Yeast Peptone Glucose Research Articles

Thermal Inactivation Kinetics of Sporolactobacillus nakayamae Spores, a Spoilage Bacterium Isolated from a Model Mashed Potato–Scallion Mixture

Sporolactobacillus species have been occasionally isolated from spoiled foods and environmental sources. Thus, food processors should be aware of their potential presence and characteristics. In this study, the heat resistance and influence of the growth and recovery media on apparent heat resistance of Sporolactobacillus nakayamae spores were studied and described mathematically. For each medium, survivor curves and thermal death curves were generated for different treatment times (0 to 25 min) at different temperatures (70, 75, and 80°C) and Weibull and first-order models were compared. Thermal inactivation data for S. nakayamae spores varied widely depending on the media formulations used, with glucose yeast peptone consistently yielding the highest D-values for the three temperatures tested. For this same medium, the D-values ranged from 25.24 ± 1.57 to 3.45 ± 0.27 min for the first-order model and from 24.18 ± 0.62 to 3.50 ± 0.24 min for the Weibull model at 70 and 80°C, respectively. The z-values determined for S. nakayamae spores were 11.91 ± 0.29°C for the Weibull model and 11.58 ± 0.43°C for the first-order model. The calculated activation energy was 200.5 ± 7.3 kJ/mol for the first-order model and 192.8 ± 22.1 kJ/mol for the Weibull model. The Weibull model consistently produced the best fit for all the survival curves. This study provides novel and precise information on thermal inactivation kinetics of S. nakayamae spores that will enable reliable thermal process calculations for eliminating this spoilage bacterium.

An original method for producing acetaldehyde and diacetyl by yeast fermentation.

In this study a natural culture medium that mimics the synthetic yeast peptone glucose medium used for yeast fermentations was designed to screen and select yeasts capable of producing high levels of diacetyl and acetaldehyde. The presence of whey powder and sodium citrate in the medium along with manganese and magnesium sulfate enhanced both biomass and aroma development. A total of 52 yeasts strains were cultivated in two different culture media, namely, yeast peptone glucose medium and yeast acetaldehyde-diacetyl medium. The initial screening of the strains was based on the qualitative reaction of the acetaldehyde with Schiff's reagent (violet color) and diacetyl with Brady's reagent (yellow precipitate). The fermented culture media of 10 yeast strains were subsequently analyzed by gas chromatography to quantify the concentration of acetaldehyde and diacetyl synthesized. Total titratable acidity values indicated that a total titratable acidity of 5.5 °SH, implying culture medium at basic pH, was more favorable for the acetaldehyde biosynthesis using strain D15 (Candida lipolytica; 96.05 mg L−1 acetaldehyde) while a total titratable acidity value of 7 °SH facilitated diacetyl flavor synthesis by strain D38 (Candida globosa; 3.58 mg L−1 diacetyl). Importantly, the results presented here suggest that this can be potentially used in the baking industry.

PM 7/60 (2) Pantoea stewartii subsp. stewartii

Specific scopeThis Standard describes a diagnostic protocol for Pantoea stewartii subsp. stewartii.Specific approval and amendmentApproved in 2005‐09.Revised in 2016‐04.

Characterization of PGP Traits of a Hexavalent Chromium Resistant Raoultella sp. Isolated from the Rice Field near Industrial Sewage of Burdwan District, WB, India

ABSTRACTChromium (Cr) is the most toxic at its hexavalent state. Widespread use of chromium for various anthropogenic activities causing rapid decline of the agricultural productivity is now a major global concern. The purpose of this study was to isolate the plant growth promoting (PGP) chromium-resistant bacteria and characterize it before being applied for bioremediation. A potent Cr-resistant rhizobacterium (CrS2) was isolated from the rice field near an industrial sewage and identified as Raoultella sp. based on 16S rDNA sequence homology with some phenotypic characteristics. The strain exhibited Cr(VI) resistance up to 25 mM and also possesses some important PGP traits. The selected CrS2 strain has varied degrees of resistance to other toxic heavy metals/metalloids like arsenic, cadmium, and lead. The removal capacity of chromium was studied in broth cultures. The appropriate growth media for the strain is peptone yeast glucose media with glucose (0.5%) and peptone (1%) as carbon and nitrogen sources, respectively. The strain removed substantial amount of chromium after media optimization. The chromate reductase (EC.1.6.5.2) activity was constitutive in nature of this strain. Thus, the strain CrS2 may be exploited for bioremediation of Cr(VI) in Cr-contaminated agricultural soil, where it might also enhance plant growth promotion.

Biodegradation and decolorization of melanoidin solutions by manganese peroxidase yeasts.

The ability of selected manganese peroxidase (MnP) yeast strains, isolated from the mixed liquor of an activated sludge bioreactor treating melanoidins wastewater, was investigated in this work, aiming to examine the degradation potential of melanoidins, in the presence or absence of nutrients. Ten yeast strains were initially isolated from the mixed liquor; four yeast strains (Y1, Y2, Y3 and Y4) were selected for further studies, based on their tolerance towards synthetic melanoidins (SMs) degradation and MnP activity onto solid agar medium. The Y1 strain exhibited almost 98% homology to Candida glabrata yeast, based on 28S rRNA identification studies. During experiments carried out using SM at 30 °C, the four isolated yeast cultures showed a noticeable organic matter reduction and decolorization capacity reaching up to 70% within 2-5 days. However, the corresponding yeast cultures grown in glucose peptone yeast extract medium using real melanoidin wastewater at 30°C showed lower organic matter and color removal capacity, reaching about 60% within 2-5 days. Nevertheless, it was found that the removal of real and synthetic melanoidins could be carried out by these strains under non-aseptic conditions, without requiring further addition of nutrients.

Extracts from Flammulina velutipes inhibit the adhesion of pathogenic fungi to epithelial cells

Background:Recently, extracts from natural sources have been tested for their antifungal properties. In this aspect, Flammulina velutipes extracts possess a significant amount of branch-chained carbohydrates with mannose moieties that, hypothetically, can reduce the adhesion.Objective:In this study, we assessed the capacity of extracts from F. velutipes (wild-type AQF-1 and ATCC 34574 as the reference strain) to inhibit the adhesion of S. schenkii and C. albicans to epithelial cells.Materials and Methods:The aqueous extracts from F. velutipes strains were obtained by sonication, total carbohydrate and protein was analyzed by Dubois and Lowry methods respectively. Effect of the extracts (50, 100 and 150 μg/mL) on the fungi adhesion to host cells was evaluated after 1 h interaction, and the percentage of inhibition of adhesion was measured. After of interaction the cytoskeleton from cell was analyzed with phalloidin-FITC.Results:The extract from strain AQF-1 (50, 100 and 150 μg/mL) inhibited the adhesion of: S. schenkii in a dose-dependent manner (4.9, 7.5 and 12.7%, respectively) and C. albicans in a dose-independent manner (5.2%). The percentage of inhibition by extracts from the strain ATCC34574 at the same concentrations, shown that are dose independent for both fungi: 3.9% for S. schenkii and 2.6% for C. albicans.Conclusion:The extracts from F. velutipes inhibit the adhesion of pathogenic fungi to host cells. The mechanism molecular is unknown; however, is probably an interaction between the polysaccharides from extracts with the fungi receptors. This aspect is currently analyzed.SUMMARY The yields of mycelium from two strains of F. velutipes and the extract from it were similar.Extracts from both strains have inhibited adhesion of S. schenkii and C. albicans to epithelial cells in vitro, but the extract from strain AQF-1 was more effective.The extracts have not prevented damage to epithelial cells caused by pathogenic fungi. Abbreviation Used: YPG: Yeast peptone glucose, DMEM: Dulbecco's Modified Eagle's medium, FITC: Fluorescein isothiocyanate

Reclassification of Eubacterium rectale (Hauduroy et al. 1937) Prévot 1938 in a new genus Agathobacter gen. nov. as Agathobacter rectalis comb. nov., and description of Agathobacter ruminis sp. nov., isolated from the rumen contents of sheep and cows.

Three strains of a butyrate-producing bacterium were isolated from the rumen contents of grazing sheep and cows. The strains were anaerobic, with Gram-positive cell walls, straight-to-slightly-curved, rod-shaped, non-spore-forming and single flagellate. C14 : 1, C14 : 0, C16 : 0 and C16 : 1 were the predominant fatty acids. The cell-wall peptidoglycan type was A1γ. The DNA G+C content varied from 41.4 to 42.2 mol%. 16S rRNA gene sequence similarities between the isolates and Eubacterium rectale, Roseburia hominis and Roseburia intestinalis were found to be 96, 95 and 95 %, respectively. The phylogenetic tree showed that the strains constituted a different taxon, separate from other taxa with validly published names and forming a cluster with strains of Eubacterium rectale. On the basis of phenotypic, chemotaxonomic and phylogenetic results (16S RNA, dnaK, groEL, atpA genes), the isolates are considered to represent a novel species of a new genus of the family Lachnospiraceae, for which the name Agathobacter ruminis gen. nov., sp. nov. is proposed (type strain JK623T = DSM 29029T = LMG 28559T). We also propose the transfer of Eubacterium rectale to the new genus as Agathobacter rectalis gen. nov., comb nov. This new genus represents saccharoclastic, chemo-organotrophic and obligatory anaerobic, non-spore-forming rods with Gram-positive membrane. The main fermentation products on peptone yeast glucose (PYG) medium were butyrate, acetate, hydrogen and lactate. The type species of the genus is Agathobacter rectalis gen. nov., comb nov. (Prévot, 1938) with type strain ATCC 33656T ( = JCM 17463T).

Fecal detection of enterotoxigenic Bacteroides fragilis.

Bacteroides fragilis is a common colonic symbiote of which one subtype, enterotoxigenic Bacteroides fragilis (ETBF), causes inflammatory diarrhea. However, asymptomatic ETBF colonization is common. Through its primary virulence factor, B. fragilis toxin (BFT), ETBF causes asymptomatic, chronic colitis in C57BL/6 mice and increased colon tumorigenesis in multiple intestinal neoplasia mice. Human studies suggest an association between ETBF infection, inflammatory bowel disease, and colon cancer. Additional studies on ETBF epidemiology are, therefore, crucial. The goal of this study is to develop a reliable fecal diagnostic for ETBF. To develop a sensitive assay for ETBF, we tested multiple protocols on mouse stools spiked with serially diluted ETBF. Each assay was based on either touchdown or quantitative polymerase chain reaction (qPCR) and used primers targeted to bft to detect ETBF. Using touchdown PCR or qPCR, the mean ETBF detection limit was 1.55 × 10(6) colony-forming units (CFU)/g stool and 1.33 × 10(4) CFU/g stool, respectively. Augmentation of Bacteroides spp. growth in fecal samples using PYGB (Peptone Yeast Glucose with Bile) broth enhanced ETBF detection to 2.93 × 10(2) CFU/g stool using the touchdown PCR method and 2.63 × 10(2) CFU/g stool using the qPCR method. Fecal testing using combined culture-based amplification and bft touchdown PCR is a sensitive assay for the detection of ETBF colonization and should be useful in studying the role of ETBF colonization in intestinal diseases, such as inflammatory bowel disease and colon cancer. We conclude that touchdown PCR with culture-based amplification may be the optimal ETBF detection strategy, as it performs as well as qPCR with culture-based amplification, but is a less expensive technique.

Bacterial communities in the fruit bodies of ground basidiomycetes

Fruit bodies of basidiomycetes at different stages of decomposition serve as specific habitats in forest biocenoses for bacteria and differ significantly with respect to the total bacterial population and abundance of particular bacterial genera. A significant increase in the total bacterial population estimated by the direct microscopic method with acridine orange staining and in the population of saprotrophic bacteria (inoculation of glucose peptone yeast agar) in fruit bodies of basidiomycetes Armillaria mellea and Coprinus comatus was recorded at the final stage of their decomposition in comparison with the initial stage. Gramnegative bacteria predominated in the tissues of fruit bodies at all the stages of decomposition and were represented at the final stage by the Aeromonas, Vibrio, and Pseudomonas genera (for fruit bodies of A. mellea) the Pseudomonas genus (for fruit bodies of C. comatus). The potential influence of bacterial communities in the fruit bodies of soil basidiomycetes on the formation of bacterial communities in the upper soil horizons in forest biocenoses is discussed. The loci connected with the development and decomposition of fruit bodies of basidiomycetes on the soil surface are promising for targeted search of Gram-negative bacteria, the important objects of biotechnology.

Growth Inhibition of Listeria monocytogenes, Salmonella enterica, and Escherichia coli O157:H7 by D-Tryptophan as an Incompatible Solute

Under osmotic stress, bacterial cells uptake compatible solutes such as glycine-betaine to maintain homeostasis. It is unknown whether incompatible solutes exist that are similar in structure to compatible solutes but have adverse physiological effects on bacterial physiology. The objective of this study was to evaluate solute incompatibility of various amino acids against bacterial growth. Bacterial growth was evaluated by changes in optical density at 595 nm in peptone-yeast-glucose (PYG) broth. Twenty-three amino acids with l and/or d isomers were examined for the effect of bacterial growth inhibition. Among the various amino acids examined, d-tryptophan (~ 40 mM) in PYG broth supplemented with 0 to 4% (wt/vol) salt inhibited the growth of Listeria monocytogenes, Salmonella enterica, and Escherichia coli O157:H7 at 25°C. d-Tryptophan (30 to 40 mM) completely inhibited the growth of E. coli O157:H7 and Salmonella in the presence of <3% salt, but the growth of L. monocytogenes was not completely inhibited under the same conditions. Low concentrations of salt (0 to 2% NaCl) with d-tryptophan did not significantly inhibit the growth of all bacteria except L. monocytogenes, which was relatively inhibited at 0% NaCl. The effect of d-tryptophan differed depending on the bacterial species, illustrating the difference between gram-positive and gram-negative bacteria. These results indicate that the uptake of d-tryptophan as a compatible solute during osmotic stress may inhibit bacterial growth. The antibacterial effect of d-tryptophan found in this study suggests that d-tryptophan could be used as a novel preservative for controlling bacterial growth in foods.

CHARACTERIZATION OF ENDOPHYTIC MICROFLORA OF ROSA CANINA FRUITS

There aren’t a lot of studies about the bacterial communities associated with the Rosa canina and the aim of this study was to characterize endophytic bacteria from fruit of Rosa canina. The fruits of R. canina, which is growing wild in Slovakia, were collected in May 2013 from four locations: Nitra-Zobor, Vrbové-Baraní dvor, Rišňovce, Modra pažiť, Slovakia. Microbiological analyses were conducted by use of standard microbiological methods by spreading of fruits homogenates onto agar plate. Total viable count and mesophilic anaerobic sporulating bacteria were determined on Plate Count Agar after incubation for 2 days at 37 °C. Pseudomonas aeruginosa enumeration was carried out after incubation of Pseudomonas Isolation agar at 48 h at 35 °C. For members of the family Enterobacteriaceae (45 °C) Violet Red Bile Glucose agar were used and incubation was carried out for 24 h at 37 °C. For determinations of fungal colonies Malt agar and Czapek-Dox agar were inoculated using the spread-plate technique and incubated at 25 °C for 5 days. The yeasts were grown in Glucose Yeast Peptone agar (aerobiosis) at 25 °C during 72 hours. The total viable count of fruits ranged from 4.07 log cfu.g-1 in Rišňovce to 4.84 log cfu.g-1 in Vrbové Baraní dvor. Number of mesophilic anaerobic sporulating bacteria ranged from 4.09 in Vrbové Baraní dvor to 4.82 log cfu.g-1 in Modrá pažiť. Number of Pseudomonas aeruginosa count ranged from 2.00 in Nitra Zobor and Vrbové Baraní dvor to 3.94 log cfu.g-1 in Modrá pažiť. In our study the number of Enterobacteriaceae genera ranged from 3.38 in Nitra Zobor to 4.25 log cfu.g-1 in Vrbové Baraní dvor. Number of yeasts ranged from 3.36 in Vrbové Baraní dvor to 3.85 log cfu.g-1 in Modrá pažiť. Number of microscopic filamentous fungi ranged from 2.60 in Modrá Pažiť to 3.52 log cfu.g-1 in Nitra Zobor. Our findings indicate that Rose plant is naturally associated with a variety of endophytic microorganisms, which have different physiological and biochemical properties.

BACTERIAL WILT OF LIMA BEAN (PHASEOLUS LUNATUS) CAUSED BY CURTOBACTERIUM FLACCUMFACIENS PV. FLACCUMFACIENS, A NEW DISEASE IN IRAN

In the summer of 2013, during surveys in lima bean (Phaseolus lunatus) (cv. Christmas Pole) fields of East Azerbaijan, Northwest Iran, interveinal necrotic lesions and marginal chlorosis were observed on the leaves. The isolation of bacterial was done on Yeast Peptone Glucose Agar (YPGA) medium (EPPO, 2011). Yellow-colored colonies 1-2 mm in diameter were present on YPGA plates after incubation at 25°C for 48 h. All isolates were Gram-positive, of oxidative but not fermentative metabolism, and had the ability to grow at 37°C. All hydrolyzed aesculin, casein, and gelatin, produced acid from inositol, mannose and maltose but not from mannitol and erythritol, were of positive catalase and oxidase, but of negative urease and indole production (EPPO, 2011). Bacterial strains were identified as Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) based on biochemical test results. The pathovar-specific primer pair CffFOR2 and CffREV4 amplified a 306 bp fragment of the isolates and confirmed them as Cff (Tegli et al., 2002). The strains were deposited in the University of Tehran Microorganisms Collection (Accession No. Cffcb123). Pathogenicity test was conducted on 20 day old lima bean (cv. Christmas Pole) plants. The Cff suspensions (1×108 CFU/ml) were prepared from 48 h old culture on YPGA. Node infiltration method was conducted for the inoculation of plants (Hsieh et al., 2003). Disease symptoms appeared 10-15 days after inoculation. First trifoliate leaves of the inoculated plants exhibited symptoms of marginal necrosis and interveinal yellowing. Cff was consistently re-isolated from artificially infected lima bean tissues on YPGA and re-identified using CffFOR2 and CffREV4 primer pairs. This is the first report of Cff causing bacterial wilt in lima bean in Iran.

First report of potato bacterial ring rot caused by Clavibacter michiganensis subsp. sepedonicus in Africa

In 2014, potato tubers (cv. Diamant and cv. Spunta) showing typical symptoms of bacterial ring rot disease caused by Clavibacter michiganensis subsp. sepedonicus (Cms) were observed in Gharbia, Menoufia, Minia, Assiut and Sohag governorates, Egypt, in 10 out of 10,000 samples examined at the time of planting. Splitting infected tubers toward the stem end revealed a yellow to brown discolouration of the vascular tissue. The discoloured area had a cheesy appearance and exuded a milky ooze when squeezed (Fig. 1). Samples were tested for the presence of ring rot disease, according to the EC Directive 93/85/EEC (Anon., 1). Extracts from 1 cm tuber heel-end cores were streaked onto NCP-88 medium (de la Cruz et al., 2), yeast peptone glucose agar (Anon., 1) and yeast peptone glucose agar with the addition of neomycin (3.5 mg/l), polymyxin B sulphate (16250 IU) and clotrimazole (10 mg/l). The resultant colonies (white to cream, round to irregular with entire margins, raised, smooth, mucoid and glistening) were selected and purified. Suspensions of isolates in distilled water (106 cfu/ml) were injected (EU, 4) into stems of eight Solanum melongena plants (cv. Black Beauty) per isolate at the three leaf stage. Plants were incubated at 21 ± 2°C and 70-80% RH. Control plants were inoculated with sterile water. After 14 days plants began to wilt, wilted tissue appeared dark green or mottled but turned paler before becoming necrotic. Inter-veinal wilts had a greasy water-soaked appearance. Necrotic tissue had a bright yellow margin. Some plants were killed completely. No symptoms were observed in control plants. Bacteria were re-isolated from symptomatic inoculated plants and identified. Pure cultures of ten Gram-positive isolates hydrolysed aesculin, utilized acetate and produced catalase. They produced acid from mannitol and sorbitol, but not from glucose, glycerol, lactose and salicin. They were negative for oxidase activity, urease activity, hydrogen sulphide production, indole production, growth at 37°C, tolerance of 7% NaCl, and gelatin liquefaction. They gave negative or weak reactions for starch hydrolysis (Anon., 1). Identification of the isolates was confirmed by PCR using primers Cms50F/Cms50R (Gudmestad et al., 3) that yield an amplicon size of 192 bp. This is the first report of potato bacterial ring rot caused by Cms in Egypt. To our knowledge, this is the first report of Cms in Africa.

Screening of Antitumor Bioactivity of Fungi Associated with Macro Algae and Sponge from Indrayanti Beach, Jogjakarta

This research was aimed to isolate marine derived-fungi which associated with macro algae and sponge from Indrayanti Beach, Jogjakarta and to screen the antitumor (T47D and HeLa) bioactivity of the fungi extracts. Three solid media of MEA (malt extract agar), GPY (glucose peptone yeast) and MFM (minimal fungi medium) were used as isolation medium. Each of the pure fungi isolates was then cultivated in 100 ml of liquid medium for 4 weeks at room temperature (27-28°C) in static conditions. The antitumor activity of the fungi extracts were tested against breast tumor cells (T47D) and cervical cancer cells (HeLa) using Thiazolyl Blue Tetrazolium Blue (MTT) assay method. A number of 21 isolates of fungi were isolated from 4 macro algae and 1 sponge samples. The identification of fungi isolate was conducted using combination of molecular approach (ITS1-5.8S-ITS4 DNA regions) and macro-micro morphological characteristics. Among those 21 marine fungi species isolated, MFGK-21 extract showed the best anti-servical tumor (HeLa) with an IC50 value of 240.1 µg/ml and MFGK-27 extract showed the best anti-breast tumor (T47D) with an IC50 value of 59.6 µg/ml. The MFGK-21 fungi isolate was identified as Penicillium steckii, while the MFGK-27 fungi isolate was identified as Aspergillus sydowii.

Host-centric Proteomics of Stool: A Novel Strategy Focused on intestinal Responses to the Gut Microbiota

The diverse community of microbes that inhabits the human bowel is vitally important to human health. Host-expressed proteins are essential for maintaining this mutualistic relationship and serve as reporters on the status of host-microbiota interaction. Therefore, unbiased and sensitive methods focused on host proteome characterization are needed. Herein we describe a novel method for applying shotgun proteomics to the analysis of feces, focusing on the secreted host proteome. We have conducted the most complete analysis of the extracellular mouse gut proteome to date by employing a gnotobiotic mouse model. Using mice colonized with defined microbial communities of increasing complexity or a complete human microbiota ('humanized'), we show that the complexity of the host stool proteome mirrors the complexity of microbiota composition. We further show that host responses exhibit signatures specific to the different colonization states. We demonstrate feasibility of this approach in human stool samples and provide evidence for a "core" stool proteome as well as personalized host response features. Our method provides a new avenue for noninvasive monitoring of host-microbiota interaction dynamics via host-produced proteins in stool.

Batch fermentative hydrogen production by enriched mixed culture: Combination strategy and their microbial composition

The effect of individual and combined mixed culture on dark fermentative hydrogen production performance was investigated. Mixed cultures from cow dung (C1), sewage sludge (C2), and pig slurry (C3) were enriched under strict anaerobic conditions at 37°C with glucose as the sole carbon source. Biochemical hydrogen production test in peptone-yeast-glucose (PYG) and basal medium was performed for individual mixed cultures (C1, C2 and C3) and their combinations (C1-C2, C2-C3, C1-C3 and C1-C2-C3) at a glucose concentration of 10 g/L, 37°C and initial pH 7. Maximum hydrogen yields (HY) of 2.0 and 1.86 [Formula: see text] by C2, and 1.98 and 1.95 mol(H2)/mol(glucose) by C2-C3 were obtained in PYG and basal medium, respectively. Butyrate and acetate were the major soluble metabolites produced by all the cultures, and the ratio of butyrate to acetate was ∼2 fold higher in basal medium than PYG medium, indicating strong influence of media formulation on glucose catabolism. The major hydrogen-producing bacterial strains, observed in all mixed cultures, belonged to Clostridium butyricum, C. saccharobutylicum, C. tertium and C. perfringens. The hydrogen production performance of the combined mixed culture (C2-C3) was further evaluated on beverage wastewater (10 g/L) at pH 7 and 37°C. The results showed an HY of 1.92 mol(H2)/mol(glucose-equivalent). Experimental evidence suggests that hydrogen fermentation by mixed culture combination could be a novel strategy to improve the HY from industrial wastewater.

Growth Limiting pH, Water Activity, and Temperature for Neurotoxigenic Strains of Clostridium butyricum

Some rare strains of Clostridium butyricum carry the gene encoding the botulinal type E neurotoxin and must be considered as possible hazards in certain types of food. The limiting growth conditions for C. butyricum were determined in peptone yeast glucose starch (PYGS) broth incubated anaerobically at 30°C for up to 42 days. The minimum pH values permitting growth depended on the acidulant and strain. Organic acids were more effective at inhibiting growth than HCl as expected. The lowest pH values at which growth of toxigenic and nontoxigenic strains of C. butyricum was observed in broth acidified with HCl were 4.1 and 4.2, respectively. In organic acids, however, the minimum pH varied between 4.4 and 5.1 depending on acid type and concentration. The minimum water activity for growth of toxigenic strains of C. butyricum was 0.96. The minimum growth temperatures of the toxigenic strains of C. butyricum (ca 10-11°C) were somewhat higher than for non-toxigenic ones (8°C). It was concluded that control of toxigenic C. butyricum in the food industry needs to allow for the greater pH tolerance of this species compared with proteolytic C. botulinum.

Copper induction of laccases by Lentinus polychrous under liquid-state fermentation

Abstract The fungus Lentinus polychrous , an edible mushroom popular in Northeast Thailand secretes ligninolytic enzymes, mainly laccases and manganese peroxidases. This research investigates the production of ligninolytic enzymes by the fungus culture in liquid medium in the presence of two well-known laccase inducers. Using Basidiomecetes synthetic medium (BSM), higher laccase activity of 350 U L −1 was obtained at day 14, when the culture was induced in the presence of 1.0 mM CuSO 4 , but not with 1.0 mM 2,5-xylidine. Higher concentration (3.0 mM) CuSO 4 could inhibit enzyme production and the fungal growth. Optimum inducer concentration for laccase production by L. polychrous was 0.1 mM CuSO 4, which yielded the highest laccase activity per biomass (67.9 U g −1 ). When the fungus was cultured in Erlenmeyer flasks in Glucose Yeast Peptone (GYP) medium, the maximum production of laccase was found to be approximately 2000 U L −1 with 0.3 mM CuSO 4 as inducer for 2 weeks. Laccase production in a bioreactor yielded more than 1000 U L −1 laccase at 8 days culture, making this system feasible for enhancement of high laccase production.

First Report of Xanthomonas arboricola pv. pruni in Ornamental Prunus laurocerasus in the Netherlands.

In 2008, Dutch ornamental plant growers observed a leaf spot of cherry laurel (Prunus laurocerasus) at a greater incidence (5 to 50%) than the usual sporadic level (<1%). For advice on disease control, ~5 to 10% of these growers contacted Dutch regulatory officials. In November and December 2008, six symptomatic samples from northern and southern parts of the Netherlands were submitted for diagnosis. Leaf spots were chlorotic, most had a necrotic brown center with a distinct margin, and the spots readily abscised, resulting in a "shot-hole" appearance. Leaf spots from the samples were surface sterilized (2 s in 70% vol/vol alcohol), blotted dry on tissue paper, chopped into pieces (1 to 2 mm in diameter), and incubated for 30 min in 10 mM phosphate-buffered saline (PBS) (1). A 20-μl aliquot of extract per sample was streaked by dilution plating on four plates of yeast peptone glucose agar medium (1), and the plates were incubated for 2 to 3 days at 28°C. Isolations from all six samples yielded Xanthomonas-like colonies. After purification, characterization of all six isolates revealed oxidative, nonfermentative metabolism of glucose by rod-shaped, gram-negative bacterial cells. All six isolates were identified as Xanthomonas arboricola pv. pruni based on biochemical tests (1), fatty acid analysis (4), and immunofluorescence (IF) using polyclonal antibodies (Plant Research International, the Netherlands). Pathogenicity was tested on potted peach plants (cvs. Peregrine and Vaes Oogst) and on detached leaves of P. laurocerasus (cv. Novita) (1). The six field isolates from 2008 were each inoculated (108 CFU/ml) onto four leaves per plant of each of two peach plants (replicates). As positive control treatments, two reference strains (ATCC 19312 and PD740) were each inoculated onto the same number of leaves and plants, and as a noninoculated negative control treatment, leaves of two peach plants were treated with sterile 10 mM PBS buffer (1). All leaves inoculated with the six field isolates and the two reference strains developed typical bacterial spot symptoms in 3 to 4 weeks. Negative control plants showed no symptoms. The detached leaf assay performed with the same treatments on each of two leaves (replicates) showed identical results. The bacterium was reisolated from leaf spots associated with each of the eight symptomatic treatments and identity of the reisolates was confirmed by IF. Additionally, genotypic variation of 35 Dutch isolates of X. arboricola pv. pruni was assessed by BOX-PCR assay with the BOX A1R primer set (3), and Gyrase B gene sequencing (2). Both methods revealed 100% homology among the 35 isolates, suggesting a single, recent introduction of X. arboricola pv. pruni into the Netherlands. In a 2009 survey to assess distribution of the disease in the Netherlands, X. arboricola pv. pruni was found in 41 fields. Infected hosts included P. laurocerasus cvs. Otto Luyken, Rotundifolia, Novita, Etna, Anbri, Herbergii, Mischeana, and Caucasia. X. arboricola pv. pruni is a quarantine organism in countries affiliated under the EPPO (European and Mediterranean Plant Protection Organization). Phytosanitary measures were taken to prevent movement of infested plants from nurseries where X. arboricola pv. pruni was detected.

Survival of Clavibacter michiganensis subsp. sepedonicus on surface of selected materials in different temperature conditionsPrzeżycie Clavibacter michiganensis subsp. sepedonicus na powierzchniach wybranych materiałów w warunkach różnych temperatur

Study were conducted at the Plant Breeding and Acclimatization Institute Research, Division Bydgoszcz in 2005−2007. The aim of this study was to determine a period of Clavibacter michiganenis subsp. sepedonicus (Cms) survival on storage surface of machinery, materials, and equipment contaminated by infected tubers with the bacteria during seeding operations, cultivation, harvest, storage and transport at different temperatures. BPR IOR 527 Cms strain was used. Six materials: wood, rubber, jute, plastic, paper, steel were contaminated with bacterial suspension at the concentration of 10 cfu/ml and put in Petri dishes and incubated at four temperatures. The survival of bacteria, by isolation on yeast peptone glucose agar (YPGA – Yeast peptone glucose agar) and virulence in eggplant test, periodically were controlled. The study confirmed that Cms can survive for lengthy period on different surface tested.