Environmental Microbiology: Bacteria & Fungi on the Foods We Eat

Molecular typing of VTEC strains isolated from food, feed and animals

This study was carried out to determine the effect of Ecklonia maxima type seaweed extract applied to growth media on mycelium growth of oyster mushroom (Pleurotus ostreatus). In the experiment, most common 2 growth media [Malt Extract Agar (MEA) and Potato Dextrose Agar (PDA)] were used. After the prepared MEA (48 g L 1) and PDA (39 g L 1) medium was autoclaved at 121 ° C for 20 minutes, half was separated and 2% E. maxima seaweed extract (DY) was added. The experiment consisted of 4 growth media: MEA, PDA, MEA + DY and PDA + DY. While the prepared environments were warm and fluidal, they were filled in petri dishes under UV light in a sterile cabinet and left to cool. After surface disinfection of oyster mushrooms, clones were taken and placed on the medium in petri dishes and petri dishes were closed with parafilm. The petri dishes (n=15) were placed in the incubator at 24 °C. Daily mycelia lengths and weight of petri dishes were measured and mycelia growrth pwriod (day) and rate (cm day 1) were calculated. Among the used growth media, PDA was given more and heavier mycelia growth in a shorter time than MEA. DY application was increased mycelia growth period and reduced growth rate. DY was showed better performance in PDA medium. As a result of the research, it has been determined that the addition of liquid seaweed extract preparation to PDA at a rate of 2% (PDA + DY) increased micelle growth and shortened micelle growth period. Keywords: PDA, MEA, Ecklonia maxima, Oyster mushroom DOI: 10.7176/JSTR/7-03-02

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

This paper describes the development of a course sequence in High Frequency Electronics at Baylor University.This sequence has been designed to provide students with a balanced learning experience consisting of classroom theory, CAD design, and hands-on measurement experience.The first semester course consists of lectures in basic RF/microwave theory and passive circuits combined with weekly hands-on and computer-aided design laboratory experiences.The second semester course consists of lectures on active RF/microwave circuits and provides the culmination of the sequence with an amplifier design project.The course has provided an effective means of training students both in theory and practical working knowledge in the subject, while efficiently utilizing the microwave faculty of the department.

Combination of Immunomagnetic Separation with Real-Time PCR for Rapid Detection of Salmonella in Milk, Ground Beef, and Alfalfa Sprouts

An experiment was conducted during January–June, 2022 at Department of Plant Pathology, Uttar Banga Krishi Viswavidyalaya for the evaluation of the different culture media on the growth of the fungus Bipolaris sorokiniana causing spot blotch disease in wheat. Five different growth media, viz., Potato Dextrose Agar (PDA), wheat seed extract+PDA (WSPDA), wheat leaf decoction+PDA (WLPDA), carrot juice extract+PDA (CPDA), and oatmeal agar (OMA), were used in the experiment. PDA supplemented with different plant extracts exhibited differential growth and sporulation patterns on B. sorokiniana. The maximum colony diameter of 8.09 mm at 9 days after inoculation demonstrated that the OMA provided the best growth conditions. Moreover, based on the Tukey HSD test, the AUGPC of OMA was found to be the highest (34.68±1.3 cm2) and significantly different from all the other media used in the study. The OMA was followed by the WLPDA, which had an AUGPC of 22.6±1.79 cm2. The fungus sporulated in all the media considered for the present study, with OMA recording the highest sporulation with 44×104 spores ml-1, followed by WLPDA with 41×104 spores ml-1. The lowest level of sporulation was seen in CPDA, with a concentration of 15×103 spores ml-1. Based on the aforementioned results, it can be inferred that oatmeal agar was the most suitable medium for the development and sporulation of B. sorokiniana, followed by a mixture of wheat leaf decoction and PDA. On the other hand, PDA alone and carrot juice PDA were shown to be the least suitable media.

Members of the genus Bacillus were biocontrol agents against various phytopathogenic fungi. Several factors affected the regulation and production of nonribosomal peptides (NRPs) in Bacillus species. The aim of this study was to examine how culture media infl uenced the antagonistic activities and gene expression of Bacillus siamensis 1021. The bacterial supernatant from potato dextrose broth (PDB) exhibited higher inhibitory effects against mycelia of Pyricularia oryzae and Colletotrichum fructicola, when compared with those from nutrient broth (NB) and minimal salt medium (MSM). However, the biocontrol activities of these supernatants were not signifi cantly different when they were tested against P. oryzae and C. fructicola conidia. Additionally, the bacterial supernatant from PDB signifi cantly reduced the disease severity caused by P. oryzae in rice seedlings when compared with the water-treated control group. The genome of strain 1021 was sequenced, and biosynthetic gene clusters of nonribosomal peptides surfactin, fengycin and bacillibactin were identifi ed. Effects of PDB, NB and MSM media on expression levels of core biosynthetic genes of surfactin (srfAA), fengycin (fenC) and bacillibactin (dhbE) gene clusters were determined by reverse-transcription quantitative PCR. fenC expression was signifi cantly increased in PDB and corresponded with the antagonistic activities against fungal mycelia. Conversely, expression of the regulatory genes comA and codY in PDB were highly reduced in PDB, indicating their negative relation with fenC expression. This expression analysis indirectly suggested that fengycin was potentially the bioactive compound of B. siamensis 1021 against P. oryzae and C. fructicola

Molecular Subtyping and the Transformation of Public Health

Lichtheimia ramosa is one of the predominant filamentous fungi in Korean traditional nuruk. The nonvolatile and volatile metabolites of L. ramosa cultivated in three growth media: complete medium (CM), potato dextrose broth (PDB), and sabouraud dextrose broth (SDB), were investigated and compared. Among nonvolatile metabolites, serine, lysine, and ornithine increased in CM and PDB cultivated with L. ramosa during the exponential phase. In addition, glucose level increased in CM whereas decreased in PDB and SDB. The major volatile metabolites in the extract samples were acetic acid, ethanol, 3-methyl-2-buten-1-ol, 2-phenylethanol, ethylacetate, 2-furaldehyde, 5-(hydroxymethyl)-2-furaldehyde, 2,3-dihydro-3,5,-dihydroxy-6-methyl-4H-pyran-4-one, and α-humulene. In particular, the levels of volatile metabolites related to makgeolli (e.g., acetic acid, ethanol, and ethyl acetate) were highest in extracts cultivated in CM. On the other hand, the level of 2-phenylethanol was relatively higher in PDB and SDB, possibly due to there being more phenylalanine present in the biomass sample in media.

The aims of the study are to identify an effective and versatile fungal strain for bioengineering mycelium composites. The influence of temperature and four different growth media on mycelium growth of two white rot fungi, Pleurotus ostreatus (Winter Oyster) and Ganoderma lucidum (Reishi) were investigated in laboratory conditions. The results of the experiment indicated that potato dextrose agar (PDA) was the most suitable growth media for mycelium growth of fungal strains, P. ostreatus and G. lucidum. However, P. ostreatus was the better performing strain, with highest mean mycelium growth of 23.28cm, compared to G. lucidum at 9.03cm on PDA after 12 days of inoculation. Potato dextrose agar (23.28cm) and potato dextrose agar supplemented with yeast extract (14.74cm) were more favorable for mean radial mycelium growth of P. ostreatus, followed by sabouraud dextrose agar (9.85cm) and iron sulphite agar (8.35cm). The fungal strain, P. ostreatus obtained improved mycelium morphology on potato dextrose agar (PDA) supplemented with yeast extract and obtained cottony textured mycelium with good density and growth on potato dextrose agar (PDA) and sabouraud dextrose agar (SDA). Iron sulphite agar (ISA) was least favourable growth media for mean radial mycelium growth and mycelium morphology. Fungal strain, G. lucidum only mycelium growth was obtained on potato dextrose agar (PDA) as a result of this study, was the least favourable fungal strain studied. Optimal temperature for mycelium growth for both fungal strains, P. ostreatus and G. lucidum was obtained at 22 °C.

Culture medium is very important for growth of fungus mycelium in laboratory under controlled conditions. The pure culture of Hericium erinaceus was obtained from Mushroom Technology Laboratory of Department of Plant Pathology, CCS HAu, Hisar. Initial culturing was done on potato dextrose agar (PDA) media. The disc (5mm in diameter) from actively growing culture was plated on fresh media plates of potato dextrose agar (PDA), malt extract agar (MEA), yeast extract agar (YEA), oat meal agar (OMA) and Czapek-Dox agar media (CDA). The growth of mycelial disc was recorded daily. The results indicated that PDA was the best medium for mycelium growth. The maximum growth was observed on PDA (90.0 mm) followed by MEA (73.7 mm) and CDA (73.7 mm) in 15 days. It was also observed that the mycelium growth was started after 4 days of inoculation on PDA, MEA and YEA, on the other hand the mycelial growth was started after 5 days on Czapek-Dox agar media. The mycelium fully covered the Petri-plate on 15th day of inoculation on PDA followed by MEA medium in 18 days then YEA in 19 days whereas in Czapek-Dox medium mycelium took 20 days to fully colonize. The density of mycelium on PDA and MEA was very thick and white in color whereas on CDA and YEM mycelium had very sparse growth, less thick and less whitish in nature. The morphological characteristics of mycelium of H. erinaceus mushroom were also recorded.

Early blight is most common and devastating disease in tomato plant caused by deuteromycotina fungi, Alternaria solani. This fungus grows well in potato dextrose agar and Richard’s broth medium in vitro. The growth of the fungi were tested under culture in twelve different liquid and solid media and compared with each other. Potato dextrose agar and oat meal agar among solid media and Richard’s broth and Sabouraud’s broth among liquid media appeared to be better than other media for growth of tomato early blight causing fungi. The growth characteristics such as color of colony and substrate, margin of colony, topography of mycelium along with the sporulation of the test fungus were studied on these solid media. Fungus sporulation was best in oat meal agar media. Maximum growth of the fungus was observed at 8 days after inoculation with continuous increasing growth in the potato dextrose broth (PDB) medium, although growth rate was decreasing after the 2 days of inoculation. This study will be helpful for further investigations on the physiology of the fungus and management of the disease. This investigation may be useful for taxonomic study of the fungus.

ABSTRACT: Metabolites of Aspergillus niger, prepared in malt extract (ME) broth and potato dextrose (PD) broth, were evaluated for their herbicidal activity against a noxious parthenium weed (Parthenium hysterophorus). In laboratory assays, original (X) and diluted (½ X) fungal metabolites significantly reduced germination and seedling growth of weed. However, metabolites prepared in ME broth proved to have greater herbicidal activity than metabolites prepared in other growth medium. Original metabolites prepared in ME broth have completely hinder the germination of parthenium seeds; while those prepared in PD broth have reduced germination by 89% over control. In pot trials, one-week, two-week and three-week-old parthenium seedlings were sprayed three times with original and concentrated (2X) metabolites of A. niger prepared in ME broth. Plants were harvested after 40 days of sowing. One-week treatment plants were most susceptible to fungal metabolites spray, followed by two-week and three-week treatment plants, respectively. Original and concentrated metabolites have significantly reduced shoot biomass of one-week-old plants by 57% and 68%, and root biomass by 50% and 75%, respectively. The present study has come to the conclusion that A. niger metabolites prepared in ME broth can effectively control germination and growth of parthenium.

The effect of Pistacia atlantica Subsp. Kurdica essential oil (EO) and acetic acid against Botrytis cinerea growth was investigated in synthetic media, cucumber and grape fruits. The antifungal assay was determined on PDA plates amended with thirty-three concentrations of this oil (250, 1000, 1500 to 26000 μι/ι). This study was conducted for acetic acid of 0.1% alone at concentrations of 5, 15 and 25% .Also 0.1% of each dilutions of acetic acid were added to a series of sterile molten PDA that contain different concentrations of essential oil ranging from 50 to 3000 μι/ι. EO inhibited radial growth on potato dextrose agar (PDA) in a dose-dependent manner. The growth was completely prevented by EO at 26000 ppm on PDA. In combination with 0.1% acetic acid 25% in fungal growth medium, minimum inhibitory concentration (MIC) of EO reduced to 3000 ppm. During 31 days of cold storage of cucumber and 60 days of grape at 4°C, the decay of these fruits caused by B. cinerea was reduced to 10% by using MIC of EO. Scanning electron microscopy (SEM) was done to study the mode of action of the oil in Botrytis cinerea and it was observed that treatment with the oil leads to distortion and thinning of the hyphal wall and the reduction in hyphal diameter. The results suggested the potential substitution of the antifungal chemicals by this EO and acetic acid as a natural inhibitor to control the growth of this mold in fruits such as cucumber and grape.

Pleurotus species, because of their flexible temperature and environmental requirements, have more cultivated species than any other mushrooms. As one of the preliminary experiments for standardizing the cultivation technique of Pleurotus citrinopileatus and Pleurotus platypus, this work was done to find out the basic nutrient requirements and hence the effect of seven different growth media namely Potato dextrose agar (PDA), Malt extract agar (MEA), Yeast malt agar (YMA), Sabouraud's dextrose agar (SDA), Czapek dox agar (CDA), Glucose peptone agar (GPA) and Oat meal agar (OMA) on the mycelial growth of these mushrooms at room temperature(28°C) for a period of 8 days. Since the mycelium of Pleurotus platypus showed a non-symmetrical spreading pattern, the average growth was measured drawing cross sections on the petriplate. The experiments were done in six replications and colony diameter (CD), mycelial density (MD), growth rate (GR) of the mycelium were recorded. The CD of both Pleurotus citrinopileatus and Pleurotus platypus showed outstanding results in PDA medium with a GR of 1.13cm/day and 0.75cm/day respectively. The highest MD for Pleurotus citrinopileatus was indicated in PDA and MEA and for Pleurotus platypus it was in PDA, MEA and YMA. Though mycelial density did not follow the same pattern of inference as colony diameter, there was a positive correlation between CD and MD in all the experimental plates. The overall study proved PDA followed by MEA to be the most suitable media for culturing both Pleurotus citrinopileatus and Pleurotus platypus under in vitro conditions.