Observations on organic carbon utilization by photosynthetic marine microalgae

Organic carbon utilization was studied in 13 species of axenic unicellular marine algae. The compounds tested were 15 sugars, 19 acids, and 16 alcohols. Heterotrophy occurred in only three chlorophyte strains with acetate and ethanol; one strain with glucose. Mixotrophy was observed with the following compounds: glyceraldehyde, 1 species; acetate, 4 species; glycolic acid, 5 species; pyruvic acid, 9 species; caproic acid, 3 species; lactic acid, 1 species; ethanol, 3 species; glycerol, 9 species. Some ecological implications are discussed.     

不同碳源培养条件下假丝酵母菌产槐糖脂的结构及性能

采用不同碳源,如油酸、菜籽油、棉籽油和煎炸废油作为假丝酵母菌(Candida.bombicola)ATCC 22214发酵生产槐糖脂的脂溶性碳源,考察了在不同碳源条件下该菌株合成槐糖脂的能力、所产槐糖脂的结构及表面活性特点.结果表明,以油酸、菜籽油及棉籽油为脂溶性碳源时,该菌株有着较高的槐糖脂产量,分别为101、73、51 g·L-1;通过高效液相色谱-高分辨质谱(HPLC-MS/MS)对以不同脂溶性碳源为发酵底物产生的槐糖脂进行分析,发现所产槐糖脂均由乙酰基取代的内酯型和酸型槐糖脂同系物构成且以内酯型槐糖脂结构为主.槐糖内酯中脂肪酸基的结构有所差异,但主要以脂肪链不饱和度为1的十八烯酸(C18∶1)结构为主.所产槐糖脂具有较低的表面张力和临界胶束浓度(CMC),其中最低表面张力结果一致约36.0—37.0 m N·m-1,而CMC有所差异.同时,该槐糖脂具有良好的稳定性,其水溶液的最低表面张力在100℃下保持2 h基本不变,在0—20%的Na Cl盐溶液及p H值为2—10范围内均保持良好的表面活性.     

Ammonium regeneration by microzooplankton in the Oslofjord

Concentrations of dissolved inorganic nitrogen compounds above the pycnocline in the Oslofjord are very low in the summer, with turnover times of the inorganic N pools of no more than a few hours. To investigate the possibility that continued phytoplankton growth in the summer depends on ammonium excretion by microzooplankton, rates of NH ₄ ⁺ regeneration and assimilation were measured by a ¹⁵N isotope dilution method. Daytime regeneration rates at 0–2 m depth were 0–28% of the calculated assimilation rates at ambient NH ₄ ⁺ concentrations. Regeneration was faster during a dinoflagellate bloom in August than in mixed diatom-dinoflagellate blooms in June and September. Most of the NH ₄ ⁺ appeared to be produced by juvenile copepods, rotifers, tintinnids, and heterotrophic dinoflagellates in the size fraction 45–200 m.     

Transformation of progesterone by marine bacteria

The progesterone transforming ability of marine bacteria has been determined. 20 of the 53 marine cultures tested were found capable of transforming progesterone to 6-hydroxyprogesterone and/or to 11,17-dihydroxyprogesterone.     

The utilisation of alkylated amines by marine bacteria

Six species of bacteria and a marine yeast which are able to use alkylated amines as a sole source of nitrogen have been isolated from marine mud and tentatively assigned to genera. One isolate (Micrococcus sp.) has been studied in greater detail. This organism has a constitutive ability to utilise trimethylamine and the lesser methylated amines as a sole source of nitrogen. Growth and metabolic studies suggest that the methylated amines are metabolized by a pathway involving a stepwise demethylation process. The implications of the results obtained on the route of regeneration and recycling of amine nitrogen in the marine environment is discussed.     

Influence of bacteria on growth and hemolysin production by the marine dinoflagellate Amphidinium carterae

The effect of various bacteria on the growth of and hemolysin production by Amphidinium carterae was studied. The algal culture had an indigenous bacterial flora of Moraxella and Pseudomonas and these could not be eliminated by treatment with bactericidal antibiotics like gentamicin. Various bacteria like Micrococcus, Aeromonas, Vibrio, and Moraxella-like bacteria were added to A. carterae cultures to study their effect on growth and hemolysin production. Micrococcus and Aeromonas were found to improve the growth marginally. Hemolysin titres were considerably higher in A. carterae cultures supplemented with bacteria. Received: 27 May 1997 / Accepted: 22 July 1997     

Feeding of marine planktonic copepods on mixed phytoplankton

The feeding of juveniles and adults of the copepods Eucalanus pileatus, Temora stylifera and T. turbinata fed a mixture of the phytoplankton Skeletonema costatum, Leptocylindrus danicus and Rhizosolenia alata f. indica was studied at 20°C. E. pileatus nauplii, copepodids and adult females ingest similar percentages of the 3 algae in terms of carbon. Temora juveniles younger than CII ingest mainly S. costatum; at more advanced developmental stages, the ingestion rate on S. costatum remains constant whereas feeding on L. danicus and R. alata f. indica increases with increasing body weight. Feeding on high concentrations of large particles reduces the grazing pressure on small particles, thus favoring zooplankton which require small-sized food.     

Ammonium regeneration and assimilation in eelgrass (Zostera marina) beds

Regeneration and assimilation of ammonium in the water column and in sediments of eelgrass (Zostera marina L.) beds of Izembek Lagoon and Crane Cove, Alaska, USA and Mangoku-Ura, northeastern Japan, were investigated by using a ¹⁵N isotope dilution technique. In the water column of Mangoku-Ura, ammonium was regenerated at a rate of 12 nmol l^-1 h^-1 and assimilated at a rate of 74 nmol l^-1 h^-1. The ammonium regeneration rate in sediments ranged from 2 to 150 nmol g^-1 h^-1, and with one exception, exceeded ammonium assimilation in sediments (0.3 to 77 nmol g^-1 h^-1). The ammonium regeneration in the water column was of little significance for the nitrogen supply to the eelgrass bed ecosystem. Net ammonium production (regeneration minus assimilation) in the sediment of Izembek Laggon met nitrogen demand for eelgrass growth, suggesting that ammonium regeneration in the sediments was very important for the nitrogen cycle in the eelgrass bed ecosystem.     

Respiration and physiological state in marine bacteria

The relationship between oxygen consumption (R) and respiratory electron-transport-system (ETS) activity was investigated in batch cultures of 5 species of marine bacteria, Vibrio adaptatus, V. anguillarum, a partially identified Vibrio sp. SA774, Serratia marinorubra, and Pseudomonas perfectomarinus. Although cellular levels of R and ETS varied widely among the species tested, the R:ETS ratios for growing or senescent populations were relatively constant among the species; these ratios were 5.02 in growth and 0.426 in senescence, with coefficients of variation of 29 and 20%, respectively. The lower senescent-phase R:ETS ratio was due to a depression of the respiration rates following growth termination. The regression log (R per cell) = 0.832 log (ETS per cell) + 0.727 for the growing populations was similar to that determined for marine zooplankton. The slight dependency of the R:ETS ratio on organism dry weight found for zooplankton was supported by our data. Planktonic respiration rates estimated from measured ETS-depth profiles in the eastern tropical North Pacific Ocean using the senescent-phase R:ETS ratio were similar to published oxygen consumption rates in the deep sea.Contribution No. M79-61 from the University of Washington's Department of Oceanography, and No. 79032 from the Bigelow Laboratory for Ocean Sciences.     

Arsenic metabolism in marine bacteria and yeast

Arsenic metabolism was studied for two marine microorganisms, a facultative anaerobic bacterium, Serratia marinorubra, and an obligately aerobic yeast, Rhodotorula rubra. Both were cultivated in media with (⁷⁴As) arsenate (As V), and the products of arsenate metabolism were determined qualitatively. Both the bacterium and the yeast produced arsenite (AS III) and methylarsonic acid [CH₃AsO(OH)₂]. In addition to the foregoing, only the yeast produced dimethylarsinic acid (CH₃)₂AsO(OH) and volatile alkylarsines. In contrast, the bacterium growing anaerobically with cobalamine as a cofactor did not synthesize gaseous forms of arsenic such as methylarsines. Neither organism synthesized arsoniumphospholipids such as those produced by marine phytoplankton or terrestrial fungi. The yeast did not accumulate arsenite, but instead transported some of it into the culture medium and methylated the remainder first to methylarsonic acid and then to dimethylarsinic acid. Finally, the latter compound was methylated further and volatile alkylarsines were formed. In contrast, the bacterium retained all products of arsenate metabolism intracellularly. Both the bacterium and the yeast, therefore, converted relatively toxic arsenate, the most abundant arsenic compound in seawater, to products that were presumably less toxic.     

Sulfide and thiosulfate-oxidizing bacteria in anoxic marine basins

The occurrence of sulfide and thiosulfate-oxidizing bacteria was examined in waters and sediments of the Black Sea and the Caraco Trench. Isolates obtained by enrichment-culture techniques exhibited facultative autotrophic-growth characteristics and oxidized thiosulfate or sulfide. Acid was not formed during growth in mineral medium. Most of the isolates were facultatively anaerobic, using nitrate as the terminal hydrogen acceptor. Strictly aerobic bacteria were found only in oxygenated waters. Comparison of the metabolic capabilities of the isolates during growth in sulfide and thiosulfate media with chemical parameters measured in the Black Sea and Cariaco Trench waters suggests that the biological oxidation of thiosulfate is the rate-limiting step in the oxidative turnover of sulfur compounds in the basins. Evidence for the oxidation of sulfide in the anoxic waters is presented, and possible explanations for the occurrence of this process in the absence of suitable electron acceptors (O₂. NO₃) are discussed. A maximum dark assimilation of carbon dioxide was located just below the oxygen-sulfide interface in the Cariaco Trench. Problems of interpreting these data are considered.Contribution No. 2958 of the Woods Hole Occanographic Institution. Supported by the National Science Foundation Grants GA 29665 and GA 33405.     

Selective targeted adsorption and inactivation of antibiotic-resistant bacteria by Cr-loaded mixed metal oxides

• LDHs and MMOs was synthesized by ultrasound-assisted one-step co-precipitation. • MMOs performs the best for Cr(VI) and E. coli_NDM-1 simultaneous removal. • Possible antibacterial pathways of Cr-MMOs were proposed. Herein we provide a novel high-efficiency nanocomposite for bacterial capture based on mixed metal oxides (MMOs) with deleterious chromium properties. With both the layer structure of layered double hydroxides (LDHs) and the magnetic properties of Fe, MMOs enrich the location of ionic forms on the surface, providing a good carrier for adsorption of the heavy metal Cr(VI). The capacity for adsorption of Cr(VI) by MMOs can be as high as 98.80 mg/g. The prepared Cr(VI)-MMOs achieved extremely expeditious location of gram-negative antibiotic-resistant E. coli_NDM-1 by identifying lipid bilayers. Cr-MMOs with a Cr loading of 19.70 mg/g had the best bactericidal effect, and the concentration of E. coli_NDM-1 was decreased from ~10⁸ to ~10³ CFU/mL after 30 min of reaction. The binding of nitrogen and phosphorus hydrophilic groups to chromate generated realistic models for density functional theory (DFT) calculations. The specific selectivity of MMOs toward bacterial cells was improved by taking Cr(VI) as a transferable medium, thereby enhancing the antibacterial activity of Cr-MMOs. Under the combined action of chemical and physical reactions, Cr(VI)-MMOs achieved high capacity for inactivation of bacteria. Moreover, the metallic elements ratio in Cr-MMOs remained stable in their initial valence states after inactivation. This guaranteed high removal efficiency for both heavy metals and bacteria, allowing recycling of the adsorbent in practical applications.     

Enhanced primary production and nutrient regeneration within aggregated marine diatoms

Blooms of chain-forming diatoms often terminate with the mass flocculation and subsequent settlement of cells from the nutrient-depleted euphotic zone. While mass diatom aggregation has been suggested as an adaptive mechanism for placing resting spores in the deep sea, we hypothesized that aggregation may confer an immediate adaptive advantage to the associated diatoms as well. We tested this hypothesis by comparing the photosynthetic activity, pigment composition and nutrient-uptake rates of aggregated and suspended diatoms over time. Diatom aggregates were collected by SCUBA divers in the Santa Barbara Channel (34°23N; 119°50W) on 4 March 1987 and monitored for 9 d in the laboratory. Diatom aggregates sustained chlorophyll a-specific primary production rates two to nine times higher than those of freely suspended diatoms from the surrounding seawater. The timing of maximum productivity was strongly correlated with the appearance of remineralized ammonia within the aggregates. Chlorophyll a-specific nitrate-uptake rates were routinely three to nine times lower in diatom aggregates than in the surrounding seawater. Primary production and pigment concentrations of diatom aggregates aged in situ displayed changes similar to those observed in the laboratory. These results suggest that diatoms associated with aggregates maintain higher photosynthetic rates than freely suspended diatoms by efficiently exploiting remineralized ammonia within the aggregate microenvironment, in preference to external nitrate sources. The enhanced nutrient environment within aggregates may be important for understanding the adaptive significance of the mass flocculation of diatom blooms.     

Release of photoassimilated carbon as dissolved organic matter by marine phytoplankton

The release of photoassimilated carbon as dissolved organic matter was studied in situ in oligotrophic and eutrophic marine waters and in axenic laboratory cultures. Percentage extracellular release (PER), integrated for the trophogenic zone, ranged from 6 to 12% in eutrophic waters and from 17 to 27% in oligotrophic seas. Most of the algal cultures released low amounts of dissolved organic matter (5%) during exponential growth. The highest levels of PER were observed in surface and deep samples, possibly as a result of elevated photorespiration and senescent cells. The generally lower values for extracellular release reported in this work as compared to other studies may be partly due to improved experimental techniques which minimized previously encountered artifacts.     

Uptake of dissolved organics by marine bacteria as a function of fluid motion

A mass transfer analysis predicts that fluid motion can increase the assimilation of dissolved organics by attached compared to free-living microorganisms under certain conditions. To test this we examined the effect of advective flow and fluid shear on the uptake of model compounds (leucine and glucose) by natural assemblages of heterotrophic bacteria, collected from Roosevelt Inlet, Delaware Bay (USA), in 1989. We found that [³H]leucine uptake by cells held in fluid moving at 20 to 70 m d^–1 was eight times larger than uptake by cells at a velocity of 3 m d^–1. This effect was only observed at low leucine concentrations (ca. 1 nM), when uptake was likely not saturated. When we added leucine at concentrations expected to saturate leucine uptake (ca. 11 nM), fluid motion past cells did not affect uptake. Fluid flow past bacteria did not increase [³H]glucose uptake, and laminar shear rates of 0.5 to 2.1 s^–1 did not increase either glucose or leucine uptake by suspended bacteria. These results indicate that fluid motion increases bacterial uptake of certain lowmolecular-weight dissolved organics only when the microorganism exists in an advective flow field. As predicted from a mass transfer model, fluid shear rates in natural systems are too low to affect bacterial uptake of such compounds.     

Inorganic nitrogen metabolism in marine bacteria: Nitrate uptake and reduction in a marine pseudomonad

Growth experiments in batch cultures indicated that the uptake of nitrate by the marine pseudomonad PL1 was inhibited in the presence of ammonia provided that the ammonia concentration was higher than 1 mM. At ammonia concentrations of less than about 1 mM, however, both nitrate and ammonia were utilised simultaneously. The saturation constants for nitrate and ammonia uptake were both 2.6x10^-4 M, and similar to the Michaelis constants of nitrate reductase for nitrate (2.9x10^-4 M) and glutamine synthetase for ammonia (2x10^-4 M). Nitrate reductase activity linked to NADH was detected in chemostat-grown cultures with nitrate as nitrogen source, and in cultures containing limiting concentrations of nitrate and ammonia, ammonia or glutamate. Enzyme synthesis appeared to be repressed in cultures containing an excess of ammonia or glutamate. Chemostat cultures utilised ammonia or glutamate in preference to nitrate, while there was no marked preference between ammonia and glutamate.     

Kinetics of glucose and amino acid uptake by attached and free-living marine bacteria in oligotrophic waters

Kinetics of glucose and amino acid uptake by attached and free-living bacteria were compared in the upper 70 m of the oligotrophic north-western Mediterranean Sea. Potential uptake rates of amino acids were higher than those of glucose in all the samples analysed. Cell-specific potential uptake rates of attached bacteria were up to two orders of magnitude higher than those of total bacteria, both for amino acids and glucose (0.72–153 amol amino acids cell⁻¹ h⁻¹ and 0.05–58.42 amol glucose cell⁻¹ h⁻¹ for attached bacteria and 0.34–1.37 amol amino acids cell⁻¹ h⁻¹ and 0.07–0.22 amol glucose cell⁻¹ h⁻¹ for total bacteria). The apparent K _m values were also higher in attached bacteria than in total bacteria, both for amino acids and glucose. These results would reflect the presence of different uptake systems in attached and free-living bacteria, which is in accordance with the different nutrient characteristics of their microenvironments, ambient water and particles. Attached bacteria show transport systems with low affinity, which characterise a bacterial community adapted to high concentration of substrates. Received: 13 June 2000 / Accepted: 6 December 2000     

Biodegradation of 2-methylisoborneol by bacteria enriched from biological activated carbon

One of the most common taste and odour compounds (TOCs) in drinking water is 2-methylisoborneol (2-MIB) which cannot be readily removed by conventional water treatments. Four bacterial strains for degrading 2-MIB were isolated from the surface of a biological activated carbon filter, and were characterized as Micrococcus spp., Flavobacterium spp., Brevibacterium spp. and Pseudomonas spp. based on 16S rRNA analysis. The removal efficiencies of 2-MIB with initial concentrations of 515 ng·L^-1 were 98.4%, 96.3%, 95.0%, and 92.8% for Micrococcus spp., Flavobacterium spp., Brevibacterium spp. and Pseudomonas spp., respectively. These removal efficiencies were slightly higher than those with initial concentration at 4.2 mg·L^-1 (86.1%, 84.4%, 86.7% and 86.0%, respectively). The kinetic model showed that biodegradation of 2-MIB at an initial dose of 4.2 mg·L^-1 was a pseudo-first-order reaction, with rate constants of 0.287, 0.277, 0.281, and 0.294 d^-1, respectively. These degraders decomposed 2-MIB to form 2-methylenebornane and 2-methyl-2-bornane as the products.     

Impact of conditions of cultivation and adsorption on antimicrobial activity of marine bacteria

The potency of free-living and animal-associated marine bacteria to produce antimicrobial substances has been studied in 491 strains isolated from northern and southern parts of the Pacific Ocean. A total of 26% (126 out of 491) of the strains examined produced antimicrobial compounds against 11 test bacterial strains (TBS) including the fish pathogens Aeromonas hydrophila and Vibrio anquillarum. Antimicrobial substances (AS) produced by marine bacteria were especially active against Staphylococcus epidermidis, Proteus vulgaris, Enterococcus faecalis, and Candida albicans. Twelve strains, isolated from different sources, were chosen as promising candidates, producing a number of AS. Production of AS varied within 24 to 72 h, increasing in a culture medium based on natural sea water with Br-ions, and after attachment to polymeric surfaces. In order to study the influence of adsorption, selected strains with a high potential for antimicrobial production were cultivated on polymeric surfaces with different hydrophobicities and chemical functionalities. These parameters of the surface hydrophobicity (measured by means of water contact angles) and chemical functionality of the surfaces were manipulated using the photo- and thermochemistry of a polymeric system (diazo-naphto-quinone/novolak) commonly used as a photoresistant material in semiconducto-manufacturing. The highest antimicrobial activities occurred on hydrophilic surfaces (standard exposed photoresistant films), whereas the number of attached cells was greater on hydrophobic surfaces, characterized as unexposed resistant films. These results suggest that the chemical nature of induced hydrophilicity may also be a major factor in controlling antimicrobial activity of adsorbed bacteria. Received: 5 March 1997 / Accepted: 24 August 1997