Colony Radius Research Articles

White rot fungi to decompose organophosphorus insecticides and their relation to soil microbial load and ligninolytic enzymes

The functional and structural features of microbial load in soil are influenced by the presence of insecticides. This study examined the impact of two organophosphorus insecticides, dimethoate and parathion on the microbial load of soil. The colony count of fungi, actinomycetes, bacteria, and nitrogen fixing bacteria was reduced after insecticides application at 7 and 14 days, but at 28 days the colony count began to increase. The growth of two white rot fungi including Pleurotus sajor-caju and Phanerochaete chrysosporium was affected by parathion, which was reflected by a decrease in colony radius to 1.85±0.05 and 0.75±0.06 cm, respectively, and by dimethoate, reflected by a decrease in colony radius to 3.33±0.12 and 1.85±0.05 cm, respectively at 40 mg/L compared to colony radius at control 7.90±0.12 and 7.50±0.06 cm, respectively. The applied low concentration (10 mg/L) encouraged P. sajor-caju and P. chrysosporium to remove up to 87.7% and 81.8% of dimethoate, respectively, and 69.20 and 68.30% of parathion, respectively compared with the decomposition at high dose (40 mg/L) at 28 days. The presence of insecticides induced the production of ligninolytic enzymes lignin peroxidase, laccase, and manganase peroxidase.

Evaluation of lignocellulatic activity of enzymes from microwave-irradiated Pleurotus sajor-caju cultivated with wheat straw

The production of lignocellulytic enzymes by microwave-radiated Pleurotus sajor-caju was assayed. Wheat straw was employed as substrate to P. sajor-caju for production of laccase, manganese peroxidase (MnPase), filter-paperase (FPase), carboxmethyl cellulase (CMCase), and cellulase (as evaluated using microcrystalline cellulose). P. sajor-caju exposed to 10 s of microwave radiation (MR) showed maximum growth with colony radius of 7.17 ± 0.45 cm, while with increasing the exposure time up to 50 s the growth decreased up to 2.67 ± 0.22 cm. Moreover, it failed to grow at 80 s of exposure time. Cellulase, MnPase, FPase, CMCase, and laccase activities were induced to 37 ± .0.54, 49 ± 2.36, 189 ± 2.12, 0.37 ± 0.06, and 1.58 ± 0.03 U/mL compared to that at control 31 ± 0.25, 46 ± 1.25, 177 ± 1.65, 0.28 ± 0.03, and 1.37 ± 0.12 U/mL, respectively as a result of P. sajor-caju exposure to 10 s of MR. As the exposure time increased, these enzymes activity decreased. Different levels of moisture with surfactant (polysorbate 80) were applied to optimize the enzymes activities at 10 s of exposure time. The optimum activities 3.15 ± 0.23, 0.62 ± 0.06, 269 ± 5.36, 65 ± 1.63, and 48 ± 0.98 U/mL were recorded for cellulase, MnPase, FPase, CMCase, and laccase, respectively at 70% of moisture and 0.15 mL/L of polysorbate 80.

Discover the Most Effective Disease Management Strategies for Fusarium Dry Rot of Potato through Comprehensive Bio-assay of Three Techniques (Chemical, Plant extracts, and Bio-control)

Potato (Solanum tuberosum) is a multicultural staple food and cash crop. Unfortunately, production of potatoes is predominantly constrained by diseases including dry rots. To evaluate management of dry rots, three in vitro sub-trials were set up using the completely randomized design with each treatment replicated thrice for each trial. Firstly, synthetic fungicides were assayed against Fusarium oxysporum f.sp. tuberosi. Secondly, plant extracts were assessed against F. oxysporum. Finally, the efficacy of Trichoderma harzianum applied against F. oxysporum was evaluated. The colony radii were measured. The inhibition of F. oxysporum by Ketoconazole (at 100% concentration) was significantly (p≤0.05) highest, followed by Ketoconazole (50% concentration), Itraconazole (100% concentration), Itraconazole (50% concentration), Sulphur (100% concentration), Ridomil (100% concentration), Sulphur (50% concentration), and finally Ridomil (50% concentration). Percentage inhibition of the growth of the Fusarium species by fungicides ranged from 39.5-95.7%. Blue gum (Eucalyptus globulus) (at 100% concentration) gave the highest inhibition, followed by blue gum (50% concentration), Sweet alligator-pepper (Aframomum melegueta) at 100% concentration, locust bean (Parkia biglobosa) at 100% concentration, Sweet alligator-pepper (50% concentration), candle bush (Senna alata) (100% concentration), locust bean (50% concentration), and Senna alata (50% concentration) in descending order of percentage inhibition. Plant extracts caused a percentage inhibition of the fungus between 20.6-100% inhibition with time. Inhibition of Fusarium by T. Harzianum isolate BGMZ4 was significantly (p≤0.05) highest, followed by T. Harzianum isolate NSBM then T. Harzianum isolate BGMZ3. Control of F. Oxysporum by T. Harzianum ranged from 23.5-94.1% inhibition. All the methods evaluated successfully inhibited the pathogen compared to the control.

Enhancing high-efficiency breeding and microbial microdroplet cultivation techniques for Ganoderma lucidum.

Ganoderma lucidum is known for its bioactive compounds, such as polysaccharides and triterpenoids, which are crucial in food and medicine. However, liquid fermentation encounters challenges in terms of strain differentiation and stability. In this research, we employed atmospheric room temperature plasma mutation and a microbial microdroplet culture system to identify strains with enhanced biomass and triterpenoid production. The three mutant strains, YB05, YB09, and YB18, exhibited accelerated growth rates and antagonized the initial strain G0023 more effectively than the controls. Notably, YB18 displayed the fastest growth, with a 17.25% increase in colony radius. Shake flask cultivation demonstrated that, compared with the initial strain, YB05 and YB18 had 26.33% and 17.85% greater biomass, respectively. Moreover, the triterpenoid production of YB05 and YB18 surpassed that of the control by 32.10% and 15.72%, respectively, as confirmed by colorimetric detection. Importantly, these mutant strains remained stable for five generations. This study revealed a comprehensive screening system utilizing atmospheric pressure, room temperature plasma mutation technology and microbial droplet cultivation. This innovative approach offers a promising pathway for obtaining advantageous Ganoderma strains for liquid fermentation. The methodology of atmospheric room temperature plasma mutation and microbial microdroplet culture systems is detailed for better comprehension.

Taxonomy and systematics of the fungus-growing ant associate Escovopsis (Hypocreaceae)-SUPP

Supplementary files:<br />Table S1. Culture media used to standardize the parameters to assess morphological characters of Escovopsis species.<br />Table S2. Measurements of the colony radius of the Escovopsis ex-type cultures, and the new described species.<br />Table S3. Molecular markers, primers and Polymerase Chain Reaction (PCR) conditions.<br />Table S4. Strains and their associated metadata used to reveal the phylogenetic relationships of Escovopsis species described by Marfetán et al. (2019) (Fig. S2).<br />Table S5. Morphological features used to construct the dichotomous key of Escovopsis species.<br />Table S6. Data recoding sheet to evaluate the macroscopic characters of the colonies of Escovopsis species.<br />Table S7. Data recoding sheet to evaluate the microscopic characters of Escovopsis species.<br />Fig. S1. Phylogeny revealing relationship among 19 species of Escovopsis, based on each molecular marker: (A) rpb2, (B) tef1, (C) ITS, (D) rpb1, (E) LSU, and (E) the combination of all of them (concatenated). Phylogenies shown were inferred using Bayesian Inference (BI) and Sympodiorosea kreiselii CBS 139320 was used as the outgroup. Numbers on branches indicate BI posterior probabilities (PP) and Maximum Likelihood bootstrap support values (MLB), respectively. Hyphens (--) indicate MLB < 70 %. ET indicates ex-type cultures and red crosses the non-viable strains. See Table 1 for all strains and their associated metadata used to infer these phylogenetic trees.<br />Fig. S2. Phylogeny revealing the relationship between Escovopsis species described by Marfetán et al. (2018). The tree was reconstructed to include the LSU sequences (in the green box) generated by Marfetán et al. (2018). The phylogeny was reconstructed using Bayesian Inference (BI) and Maximum Likelihood (ML) and and Sympodiorosea kreiselii CBS 139320 was used as the outgroup. Numbers on branches indicate BI posterior probabilities (PP) and Maximum Likelihood bootstrap support values (MLB), respectively. Hyphens (--) indicate MLB < 70 %. ET indicates ex-type cultures and red crosses the non-viable strains. See Table S4 for all strains and their associated metadata.<br />Fig. S3. Dichotomous key, in a cladogram format, revealing the relationship among Escovopsis species. The cladogram was reconstructed using 68 morphological features from species of Escovopsis in “rpart” library (Therneau & Atkinson 2019) in R v. 3.6.3. The final cladogram was manually edited using Adobe Illustrator CC v. 17.1. Information on branches was used to construct the taxonomic key and the leaves correspond to each Escovopsis species. See Table S5 for all associated data used to infer this cladogram.

Quantitative trait locus mapping of osmotic stress response in the fungal wheat pathogen Zymoseptoria tritici.

Osmotic stress is a ubiquitous and potent stress for all living organisms, but few studies have investigated the genetic basis of salt tolerance in filamentous fungi. The main aim of this study was to identify regions of the genome associated with tolerance to potassium chloride (KCl) in the wheat pathogen Zymoseptoria tritici. A secondary aim was to identify candidate genes affecting salt tolerance within the most promising chromosomal regions. We achieved these aims with a quantitative trait locus (QTL) mapping study using offspring from 2 crosses grown in vitro in the presence or absence of osmotic stress imposed by 0.75 M KCl. We identified significant QTL for most of the traits in both crosses. Several QTLs overlapped with QTL identified in earlier studies for other traits, and some QTL explained trait variation in both the control and salt stress environments. A significant QTL on chromosome 3 explained variation in colony radius at 8-day postinoculation (dpi) in the KCl environment as well as colony radius KCl tolerance at 8 dpi. The QTL peak had a high logarithm of the odds ratio (LOD) and encompassed an interval containing only 36 genes. Six of these genes present promising candidates for functional analyses. A gene ontology (GO) enrichment analysis of QTL unique to the KCl environment found evidence for the enrichment of functions involved in osmotic stress responses.

Algal biomass extract as mediator for copper oxide nanoparticle synthesis: Applications in control of fungal, bacterial growth, and photocatalytic degradations of dyes

Recently, algae have attracted the attention of investigators as a renewable source of compounds that can contribute to nanoparticle creation. The use algae biomass to facilitate preparation of copper oxide nanoparticles (CuONPs), as well as their application, were the aims of the present study. High performance liquid chromatography analysis of algal biomass indicated the presence of daidzein (2550 µg/mL), followed by ellagic acid (596 µg/mL). Algal biomass extract was successful as a bio-reducing agent for CuONPs fabrication at different temperatures up to 50 °C. Transmission electron microscopy characterized the created CuONPs with average size 5 to 17 nm. The colony radius of M. anisopliae, T. harzianum, C. lunata, F. oxysporium, A. flavus, and A. terreus was 1.84 ± 0.08, 1.97 ± 0.03, 1.00 ± 0.08, 2.04 ± 0.03, 2.32 ± 0.06, and 2.42 ± 0.05 cm, respectively at 200 mg of CuONPs. CuONPs exhibited inhibition zones of 26, 23, 25, and 22 mm when tested against B. subtilis, E.coli, K. pneumoniae, and S. aureus, respectively. Methyl orange and methyl green dyes were degraded by CuONPs with percentages ranging from 9.5 to 63.7% and from 22.3 to 75.7% at 15 to 90 min, respectively. Therefore, the created CuONPs can be regarded as excellent candidates for controlling fungal/bacterial development and dyes degradation.

Isolation and characterization of indigenous microorganisms for antagonizing Fusarium incarnatum and preventing swollen swim bladder disease in Pangasius hypophthalmus

Fusarium incarnatum is known to cause swollen swim bladder disease in Pangasius hypophthalmus, leading to significant losses for aquaculture households. The objective of this study was to isolate local strains of microorganisms capable of antagonizing F. incarnatum, in order to reduce the use of antibiotics that may have adverse effects on both the environment and human health. Samples were collected from five Pangasius hypophthalmus fish, five water sources, and five sludge samples from fish ponds located in Lap Vo district, Dong Thap province. A total of 24 bacterial strains were isolated and subjected to the dual culture method to identify the 20 strains with the ability to antagonize F. incarnatum. The inhibitory ability of F. incarnatum was then evaluated using the two-culture method with the 20 selected strains. Results revealed that two strains, B19 (with a colony radius of 1.42 cm and corresponding inhibitory effect of 77.51% after 12 days) and B23 (with a colony radius of 1.55 cm and corresponding inhibitory effect of 75.40% after 12 days), demonstrated the strongest antagonistic effects against F. incarnatum. The identified strains were found to be Bacillus sp. (with a similarity of 90.22%) and Bacillus amyloliquefaciens (with a similarity of 92.41%). These results suggest that the use of Bacillus spp. can be an effective strategy to inhibit swollen swim bladder disease caused by F. incarnatum, and maybe a viable alternative to the use of antibiotics in the future.

Amanita sp. from subtropical region of Saudi Arabia as a source of chitinase enzyme and its antifungal activity

Mushroom products have been used as a biotechnological tool for many applications. Particularly, thermostable chitinase plays a vital role in biowaste management and biological control. In the present investigation, Amanita sp. was recorded in the subtropical region of Saudi Arabia, therefore, it was utilized for chitinase production using substrates chitin and dead fungal mycelia (DFM). Compared with the DFM, chitin was more suitable for chitinase activity at different temperatures and pH. Amanita sp. produced chitinase up to 70 °C, but the optimum was 50 °C. The chitinase activity was 4.98, 3.5, and 0.9 U.mg-1 with the use of chitin, while it was 4.6, 3.1, and 0.6 U.mg-1 with the use of DFM at 50, 60, and 70 °C, respectively. Chitinase activity was stable up to 60 °C, then it began to decrease at 70 °C. The chitinase activity was better at pH 4 and 5 than pH 8 and 9. The antifungal effect of the produced chitinase at 50 °C was more effective than at 60 °C. For instance, the Alternaria alternata colony radius was 3.50 cm and 2.26 cm at 50 °C while it was 4.35 cm and 4.13 cm at 60 °C when using DFM and chitin, respectively.

Contrasting effects of landscape on nest founding and colony success of bumble bees in a mixed‐crop agroecosystem

Abstract Nest‐founding bumble bee queens search landscapes broadly for a nest site, whose later‐developed workers are constrained to foraging around the nest. Landscape could therefore have different influences on nest site selection and subsequent colony success. Additionally, the density of bumble bees in a landscape reflects the product of their nest density and nest success. To examine separate landscape effects on nest density and success, we examined nest occupancy (reflecting nest density) and colony size (reflecting nest success) using ground‐installed nest boxes placed adjacent to blueberry (Vaccinium corymbosum) fields in the Lower Mainland of British Columbia, Canada. Nest‐searching queens occupied 59% of these boxes. We classified landscapes in a 1.5 km radius of colonies using habitats of a priori relevance to bumble bees: beneficial (i.e. flowering) agriculture, non‐beneficial agriculture (NBA), forest, open semi‐natural, suburban, and their configuration (habitat edge density). Landscape strongly affected nest founding but only weakly affected colony success. Nest founding increased in landscapes with more forest habitat, more open semi‐natural habitat (and little NBA), and more habitat edge (and little NBA). Colony success increased in landscapes with more edge density (and much NBA). Overall, edge habitats enhanced bumble bee populations, but enhancement was conditional: edge increased nest occupation in landscapes with little NBA and nest success in landscapes with a lot of NBA. Populations of crop‐pollinating bumble bees might therefore best be enhanced by locally enhancing nesting: protecting forests, 2D semi‐natural habitats (when flowering crops are uncommon), and edge habitats.

First report of Calonectria canadiana causing peach fruit rot in China.

Peach (Prunus persica (L.) Batsch) is one of the most popular fruits grown in Northern China. In July 2021, a fruit rot outbreak on the peach cultivar "Yonglian Sweet" occurred after unusual rains in Baoding, Hebei Province, China. Sixty peach trees from three orchards were assessed, and a 30% disease incidence was estimated. The disease initiated as a small concave spot on the fruit surface expanding circularly rotting the fruit (3-5 cm deep) with the appearance of grayish-white mycelia (Figure S1A). The infected fruit did not disintegrate but turned light brown. To identify the pathogen, 20 infected fruits were collected, and fruit tissues from lesion margins were inoculated on the potato dextrose agar (PDA) medium. A total of 15 fungal pure cultures with highly similar morphological characteristics were obtained by the hyphal-tipping method. The fungal culture formed smooth-edged colonies of extensive, dense, wooly aerial mycelium, with color changing from sienna to luteous, and to grayish-white along the radius of colonies (Figure S1B) Chlamydospores were extensive and developed micro-sclerotia after 20 d of growth. The conidiophore produced three branches in a "broom" shape, with the primary branch ranging 7.5-25.0 μm in length, the secondary branch 5.5-15.5 μm, and the tertiary branch 10-12.5 μm (N = 30). The top of the tertiary branch tapered and produced conidia. Conidia were colorless and culm-like, 40.0-57.5 μm long and 3.8-6.25 μm wide (N = 30). Hyphae occasionally produced spherical chlamydospores with a diameter of around 7.5 μm (N = 30). Conidia germinated after 12 h in moist conditions, and germ tubes originated from multiple points on the conidia. Based on these morphological features, the isolated fungus was identified as Calonectria spp. (Lombard et al. 2010). Six loci, including ITS, act, cmdA, his3, tef1, and tub2, were amplified and sequenced for molecular identification of an isolate F099 using primers listed in Table S1. The obtained ITS (528 bp, GenBank accession no. OL635556), act (263 bp, OL694221), cmdA (470 bp, OL694222), his3 (432 bp, OL694223), tef1 (487 bp, OL694224), and tub2 (535 bp, OL694225) sequences showed 100% similarity to the ex-type strain of Calonectria canadiana, CMW 23673 (accession nos. MT359667, MT334976, MT335206, MT335446, MT412737, and MT412958, respectively; Figure S1D) (Kang et al. 2001, Lechat et al. 2010, Liu et al. 2020). The isolate F099 of C. canadiana was further subjected to pathogenicity tests. Koch's postulates were performed by placing three mycelial disks (ten-day old, 5 mm) with conidia on the sterile needle-acupunctured surface of healthy fruits of the peach cultivar "Yonglian Sweet" (N= 10). Mock inoculations with sterile PDA disks were served as a control. All the inoculated fruits were kept in a moist chamber (25℃, 16-h light and 8-h dark period). The inoculation assay was repeated twice. Rotting symptoms developed on all the inoculated fruits about 5 days post-inoculation (dpi) and grayish-white mycelia appeared around ten days post inoculation while mock inoculated fruits did not show any rotting. The pathogen of interest was re-isolated from the inoculated fruits and validated as C. canadiana by ITS and tef1 sequences. All above evidence collectively indicates that the fungal pathogen causing the peach fruit rot is C. canadiana. The new host plant and new geographic distribution reported here will inform future management of this fungal species.

First Report of Trichoderma afroharzianum Causing Seed Rot on Maize in Italy.

Maize (Zea mays L.) is a cereal crop of great economic importance in Italy; production is currently of 60,602,320 t, covering 588,597 ha (ISTAT 2021). Trichoderma species are widespread filamentous fungi in soil, well known and studied as biological control agents (Vinale et al., 2008). Seeds of a yellow grain hybrid (class FAO 700, 132 days) were collected in September 2020 from an experimental field located in Carmagnola (TO, Italy: GPS: 44°53'11.0"N 7°40'60.0"E) and tested with blotter test (Warham et al., 1996) to assess their phytosanitary condition. Over the 400 seeds tested, more than 50% showed rotting and development of green mycelium typical of the genus Trichoderma. Due to the high and unexpected percentage of decaying kernels, ten colonies were identified by morphological and molecular methods. Single conidia colonies of one Trichoderma (T5.1) strain were cultured on Potato Dextrose Agar (PDA) for pathogenicity tests, and on PDA and Synthetic Nutrient-Poor Agar (SNA) for morphological and molecular identification. The colonies grown on PDA and SNA showed green, abundant, cottony, and radiating aerial mycelium, and yellow pigmentation on the reverse. Colony radius after 72 h at 30°C was of 60-65 mm on PDA and of 50-55 mm on SNA. The isolates produced one cell conidia 2.8 - 3.8 µm long and 2.1 - 3.6 µm wide (n=50) on SNA. Conidiophores and phialides were lageniform to ampulliform and measured 4.5 - 9.7 µm long and 1.6 - 3.6 µm wide (n=50); the base measure 1.5 - 2.9 µm wide and the supporting cell 1.4 - 2.8 µm wide (n=50). The identity of one single-conidia strain was confirmed by sequence comparison of the internal transcribed spacer (ITS), the translation elongation factor-1α (tef-1α), and RNA polymerase II subunit (rpb2) gene fragments (Oskiera et al., 2015). BLASTn searches of GenBank using ITS (OL691534) the partial tef-1α (OL743117) and rpb2 (OL743116) sequences of the representative isolate T5.1, revealed 100% identity for rpb2 to T. afroharzianum TRS835 (KP009149) and 100% identity for tef-1α to T. afroharzianum Z19 (KR911897). Pathogenicity tests were carried out by suspending conidia from a 14-days old culture on PDA in sterile H2O to 1×106 CFU/ml. Twenty-five seeds were sown in pots filled with a steamed mix of white peat and perlite, 80:20 v/v, and maintained at 23°C under a seasonal day/night light cycle. Twenty primary ears were inoculated, by injection into the silk channel, with 1 ml of a conidial suspension of strain T5.1 seven days after silk channel emergence (BBCH 65) (Pfordt et al., 2020). Ears were removed four weeks after inoculation and disease severity, reaching up to 75% of the kernels of the twenty cobs, was assessed visually according to the EPPO guidelines (EPPO, 2015). Five control cobs, inoculated with 1 ml of sterile distilled water were healthy. T. afroharzianum was reisolated from kernels showing a green mold developing on their surface and identified by resequencing of tef-1α gene. T. afroharzianum has been already reported on maize in Germany and France as causal agent of ear rot of maize (Pfordt et al. 2020). Although several species of Trichoderma are known to be beneficial microorganisms, our results support other findings that report Trichoderma spp. causing ear rot on maize in tropical and subtropical areas of the world (Munkvold and White, 2016). The potential production of mycotoxins and the losses that can be caused by the pathogen during post-harvest need to be explored. To our knowledge this is the first report of T. afroharzianum as a pathogen of maize in Italy.

Laser speckle imaging for early detection of microbial colony forming units.

In this study, an optical contactless laser speckle imaging technique for the early identification of bacterial colony-forming units was tested. The aim of this work is to compare the laser speckle imaging method for the early assessment of microbial activity with standard visual inspection under white light illumination. In presented research, the growth of Vibrio natriegens bacterial colonies on the solid medium was observed and analyzed. Both - visual examination under white light illumination and laser speckle correlation analysis were performed. Based on various experiments and comparisons with the theoretical Gompertz model, colony radius growth curves were obtained. It was shown that the Gompertz model can be used to describe both types of analysis. A comparison of the two methods shows that laser speckle contrast imaging, combined with signal processing, can detect colony growth earlier than standard CFU counting method under white light illumination.

Вплив гібереліну на культуральні та ростові ознаки вегетативного міцелію штамів грибів роду Pleurotus за культивування на агаризованих живильних середовищах

Вплив гібереліну на культуральні та ростові ознаки вегетативного міцелію штамів грибів роду Pleurotus за культивування на агаризованих живильних середовищах

First Report of Anthracnose Disease Caused by Colletotrichum truncatum on the Velvetleaf (Abutilon theophrasti) in China

Velvetleaf (Abutilon theophrasti), an annual plant in the family Malvaceae, is an important source of fiber and medicine (Flora of China 2007; Su et al. 2010). Dark brown lesions were observed on the leaves of A. theophrasti in the Herbal Garden of Jilin Agricultural University (125.23°E, 43.47°N), Jilin Province, China, in July 2015 and 2016, respectively. The disease incidence was about 20%. The lesions appeared initially as small, light brown spots on the leaves. These enlarged gradually and coalesced with others to form large spots having irregular edges. Finally, the central portions of the lesions broke open leaving small holes on the leaves. A small piece of tissue was cut from the lesion margin of 30 leaves and then surface sterilized in 75% ethanol for 30 s followed by 1.5% NaClO for 1 min, washed three times with sterilized distilled water, and then dried on sterilized filter paper. Each tissue piece was incubated on potato dextrose agar at 25°C in the dark for 7 days. Colonies formed and were light olive (after 3 days) and then became dark olive (after 7 days). The growth rate (colony radius) ranged from 3.5 to 5.2 mm per day. Conidia were hyaline, aseptate, both ends were bent slightly, and measured 21.9 to 28.0 (25.4 ± 1.4) μm in length and 3.2 to 5.8 (4.3 ± 0.6) μm in width. The hyphae were hyaline, septate, and branched. Appressoria were light to dark brown, solitary, with the outline roundish to ellipsoidal, and 7.3 to 9.8 × 4.8 to 6.3 μm in size. Setae were dark brown, two to five septate, and measured 79.2 to 162.6 μm in length. The morphological characteristics corresponded to Colletotrichum truncatum more clearly and directly (Damm et al. 2009). To further confirm the identity of the pathogen, DNA was extracted from one single-spore isolate, CT12. The following loci were amplified according to Weir et al. (2012): the internal transcribed spacer (ITS) region of ribosomal DNA and the glyceraldehyde-3-phosphate dehydrogenase (GAPDH), β-tubulin-2 (TUB2), and chitin synthase (CHS-1) genes. The numbers of base pairs matching were 548/550 for ITS, 225/228 for GAPDH, 241/242 for CHS-1, and 683/683 for TUB2 compared with the sequences of C. truncatum in GenBank (KX621963 for ITS, MK359986 for GAPDH, MK118057 for CHS-1, and MH925229 for TUB2). Maximum likelihood analysis of the combined four gene sequences and reference sequences of Colletotrichum spp. from GenBank and the results of the phylogenetic tree showed that CT12 belonged in C. truncatum with 100% bootstrap support. Sequences of the representative isolate CT12 were deposited in NCBI GenBank (MG993325 [ITS, 558 bp], MH038172 [GAPDH, 225 bp], MH038171 [TUB2, 683 bp], and MH038173 [CHS-1, 242 bp], respectively). Conidial suspension (10⁶ conidia/ml) of CT12 was sprayed on 10 healthy, 3-month-old velvetleaf leaves, and sterilized distilled water was sprayed on 10 healthy 3-month-old velvetleaf leaves as a control. The experiment was conducted three times. All plants were incubated in a controlled incubator with a 12-h photoperiod and 90% relative humidity at 25°C. After 5 days, necrotic lesions occurred on the inoculated leaves but not on the control plants. The same fungus was reisolated from the infected leaf tissues. C. truncatum has been reported to cause anthracnose on soybean, pepper, tomato, eggplant, muskmelon, chickpea, grapes, and other plants (Damm et al. 2009; Diao et al. 2014). To our knowledge, this is the first report of C. truncatum causing anthracnose on velvetleaf in China. The identification of the pathogen will provide a theoretical basis for the identification and control of the disease and reduce economic losses.

Comprehensive Survey of Area-Wide Agricultural Pesticide Use in Southern United States Row Crops and Potential Impact on Honey Bee Colonies.

Honey bees forage across a large area, continually scouting the local landscape for ephemeral food resources. Beekeepers often rely on flowering plants in and around irrigated farmland to maintain their colonies during dry seasons, despite the potential risk of pesticide exposure. Recent declines in pollinator abundance and diversity have focused attention on the role of pesticides and their effects on honey bee health. This investigation examined two types of landscapes within a two-mile (3.2 km) radius of honey bee colonies: an intensive agricultural setting and a rural setting without intensive agriculture. More than 10,000 acres of agricultural land was surveyed to quantify the area of cultivated crops and the area treated with pesticides, including seed treatments and foliar applications of insecticides. Samples of honey, bee bread (stored pollen), beeswax, and adult bees were collected from hives in both landscape types and screened for pesticide residues to determine if foraging bees were transporting pesticides to hives. Some samples of bee bread and honey did contain pesticide residues, but these were below known lethal dose (LD50) levels for honey bees. Beeswax samples contained the highest levels of contamination, but most were still relatively low. Samples were screened for 174 common agricultural pesticides and metabolites, but only 26 compounds were detected during the two-year study. These included one defoliant, one insect growth regulator, five herbicides, six fungicides, six insecticides never used in beekeeping, and five insecticides/miticides and their metabolites, which are used in beekeeping and for various other agricultural purposes, as well as two miticides exclusively used by beekeepers to control Varroa destructor. Bee colonies foraging in agricultural landscapes are potentially exposed to numerous pesticide applications. While the residues detected in this study did not pose an acute lethal risk to adult honey bees, this study did not measure sublethal effects on bee colony health or performance, which merit further investigation.

Food Microstructure and Fat Content Affect Growth Morphology, Growth Kinetics, and Preferred Phase for Cell Growth of Listeria monocytogenes in Fish-Based Model Systems.

Food microstructure significantly affects microbial growth dynamics, but knowledge concerning the exact influencing mechanisms at a microscopic scale is limited. The food microstructural influence on Listeria monocytogenes (green fluorescent protein strain) growth at 10°C in fish-based food model systems was investigated by confocal laser scanning microscopy. The model systems had different microstructures, i.e., liquid, xanthan (high-viscosity liquid), aqueous gel, and emulsion and gelled emulsion systems varying in fat content. Bacteria grew as single cells, small aggregates, and microcolonies of different sizes (based on colony radii [size I, 1.5 to 5.0 μm; size II, 5.0 to 10.0 μm; size III, 10.0 to 15.0 μm; and size IV, ≥15 μm]). In the liquid, small aggregates and size I microcolonies were predominantly present, while size II and III microcolonies were predominant in the xanthan and aqueous gel. Cells in the emulsions and gelled emulsions grew in the aqueous phase and on the fat-water interface. A microbial adhesion to solvent assay demonstrated limited bacterial nonpolar solvent affinities, implying that this behavior was probably not caused by cell surface hydrophobicity. In systems containing 1 and 5% fat, the largest cell volume was mainly represented by size I and II microcolonies, while at 10 and 20% fat a few size IV microcolonies comprised nearly the total cell volume. Microscopic results (concerning, e.g., growth morphology, microcolony size, intercolony distances, and the preferred phase for growth) were related to previously obtained macroscopic growth dynamics in the model systems for an L. monocytogenes strain cocktail, leading to more substantiated explanations for the influence of food microstructural aspects on lag phase duration and growth rate.IMPORTANCEListeria monocytogenes is one of the most hazardous foodborne pathogens due to the high fatality rate of the disease (i.e., listeriosis). In this study, the growth behavior of L. monocytogenes was investigated at a microscopic scale in food model systems that mimic processed fish products (e.g., fish paté and fish soup), and the results were related to macroscopic growth parameters. Many studies have previously focused on the food microstructural influence on microbial growth. The novelty of this work lies in (i) the microscopic investigation of products with a complex composition and/or structure using confocal laser scanning microscopy and (ii) the direct link to the macroscopic level. Growth behavior (i.e., concerning bacterial growth morphology and preferred phase for growth) was more complex than assumed in common macroscopic studies. Consequently, the effectiveness of industrial antimicrobial food preservation technologies (e.g., thermal processing) might be overestimated for certain products, which may have critical food safety implications.

Stochastic Simulation of Yeast Cells and Its Colony Growth by Using Circular Granular Model for Cases of Growth and Birth Probabilities Depends on Position

Until now, many studies were conducted on microorganisms in order to make the best use of them and prevent the loss. As a type of microorganism that is widely utilized by humans, the yeast has a simple single cell structure that can represent many other complex cell processes and generally has almost elliptical shapes making it easier to model for further investigation. In this study, we model yeast cells with two dimensional circular granular particles and the interaction between them are modeled by the force of gravity, normal force, and Stokes force. The growth and birth factor of yeast cells are modeled stochastic with the simulation is done by using javascript programming language. From the simulation results obtained, showing the growth of yeast cells in the colony has a behavior that is in accordance with the theory, which grows exponentially, as well as the growth of the size of the colony radius whose growth rate is half to the rate of growth of its number of cells.

Pressure-driven collective growth mechanism of planar cell colonies

The growth of cell colonies is determined by the migration and proliferation of the individual cells. This is often modeled with the Fisher–Kolmogorov (FK) equation, which assumes that cells diffuse independently from each other, but stop to proliferate when their density reaches a critial limit. However, when using measured, cell-line specific parameters, we find that the FK equation drastically underestimates the experimentally observed increase of colony radius with time. Moreover, cells in real colonies migrate radially outward with superdiffusive trajectories, in contrast to the assumption of random diffusion. We demonstrate that both dicrepancies can be resolved by assuming that cells in dense colonies are driven apart by repulsive, pressure-like forces. Using this model of proliferating repelling particles, we find that colony growth exhibits different dynamical regimes, depending on the ratio between a pressure-related equilibrium cell density and the critial density of proliferation arrest.

Simulation of Escherichia coli Dynamics in Biofilms and Submerged Colonies with an Individual-Based Model Including Metabolic Network Information.

Clustered microbial communities are omnipresent in the food industry, e.g., as colonies of microbial pathogens in/on food media or as biofilms on food processing surfaces. These clustered communities are often characterized by metabolic differentiation among their constituting cells as a result of heterogeneous environmental conditions in the cellular surroundings. This paper focuses on the role of metabolic differentiation due to oxygen gradients in the development of Escherichia coli cell communities, whereby low local oxygen concentrations lead to cellular secretion of weak acid products. For this reason, a metabolic model has been developed for the facultative anaerobe E. coli covering the range of aerobic, microaerobic, and anaerobic environmental conditions. This metabolic model is expressed as a multiparametric programming problem, in which the influence of low extracellular pH values and the presence of undissociated acid cell products in the environment has been taken into account. Furthermore, the developed metabolic model is incorporated in MICRODIMS, an in-house developed individual-based modeling framework to simulate microbial colony and biofilm dynamics. Two case studies have been elaborated using the MICRODIMS simulator: (i) biofilm growth on a substratum surface and (ii) submerged colony growth in a semi-solid mixed food product. In the first case study, the acidification of the biofilm environment and the emergence of typical biofilm morphologies have been observed, such as the mushroom-shaped structure of mature biofilms and the formation of cellular chains at the exterior surface of the biofilm. The simulations show that these morphological phenomena are respectively dependent on the initial affinity of pioneer cells for the substratum surface and the cell detachment process at the outer surface of the biofilm. In the second case study, a no-growth zone emerges in the colony center due to a local decline of the environmental pH. As a result, cellular growth in the submerged colony is limited to the colony periphery, implying a linear increase of the colony radius over time. MICRODIMS has been successfully used to reproduce complex dynamics of clustered microbial communities.