Dietary overlap among early juvenile stages in an Antarctic notothenioid fish assemblage at Potter Cove,South Shetland Islands

To date, studies of food overlap in Antarctic fish have been performed on a mixture of late juvenile and adult stages, leaving the young immature specimens (TL ≤ 10 cm) practically unexplored. We studied diet overlap and potential competition among early juvenile individuals in a coastal notothenioid community at Potter Cove, by analysing the stomach contents of 225 fish of 5 species collected in the summer of 2009–2010. We used frequency of occurrence (F %) and the coefficient “Q” for diet evaluation and the method of Tyler and the similarity index “S” for food overlap. Amphipods of the suborder Gammaridea were the main (Q > 2.900) and most frequent (% F) prey for all species, although Notothenia coriiceps also consumed gastropods of the family Littorinidae, mostly Laevilitorina antarctica. Secondary prey were algae for Notothenia rossii and N. coriiceps, calanoid (pelagic) and harpacticoid (benthic) copepods for Trematomus newnesi and the latter copepods and isopods of the family Munnidae for Lepidonotothen nudifrons. The reoccurrence of prey among fish species was 39.6 % and food overlap between 90 % of species pairs was under 58 %. Because similarly low values of diet overlap were reported for intermediate/advanced juveniles and adults of the same species at the same site, we conclude that there is no difference in the degree of interspecific food overlap and therefore potential competition between the immature and mature fraction of the fish community. Food competition is avoided by resource partitioning along a depth gradient or by different prey species.     

Ontogeny of feeding in two native and one alien fish species from the Murray-Darling Basin, Australia

Investigations into the feeding of the early stages of fishes can provide insights into processes influencing recruitment. In this study, we examined ontogenetic changes in morphology and feeding behaviour of two native Australian freshwater species, Murray cod, Maccullochella peelii peelii, and golden perch, Macquaria ambigua, and the alien species, common carp, Cyprinus carpio. Murray cod free embryos are large and well developed at the onset of feeding, whereas the other two species begin exogenous feeding much younger and are smaller and less-developed. Carp commence exogenous feeding 3 days earlier than golden perch, and show more advanced development of the eyes and ingestive apparatus. We conducted feeding experiments, presenting larvae of the three species with a standardised prey mix (comprising equal numbers of small calanoid copepods, large calanoid copepods, small Daphnia, and large Daphnia). Larvae of most tested ages and species showed a preference for mid-sized prey (300–500 μm wide). This was true even when their gapes substantially exceeded the largest prey offered. Daphnia were consumed more than similar-sized copepods. The results of this study suggest that survival through their larval period will be threatened in all three species if catchable prey <500 μm in width are not available throughout such time. They also suggest that interspecific competition for prey may occur, especially when larvae are very young. The precocious development of structures involved in feeding and the extended transition from endogenous to exogenous feeding of early carp larvae are likely to have contributed to the success of this species since its introduction to Australia.     

The plankton community of Lake Matano: factors regulating plankton composition and relative abundance in an ancient,tropical lake of Indonesia

Recent evidence reveals that food webs within the Malili Lakes, Sulawesi, Indonesia, support community assemblages that are made up primarily of endemic species. It has been suggested that many of the species radiations, as well as the paucity of cosmopolitan species in the lakes, are related to resource limitation. In order to substantiate the possibility that resource limitation is playing such an important role, a study of the phytoplankton and zooplankton communities of Lake Matano was implemented between 2000 and 2004. We determined species diversity, relative abundances, size ranges, and total biomass for the phytoplankton and zooplankton, including the distribution of ovigerous individuals throughout the epilimnion of Lake Matano in three field seasons. The phytoplankton community exhibited very low biomass (<15 μg l^?1) and species richness was depressed. The zooplankton assemblage was also limited in biomass (2.5 mg l^?1) and consisted only of three taxa including the endemic calanoid Eodiaptomus wolterecki var. matanensis, the endemic cyclopoid, Tropocyclops matanensis and the rotifer Horaella brehmi. Zooplankton were very small (<600 μm body length), and spatial habitat partitioning was observed, with Tropocylops being confined to below 80 m, while rotifer and calanoid species were consistently observed above 80 m. Less than 0.1% of the calanoid copepods in each year were egg-bearing, suggesting very low population turnover rates. It was concluded that chemical factors as opposed to physical or biological processes were regulating the observed very low standing crops of phytoplankton which in turn supports a very minimal zooplankton community restricted in both species composition and abundance. As chemical factors are a function of the catchment basin of Lake Matano, it is predicted that resource limitation has long played an important role in shaping the unique endemic assemblages currently observed in the food web of the lake.     

Dietary characteristics of co-occurring polar cod (<Emphasis Type="Italic">Boreogadus saida</Emphasis>) and capelin (<Emphasis Type="Italic">Mallotus villosus</Emphasis>) in the Canadian Arctic,Darnley Bay

Reduction in sea ice due to climate change is expected to have a negative impact on habitat availability for Arctic marine fishes and induce range expansion of species from southern environments. Such an effect will likely be observed in the abundance of polar cod, Boreogadus saida (Lepechin, 1774), as well as interspecific interactions of this intermediate-level trophic taxon, particularly in more southerly fringing seas in the Arctic. Polar cod and capelin, Mallotus villosus (Müller, 1776), are pelagic, planktivorous forage fishes, which occupy similar dietary niches and are the primary prey of marine predators. Co-occurring polar cod and capelin were collected at seven stations in Darnley Bay, NT, during August 2013. Standard length (SL), used as a proxy for age, suggested that polar cod (mean ± 1 SD: 71.1 ± 10.3 mm) were predominantly age 1+ and capelin (96.2 ± 13.4 mm) were mostly age 2+. Stomach content analyses indicated that both species feed extensively on calanoid copepods (Calanus hyperboreus, C. glacialis, Metridia longa) and amphipods (Themisto libellula). There was high dietary overlap between capelin and polar cod, evidenced by Schoener’s index (0.80). Additionally the quantity of dietary items, biomass and energetic content consumed differed among size classes in both capelin (SL, 70.5–132.0 mm) and polar cod (SL, 42.1–114.4 mm). This study illustrates that the diets of these sympatric forage fishes in an Arctic ecosystem are very similar, indicating a high potential for interspecific competition as the sub-Arctic capelin expands its range into Arctic regions with climate change.     

Bioprospecting of thermo- and osmo-tolerant fungi from mango pulp–peel compost for bioethanol production

The persistent edaphic stress on microbial succession due to dynamic changes during composting was explored for selection of multi-stress tolerant microbe(s) desirable for ethanol production. A total of 23 strains were isolated from mango compost using four successive enrichments in YP broth (g l^?1): glucose, 100; 150; 250 with ethanol (40) and cycloheximide (0.4) at 40 °C, pH 6.0. Based on multi-gene ribotyping, 14 yeasts (61 %) of Saccharomycetaceae, 2 filamentous fungi (8.6 %) and 7 bacteria (30.4 %) were obtained. Phenetic and phylogenetic analysis of the 14 yeasts revealed 64.3 % tolerant to 500 g l^?1 glucose, growth at 45 °C and resemblance to Candida sp. (14.3 %), Kluyveromyces marxianus (35.7 %), Pichia kudriavzevii (21.4 %) and Saccharomyces cerevisiae (28.6 %). Assessment of the 14 yeasts in glucose fermentation medium (pH 4.5 at 40 °C) showed ethanol productivity of ≥92 % by 12 yeasts with theoretical yields of 90–97 %. Fermentation of molasses (150 g l^?1 glucose equivalent) by P. kudriavzevii D1C at 40 °C resulted in 73.70 ± 0.02 g l^?1 ethanol and productivity of 4.91 ± 0.01 g l^?1 h^?1. Assessment of P. kudriavzevii D1C revealed multi-stress tolerance towards 5-hydroxymethyl furfural, ethanol (20 %, v/v), high gravity and H₂O₂ (0.3 M) indicating suitability for ethanol production using high gravity molasses and pre-treated lignocellulosic biomass fermentation.     

Increased production of γ-lactones from hydroxy fatty acids by whole Waltomyces lipofer cells induced with oleic acid

Among several fatty acids tested, oleic acid was selected as the most efficient inducer for the production of 4-hydroxydodecanoic acid, a metabolite of β-oxidation, by Waltomyces lipofer. Cells were induced by incubation for 12 h in a medium containing 10 g l^?1 yeast extract, 10 g l^?1 peptone, 5 g l^?1 oleic acid, 1 g l^?1 glucose, and 0.05 % (w/v) Tween 80. The optimal reaction conditions for the production of γ-lactones by induced cells were pH 6.5, 35 °C, 200 rpm, 0.71 M Tris, 60 g l^?1 hydroxy fatty acid, and 20 g l^?1 cells. Non-induced cells produced 38 g l^?1 γ-dodecalactone from 60 g l^?1 10-hydroxystearic acid after 30 h, with a conversion yield of 63 % (w/w) and a productivity of 1.3 g l^?1 h^?1 under the optimized conditions, whereas induced cells produced 51 g l^?1 γ-dodecalactone from 60 g l^?1 10-hydroxystearic acid after 30 h, with a conversion yield of 85 % (w/w) and a productivity of 1.7 g l^?1 h^?1. The conversion yield and productivity of induced cells were 22 % and 1.3-fold higher, respectively, than those of non-induced cells. Induced cells also produced 28 g l^?1 γ-decalactone and 12 g l^?1 γ-butyrolactone from 60 g l^?1 12-hydroxystearic acid and 60 g l^?1 10-hydroxydecanoic acid, respectively, after 30 h. The concentration, conversion yield, and productivity of γ-dodecalactone and γ-decalactone are the highest reported thus far. This is the first study on the biotechnological production of γ-butyrolactone.     

Somatic organic content of the ctenophores <Emphasis Type="Italic">Mnemiopsis leidyi</Emphasis> (Ctenophora: Lobata) and <Emphasis Type="Italic">Beroe ovata</Emphasis> (Ctenophora: Beroida) in early ontogenetic stages

The organic matter content in the eggs and early larvae of the ctenophores Mnemiopsis leidyi and Beroe ovata from the Black Sea was determined using the adapted microtechnique of dichromate oxidation. The content of organic matter in the eggs of M. leidyi (0.25 μg/indiv.) was 5 times less than in B. ovata (1.28 ± 0.29 μg/indiv.). The somatic content of organic matter was 0.25 ± 0.09 μg/indiv. (25.1 ± 8.3 μg/mg, wet wt) for 2-day-old larvae of M. leidyi (0.2–0.3 mm in body length) and 1.37 ± 0.19 μg/indiv. (67.1 ± 5.7 μg/mg wet wt) for larvae of B. ovata (0.4 mm in body length). The specific organic content of larvae of both species steadily decreased with an increase in ctenophore body size and weight, approaching 3–4 μg/mg of wet weight for 2 mm specimens of M. leidyi and 3–5 μg/mg of wet weight for 6 mm B. ovata. The specific organic content of early larvae was 20–30 times higher than that of adult ctenophores. The results of this investigation could be useful in the evaluation of the energy budget for somatic growth and generative production in these species. Calculations indicate that with specific wet weight growth rates of 0.43/day for M. leidyi larvae and 0.29/day for B. ovata larvae, their true organic increases are respectively 30 and 38% less, i.e., no more than 0.31/day for the former and 0.18/day for the latter species.     

The effect of hexose ratios on metabolite production in Saccharomyces cerevisiae strains obtained from the spontaneous fermentation of mezcal

Mezcal from Tamaulipas (México) is produced by spontaneous alcoholic fermentation using Agave spp. musts, which are rich in fructose. In this study eight Saccharomyces cerevisiae isolates obtained at the final stage of fermentation from a traditional mezcal winery were analysed in three semi-synthetic media. Medium M1 had a sugar content of 100 g l^?1 and a glucose/fructose (G/F) of 9:1. Medium M2 had a sugar content of 100 g l^?1 and a G/F of 1:9. Medium M3 had a sugar content of 200 g l^?1 and a G/F of 1:1. In the three types of media tested, the highest ethanol yield was obtained from the glucophilic strain LCBG-3Y5, while strain LCBG-3Y8 was highly resistant to ethanol and the most fructophilic of the mezcal strains. Strain LCBG-3Y5 produced more glycerol (4.4 g l^?1) and acetic acid (1 g l^?1) in M2 than in M1 (1.7 and 0.5 g l^?1, respectively), and the ethanol yields were higher for all strains in M1 except for LCBG-3Y5, -3Y8 and the Fermichamp strain. In medium M3, only the Fermichamp strain was able to fully consume the 100 g of fructose l^?1 but left a residual 32 g of glucose l^?1. Regarding the hexose transporters, a high number of amino acid polymorphisms were found in the Hxt1p sequences. Strain LCBG-3Y8 exhibited eight unique amino acid changes, followed by the Fermichamp strain with three changes. In Hxt3p, we observed nine amino acid polymorphisms unique for the Fermichamp strain and five unique changes for the mezcal strains.     

Spatio-temporal overlap of the alien invasive ctenophore <Emphasis Type="Italic">Mnemiopsis leidyi</Emphasis> and ichthyoplankton in the Bornholm Basin (Baltic Sea)

In 2007 the alien invasive ctenophore Mnemiopsis leidyi A. Agassiz 1865 was recorded for the first time in the Bornholm Basin, an area which serves as important spawning ground for Baltic fish stocks. Since M. leidyi is capable of preying upon early life stages of fish and further might act as food competitor for fish larvae, it is of major concern to investigate the potential threat that this non-indigenous species poses to the pelagic ecosystem of the Baltic Sea. The present study investigates the temporal and spatial overlap of M. leidyi with eggs and larvae of Baltic cod (Gadus morhua L.) and sprat (Sprattus sprattus L.) in order to assess the potential impact of this new invader on two of the most important Baltic fish stocks. Results show variable inter-seasonal distribution and overlap dynamics and thus different seasonal threat-scenarios for the early life stages of cod and sprat. The spatial overlap between M. leidyi and ichthyoplankton was low for most of the period observed, and we conclude that M. leidyi presently does not have a strong impact. However, we detected situations with high overlaps, e.g. for sprat larvae and cod eggs in spring. As the population dynamics of M. leidyi in the central Baltic are not yet fully understood, a future population explosion of the alien ctenophore with possible effects on fish recruitment cannot be ruled out. Furthermore, a possible shift in peak spawning of cod to the early season, when ctenophore abundances were relatively high, might increase the impact of M. leidyi on cod.     

Food and feeding ecology of postlarval and juvenile Pleuragramma antarcticum (Pisces; Notothenioidei) in the seasonal pack ice zone off the Antarctic peninsula

Summary Stomach contents of 275 postlarval and 269 one year old juvenile Pleuragramma antarcticum caught in February 1982, March 1981 and November 1977 in the Bransfield Strait and adjacent waters were investigated. Juveniles in November 1977 fed mainly on calanoid copepods and Oithona spp. The principal food of postlarvae in February 1982 were Oncaea spp., eggs of calanoid copepods and tintinnids whereas the staple food of juveniles in February 1982 consisted of calanoid copepods of which copepodites of Calanus propinquus were most abundant. Eggs of Euphausia superba were frequently ingested by postlarvae and were the main component of the juvenile diet in the Antarctic Sound. Postlarvae in March 1981 preyed on Oncaea spp. and calanoid eggs. There was a shift from feeding on cyclopoid copepods by postlarvae to feeding on calanoids by juveniles. The food particle size increased as a function of fish length. Maximum prey size was controlled by mouth width up to at least 45 mm standard length. Prey selection was apparently food density dependent with an inverse relationship between food abundance and selective feeding. Density dependent size selection may have resulted in resource partitioning among postlarval and juvenile fishes in February. This specific feeding behaviour is likely to be an adaptation to the low zooplankton stocks of the high Antarctic shelf waters to minimize food competition among the youngest age classes. Predation on krill eggs indicated that the frequent association of one year old juvenile Pleuragramma antarcticum with the Antarctic krill is related to local spawning events.     

Latitude and elevation as factors controlling occurrence of calanoid copepods in marginal lotic waters in New South Wales,Australia

Freshwater calanoid copepods develop abundant populations in lentic water bodies such as lakes, reservoirs and lagoons. In this study, we examined the potential habitat value of edges in lotic systems such as creeks and rivers where waters tend to stagnate, providing lentic-like environments. We examined a total of 353 edge samples collected from 321 sites across the state of New South Wales, Australia, with latitudes in the range 28.3–37.4°S and elevations in the range 2–1834 m above sea level. Of the total samples examined, calanoid copepods were found in 94 samples, with the frequency of occurrences of species decreasing in the order: Boeckella fluvialis Henry, B. triarticulata (Thomson), Gladioferens spinosus Henry, G. pectinatus (Brady), B. major Searle, B. minuta Sars, and Calamoecia lucasi Brady. The probability of occurrence of the calanoid copepods was related negatively to both latitude (as absolute values) and elevation, based on logistic regression models. We conclude that the edges of many lotic systems provide additional habitats for some species of freshwater calanoid copepods, with constraints on their distributions along latitudinal and elevational gradients.     

Cryopreservation of in vitro-grown shoot tips of Alnus glutinosa (L.) Gaertn.

In vitro-grown shoot tips of Alnus glutinosa (L.) Gaertn. were successfully cryopreserved by vitrification. Shoot tips (0.5–1 mm) excised from 6-week-old shoots were precultured in hormone-free Woody Plant Medium (WPM) supplemented with 0.2 M sucrose, for 2 days at 4 °C in the dark, and then treated with a mixture of 2 M glycerol plus 0.4 M sucrose, for 20 min at 25 °C. Osmoprotected shoot tips were first dehydrated with 50 % vitrification solution (PVS2), for 30 min at 0 °C, and then placed in 100 % PVS2, for 30 min at 0 °C. The solution was replaced with fresh 100 % PVS2, and the shoot tips were plunged directly into liquid nitrogen. The shoot tips were rewarmed in a water bath at 40 °C for 2 min, and then washed twice, for 10 min at 25 °C, with 1.2 M sucrose solution, before being transferred onto WPM supplemented with 0.5 mg l^?1 N ⁶-benzyladenine, 0.5 mg l^?1 indole-3-acetic acid, 0.2 mg l^?1 zeatin, 20 g l^?1 glucose and 6 g l^?1 Difco Bacto agar. The shoot tips were kept in darkness for 1 week and under dim lighting for another week, before being exposed to standard culture conditions (16 h photoperiod). This protocol was successfully applied to three alder genotypes, with recovery rates higher than 50 %.     

Biomass and Total Lipid Content Assessment of Microalgal Cultures Using Near and Short Wave Infrared Spectroscopy

The technique of near and short wave near-infrared spectroscopy was assessed with respect to analysis of dry matter and lipid content of microalgae with potential for biodiesel production. Microalgal culture samples were filtered through GF/C filter papers and spectral measurements of wet and oven dried (60 °C overnight) filter papers over the ranges of 300–1,100 nm and 1,100–2,500 nm were recorded. Partial least square models on culture biomass and lipid content for combined species data were poor in terms of RMSECV, R _CV and the ratio of RMSECV to SD. A single species model for C. vulgaris based on 1,100–2,500 nm spectra of dry filtrate supported a model with RMSECV, R _CV and SDR values of 0.32 g L^?1, 0.955 and 3.38 for biomass and 0.089 g L^?1, 0.874 and 2.06 with lipid, respectively. However, the dry filtrate models on biomass and lipid content performed poorly in the prediction of samples drawn from an independent series of C. vulgaris cultured under N-, P- and Fe-limited growth trial. Thus, while the near-infrared spectroscopy technique has potential for assessment of dry matter and lipid content of microalgal cultures using a dried filtrate sample, further work is required to examine the limits to model robustness.     

A plague of waterfleas (<Emphasis Type="Italic">Bythotrephes</Emphasis>): impacts on microcrustacean community structure,seasonal biomass,and secondary production in a large inland-lake complex

The spiny cladoceran (Bythotrephes longimanus) is an invasive, predaceous zooplankter that is expanding from Great Lakes coastal waters into inland lakes within a northern latitudinal band. In a large, Boundary Water lake complex (largely within Voyageurs National Park), we use two comparisons, a 2-year spatial and a 12-year temporal, to quantify seasonal impacts on food webs and biomass, plus a preliminary calculation of secondary production decline. Bythotrephes alters the seasonal biomass pattern by severely depressing microcrustaceans during summer and early fall, when the predator is most abundant. Cladoceran and cyclopoid copepods suffer the most serious population declines, although the resistant cladoceran Holopedium is favored in spatial comparisons. Microcrustacean biomass is reduced 40–60 % and secondary production declines by about 67 %. The microcrustacean community shifts towards calanoid copepods. The decline in secondary production is due both to summer biomass loss and to the longer generation times of calanoid copepods (slower turnover). The Bythotrephes “top-down” perturbation appears to hold across small, intermediate, and large-sized lakes (i.e. appears scale-independent), and is pronounced when Bythotrephes densities reach 20–40 individuals L^?1. Induction tests with small cladocerans (Bosmina) suggest that certain native prey populations do not sense the exotic predator and are “blind-sided”. Failure of prey to deploy defenses could explain the disproportionate community impacts in New World versus Old World lakes.     

Grazing impact on the cyanobacterium Microcystis aeruginosa by the heterotrophic flagellate Collodictyon triciliatum in an experimental pond

We estimated the grazing impact of the heterotrophic flagellate Collodictyon triciliatum on the harmful, bloom-forming cyanobacterium Microcystis aeruginosa in an experimental pond during a Microcystis bloom from summer to winter in 2010. For these experiments, we calculated the grazing rates from the digestion rate of C. triciliatum and its food vacuole contents. During the study period, M. aeruginosa exhibited one bloom event with a maximum density of 1.1 × 10⁵ cells ml^?1. The cell density of C. triciliatum fluctuated from below the detection limit to 291 cells ml^?1. The number of M. aeruginosa cells ingested by C. triciliatum food vacuoles ranged between 0.4 and 10.8 cells flagellate^?1, and the digestion rate of C. triciliatum at 25 °C was 0.73 % cell contents min^?1. The grazing rate of C. triciliatum on the M. aeruginosa prey was 0.2–6.9 cells flagellate^?1 h^?1, and its grazing impact was 0.0–25.3 % standing stock day^?1. The functional response of C. triciliatum to the M. aeruginosa prey followed the Michaelis–Menten model of significance (r ² = 0.873, p < 0.001) in our experimental systems, in which the prey concentration varied from 1.0 × 10⁴ to 2.1 × 10⁶ cells ml^?1. The maximum grazing rate was 6.2 prey cells grazer^?1 h^?1, and the half-saturation constant was 1.2 × 10⁵ cells ml^?1. We present evidence that C. triciliatum grazing explained the remarkable decrease in M. aeruginosa cell density in the pond. The present study is the first demonstration of the high potential of protistan grazing on M. aeruginosa to reduce cyanobacterial blooms.     

Comparison of agarophytes (Gelidium, Gracilaria, and Gracilariopsis) as potential resources for bioethanol production

This study explores the possibility of producing ethanol using the acid hydrolysate of three abundant agar-containing red seaweeds (agarophytes): Gelidium amansii, Gracilaria tenuistipitata, and Gracilariopsis chorda. The main component in the seaweed samples was agar, which ranged from 20 to 51 % (g g^?1 dry weight). After optimizing acid hydrolysis, 100 g of seaweed was hydrolyzed at 130 °C for 15 min with 0.2 M H₂SO₄. Then, 120 mL of a 1:2 mixture of the hydrolysate broth and basal medium was fermented in a 200-mL bottle at 30 °C for 96 h. Of the three seaweeds, G. amansii had the best ethanol yield, producing 0.23 g g^?1 of galactose or 45 % of the theoretical yield. This yield increased to 60 % after detoxification of the hydrolysate with activated carbon.     

Phosphate solubilization potential and modeling of stress tolerance of rhizobacteria from rice paddy soil in northern Iran

The purposes of this study were to evaluate the phosphate solubilization activity of bacteria isolated from the rhizosphere of rice paddy soil in northern Iran, and to study the effect of temperature, NaCl and pH on the growth of these isolates by modeling. Three of the most effective strains from a total of 300 isolates were identified and a phylogenetic analysis was carried out by 16S rDNA sequencing. The isolates were identified as Pantoea ananatis (M36), Rahnella aquatilis (M100) and Enterobacter sp. (M183). These isolates showed multiple plant growth-promoting attributes such as phosphate solubilization activity and indole-3-acetic acid (IAA) production. The M36, M100 and M183 isolates were able to solubilize 172, 263 and 254 µg ml^?1 of Ca₃(PO₄)₂ after 5 days of growth at 28 °C and pH 7.5, and to produce 8.0, 2.0 and 3.0 μg ml^?1 of IAA when supplemented with l-tryptophan (1 mg ml^?1) for 72 h, at 28 °C and pH 7.0, respectively. The solubilization of insoluble phosphate was associated with a drop in the pH of the culture medium and there was an inverse relationship between pH and solubilized P (r = ?0.98, P < 0.0952). There were no significant differences among isolates in terms of acidity tolerance based on their confidence limits as assessed by segmented model analysis and all isolates were able to grow at pH 4.3–11 (with optimum at 7.0–7.5). Based on a sigmoidal trend of a three-parameter logistic model, the salt concentration required for 50 % inhibition was 8.15, 6.30 and 8.23 % NaCl for M36, M100 and M183 isolates, respectively. Moreover, the minimum and maximum growth temperatures estimated by the segmented model were 5.0 and 42.75 °C for M36, 12.76 and 40.32 °C for M100, and 10.63 and 43.66 °C for M183. The three selected isolates could be deployed as inoculants to promote plant growth in an agricultural environment.     

Improvement of 5-aminolevulinic acid production by Rubrivivax benzoatilyticus PS-5 with self-flocculation by co-fermentation of precursors and volatile fatty acids under pH-controlled conditions

Photosynthetic bacteria are known to utilize volatile fatty acids as a carbon source for growth and product formation. In this study, a new isolate, Rubrivivax benzoatilyticus PS-5, possessing self-flocculation properties, was cultivated in modified glutamate-malate (GM) medium containing glutamate and malate as carbon sources. The effect of acetic acid, propionic acid and butyric acid (at 1–4 g L^?1) as co-substrates and 7.5 mM glycine, 10 mM succinic acid as precursors for 5-aminolevulinic acid (ALA) production from R. benzoatilyticus PS-5 was investigated. Among the volatile fatty acids tested, acetic acid was preferred to butyric acid and propionic acid, with the optimum concentrations of 3 g L^?1, 1 g L^?1 and 3 g L^?1, respectively. The highest ALA production was 169.71 μM, 162.16 μM and 46.18 μM, respectively, while the highest productivity was 2.57 μM h^?1, 2.25 μM h^?1 and 0.96 μM h^?1, respectively. The precursor was consumed completely (100 %) while the assimilation of the acetic acid and butyric acid was 62.50 % and 48.65 %, respectively. Supplementation of propionic acid (at 1–4 g l^?1) had a negative effect on growth and ALA production. To increase production efficiency, the pH-control strategy (at pH 6.0–8.0) during fermentation was tested. The optimum pH was 7.0, giving the maximum ALA production of 286.18 μM and a productivity of 3.97 μM h^?1. These values were 1.68-fold and 1.54-fold higher, respectively, than those under uncontrolled pH conditions.     

Feeding Ecology of Northeast Atlantic Mackerel,Norwegian Spring-Spawning Herring and Blue Whiting in the Norwegian Sea

The Norwegian spring-spawning (NSS) herring (Clupea harengus), blue whiting (Micromesistius poutassou) and Northeast Atlantic (NEA) mackerel (Scomber scombrus) are extremely abundant pelagic planktivores that feed in the Norwegian Sea (NS) during spring and summer. This study investigated the feeding ecology and diet composition of these commercially important fish stocks on the basis of biological data, including an extensive set of stomach samples in combination with hydrographical data, zooplankton samples and acoustic abundance data from 12 stock monitoring surveys carried out in 2005–2010. Mackerel were absent during the spring, but had generally high feeding overlap with herring in the summer, with a diet mainly based on calanoid copepods, especially Calanus finmarchicus, as well as a similar diet width. Stomach fullness in herring diminished from spring to summer and feeding incidence was lower than that of mackerel in summer. However, stomach fullness did not differ between the two species, indicating that herring maintain an equally efficient pattern of feeding as mackerel in summer, but on a diet that is less dominated by copepods and is more reliant on larger prey. Blue whiting tended to have a low dietary overlap with mackerel and herring, with larger prey such as euphausiids and amphipods dominating, and stomach fullness and feeding incidence increasing with length. For all the species, feeding incidence increased with decreasing temperature, and for mackerel so did stomach fullness, indicating that feeding activity is highest in areas associated with colder water masses. Significant annual effects on diet composition and feeding-related variables suggested that the three species are able to adapt to different food and environmental conditions. These annual effects are likely to have an important impact on the predation pressure on different plankton groups and the carrying capacity of individual systems, and emphasise the importance of regular monitoring of pelagic fish diets.     

d-Tagatose production in the presence of borate by resting Lactococcus lactis cells harboring Bifidobacterium longum l-arabinose isomerase

Bifidobacterium longum NRRL B-41409 l-arabinose isomerase (l-AI) was overexpressed in Lactococcus lactis using a phosphate depletion inducible expression system. The resting L. lactis cells harboring the B. longum l-AI were used for production of d-tagatose from d-galactose in the presence of borate buffer. Multivariable analysis suggested that high pH, temperature and borate concentration favoured the conversion of d-galactose to d-tagatose. Almost quantitative conversion (92 %) was achieved at 20 g L^?1 substrate and at 37.5 °C after 5 days. The d-tagatose production rate of 185 g L^?1 day^?1 was obtained at 300 g L^?1 galactose, at 1.15 M borate, and at 41 °C during 10 days when the production medium was changed every 24 h. There was no significant loss in productivity during ten sequential 24 h batches. The initial d-tagatose production rate was 290 g L^?1 day^?1 under these conditions.