Novel members of the family Flavobacteriaceae from Antarctic maritime habitats including Subsaximicrobium wynnwilliamsii gen. nov., sp. nov., Subsaximicrobium saxinquilinus sp. nov., Subsaxibacter broadyi gen. nov., sp. nov., Lacinutrix copepodicola gen. nov., sp. nov., and novel species of the genera Bizionia, Gelidibacter and Gillisia.
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Several orange- and yellow-pigmented, halophilic, strictly aerobic, chemoheterotrophic, Gram-negative strains were isolated during investigations of maritime Antarctic habitats, including coastal fast sea-ice brine and algae, crustaceans and quartz stone sublithic cyanobacterial biofilms. Isolates investigated in this study belonged to the marine clade of the family Flavobacteriaceae and represented lineages that were either distinct from species with validly published names or appeared to be distinct species within existing genera. A polyphasic taxonomic analysis demonstrated the novelty of these strains, and several new taxa are proposed. Strains from quartz stone sublithic communities were grouped into two new genera designated Subsaximicrobium gen. nov. and Subsaxibacter gen. nov. The genus Subsaximicrobium included the species Subsaximicrobium wynnwilliamsii sp. nov. (type species; type strain G#7(T)=ACAM 1070(T)=CIP 108525(T)) and Subsaximicrobium saxinquilinus sp. nov. (type strain Y4-5(T)=ACAM 1063(T)=CIP 108526(T)). The genus Subsaxibacter contained a single species designated Subsaxibacter broadyi sp. nov. (type strain P7(T)=ACAM 1064(T)=CIP 108527(T)). A novel bacterial strain isolated from the lake-dwelling, calanoid copepod Paralabidocera antarctica was given the name Lacinutrix copepodicola gen. nov., sp. nov. (type strain DJ3(T)=ACAM 1055(T)=CIP 108538(T)). Four novel species of the genus Bizionia were discovered, Bizionia algoritergicola sp. nov. (type strain APA-1(T)=ACAM 1056(T)=CIP 108533(T)) and Bizionia myxarmorum sp. nov. (type strain ADA-4(T)=ACAM 1058(T)=CIP 108535(T)), which were isolated from the carapace surfaces of sea-ice algae-feeding amphipods, and Bizionia gelidisalsuginis sp. nov. (type strain IC164(T)=ACAM 1057(T)=CIP 108536(T)) and Bizionia saleffrena sp. nov. (type strain HFD(T)=ACAM 1059(T)=CIP 108534(T)), which were isolated from sea-ice brines. Several other novel species were also isolated from sea-ice samples, including two novel species of the genus Gelidibacter, Gelidibacter gilvus sp. nov. (type strain IC158(T)=ACAM 1054(T)=CIP 108531(T)) and Gelidibacter salicanalis sp. nov. (type strain IC162(T)=ACAM 1053(T)=CIP 108532(T)), as well as three novel species of the genus Gillisia, Gillisia illustrilutea sp. nov. (type strain IC157(T)=ACAM 1062(T)=CIP 108530(T)), Gillisia sandarakina sp. nov. (type strain IC148(T)=ACAM 1060(T)=CIP 108529(T)) and Gillisia hiemivivida sp. nov. (type strain IC154(T)=ACAM 1061(T)=CIP 108528(T)). (+info)
Novel point mutation in the sodium channel gene of pyrethroid-resistant sea lice Lepeophtheirus salmonis (Crustacea: Copepoda).
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Knockdown resistance (kdr) to pyrethroid insecticides is caused by point mutations in the pyrethroid target site, the para-type sodium channel of nerve membranes. This most commonly involves alterations within the domain II (S4-S6) region of the channel protein, where several different mutation sites have been identified across a range of insect species. To investigate the possibility that a kdr-type mechanism is responsible for pyrethroid resistance in sea lice, a domain II region of the Lepeophtheirus salmonis sodium channel gene was PCR amplified and sequenced. To our knowledge, this is the first published sodium channel sequence from a crustacean. Comparison of sequences from a range of samples, including several individuals from areas in which control failures had been reported, failed to identify any of the mutations within this region that have previously been linked with resistance. Instead, a novel glutamine to arginine mutation, Q945R, in transmembrane segment IIS5 was consistently found in the samples from areas of control failure and may therefore be associated with resistance to pyrethroids in this species. (+info)
Critical factors influencing the occurrence of Vibrio cholerae in the environment of Bangladesh.
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The occurrence of outbreaks of cholera in Africa in 1970 and in Latin America in 1991, mainly in coastal communities, and the appearance of the new serotype Vibrio cholerae O139 in India and subsequently in Bangladesh have stimulated efforts to understand environmental factors influencing the growth and geographic distribution of epidemic Vibrio cholerae serotypes. Because of the severity of recent epidemics, cholera is now being considered by some infectious disease investigators as a "reemerging" disease, prompting new work on the ecology of vibrios. Epidemiological and ecological surveillance for cholera has been under way in four rural, geographically separated locations in Bangladesh for the past 4 years, during which both clinical and environmental samples were collected at biweekly intervals. The clinical epidemiology portion of the research has been published (Sack et al., J. Infect. Dis. 187:96-101, 2003). The results of environmental sampling and analysis of the environmental and clinical data have revealed significant correlations of water temperature, water depth, rainfall, conductivity, and copepod counts with the occurrence of cholera toxin-producing bacteria (presumably V. cholerae). The lag periods between increases or decreases in units of factors, such as temperature and salinity, and occurrence of cholera correlate with biological parameters, e.g., plankton population blooms. The new information on the ecology of V. cholerae is proving useful in developing environmental models for the prediction of cholera epidemics. (+info)
Nature of phosphorus limitation in the ultraoligotrophic eastern Mediterranean.
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Phosphate addition to surface waters of the ultraoligotrophic, phosphorus-starved eastern Mediterranean in a Lagrangian experiment caused unexpected ecosystem responses. The system exhibited a decline in chlorophyll and an increase in bacterial production and copepod egg abundance. Although nitrogen and phosphorus colimitation hindered phytoplankton growth, phosphorous may have been transferred through the microbial food web to copepods via two, not mutually exclusive, pathways: (i) bypass of the phytoplankton compartment by phosphorus uptake in heterotrophic bacteria and (ii) tunnelling, whereby phosphate luxury consumption rapidly shifts the stoichiometric composition of copepod prey. Copepods may thus be coupled to lower trophic levels through interactions not usually considered. (+info)
Temperature compensation in the escape response of a marine copepod, Calanus finmarchicus (Crustacea).
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Calanus finmarchicus, the dominant mesozooplankter of the North Atlantic, is an important food source for many fishes and other planktivores. This species, which has limited diel vertical migration, depends on its fast-start escape response to evade predators. It has myelinated neuronal axons, which contribute to its rapid and powerful escape response. The thermal environment that C. finmarchicus inhabits ranges from below 0 degrees C to 16 degrees C. Previous studies have shown that respiration, growth, and reproductive rates are strongly dependent on temperature, with Q10 > 2.5. A comparable dependence of the escape response could place the animal at higher risk for cold-compensated predators. Our work focused on the temperature dependence of the behavioral response to stimuli that mimic predatory attacks. We found that in contrast to other biological processes, all aspects of the escape response showed a low dependence on temperature, with Q10 values below 2. This low temperature dependence was consistent for escape parameters that involved neural as well as muscle components of the behavioral response. These findings are discussed in the contexts of the predator-prey relations of copepods and the thermal dependence of behavior in other taxa. (+info)
Fatty acid utilisation and metabolism in caecal enterocytes of rainbow trout (Oncorhynchus mykiss) fed dietary fish or copepod oil.
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A combined fatty acid metabolism assay was employed to determine fatty acid uptake and relative utilisation in enterocytes isolated from the pyloric caeca of rainbow trout. In addition, the effect of a diet high in long-chain monoenoic fatty alcohols present as wax esters in oil derived from Calanus finmarchicus, compared to a standard fish oil diet, on caecal enterocyte fatty acid metabolism was investigated. The diets were fed for 8 weeks before caecal enterocytes from each dietary group were isolated and incubated with [1-14C]fatty acids: 16:0, 18:1n-9, 18:2n-6, 18:3n-3, 20:1n-9, 20:4n-6, 20:5n-3, and 22:6n-3. Uptake was measured over 2 h with relative utilisation of different [1-14C]fatty acids calculated as a percentage of uptake. Differences in uptake were observed, with 18:1n-9 and 18:2n-6 showing the highest rates. Esterification into cellular lipids was highest with 16:0 and C18 fatty acids, accounting for over one-third of total uptake, through predominant incorporation in triacylglycerol (TAG). The overall utilisation of fatty acids in phospholipid synthesis was low, but highest with 16:0, the most prevalent fatty acid recovered in intracellular phosphatidylcholine (PC) and phosphatidylinositol (PI), although exported PC exhibited higher proportions of C20/C22 polyunsaturated fatty acids (PUFA). Other than 16:0, incorporation into PC and PI was highest with C20/C22 PUFA and 20:4n-6 respectively. Recovery of labelled 18:1n-9 in exported TAG was 3-fold greater than any other fatty acid which could be due to multiple esterification on the glycerol 'backbone' and/or increased export. Approximately 20-40% of fatty acids taken up were beta-oxidised, and was highest with 20:4n-6. Oxidation of 20:5n-3 and 22:6n-3 was also surprisingly high, although 22:6n-3 oxidation was mainly attributed to retroconversion to 20:5n-3. Metabolic modification of fatty acids by elongation-desaturation was generally low at <10% of [1-14C]fatty acid uptake. Dietary copepod oil had generally little effect on fatty acid metabolism in enterocytes, although it stimulated the elongation and desaturation of 16:0 and elongation of 18:1n-9, with radioactivity recovered in longer n-9 monoenes. The monoenoic fatty acid, 20:1n-9, abundant in copepod oil as the homologous alcohol, was poorly utilised with 80% of uptake remaining unesterified in the enterocyte. However, the fatty acid composition of pyloric caeca was not influenced by dietary copepod oil. (+info)
Evolutionary implications of the adaptation to different immune systems in a parasite with a complex life cycle.
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Many diseases are caused by parasites with complex life cycles that involve several hosts. If parasites cope better with only one of the different types of immune systems of their host species, we might expect a trade-off in parasite performance in the different hosts, that likely influences the evolution of virulence. We tested this hypothesis in a naturally co-evolving host-parasite system consisting of the tapeworm Schistocephalus solidus and its intermediate hosts, a copepod, Macrocyclops albidus, and the three-spined stickleback Gasterosteus aculeatus. We did not find a trade-off between infection success in the two hosts. Rather, tapeworms seem to trade-off adaptation towards different parts of their hosts' immune systems. Worm sibships that performed better in the invertebrate host also seem to be able to evade detection by the fish innate defence systems, i.e. induce lower levels of activation of innate immune components. These worm variants were less harmful for the fish host likely due to reduced costs of an activated innate immune system. These findings substantiate the impact of both hosts' immune systems on parasite performance and virulence. (+info)
Tracing hybrid incompatibilities to single amino acid substitutions.
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Deleterious interactions among genes cause reductions in fitness of interpopulation hybrids (hybrid breakdown). Identifying genes involved in hybrid breakdown has proven difficult, and few studies have addressed the molecular basis of this widespread phenomenon. Because proper function of the mitochondrial electron transport system (ETS) requires a coadapted set of nuclear and mitochondrial gene products, ETS genes present an attractive system for studying the evolution of coadapted gene complexes within isolated populations and the loss of fitness in interpopulation hybrids. Here we show the effects of single amino acid substitutions in cytochrome c (CYC) on its functional interaction with another ETS protein, cytochrome c oxidase (COX) in the intertidal copepod Tigriopus californicus. The individual and pairwise consequences of three naturally occurring amino acid substitutions in CYC are examined by site-directed mutagenesis and found to differentially effect the rates of CYC oxidation by COX variants from different source populations. In one case, we show that interpopulation hybrid breakdown in COX activity can be attributed to a single naturally occurring amino acid substitution in CYC. (+info)