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Phaeodactylum tricornutum is a marine diatom in the class Bacillariophyceae and is important ecologically and industrially with regards to ocean primary production and lipid accumulation for biofuel production, respectively. Triacylglyceride (TAG) accumulation has been reported in P. tricornutum under different nutrient stresses, and our results show that lipid accumulation can occur with nitrate or phosphate depletion. However, greater lipid accumulation was observed when both nutrients were depleted as observed using a Nile Red assay and fatty acid methyl ester (FAME) profiles. Nitrate depletion had a greater effect on lipid accumulation than phosphate depletion. Lipid accumulation in P. tricornutum was arrested upon resupplementation with the depleted nutrient. Cells depleted of nitrogen showed a distinct shift from a lipid accumulation mode to cellular growth post-resupplementation with nitrate, as observed through increased cell numbers and consumption of accumulated lipid. Phosphate depletion caused lipid accumulation that was arrested upon phosphate resupplementation. The cessation of lipid accumulation was followed by lipid consumption without an increase in cell numbers. Cells depleted in both nitrate and phosphate displayed cell growth upon the addition of both nitrate and phosphate and had the largest observed lipid consumption upon resupplementation. These results indicate that phosphate resupplementation can shut down lipid accumulation but does not cause cells to shift into cellular growth, unlike nitrate resupplementation. These data suggest that nutrient resupplementation will arrest lipid accumulation and that switching between cellular growth and lipid accumulation can be regulated upon the availability of nitrogen and phosphorus.

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There is a considerable body of information regarding bacterially enhanced corrosion, however, this review focuses on diatoms (unicellular algae) whose contribution to biocorrosion is less well studied. The reasons why diatoms have been neglected in studies of biocorrosion in natural waters are discussed and the question whether diatoms should be considered as inert with respect of electrochemical processes is considered. A particular focus is given to the case of stainless steels (SS), which are widely used in variety of applications in natural waters. Basic information on the cell biology of diatoms is included in the review, particularly with respect to their ability to 'sense' and adhere to surfaces. Investigations at the nanoscale are reviewed as these studies provide information about the behavior of cells at interfaces. Recent advances include the use of atomic force microscopy (AFM), although only a few studies have been applied to diatoms. Regarding the electrochemical behavior of SS, the mechanisms by which diatoms influence the potential ennoblement process is discussed. Such studies reveal the association of diatoms, in addition to bacteria, with biocorrosion processes.

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The degradation in performance of submerged marine structures through their colonization by micro- and macrobiota is well known. Historically, toxic surface coatings have been used to control both types of fouling. Legislative requirements worldwide now require alternative non- or minimally toxic coatings to be used. Here we report on the potential for synthetic 2-pentyl-4-quinolinol (PQ), an antibiotic from an Alteromonas sp., as a candidate antifoulant. Hundred micromolar PQ reduces the growth of four marine diatoms that usually grow as biofilms. Furthermore, PQ inhibits the initial adhesive process in Amphora coffeaeformis in a logarithmic dose-dependent manner, but not the adhesion of a Navicula sp., indicating differing adhesive processes in these two diatoms. Treatment of established biofilms with PQ causes a rapid and complete loss of motility in both Amphora and Navicula and eventually, as seen by Sytox Green staining, cell death, and lysis. We conclude that PQ, or one of its chemical analogues, holds promise as an antifoulant molecule for inclusion in marine surface coating.

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The objective of this research was to observe the effect of chlorine dioxide (ClO2) combined with modified atmosphere packaging on the quality of fresh chicken breasts under refrigerated storage for 15 days. Each chicken breast was inoculated with a 4-log CFU/ml culture of Salmonella Typhimurium (nalidixic acid-resistant strain) and placed into a barrier foam tray. Fast- or slow-release ClO2 sachets were placed next to the chicken in each package. A control set of packages that did not contain a ClO2 sachet was also included in the study. Packages were flushed with either 100% N2 or 75% N2-25% CO2 and stored at 3 degrees C. Microbial analysis, CIE L.a.b. color, and sensory (appearance and aroma) were performed every 3 days for 15 days. Total plate counts for chicken increased steadily after 6 to 9 days of storage regardless of package atmosphere or ClO2 treatment. However, those treated with ClO2 sachets had 1 to 1.5 log CFU per chicken breast lower total plate counts compared with those without ClO2 sachets. After 15 days, samples treated with ClO2 (fast- and slow-release sachets) had significantly lower Salmonella Typhimurium (nalidixic acid-resistant strain) populations (approximately 1 log) compared with chicken that did not contain ClO2 sachets. The ClO2 adversely affected the color of the chicken in areas close to the sachet. No off-odor was detected by the sensory panelists.

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Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS) was used to study compositional characteristics of Extracellular Polymeric Substances (EPS) and compared these to characteristics of the EPS-matrix of intact diatom biofilms. Three benthic diatoms species were investigated, Cylindrotheca closterium, Navicula mutica and Nitzschia cf. brevissima. Comparison of the ToF-SIMS spectra of sequentially extracted EPS-fractions by cluster analysis and multidimensional scaling analysis (MDS) indicated that soluble and bound EPS were not distinguishable based on their ion spectra. On the contrary the water insoluble bicarbonate soluble (WIBS)-EPS-fraction formed a distinct cluster showing that this material was compositionally different from the other EPS-fractions. Ion spectra of the EPS-fractions were dissimilar to results obtained from intact biofilms. This suggested that during the extraction procedure, the structure of the EPS irreversibly changed, which alters the fragmentation patterns of the extracellular surface layer. Furthermore, from the examination of the positive ion spectra it was shown that the overall composition of EPS in the intact biofilms was different between diatom species. In spite of these differences, several common peak patterns were shared between different species. This suggests the presence of common structural components in the EPS of these diatoms that may play a role in building the surface EPS-layer.

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Unicellular algae are the predominant microbial mat-forming phototrophs in the extreme environments of acidic geothermal springs. The ecology of these algae is not well known because concepts of species composition are inferred from cultivated isolates and microscopic observations, methods known to provide incomplete and inaccurate assessments of species in situ. We used sequence analysis of 18S rRNA genes PCR amplified from mat samples from different seasons and different temperatures along a thermal gradient to identify algae in an often-studied acidic (pH 2.7) geothermal creek in Yellowstone National Park. Fiber-optic microprobes were used to show that light for algal photosynthesis is attenuated to < 1% over the 1-mm surface interval of the mat. Three algal sequences were detected, and each was present year-round. A Cyanidioschyzon merolae sequence was predominant at temperatures of > or = 49 degrees C. A Chlorella protothecoides var. acidicola sequence and a Paradoxia multisita-like sequence were predominant at temperatures of < or = 39 degrees C.

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Antimicrobial additives have been used successfully for many years as direct food additives. The literature provides evidence that some of these additives may be effective as indirect food additives incorporated into food packaging materials. Antimicrobial food packaging is directed toward the reduction of surface contamination of processed, prepared foods such as sliced meats and Frankfurter sausages (hot dogs). The use of such packaging materials is not meant to be a substitute for good sanitation practices, but it should enhance the safety of food as an additional hurdle for the growth of pathogenic and/or spoilage microorganisms. Studies have focused on establishing methods for coating low-density polyethylene film or barrier films with methyl cellulose as a carrier for nisin. These films have significantly reduced the presence of Listeria monocytogenes in solutions and in vacuum packaged hot dogs. Other research has focused on the use of chitosan to inhibit L. monocytogenes and chlorine dioxide sachets for the reduction of Salmonella on modified atmosphere-packaged fresh chicken breasts. Overall, antimicrobial packaging shows promise as an effective method for the inhibition of certain bacteria in foods, but barriers to their commercial implementation continue to exist.

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Most wetted surfaces that are illuminated support a population of phototrophs. The marine sediment is no exception and there the major component of the microphytobenthic population is diatoms. These organisms are credited with stabilizing the sediment against physical disturbance by virtue of the extracellular carbohydrate polymers that they elaborate. However, diatoms synthesize and secrete several carbohydrate polymers and it is not certain which of them is involved in the stabilization process. In order to investigate this, we have constructed small glass bead-filled flow through bioreactors to mimic marine sediments. The flow rate through the bioreactors was found to reflect the physical stability of the bead bed. Thus flow rate was measured as a function of diatom growth and the production of three operationally-defined polymers, i.e., those soluble in the medium, those soluble in 0.5 M NaHCO3 at 90 degrees C and those not soluble in either solvent (matrix polymer). Growth of the diatoms did not change the hydraulic conductivity of the bioreactors. For Amphora coffeaeformis, neither did the production of medium-soluble nor NaHCO3-soluble polymers. However, matrix polymer accumulation was directly correlated with a reduction in flow (regression coefficient R2 = 0.96) and stabilization against physical disturbance. Results with species of Navicula were not as clear. Both NaHCO3-soluble and matrix polymers were involved in producing the flow reduction. In the same manner we also measured the effect of Pseudoalteromonas haloplanktis growth on bead bed hydraulic conductivity and bead bed stability. Growing alone, no effect was found, but in co-culture with a single diatom species, the bacteria reduced the diatom effect on flow through the bioreactors seen earlier, however did not reduce the extent of their growth. Confocal scanning laser microscopy of beads colonized with diatoms alone, or diatoms in co-culture with bacteria, revealed that P. haloplanktis was able to inhibit diatom adhesion to the beads. When the bacteria were present there was less matrix polymer evident. We speculate that this interference with diatom metabolic activity was either the result of less matrix polymer synthesis, or its hydrolysis by the bacteria. The results are applicable to mixed species biofilms of this type on surfaces other than sediments.

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In 1995 and in 1998 the University of North Carolina at Chapel Hill received R25 grant support to create interactive CD-ROMs for teaching nutrition and nutritional biochemistry to medical students, the Nutrition In Medicine (NIM) series. Seven of the proposed ten titles have been created. Three series (Disease, Lifecycle, and Special Topics in Nutrition) teach nutrition concepts using computer-aided instruction (CAI) with emphasis on interactive learning. Patient cases with television-quality interactive videos allow students to apply nutrition knowledge to clinical problems. Pop quizzes, text-based interactions, and multiple-choice examinations help the student self-evaluate progress via immediate feedback. Educators using the programs get instructional support and updates through a dedicated Web site, printed material, telephone support, e-mail, and CD-ROM-based computer programs. Implementation at medical and osteopathic schools is continuously surveyed through questionnaires and follow-up telephone interviews. By 1999, 120 of 137 eligible U.S. medical schools owned copies of NIM CAI programs, of which 76 indicated that they were currently implementing the programs.

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Despite awareness of the importance of nutrition as part of medical student's education, numerous barriers exist to incorporating nutrition education into the medical school curriculum. Chief among such barriers is that most medical schools do not have faculty trained specifically in nutrition. A curriculum is needed that can deliver comprehensive nutrition information that is consistent across medical schools. One way to deliver this information is to use computer-assisted instruction (CAI). To meet the different needs of medical schools and provide a consistent base of nutrition information, we developed a series of interactive, multimedia educational programs (Nutrition in Medicine) that teach the basic principles of nutritional science and apply those principles in a case-oriented approach. Curriculum content is derived from the American Society for Clinical Nutrition consensus guidelines. These modules offer the advantages of accessibility, self-paced study, interactivity, immediate feedback, and tracking of student performance. Modules are distributed free to all US medical schools. Preliminary data from surveys gathered by our team at the University of North Carolina at Chapel Hill indicate that 73 US medical schools use, or are planning to use, these modules; more schools are currently evaluating the programs. Successful implementation of CAI requires easy program access, faculty training, adequate technical support, and faculty commitment to the programs as a valuable resource. CAI fails when the program is just placed in the library and students are told to use it when they can find the time.

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Association with a surface is an important aspect of survival for microorganisms in natural and manmade environments/Both bacteria and diatoms are involved in such associations. In many cases, this leads to surface fouling, which often results in surface deterioration and mechanical failure in industrial systems. We now know that microorganisms exploit many strategies to establish associations with surfaces. As in the case of other cellular processes, calcium ions seem to play an important role in adhesion of cells to surfaces. Calcium is involved in non-specific interactions such as neutralization of the electrical double layer between cell and substratum surface as well as specific adhesive interactions that cannot be replaced by other cations. The unique properties of calcium ions promote both specific and non-specific interactions with protein and polysaccha-ride adhesin molecules at the cell surface. As important, but less well understood, calcium ions also influence the way microbial cells interact with different substrata.

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A computer-based image analysis system that measures the behavioral response of the marine diatom Amphora coffeaeformis to potentially toxic challenges is described. At any one time the system is capable of measuring in a population of about 80 cells, changes in the number motile, their speed, direction, and if they are turning, their angular velocity and acceleration. Chemical compounds that interfere with the generation of energy, protein or glycoprotein synthesis, calcium homeostasis and cytoskeletal activity, change the motile behavior of the cell. A pre-requisite of motility is that the cells be attached to a substratum. It is proposed that the system, which requires only a 1-2 minute data collection period per replicate, could be used to screen for potential antifouling activity in chemical agents, and it is speculated that it could be used also for measuring the physicochemical interaction between attached motile organisms and their substratum, as well as in environment toxicology measurements.

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Three cDNA clones encoding rat basic fibroblast growth factor (FGF) were isolated from 10(6) independent clones prepared from a pregnant mare serum gonadotropin (PMSG)-stimulated rat ovarian cDNA library. One of the cDNA clones contained the entire coding sequence for basic FGF. The other two possessed the sequence coding the carboxy terminal 61 amino acids of rat basic FGF, the putative upstream intron sequence, and a 3'-noncoding region. The cDNAs encoding rat basic FGF predict a molecule consisting of 154 amino acid residues, which is one amino acid shorter than the human and bovine basic FGF. Otherwise, there are only 5 conservative amino acid substitutions between the rat and the human/bovine sequences. Poly A+ RNA from brain cortex and hypothalamus show a single 6.0 kb band that hybridizes to the cloned cDNA probe by Northern analyses. The observation that basic FGF mRNA is below the limits of detection in adrenal, spleen, heart, lung, kidney, liver, stomach, small intestine, large intestine, testis, and ovary support the notion that the that the high levels of the protein found in these tissues is due to storage of the mitogen in the extracellular matrix and not continuous gene expression. The significance of the abundance of mRNA in tissues which are not undergoing either active angiogenesis or cell proliferation (hypothalamus and brain cortex) is unclear but emphasizes the potential neuronotrophic function of basic FGF.

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Follistatin is a single-chain gonadal protein that specifically inhibits follicle-stimulating hormone release. By use of the recently characterized porcine follistatin cDNA as a probe to screen a human testis cDNA library and a genomic library, the structure of the complete human follistatin precursor as well as its genomic organization have been determined. Three of eight cDNA clones that were sequenced predicted a precursor with 344 amino acids, whereas the remaining five cDNA clones encoded a 317 amino acid precursor, resulting from alternative splicing of the precursor mRNA. Mature follistatins contain four contiguous domains that are encoded by precisely separated exons; three of the domains are highly similar to each other, as well as to human epidermal growth factor and human pancreatic secretory trypsin inhibitor. The genomic organization of the human follistatin is similar to that of the human epidermal growth factor gene and thus supports the notion of exon shuffling during evolution.

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Follistatin (FS), a novel gonadal protein which inhibits specifically the secretion of pituitary follicle stimulating hormone (FSH), has recently been isolated from porcine follicular fluid. cDNA cloning of the porcine ovarian FS precursor revealed two populations of cDNAs which differed at the 3'-region of the open reading frames; one population encodes a precursor of 317 amino acids while the other encodes another precursor having the same 317 amino acids, but with an additional 27 amino acids at the carboxy-terminal. Herein, we report the cloning of the porcine FS gene whose DNA structure reveals that the two populations of mRNA are generated by alternative splicing. In addition, restriction endonuclease mapping and DNA sequencing show that the FS gene is approximately 6 Kb long and consists of six exons separated by five introns. The first exon encodes the putative signal sequence, followed by four exons which encode the four domains of FS, three of which are highly homologous to each other. The last exon encodes the extra 27-amino acid carboxy-terminal domain of the 344-residued precursor.

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Attached bacterial populations cultured without an exogenous carbon source or grown in conjunction with attached diatoms incorporated [H]thymidine at a rate between four and five times lower than that of replicate bacterial populations which were dispersed before being assayed.

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Follistatin, a novel, single chain, glycosylated polypeptide bearing no homology with previously characterized inhibins but exhibiting potent and specific pituitary FSH-release inhibition has been structurally characterized by protein microsequencing, cDNA cloning, and DNA sequencing. Two populations of clones differing in their 3'-untranslated sequences were found to encode a 344 amino acid precursor protein and an identical but carboxyl terminal truncated 317 amino acid precursor, respectively. Additionally, one clone, FS18, contained two introns and probably resulted from reverse transcription of heterogeneous nuclear RNA during cDNA library construction. Follistatin is unusually cysteine-rich, containing 36 cysteines in the mature coding sequence of 315 amino acids and an extremely acidic carboxyl terminal region, FS(292-304), comprised of Glu-Asp-Thr-Glu-Glu-Glu-Glu-Glu-Asp-Glu-Asp-Gln-Asp which probably resides outside a tightly cross-linked protein sphere. The heparin-binding ability of follistatin can probably be ascribed to the basic region specified by FS(75-86), Lys-Lys-Cys-Arg-Met-Asn-Lys-Lys-Asn-Lys. Overall, follistatin is organized into three homologous domains, FS(66-135), FS(139-210), and FS(216-287) containing 70, 72, and 72 amino acids, respectively, which show a 52% homology among themselves and a 57% homology with the 56 amino acid human pancreatic secretory trypsin inhibitor protein when aligned for maximum homology.

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Two forms of inhibin (A and B), gonadal polypeptide hormones that selectively suppress the secretion of FSH from the anterior pituitary, have been characterized from the porcine and human species, each being composed of a common alpha-chain and one of two distinct, but homologous beta-chains, i.e. alpha beta A and alpha beta B. Using cDNAs encoding the porcine inhibin subunits we have cloned and sequenced the cDNAs encoding the alpha, beta A, and beta B chains of rat ovarian inhibin. Northern analyses of rat testicular RNA with rat ovarian cDNA probes show the presence of mRNAs encoding alpha and beta B chains, but no detectable mRNA encoding the beta A chain under our experimental conditions. This suggests that there may be specific and distinct physiological roles for inhibins A and B. In addition, if there is no extratesticular source of beta A mRNA, then the male rat may be devoid of the stimulators of the secretion of FSH, i.e. activin (beta A beta B) and homoactivin A (beta A beta A), which are derived from the beta subunits of the two inhibins.

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The hypothesis that movement of biological ions may be predicted by cyclotron resonance theory applied to cell membranes is tested in these experiments. Diatoms (Amphora coffeaeformis) were chosen as the biosystem since they move or don't move, depending on how much calcium is transported across the membrane. The experiments demonstrate that a particular ion (calcium) is apparently moved across the cell membrane in response to the DC and AC values of magnetic flux densities (B) and the frequency derived from the cyclotron resonance theory. A clear resonance is shown and a rather sharp frequency response curve is demonstrated. The experiments also show a dose response as the AC value of the flux density is varied, and that odd harmonics of the basic cyclotron frequency are also effective.

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