Plain Agar Research Articles

Electrical integrity and week-long oscillation in fungal mycelia

The electrical potential of the mycelia of a cord-forming wood decay fungus, Pholiota brunnescens, was monitored for over 100 days on a plain agar plate during the colonization onto a wood bait. Causality analyses of the electrical potential at different locations of the mycelium revealed a clear and stable causal relationship with the directional flow of the electrical potential from the hyphae at the bait location to other parts of the mycelium. However, this causality disappeared after 60 days of incubation, coinciding with the onset of slow electrical oscillation at the bait location, which occurred over one week per oscillation cycle. We speculated that the hyphae that initially colonized the bait may act as a temporary activity center, which generates electrical signals to other parts of the mycelium, thereby facilitating the colonization of the entire mycelial body to the bait. The week-long electrical oscillation represents the longest oscillation period ever recorded in fungi and warrants further investigation to elucidate its function and stability in response to environmental stimuli.

Detection of Methicillin-Resistant Staphylococcus aureus (MRSA) using Modified Conventional Cefoxitin-based Media as an Alternative Screening

Methicillin-resistant Staphylococcus aureus (MRSA) can cause infection with higher morbidity and mortality. In the limited-resource setting, the availability of rapid detection is scarce and may not be available; therefore, prompt detection using the alternative method is indispensable. To compare the detection rate of the modified-conventional method with chromogenic media against mucocutaneous clinical swab, a total of 80 S. aureus isolates from previous studies were cultivated and re-cultured into routine media such as blood agar (BA) and mannitol-salt agar (MSA) between June and September 2018. It directly inoculated from plain blood agar that had been incubated previous day before; it further underwent inoculation to other media, such as chromogenic media (CHROMagar), blood agar and mannitol salt agar that had been supplemented with cefoxitin (CFOX) powder manually. The sensitivity MSA-CFOX and BA-CFOX, respectively, was 96.88%. On the other hand, the sensitivity of CHROMagar and MHA-CFOX was 90.62%. The specificity of each MHA-CFOX, MSA-CFOX, and CHROMagar is 87.5% as well as 93.75% for BA-CFOX. The study has demonstrated better performance of modified-conventional method compared to the other media. Hence, the application of modified-media should not be delayed to facilitate the findings of MRSA among hospitalized patients.

Non-Thermal Plasma Decontamination Using a Multi-Hollow Surface Dielectric Barrier Discharge: Impact of Food Matrix Composition on Bactericidal Efficacy

The non-thermal plasma (NTP) treatment of food products as an alternative for thermal processing has been investigated over the last few years. This quasi-neutral gas contains a wide variety of reactive oxygen and nitrogen species (RONS), which could be lethal for bacterial cells present in the product. However, apart from only targeting bacteria, the RONS will also interact with components present in the food matrix. Therefore, these food components will protect the microorganisms, and the NTP treatment efficiency will decrease. This effect was investigated by supplementing a plain agar medium with various representative food matrix components. After inoculation with Escherichia coli O157:H7 (STEC) MB3885, the plates were treated for 30 s by a multi-hollow surface dielectric barrier discharge (MSDBD) generated in either dry air or air at 75% humidity, at constant power (25.7 ± 1.7 W). Subsequently, the survival of the cells was quantified. It has been found that the addition of casein hydrolysate (7.1 ± 0.2 m%), starch (2.0 m%), or soybean oil (4.6 m%) decreased the inactivation effect significantly. Food products containing these biomolecules might therefore need a more severe NTP treatment. Additionally, with increasing humidity of the plasma input gas, ozone levels decreased, and the bactericidal effect was generally less pronounced.

Seed dormancy concepts in orchids: Dendrobium cruentum as a model species

AbstractGenerally, orchids produce dust-like seeds in which endosperm reduction and embryo undifferentiation represent a derived state shared with species in about 11 other plant families. Orchid seeds are proposed to have a special kind of morphological or morphophysiological dormancy. We test this proposition, overcoming several design limitations of earlier studies, specifically that the in vitro germination method for orchid seeds uses pro-oxidants for disinfection and incorporates nitrate in the medium; both ‘treatments’ might contribute to dormancy breaking, potentially confounding judgement on the depth and nature of the dormant state. Seeds of the tropical orchid Dendrobium cruentum Rchb. f., were sown both in vitro, on a nutrient medium, and ex vitro, on plain agar omitting prior disinfection with sodium hypochlorite. Seeds previously stored and fresh seeds were incubated under combinations of vitro conditions, light treatments, constant or alternating temperatures and nitrate concentration. Seeds of D. cruentum are very small but have a large embryo that occupies most of the seed. Over a range of constant temperature seeds germinated to the spherical protocorm stage just as well ex vitro as in vitro. Neither light nor nitrate were prerequisites for ex vitro germination. The ability of D. cruentum seed to germinate in the absence of environmental or chemical stimuli suggests that mature seed can be non-dormant. Our results support the proposition that neither all DUST seed fit a dormancy class nor all orchids produce morphological or morphophysiological seeds. Finally, embryo/seed volume determinations in orchids may prove as valuable in studies on the evolution and ecology of germination and dormancy as embryo:seed ratios in other angiosperm species.

Effects of Tylosin, a Direct-Fed Microbial and Feedlot Pen Environment on Phenotypic Resistance among Enterococci Isolated from Beef Cattle Feces.

In two sequential replicates (n = 90 and n = 96 feedlot finisher cattle, respectively) we measured the impact of an Enterococcus faecium-based probiotic (DFM) and an altered feedlot pen environment on antimicrobial resistance among fecal enterococci in cattle fed (or, not fed) the macrolide tylosin. Diluted fecal samples were spiral-plated on plain and antibiotic-supplemented m-Enterococcus agar. In the first replicate, tylosin significantly (p < 0.05) increased the relative quantity of erythromycin-resistant enterococci. This effect was diminished in cattle fed the DFM in conjunction with tylosin, indicating a macrolide susceptible probiotic may help mitigate resistance. A similar observed effect was not statistically significant (p > 0.05) in the second replicate. Isolates were speciated and resistance phenotypes were obtained for E. faecium and E. hirae. Susceptible strains of bacteria fed as DFM may prove useful for mitigating the selective effects of antibiotic use; however, the longer-term sustainability of such an approach remains unclear.

Genetic variations and in vitro root-colonizing ability for an ericaceous host in Sarcoleotia globosa (Geoglossomycetes)

We discovered that Sarcoleotia globosa (Geoglossomycetes) fruited on the soil of ornamental Erica pot cultures, and its ascospores can germinate on plain agar. These findings prompted us to collect isolates from horticultural and natural environments in Japan and analyze their phylogeny and root colonizing ability. Pure cultures were successfully obtained from ascospores and surface-sterilized ericaceous roots. Phylogenetic analysis based on rRNA internal transcribed spacer sequences revealed that Japanese samples were separated into three strongly supported clades. Individual clade consisted of samples derived from (1) Erica pot cultures, (2) Rhododendron planted in a garden or Vaccinium pot culture, and (3) natural habitats in Hokkaido. Colony characteristics and in vitro root-colonizing morphology observed may correspond to these phylogenetic variations. Irrespective of the clades, all tested strains formed hyphal coils in vital rhizodermal cells of V. virgatum seedlings, which resembled those of ericoid mycorrhizae. Our results represent novel findings that can be the first step in unraveling the currently unknown ecology of geoglossoid fungi.

Culture Media Based on Leaf Strips/Root Segments Create Compatible Host/Organ Setup for in vitro Cultivation of Plant Microbiota

Plant microbiota have co-evolved with their associated plants in the entire holobiont, and their assemblages support diversity and productivity on our planet. Of importance is in vitro cultivation and identification of their hub taxa for possible core microbiome modification. Recently, we introduced the in situ-similis culturing strategy, based on the use of plant leaves as a platform for in vitro growth of plant microbiota. Here, the strategy is further extended by exploring plant organ compatible cultivation of plant microbiota when grown on corresponding leaf/root-based culture media. Pooling the advantages of MPN enrichment methodology together with natural plant-only-based culture media, the introduced method efficiently constructed a nutritional milieu governed by vegan nutrients of plant origin, i.e., leaf strips/root segments, immersed in plain semi-solid water agar. MPN estimates exceeded log 7.0 and 4.0 g−1 of endo-rhizosphere and endo-phyllosphere, respectively, of maize and sunflower; being proportionate to those obtained for standard culture media. With sunflower, PCR-DGGE analyses indicated divergence in community composition of cultivable endophytes primarily attributed to culture media, signaling a certain degree of plant organ affinity/compatibility. Based on 16S rRNA gene sequencing of bacterial isolates, 20 genera comprising 32 potential species were enriched; belonged to Bacteroidetes, Firmicutes, and Alpha-/Gammaproteobacteria. The described cultivation strategy furnished diversified nutritive platform in terms of homologous/heterologous plant organ-based medium and ambient/limited oxygenic cultivation procedure. Duly, cultivability extended to &amp;gt; 8 genera: Bosea, Brevundimonas, Chitinophaga, Pseudoxanthomonas, Sphingobacterium Caulobacter, Scandinavium, and Starkeya; the latter three genera were not yet reported for Sunflower, and possible unknown species or even one new putative genus. Thus, both potential members of the major microbiome and rare isolates of satellite microbiomes can be isolated using the presented method. It is a feasible addition to traditional cultivation methods to explore new potential resources of PGPB for future biotechnological applications.

Latency of Sugar Selection Behavior in German Cockroaches, Blattella germanica (Dictyoptera: Blattellidae)

Sugar is a phagostimulant component of cockroaches bait. Knowledge of the chemosensory response of German cockroaches to sugar is necessary to design bait formulations. This study was aimed to determine the behavior of sugar selection by German cockroaches, based on latency parameters toward the bait. Observation methods were done using behavior sampling with CCTV cameras. Observations were made on fifteen mixed-sex from VCRU, BKL, PDG, JKT-b, and PKU-b strains with the treatment of plain agar and agar containing four types of sugar i.e., glucose, fructose, sucrose, and maltose with a concentration of 1 M each. The observation was carried out for 12 hours. Data were analyzed using Two-way ANOVA followed by the Duncan test for p<0.05. Correlation between sugar and latency was analyzed with redundancy analysis. The result showed that the treatment but not the strain influenced the behavior of latency. The VCRU, BKL, PDG, and JKT-b strain were showed the fastest latency toward maltose and sucrose, while the PKU-b strain was toward plain agar. There was a strong correlation between sugar and latency for 0.77 (axis 1) and 0.61 (axis 2), with a total variance of 89.7% resulted from the redundancy analysis. Those indicate that the German cockroaches perform the sugar selection with a preference of maltose, and sucrose is more stimulating than glucose and fructose.

First Report of Sclerotinia Boll Rot and Stem Blight of Cotton in Arizona

Upland (Gossypium hirsutum L.) and Pima (G. barbadense L.) cotton are economically important throughout the southwestern United States. In August 2017, canopy wilting and boll rot symptoms were observed on upland cultivar Dyna-Gro 3109B2XF planted in Cochise County, Arizona. The affected field area was 8 ha with approximately 10% incidence of the disease. Limbs in proximity to the soil appeared to die first, and the infection rapidly progressed toward the upper canopy. Infected limb tips remained green and healthy for several days before wilting became evident. When the canopy was parted, bleached stems and the white cottony growth of a fungus were visible. Infections were observed on stems, bolls, and leaves. Diseased bolls appeared soft and rotted, and they were covered with white mycelium and large black irregularly shaped sclerotia. The bleached stems were surface sterilized, placed on potato dextrose agar amended with streptomycin (0.25 mg/liter). The inoculated dishes were incubated at 27°C for 3 days. The colony appearance of four isolates was identical, with white fluffy mycelium that turned gray after 7 days. Black irregularly shaped sclerotia were formed along the edge of the Petri dish, measuring 3 to 5.8 mm in length, 2.3 to 10.7 mm in width, and 0.9 to 5.3 mm in thickness. Based on these morphological characteristics, the fungus was identified as Sclerotinia sclerotiorum (Kohn 1979). Genomic DNA was extracted from the mycelia of four isolates. The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS5/ITS4, and the resulting four sequences of 586 bp were deposited in GenBank (MG249966 to MG249969). A BLASTn search revealed a 100% match with several sequences of S. sclerotiorum with a query coverage at 100% (e.g., KY750530.1, HQ833447.1, and JQ618848.1). To fulfill Koch’s postulates, pathogenicity tests were conducted using detached limbs with three bolls. Both limbs and bolls were first wounded with a sterile needle and inoculated by placing a mycelial plug (8 mm in diameter) from an actively growing region. Four limbs with 12 bolls were inoculated for each isolate. Twelve limbs with bolls were inoculated with plain agar plugs as a control. All inoculated limbs were incubated in a plastic container with over 90% relative humidity at room temperature. Symptoms similar to those observed in the field started to appear 3 days after inoculation. Sclerotia with similar size and shape were observed by the end of the second week. No symptoms were observed on control limbs or bolls. S. sclerotiorum was consistently reisolated from symptomatic plants. The pathogenicity test was repeated twice with similar results. To our knowledge, this is the first report of Sclerotinia boll rot and stem blight of cotton in Arizona. S. sclerotiorum has a wide host range, including many economically important plant species (Bolton et al. 2006). In Arizona, S. sclerotiorum can cause yield losses on lettuce and pinto bean. Due to wet and cool weather conditions during the “monsoon” season, cotton fields with a history of pinto bean production will have an increased risk of cotton boll rot and stem blight.

Establishment of seed germination and micropropagation protocols for Senegalia nigrescens, a potential anti-virulent species

ABSTRACTThis study describes seed germination and micropropagation of Senegalia nigrescens, an economic, medicinal and nitrogen-fixing species of South Africa. Seeds of S. nigrescens were subjected to pre-sowing treatments including soaking in cold water for 24 h, sulphuric acid (H2SO4) or hydrochloric acid (HCl) for 4, 8 and 12 min and mechanically scarifying seeds before sowing on Petri plates with wet filter paper. Mechanically-scarified seeds were also sown aseptically on a filter paper bridge, plain agar, ½ or full strength Murashige and Skoog (MS) basal medium. Single nodal explants from MS-derived seedlings were grown on MS media supplemented with 0.0, 0.5, 1.0 and 2.0 mg L−1 of benzylaminopurine (BAP) or kinetin (KIN) and a combination of 0.5 mg L−1 of BAP and KIN to investigate shoot multiplication. No significant differences were observed in the number of shoots produced across all treatments. However, the treatment containing 1.0 mg L−1 KIN produced a significantly higher shoot length (14.17 ± 5.20 mm) than 0.5, 1.0 and 2.0 mg L−1 BAP (7.67 ± 3.87, 6.75 ± 2.93 and 8.70 ± 3.56 mm, respectively). The highest rooting rate (16.7%) was obtained on ¼ strength MS supplemented with either indole-3-acetic acid (IAA) or indole-3-butyric acid (IBA) at concentrations 1.0 and 0.5 mg L−1, respectively. Rooted plantlets were successfully acclimatised with a 66.7% survival rate. The findings from this study would be of great benefit for the commercial propagation of S. nigrescens.

Seed micromorphology and ex vitro germination of Dendrobium orchids

Dendrobium species are adapted to disperse and germinate in various habitats. Whilst seed dispersal in orchids is known to be highly dependent on seed size and air space, little is known, generally, about seed micromorphology in Dendrobium and how this trait varies between species. In other plant families, small embryos may be used as an indicator of the presence of morphophysiological dormancy. However, the presence of seed dormancy in orchids is difficult to assess as germination is usually stimulated in vitro. We investigated the mature seed characters of nine Dendrobium species and assessed relations with seed germination. Seeds were found to be c. 0.2-0.6 mm long and 0.05-0.09 mm wide, containing embryos c. 120-240 µm long and 50-80 µm wide. The estimated seed air space around the embryo was 13 to 36% of the seed volume. Seed germination ex vitro on plain agar medium, in the absence of dormancy-breaking chemicals, progressed to the spherical protocorm stage at a broadly similar level to that observed in vitro on ½ Murashige and Skoog medium. We conclude that Dendrobium seeds with small air spaces and relatively large embryos can be non-dormant and this adaptation may allow seed germination in nature in moist, epiphytic microenvironments.

ВИЗНАЧЕННЯ ТЕРМІНУ ЗБЕРІГАННЯ ТА СТАБІЛЬНОСТІ ІНФЕКЦІЙНОЇ АКТИВНОСТІ КУЛЬТУРАЛЬНИХ АНТИГЕНІВ ШТАМУ ГВК 1 Ж ТА КЛОНУ ГВК 2 ТТ ДЛЯ ПОСТАНОВКИ РДП

Getting a culture herpesviridae antigens first and second types is possible using cell cultures inoculated epithelial pig testicles and tracheal calf respectively. The incubation herpesviridae first and second types should be conducted on the above lines in cell culture incubator at a temperature of 37,5 °C for up to 10 days. To maximize the release of virus from cell culture fluid viral after incubation need three frozen at temperatures from –18 °C to + 20 °C. The resulting liquid is purified viral the culture by centrifugation. Determining the infectious activity of the culture liquid viral performed in response hemagglutination of horse erythrocytes suspension, and the material is titrated to 1: 128 in the two recurrence. Accounting reaction was performed at 2, 4, 6 and 8 hours. Infectious material volumetric activity was 1:4. Getting antigens envisages concentrating liquid viral culture fluid by reverse dialysis. To do this, conducted a study to identify the optimal concentration of antigen suitable for setting reaction diffusion precipitation. At 1:10 antigen concentration result of different reactions, depending on the account of the diffusion precipitation reactions. When concentration of EHV–1 antigen was found that the optimum dilution for its RDP is 1:20. In assessing the EHV–2 antigen, found that suitable for setting reaction diffusion precipitation RDP is an antigen concentrated from 1:60 to 1:20. In practical terms, most rational use of antigen, concentrated 20 times.Keeping culture antigens can be conducted frozen at minus 18 ° C, for 12 months because after six months of storage of the frozen infectious activity was not decreased. And in research in 12 months noted a line of precipitation in native samples and serum diluted 1:2. Working antigens for diffuse precipitation reaction must be sterile on various forms of bacteria and fungi. Therefore, samples of viral antigens were plated on agar culture media for general purpose (plain agar), after having spent preserving antigen using 0.01% solution mertiolyatu rate of 0.1 sm3/1sm3 culture fluid. Using such an environment can detect material in the test organisms belonging to different morphological groups. Research sterility subjected to viral antigens, herpesviridae infection on the first type of herpesviridae infection and the second type.

An unique system of somatic embryogenesis in the tree fern Cyathea delgadii Sternb.: the importance of explant type, and physical and chemical factors

The effect of explant type (etiolation, age, length), physical (photoperiod, darkness) and chemical (sucrose and mineral salt concentrations) factors on somatic embryogenesis efficiency and sporophyte development in Cyathea delgadii was evaluated. Five-month-old cultures of sporophytes, which had developed 4–5 leaves, were used as a source of explants. The percentage response of stipes and the average number of somatic embryos were calculated after 2 months of culture. Etiolation of sporophytes used for culture initiation, was a critical factor in SE induction. Other factors studied significantly affected the production of somatic embryos. Optimum results were obtained when explants measuring 2.5 mm in length were excised from the youngest leaf of an etiolated sporophyte. Maximum SE efficiency (84.0 % response in explants; 42.3 somatic embryos per explant) was obtained on half-strength Murashige and Skoog medium supplemented with 1 % sucrose, under photoperiod conditions. However, light stimulated two different morphogenetic responses in explant cells: SE and apospory. In darkness, the number of somatic embryos was reduced to 32.9 per explant, but this was the only morphogenetic response observed. The presence of light alone was sufficient for somatic embryos growing on plain agar gel to reach maturity, but further development stopped shortly thereafter. The presence of both light and sucrose was necessary for the development of an embryonic leaf and root. For further sporophyte growth, mineral salts were essential. The micropropagation system described here is the first investigation into factors responsible for SE in ferns.

Induction of resistance to S. aureus in an environmental marine biofilm grown in Sydney Harbor, NSW, Australia.

The study of environmental biofilms is complicated by the difficulty of working with them under lab conditions. Nonetheless, knowledge of cellular activity and interactions within environmental biofilms could lead to novel biomedical applications. To address this problem we previously proposed a new technique for inducing resistance to Staphylococcus aureus in an intact environmental biofilm. In the current follow-up study we applied the new technique in a biogeographically distinct environment using a different strain of S. aureus. The proposed technique for inducing resistance to S. aureus in an environmental biofilm involves growing the environmental biofilms over several days in media reflecting their natural habitat on agar that contains spent culture supernatant from S. aureus over-night culture. We found in this second study that it was possible to induce resistance to S. aureus in an environmental biofilm from a biogeographically distinct environment, though not in the same way as we had previously observed. Environmental consortia from Sydney Harbor, Australia display an ability to inhibit biofilm formation by S. aureus; only in the case where the environmental biofilms were pretreated with UV radiation was there a difference in activity between environmental consortia grown on plain agar, and that grown on S. aureus agar. Application of the new technique in the current study also differs in that significant killing of cells within an established S. aureus biofilm by environmental consortia grown on S. aureus agar was possible.

Induction of resistance to Staphylococcus aureus in an environmental marine biofilm

The study of environmental biofilms is complicated by the difficulty of working with them under lab conditions. Nonetheless, knowledge of cellular activity and interactions within environmental biofilms could lead to novel biomedical applications. As a first step in this direction we propose a novel technique for inducing resistance to Staphylococcus aureus (S. aureus) in an intact environmental biofilm. Agar plates were prepared with or without the addition of 20% S. aureus spent culture media and immersed in coastal seawater (Boston Harbor, Massachusetts, USA) for four days to grow up an environmental biofilm. Nucleopore filters inoculated with an overnight culture of S. aureus were then applied to the surface of the agar plates with the environmental biofilms, incubated 4h at 37°C, removed and subsequently stained and analyzed. Marine environmental biofilms grown on agar containing S. aureus spent culture media were significantly more inhibitory of S. aureus growth than were marine environmental biofilms grown on plain agar.

Taste-independent detection of the caloric content of sugar in Drosophila

Feeding behavior is influenced primarily by two factors: nutritional needs and food palatability. However, the role of food deprivation and metabolic needs in the selection of appropriate food is poorly understood. Here, we show that the fruit fly, Drosophila melanogaster, selects calorie-rich foods following prolonged food deprivation in the absence of taste-receptor signaling. Flies mutant for the sugar receptors Gr5a and Gr64a cannot detect the taste of sugar, but still consumed sugar over plain agar after 15 h of starvation. Similarly, pox-neuro mutants that are insensitive to the taste of sugar preferentially consumed sugar over plain agar upon starvation. Moreover, when given a choice between metabolizable sugar (sucrose or D-glucose) and nonmetabolizable (zero-calorie) sugar (sucralose or L-glucose), starved Gr5a; Gr64a double mutants preferred metabolizable sugars. These findings suggest the existence of a taste-independent metabolic sensor that functions in food selection. The preference for calorie-rich food correlates with a decrease in the two main hemolymph sugars, trehalose and glucose, and in glycogen stores, indicating that this sensor is triggered when the internal energy sources are depleted. Thus, the need to replenish depleted energy stores during periods of starvation may be met through the activity of a taste-independent metabolic sensing pathway.

Development of Bacterial Biofilms on Artificial Corals in Comparison to Surface-Associated Microbes of Hard Corals

Numerous studies have demonstrated the differences in bacterial communities associated with corals versus those in their surrounding environment. However, these environmental samples often represent vastly different microbial micro-environments with few studies having looked at the settlement and growth of bacteria on surfaces similar to corals. As a result, it is difficult to determine which bacteria are associated specifically with coral tissue surfaces. In this study, early stages of passive settlement from the water column to artificial coral surfaces (formation of a biofilm) were assessed. Changes in bacterial diversity (16S rRNA gene), were studied on artificially created resin nubbins that were modelled from the skeleton of the reef building coral Acropora muricata. These models were dip-coated in sterile agar, mounted in situ on the reef and followed over time to monitor bacterial community succession. The bacterial community forming the biofilms remained significantly different (R = 0.864 p<0.05) from that of the water column and from the surface mucus layer (SML) of the coral at all times from 30 min to 96 h. The water column was dominated by members of the α-proteobacteria, the developed community on the biofilms dominated by γ-proteobacteria, whereas that within the SML was composed of a more diverse array of groups. Bacterial communities present within the SML do not appear to arise from passive settlement from the water column, but instead appear to have become established through a selection process. This selection process was shown to be dependent on some aspects of the physico-chemical structure of the settlement surface, since agar-coated slides showed distinct communities to coral-shaped surfaces. However, no significant differences were found between different surface coatings, including plain agar and agar enhanced with coral mucus exudates. Therefore future work should consider physico-chemical surface properties as factors governing change in microbial diversity.

Drosophila Evaluates and Learns the Nutritional Value of Sugars

Living organisms need to search for and ingest nutritional chemicals, and gustation plays a major role in detecting and discriminating between chemicals present in the environment. Using Drosophila as a model organism, we asked whether animals have the ability to evaluate the nutritional value of sugars. In flies, chemosensilla on the tarsi and labellum are the gustatory organs used to discriminate between edible and nonedible compounds [1, 2]. We noticed that Drosophila do not assign nutritional values to all sweet chemicals. D-arabinose is sweet to flies, but it provides them with no nutrition. By contrast, the sugar alcohol D-sorbitol is not sensed as sweet, but flies can live on it. We performed behavioral and electrophysiological measurements to confirm these gustatory and feeding responses. We found that Drosophila can learn the nutritional value of nonsweet D-sorbitol when it is associated with an odor cue. The learning process involved the synapsin molecule, suggesting that a neuronal mechanism is involved. We propose that Drosophila uses neural machinery to detect, evaluate, and learn the nutritional value of foods after ingestion.

Novel flow chamber to investigate binding strength of a lipid-based, high-frequency, ultrasonic contrast agent

In this study we design and implement a novel flow chamber to assess electrostatic and streptavidin-biotin attachment mechanisms of a high-frequency ultrasound contrast agent (UCA) under high wall shear stress (WSS). The flow chamber was calibrated up to 50 Pa WSS to investigate attachment of the UCA. Attachment of the agent was assessed through measurement of the mean backscatter from targeted microbubbles attached to an agar surface within the flow chamber. The mean backscatter from microbubbles attached via a streptavidin-biotin mechanism decreased from −20 to −30 dB with increasing WSS up to 50 Pa. Mean backscatter from microbubbles attached via electrostatic attraction was indistinguishable from that of the agar surface alone beyond 0.66 Pa WSS. At 50 Pa WSS, the mean backscatter from the streptavidin-biotin attachment mechanism was 4 dB higher than from the plain agar surface. We conclude that the streptavidin-biotin attachment mechanism is ∼75 times stronger than an electrostatic mechanism. The ability of the streptavidin-biotin bond to withstand high WSS makes this attachment mechanism suitable for use as a targeted UCA for intravascular ultrasound studies and in high-resolution small animal studies, in which WSS can reach 40 Pa.

Physiological interactions of antiauxins with auxin in roots

The compound 4,4,4-trifluoro-3-(indole-3-)butyric acid (TFIBA) typically promotes root elongation but inhibits hypocotyl elongation and therefore can be described as antiauxin. We compared the mode of action of TFIBA with the classical antiauxin p-chlorophenoxyisobutyric acid (PCIB). TFIBA, more than PCIB, promoted primary root elongation in young flax (Linum usitatissimum) roots on plain agar, but inhibited root growth in older seedlings in the presence of nutrients. The root content of indole-3-acetic acid (IAA) after TFIBA and PCIB treatment increased almost two-fold. Abscisic acid was affected only by supraoptimal TFIBA, but increased after PCIB application. TFIBA inhibited acropetal auxin transport at concentrations higher than optimal for root elongation while PCIB had no effect. Basipetal auxin transport was promoted at less than 0.1mM but inhibited at 1mM TFIBA. In contrast, PCIB promoted basipetal auxin transport between 0.1 and 0.5mM; higher concentrations had no effect. Gravitropism was promoted by TFIBA at concentrations optimal for growth, but inhibited by higher concentrations. PCIB inhibited root gravitropism in a concentration dependent manner. The selective effect of TFIBA on IAA but not ABA and the interference with auxin transport and gravicurvature indicate that the mode of action of TFIBA is different from that of PCIB despite similar functions.