Yeast Extract Peptone Dextrose Broth Research Articles

P345 The relationship between virulence of Candida albicans and environmental oxygen concentration

Poster session 3, September 23, 2022, 12:30 PM - 1:30 PMObjectives Candida species are known to colonize human skins and mucous membranes, and cause candidemia under various immunosuppressive conditions. Among these Candida species, C. albicans is reported to be the most frequently isolated species, and could colonize on skins, vaginas, gastrointestinal tracts, and medical devices. Environmental factors including oxygen concentration is thought to affect the capability of colonization and virulence of Candida species; however, most previous research was performed under aerobic condition, and few research focused on hypoxic conditions imitating inside the human bodies. Given these backgrounds, we performed murine experiments by culturing C. albicans under various oxygen conditions to evaluate the effect of environmental oxygen concentration on virulence. Through our studies, we aimed to clarify the actual behavior of C. albicans in the human body.MethodsIn this study, female C57BL/6 mice, 7-8 weeks old, were used and injected via lateral tail vein to cause C. albicans dissemination. Mice were divided into 4 groups according to the pre-culture conditions: aerobic, microaerobic (5% oxygen concentration), microaerobic (1% oxygen concentration), and anaerobic. Under each oxygen condition, C. albicans was grown at 37°C for 2 days on yeast extract peptone dextrose (YPD) agar and then incubated in YPD broth for 16-24 h. After incubation, C. albicans was collected, washed, resuspended in sterile PBS, and injected into each mouse at ∼2.5 × 105 colony-forming units. In this study, one reference strain (SC5314) and one clinically isolated strain (from bloodstream infection) were used. These infected mice were euthanatized 2 or 4 days after injection, and organ (kidneys and brain) fungal burdens were evaluated.ResultsThe kidneys’ fungal burdens were significantly higher in the microaerobic groups than those in the aerobic or anaerobic groups 2 and 4 days after injection. There were no significant differences between 5% oxygen concentration pre-cultured group and 1% oxygen concentration pre-cultured group. On gross examination, disseminated lesion formations were visible in the kidneys of the microaerobic groups. Similarly, the fungal burdens of brain were significantly higher in the microaerobically pre-cultured groups than in the aerobically or anaerobically pre-cultured groups. This tendency was similar for both the reference and clinically isolated strain.ConclusionOur results indicated that C. albicans could become more virulent under hypoxia, especially under microaerobic conditions. We assumed that some virulence factors of C. albicans were elevated under microaerobic conditions. These results implicated that C. albicans could become more virulent under hypoxic conditions in human bodies. In the future, we will continue to evaluate factors related to this change in virulence and pathological analysis of infected organs.

Determination of Optimum Conditions for Ergosterol Production by Saccharomyces cerevisiae

Ergosterol is an important provitamin in the present-day of industrial biotechnology. Seven yeast strains were obtained from the market of Basrah city and subjected to screening for their ergosterol production ability using liquid-state fermentation, the cultural conditions, and nutritional requirements for optimal production of ergosterol by Saccharomyces cerevisiae under laboratory conditions were determined. Y.6 is the best isolate of the yeast that produced ergosterol. It was identified as S. cerevisiae, with a similarity rate of 97% by using the Vitek2 device, this S. cerevisiae (Y.6) was further subjected to optimization conditions. The results showed that the best medium for production was yeast extract peptone dextrose broth. The effect of two cheaper carbon sources, molasses and date juice were investigated. Maximum ergosterol (0.55% ) was produced using a medium containing date juice, with a replacement ratio of 75%, an incubation time of 72 hours, pH 5, at a temperature of 30 °C, and an inoculation volume of 4 ml. The percentage of ergosterol was (0.47, 0.55, 0.74, 0.66, 0.68 and 0.78 %), respectively.

Antimicrobial Effect of UVC Light-Emitting Diodes against Saccharomyces cerevisiae and Their Application in Orange Juice Decontamination

UVC light-emitting diodes (UVC-LEDs) are a novel eco-friendly alternative source of UV light. This study evaluated the inactivation and membrane damage of spoilage yeast Saccharomyces cerevisiae by UVC-LEDs and their application in orange juice pasteurization. The results demonstrated that the antimicrobial effect of UVC-LED treatment against S. cerevisiae was enhanced by increased radiation dose. When the dose of UVC-LED radiation was 1,420 mJ/cm2, the population of S. cerevisiae in yeast extract peptone dextrose broth was reduced by 4.86 log CFU/mL. Through scanning electron microscopy and fluorescent staining, the structure and function of plasma membrane was observed to be severely damaged by UVC-LED treatment. The inactivation efficacy of UVC-LEDs against S. cerevisiae in orange juice also increased with increasing radiation dose. Radiation at 1,420 mJ/cm2 greatly reduced S. cerevisiae in orange juice by 4.44 log CFU/mL and did not induce remarkable changes in pH, total soluble solids, titratable acidity, and color parameters. However, the total phenolic content in orange juice was found to be significantly decreased by UVC-LEDs. These findings contribute to a better comprehension of UVC-LED inactivation and provide theoretical support for its potential application in fruit and vegetable juice processing.

Aflatoxin B1 degradation by microorganisms isolated from Kombucha culture

Aflatoxin B1 (AFB1) is the most harmful mycotoxin. Aflatoxin occurrence in tea makes this beverage unsuitable for consumption and presented risks to human health. Therefore, researches in aflatoxin microbial degradation are necessary to overcome this problem. Kombucha beverage is associated with health promoting effects. Thus, novel strains (Lactic acid bacteria and yeasts) were isolated from a Kombucha culture and assessed for AFB1 degradation in the liquid medium (Man Rogosa and Sharpe broth, yeast extract peptone dextrose broth and black tea). The main strains involved in AFB1 decontamination were identified based on DNA sequencing and the toxicity of the new products was evaluated on Hep2 cells and on Brine shrimp (Artemia salina). Our results showed that after 7 days of fermentation, kombucha was able to degrade 97% of AFB1 in black tea. Moreover, the effective yeasts present in Kombucha were identified as Pichia occidentalis, Candida sorboxylosa and Hanseniaspora opuntiae and the highest AFB1 degradation capacity was accorded to P. occidentalis (59%) when cultivated in black tea. Data on cytotoxicity tests on Hep2 cells and Brine shrimp (Artemia salina) showed that the biodegraded products were less toxic than pure AFB1. These findings suggest that, kombucha isolated strains could be potential candidates for application in the food and feed industry with a potential aflatoxin B1 detoxification properties.

Endophytic Bacteria Isolated from Citrus Plants for Biological Control of Citrus Canker in Lime Plants.

Citrus canker caused by Xanthomonas citri subsp. citri is a disease affecting the yield and fruit quality of lime (Citrus aurantiifolia). This research investigated endophytic bacteria obtained from six healthy Citrus spp. to inhibit the pathogen and to control citrus canker on lime plants. Numbers of the endophytic bacteria isolated from C. aurantifolia, C. hystrix, C. maxima, C. nobilis, C. reticulata and C. sinensis were 28, 25, 29, 42, 12 and 34 isolates, respectively. The selected endophytic bacteria that were effective against X. citri subsp. citri were Bacillus amyloliquefaciens LE109, B. subtilis LE24 and B. tequilensis PO80. The optimum culture medium for an antagonistic effect on the pathogen in B. amyloliquefaciens LE109 and B. tequilensis PO80 was yeast extract peptone dextrose broth, and in B. subtilis LE24 was modified soluble starch broth. To control citrus canker in lime, young expanded leaves of lime plants were aseptically punctured and inoculated with 30 μl of bacterial suspension of the pathogen (108 CFU/ml in 0.85% NaCl) per punctured location. After the pathogenic inoculation for 24 h, the leaves were then inoculated with 30 μl of the selected endophytic bacteria (108 CFU/ml in 0.85% NaCl), and treated with 30 μl of the culture media containing bioactive compounds produced by the selected endophytic bacteria. The leaves inoculated with cell suspensions of B. amyloliquefaciens LE109 or B. subtilis LE24 could completely control citrus canker. However, the leaves inoculated with B. tequilensis PO80 displayed 10% disease incidence. Additionally, the leaves treated with the crude bioactive compounds of B. amyloliquefaciens LE109 or B. subtilis LE24 could completely control citrus canker. Notably, the leaves treated with the crude bioactive compounds of B. tequilensis PO80 displayed 5% disease incidence. The results of this study showed that the Bacillus strains play important roles in the biocontrol of citrus canker in lime.

Isolation and Identification of Yeasts from Wild Flowers Collected around Jangseong Lake in Jeollanam-do, Republic of Korea, and Characterization of the Unrecorded Yeast Bullera coprosmaensis

Several types of yeasts were isolated from wild flowers around Jangseong Lake in Jeollanam-do, Republic of Korea and identified by comparing the nucleotide sequences of the PCR amplicons for the D1/D2 variable domain of the 26S ribosomal DNA using Basic Local Alignment Search Tool (BLAST) analysis. In total, 60 strains from 18 species were isolated, and Pseudozyma spp. (27 strains), which included Pseudozyma rugulosa (7 strains) and Pseudozyma aphidis (6 strains), was dominant species. Among the 60 strains, Bullera coprosmaensis JS00600 represented a newly recorded yeast strain in Korea, and its microbiological characteristics were investigated. The yeast cell has an oval-shaped morphology measuring 1.4 × 1.7 μm in size. Bullera coprosmaensis JS00600 is an asporous yeast that exhibits no pseudomycelium formation. It grew well in vitamin-free medium as well as in yeast extract-malt extract broth and yeast extract-peptone-dextrose (YPD) broth, and it is halotolerant growing in 10% NaCl-containing YPD broth.

Diversity of culturable yeasts in phylloplane of sugarcane in Thailand and their capability to produce indole-3-acetic acid

Yeasts were isolated by the enrichment technique from the phylloplane of 94 samples of sugarcane leaf collected from seven provinces in Thailand. All sugarcane leaf samples contained yeasts and 158 yeast strains were obtained. On the basis of the D1/D2 domain of the large subunit rRNA gene sequence analysis, 144 strains were identified to 24 known species in 14 genera belonging to the Ascomycota viz. Candida akabanensis, Candida dendronema, Candida mesorugosa, Candida michaelii, Candida nivariensis, Candida rugosa, Candida orthopsilosis, Candida quercitrusa, Candida tropicalis, Candida xylopsoci, Cyberlindnera fabianii, Cyberlindnera rhodanensis, Debaryomyces nepalensis, Hannaella aff. coprosmaensis, Hanseniaspora guilliermondii, Kluyveromyces marxianus, Lachancea thermotolerans, Lodderomyces elongisporus, Metschnikowia koreensis, Meyerozyma caribbica, Millerozyma koratensis, Pichia kudriavzevii,Torulasporadelbrueckii and Wickerhamomyces edaphicus, and 12 species in six genera of the Basidiomycota viz . Cryptococcus flavescens, Cryptococcus laurentii, Cryptococcus rajasthanensis, Kwoniellaheveanensis, Rhodosporidium fluviale, Rhodosporidium paludigenum, Rhodotorula mucilaginosa, Rhodotorula sesimbrana, Rhodotorula taiwanensis, Sporidiobolus ruineniae, Sporobolomyces carnicolor and Sporobolomyces nylandii. Seven strains were identical or similar to four undescribed species. Another seven strains represented four novels species in the genus Metschnikowia, Nakazawaea, Wickerhamomyces and Yamadazyma. The results revealed 69% of the isolated strains were ascomycete yeastsand 31% were basidiomycete yeast. The most prevalent species was M. caribbica with a 23% frequency of occurrence followed by Rh. taiwanensis (11%) and C. tropicalis (10%). All strains were assessed for indole-3-acetic acid (IAA) producing capability showing that 69 strains had the capability of producing IAA when cultivated in yeast extract peptone dextrose broth supplemented with 1g/L L-tryptophan. The highest IAA concentration of 565.1mg/L was produced by R. fluviale DMKU-RK253.

Inhibition of biofilm formation and lipase in Candida albicans by culture filtrate of Staphylococcus epidermidis in vitro

Background:Candida spp. are fourth most common cause of bloodstream infection in developed countries and emerging agents of fungemia in developing countries, with considerable attributable mortality. Candidemia is associated with the formation of complex, structured microbial communities called biofilms. Biofilm formation makes treatment difficult due to improper drug penetration and factors like high cost and adverse effects of antifungal drugs available. Hence, low-cost alternatives are urgently required to treat device-associated invasive candidiasis.Objectives:To study the effect of culture filtrate of Staphylococcus epidermidis on biofilm formation and lipase expression of Candida albicans in vitro.Materials and Methods:Yeast cells isolated from clinical samples were suspended to a turbidity of 106 in (a) Yeast extract-peptone-dextrose (YPD) broth and (b) culture filtrate, and 100 μl of each were dispensed in separate wells of microtiter plate. After repeated washing and reloading with respective liquid media, readings were taken spectrophotometrically. To check for lipase inhibition, yeasts were incubated overnight in YPD and filtrate and subcultured on media containing Tween-80 and CaCl2. Positive lipase activity was denoted by haziness around colonies.Results:Mean reading of C. albicans in YPD broth was 0.579 while the same when yeasts were suspended in S. epidermidis culture filtrate was 0.281 (P < 0.05 by Z-test of significance). Lipase of C. albicans was inhibited by culture filtrate. Filtrate was found to be nontoxic to human cell line.Conclusions:Culture filtrate of S. epidermidis can hence pave the way for development of new strategies to inhibit biofilm formation in device-associated candidemia.

Enhancement in yeast separation and recycling in continuous bio‐ethanol fermentation process in Blenke cascade

AbstractBackgroundContinuous ethanol fermentation productivity strongly depends on yeast concentration. Therefore apparatuses, which can handle high cell concentrations, separation and recycling of adapted yeasts are of high interest.In our work, an enhanced sedimentation rate (ESR) settler for a Blenke cascade system, avoiding large electrical power consumption, was designed. To improve the sedimentation rate, the ESR settler was connected in series with a small conventional gravitational settler. Yeast recycling was executed in two modes, direct and activation modes. Yeast cell samples taken from both cascade and settler were counted and tested for cell viability using methylene blue staining technique and a haemocytometer. The samples were cultured on agar plate with yeast extract peptone dextrose broth and analyzed by HPLC to determine ethanol, residual sugars content and by‐products (of yeast and bacterial origin).ResultsThe results showed that, using ESR settler in series with a small conventional gravitational settler, more than 85% of the yeast cells were sedimented and were recycled by the direct or activation mode. The ethanol productivities were Qp = 19.45 ± 0.13 and Qp = 20.31 ± 0.11 g L−1 h−1 for direct and activation recycle mode, respectively. Continuous fermentation, yeast recycling and sedimentation were contamination‐free processes.ConclusionWith an ESR settler, more adapted yeast can be recycled into the continuous process. High ethanol productivity can be achieved by an activation recycling mode. © 2013 Society of Chemical Industry

Ethanol Production in Yeasts Isolated from Fermented Kitchen Waste

Microbial ethanol is a potential substitute for the non-renewable fossil fuel which is depleting. Yeasts have been long and extensively studied for ethanol production. The objectives of this study were to isolate yeasts from fermented kitchen waste and to determine their ethanol production performances. A number of fifteen yeasts were isolated from fermented kitchen waste. The yeastswere then grouped based on their ability to ferment different types of sugars. Three yeast isolates were selected for the analysis of ethanol production. Fermentation was carried out for 72 h in yeast extract peptone dextrose broth containing 18% glucose. Fourier transform infrared attenuated total reflection spectroscopy was used to monitor the ethanol production and glucose utilization. Isolate Y4 achieved the highest ethanol production at the level of 16%, while Y6 and Y8 demonstrated 12% and 11% ethanol yields, respectively. The isolates Y4, Y6 and Y8 were identified using universal fungal primers ITS1 and ITS4. The yeast isolates were closest to Saccharomyces cerevisiae (76%), Paracoccidioides brasiliensis (56%) and Saccharomyces boulardii (64%), respectively. This studyshowed that fermented kitchen waste could serve as a good source of yeasts for ethanol production.

Selection and characterization of a newly isolated thermotolerant Pichia kudriavzevii strain for ethanol production at high temperature from cassava starch hydrolysate

Pichia kudriavzevii DMKU 3-ET15 was isolated from traditional fermented pork sausage by an enrichment technique in a yeast extract peptone dextrose (YPD) broth, supplemented with 4 % (v/v) ethanol at 40 °C and selected based on its ethanol fermentation ability at 40 °C in YPD broth composed of 16 % glucose, and in a cassava starch hydrolysate medium composed of cassava starch hydrolysate adjusted to 16 % glucose. The strain produced ethanol from cassava starch hydrolysate at a high temperature up to 45 °C, but the optimal temperature for ethanol production was at 40 °C. Ethanol production by this strain using shaking flask cultivation was the highest in a medium containing cassava starch hydrolysate adjusted to 18 % glucose, 0.05 % (NH(4))(2)SO(4), 0.09 % yeast extract, 0.05 % KH(2)PO(4), and 0.05 % MgSO(4)·7H(2)O, with a pH of 5.0 at 40 °C. The highest ethanol concentration reached 7.86 % (w/v) after 24 h, with productivity of 3.28 g/l/h and yield of 85.4 % of the theoretical yield. At 42 °C, ethanol production by this strain became slightly lower, while at 45 °C only 3.82 % (w/v) of ethanol, 1.27 g/l/h productivity and 41.5 % of the theoretical yield were attained. In a study on ethanol production in a 2.5-l jar fermenter with an agitation speed of 300 rpm and an aeration rate of 0.1 vvm throughout the fermentation, P. kudriavzevii DMKU 3-ET15 yielded a final ethanol concentration of 7.35 % (w/v) after 33 h, a productivity of 2.23 g/l/h and a yield of 79.9 % of the theoretical yield.

Yeasts from phylloplane and their capability to produce indole-3-acetic acid

Yeasts were isolated from the phylloplane of various plant species collected from seven provinces in Thailand. A total of 114 yeast strains and 10 strains of a yeast-like fungus were obtained by enrichment isolation from 91 out of 97 leaf samples (93.8 %). On the basis of the D1/D2 domain of the large subunit rRNA gene sequence similarity, 98 strains were identified to be of 36 yeast species in 18 genera belonging to Ascomycota viz. Candida, Clavispora, Cyberlindnera, Debaryomyces, Hanseniaspora, Hyphopichia, Kazachstania, Kluyveromyces, Kodamaea, Lachancea, Metschnikowia, Meyrozyma, Pichia, Starmerella, Torulaspora and Wickerhamomyces, and to Basidiomycota viz. Sporidiobolus and Trichosporon. Three strains were found to represent two novels Candida species which were previously described as C. sirachaensis and C. sakaeoensis. Ten strains of yeast-like fungus were identified as Aureobasidium pullulans of the phylum Ascomycota. Ascomycetous yeast species accounted altogether for 98.0 % of the 98 strains. The prevalent species was Candida tropicalis with a low frequency of isolation (14.3 %). Diversity of yeasts other than ballistoconidium-forming yeast in phylloplane in a tropical country in Asia has been reported for the first time. All strains obtained were accessed for the capability to produce IAA and result revealed that 39 strains in 20 species, one strain each of an undescribed and a novel species, and two unidentified strains showed the capability of producing IAA when cultivated in yeast extract peptone dextrose broth supplemented with 0.1 % L-tryptophan. All five strains of Candida maltosa produced relatively high concentrations of IAA.

Genetic relatedness of Candida albicans clinical isolates from Candida bloodstream infections in a Malaysian population

Background: Invasive candidiasis, a major health concern in developing countries, has an attributable mortality of 15-40%. It is associated with biofilm formation over indwelling devices. Our study was aimed at finding low-cost alternatives to inhibit this biofilm development in-vitro. Methods: One loopful of Aspergillus flavus clinical isolates were cultured in YPD(Yeast Extract-Peptone-Dextrose) broth for 1week. Culture filtrate was prepared by filtering it through membrane filter of pore size 0.45 m. Candia albicans and C. tropicalis clinical isolates were cultured in YPD broth at 37 C for 48hours. Dilutions of yeast cell suspensions were prepared in YPD broth as well as Aspergillus culture filtrate, and yeast cell density was adjusted to 106 cells/ml in both cases. Then 100 l of each was poured in wells of a flat-bottomedmicrotitre plate. Theplatewas incubated at 37 C and washed at intervals of 90 minutes, 24 hours and 48 hours with sterile Phosphate Buffered Saline (pH 7.2). Each time after washing, wells were reloadedwith respective cell suspensions. Then the optical density(O.D.) was measured in a spectrophotometer at 450 nm wavelength after staining the wells with 1% Safranine in 95% ethanol. The plate was also observed under Invertedmicroscope to see biofilm development. Tests were done in triplicate. Results: Aspergillus filtrate significantly reduced the biofilm formation in C. albicans and C. tropicalis , as observed microscopically and spectrophotometrically.MeanO.D.value of Candida spp. in YPD broth was 0.795 0.6 and that of filtrate containing Candida spp. suspension was 0.576±0.1(p value: <0.05). Conclusion: Culture filtrate of Aspergillus flavus disrupts Candidal biofilm development in-vitro.

Aspergillus flavus culture filtrate inhibits candidal biofilm development in-vitro

Background: Invasive candidiasis, a major health concern in developing countries, has an attributable mortality of 15-40%. It is associated with biofilm formation over indwelling devices. Our study was aimed at finding low-cost alternatives to inhibit this biofilm development in-vitro. Methods: One loopful of Aspergillus flavus clinical isolates were cultured in YPD(Yeast Extract-Peptone-Dextrose) broth for 1 week. Culture filtrate was prepared by filtering it through membrane filter of pore size 0.45 μm. Candia albicans and C. tropicalis clinical isolates were cultured in YPD broth at 37 °C for 48 hours. Dilutions of yeast cell suspensions were prepared in YPD broth as well as Aspergillus culture filtrate, and yeast cell density was adjusted to 106 cells/ml in both cases. Then 100 μl of each was poured in wells of a flat-bottomed microtitre plate. The plate was incubated at 37 °C and washed at intervals of 90 minutes, 24 hours and 48 hours with sterile Phosphate Buffered Saline (pH 7.2). Each time after washing, wells were reloaded with respective cell suspensions. Then the optical density(O.D.) was measured in a spectrophotometer at 450 nm wavelength after staining the wells with 1% Safranine in 95% ethanol. The plate was also observed under Inverted microscope to see biofilm development. Tests were done in triplicate. Results: Aspergillus filtrate significantly reduced the biofilm formation in C. albicans and C. tropicalis , as observed microscopically and spectrophotometrically. Mean O.D.value of Candida spp. in YPD broth was 0.795 0.6 and that of filtrate containing Candida spp. suspension was 0.576 ± 0.1(p value: <0.05). Conclusion: Culture filtrate of Aspergillus flavus disrupts Candidal biofilm development in-vitro.

Potentized homeopathic drug Arsenicum Album 30C positively modulates protein biomarkers and gene expressions in Saccharomyces cerevisae exposed to arsenate

This study examines if homeopathic drug Arsenicum Album 30C (Ars Alb 30C) can elicit ameliorative responses in yeast (Saccharomyces cerevisiae) exposed to arsenate. The yeast S. cerevisiae 699 was cultured in a standard yeast extract peptone dextrose broth medium. It was exposed to the final concentration of 0.15 mmol/L arsenate for two intervals, 1 h and 2 h, respectively. The cell viability was determined along with the assessment of several toxicity biomarkers such as catalase (CAT), superoxide dismutase (SOD), total thiol (GSH) and glucose-6-phosphate dehydrogenase (G6PDH), lipid peroxidation, protein carbonylation and DNA damage. Reactive oxygen species (ROS) accumulation, expressions of relevant stress transcription activators like Yap-1 and Msn 2, and mRNA expression of yeast caspase-1 (Yca-1) were also measured. Treatment of arsenate increased lipid peroxidation, protein carbonylation, DNA damage, ROS accumulation and expressions of Yap-1, Msn 2 and Yca-1 and decreased GSH, G6PDH, CAT and SOD. Ars Alb 30C administration decreased lipid peroxidation, protein carbonylation, DNA damage, ROS formation and Msn 2 and Yca-1 expressions and increased cell viability, GSH, G6PDH, CAT and SOD significantly (P<0.05), except for a slight increase in Yap-1 expression. Ars Alb 30C triggers ameliorative responses in S. cerevisiae exposed to arsenate.

In situ formation of a gel microbead for indirect laser micromanipulation of microorganisms

We propose the in situ formation of gel microbeads made of a thermoreversible hydrogel for indirect laser micromanipulation of microorganisms. Irradiation, using a 1064nm laser, of an aqueous solution mixed with poly-(N-isopropylacrylamide) through a high magnification lens resulted in the formation of a gel microbead at the laser focus due to heating. The gel microbead is trapped by the laser, and is used for indirect laser micromanipulation of microorganisms. However, the laser power used to form the bead is generally too strong to perform manipulation in a stable manner. In this letter we show a method to reduce the laser power to form a gel microbead using the poly-(N-isopropylacrylamide) aqueous solution by the addition of additives. The gelation temperature and the laser absorption rate of the solution in the presence of several different additives were investigated. We selected YPD (yeast extract, peptone, dextrose) broth as an additive and measured the relationship between the laser power, irradiation time, and diameter of the gel microbead. We succeeded in reducing the laser power for gel microbead formation, and in using the laser-trapped gel microbead for the manipulation of a yeast cell and DNA.

Structure−Function Analysis of the Vanillin Molecule and Its Antifungal Properties

The aim of the present study was to evaluate which structural elements of the vanillin molecule are responsible for its observed antifungal activity. MICs of vanillin, its six direct structural analogues, and several other related compounds were determined in yeast extract peptone dextrose broth against a total of 18 different food spoilage molds and yeasts. Using total mean MICs after 4 days of incubation at 25 degrees C, the antifungal activity order was 3-anisaldehyde (1.97 mM) > benzaldehyde (3.30 mM) > vanillin (5.71 mM) > anisole (6.59 mM) > 4-hydroxybenzaldehyde (9.09 mM) > phenol (10.59 mM) > guaiacol (11.66 mM). No correlation was observed between the relative antifungal activity of the test compounds and log P(o/w). Furthermore, phenol (10.6 mM) was found to exhibit a greater activity than cyclohexanol (25.3 mM), whereas cyclohexanecarboxaldehyde (2.13 mM) was more active than benzaldehyde (3.30 mM). Finally, the antifungal order of isomers of hydroxybenzaldehyde and anisaldehyde was found to be 2- > 3- > 4- and 3- > 2- > 4-, respectively. In conclusion, the aldehyde moeity of vanillin plays a key role in its antifungal activity, but side-group position on the benzene ring also influences this activity. Understanding how the structure of natural compounds relates to their antimicrobial function is fundamentally important and may help facilitate their application as novel food preservatives.

Virulence ofCandida albicansmutants toward larvalGalleria mellonella(Insecta, Lepidoptera, Galleridae)

Culture medium affected the virulence of a strain of Candida albicans toward Galleria mellonella larvae, but the yeast growth rates in yeast extract - peptone - dextrose broth and synthetic Galleria serum were not correlated with yeast virulence. Virulent C. albicans grew rapidly in larval serum, whereas, it limited nodulation and continued development in vivo, producing toxins that damaged the hemocytes and fat body. Nonpathogenic yeast-phase cells grew slowly in larval serum but induced extensively melanized nodules in vivo and developed no further. There was no discernible relationship in 14 exo-enzymes between the virulent and avirulent yeast strains and virulence. The avirulent myosin-I-defective yeast cells were rapidly removed from the hemolymph in vivo because of lysozyme-mediated yeast agglutination and the possible binding of the yeast cells by lysozyme and apolipophorin-III. Both lysozyme and apolipophorin-III are proteins that bind beta-1,3-glucan. Finally, insects with nonpathogenic C. albicans exhibited induced immunity and were more resistant to candidiasis from the wild-type yeast cells than were noninduced insects.