absent from the Southern Ocean south of the Antarctic Convergence. We tested the hypothesis that this may be due to the reduced ability of this group to regulate Mg(2+) levels in the haemolymph ([Mg(2+)](HL)). Mg(2+) acts as an anaesthetic in marine invertebrates and its level is higher in Reptantia (crabs such as Cancer spp., Chionoecetes spp., Maja spp., 30-50 mmol l(-)(1)) than in Natantia (prawns such as Pandalus spp., Palaemon spp., Crangon spp., 5-12 mmol l(-)(1)). We varied [Mg(2+)](HL) in three species of reptant decapod crustaceans, Carcinus maenas, Hyas araneus and Eurypodius latreillei, and investigated heart rate, the rate of oxygen consumption and levels of spontaneous and forced activity at different temperatures. The rate of oxygen consumption and heart rate increased significantly with reduction in [Mg(2+)](HL) over the entire temperature range investigated in E. latreillei. In H. araneus, an increase in metabolic and heart rates compared with control values was found only at temperatures below 2 degrees C. Forced and spontaneous activity levels increased significantly in the group of [Mg(2+)](HL)-reduced animals below 0 degrees C, at which control animals were mostly inactive. At a reduced [Mg(2+)](HL) of 5-12 mmol l(-)(1), which is the [Mg(2+)](HL) of caridean shrimps in the Southern Ocean, Q(10) and activation energy were reduced for all these variables and extended the temperature range over which physiological functions were maintained. We suggest that the high [Mg(2+)](HL) in Reptantia causes relaxation of the animals and reduces their scope for activity, especially at temperatures below 0 degrees C. The hypothesis that the synergistic effects of high [Mg(2+)](HL) and low temperature probably prevented the Reptantia from recolonizing the permanently cold water of polar areas is discussed. (+info)