Agar Plate Method Research Articles

Antimicrobial potential of lemon and onion extracts against gram-positive and -negative bacteria

Antimicrobial potentials have been widely analyzed with different sources; however, plant-based antimicrobial compounds are greatly welcome due to their greener characteristics. This study revealed the importance of antimicrobial compounds from the herbal extracts of lemon and onion. The extracts were tested against gram-negative (Escherichia coli) and gram-positive (Bacillus subtitlis) bacteria. Disc-diffusion and well-diffusion on an agar plate and tributary methods were followed to demonstrate the antimicrobial potentials of the above herbal extracts. Further, different volumes of ampicillin at the concentration of 1 mg/ml were used to compare the genuine bacterial inhibition (3 µL with 1.5 cm zone). Lemon behaved excellently in a way by displaying better bacterial inhibition against both E. coli (3 µL with 1.2 cm zone) and B. Subtilis (3 µL with 0.6 cm zone), whereas onion extract was not at the level of lemon extract; however, it still displayed a good inhibition. The turbidity assay confirms the inhibition efficiency of lemon and onion against both E. coli and B. subtilis. In the liquid medium lemon shows higher inhibition (2 & 3 folds) on bacteria than that of ampicillin and onion. Cell count and UV-vis spectroscopy analysis at 600 nm also conform to the efficacy of lemon inhibition against E. coli and B. subtilis. This experiment confirms that lemon extract is an excellent and better substitute for commercially available ampicillin for bacterial inhibition.

Screening of Aflatoxin Production by Aspergillus flavus Isolates from Petroleum-contaminated Soil

Fungi are eukaryotic, heterogeneous, unicellular to filamentous, spore-bearing, and chemoorganotrophic organisms which lack chlorophyll. This present study was carried out to isolate and identify fungi from petroleum-contaminated soil. Several fungal genera which included Rhizopus spp., Mucor spp., Penicillium spp., Rhizoctonia spp., Aspergillus spp., Alternaria spp., and Cladosporiumspp. were isolated using potatoes dextrose agar, Czapek-Dox Agar, and Aspergillus flavus Differentiation Agar culture media that comparable with co-amoxiclav (1g) and chloramphenicol to prevent the growth of any bacteria. The direct plate and serial dilution agar plate methods were used for the isolation of fungi. Based on results, Aspergillusand Mucor spp. were the most predominant genera and had the highest number of colonies in the soil samples. In this investigation, seven out of 27 soil samples were morphologically (macroscopically and microscopically) identified, such as A. flavus. Aflatoxigenicity of A. flavus was detected using characteristics in Aspergillus differentiation agar and colony fluorescence on exposure to ultraviolet light. Moreover, molecular approaches were used for the detection of aflatoxigenic of the A. flavus isolates. Three structural (aflD, aflO, and aflP) and one regulatory (aflR) gene of the aflatoxin gene cluster of A. flavus were targeted for amplification by the polymerase chain reaction method. The aflatoxigenic of all six A. flavus isolates was detected molecularly which contained two structural (aflD, aflP)genes out of three structural genes, while there was no specific amplification of the aflO gene in the fourth, fifth, and sixth A. flavus which issimilar to the aflR gene in the first and second A. flavus.

Comparative Analysis of Sampling Methods for Assessing Bacterial Contamination on Hospital Partition Curtains: Moistened Swabs versus RODAC Agar Plates.

BACKGROUND Partition curtains are one of the main sources of nosocomial infection in the hospital environment. However, there are no unified standards for monitoring medical textiles across different countries or regions. This study aimed to investigate the accuracy of 2 different sampling methods - swabbing vs RODAC (replicate organism detection and counting) agar plate - in terms of detection of bacterial contamination, and their suitability as monitoring methods for partition curtains and other medical textiles. MATERIAL AND METHODS A total of 24 partition curtains were selected by stratified random sampling. The swabbing technique and RODAC agar plates were the chosen sampling methods. The number of colony-forming units was calculated and colony morphologies and strains on the plates were observed and identified after culturing. RESULTS A total of 192 samples were collected. Of them, 161 pathogenic strains were isolated via the swabbing technique and 309 pathogenic strains were isolated using the RODAC agar plates. The swabbing technique had a higher proportion for gram-positive bacteria (P=0.0004), while RODAC agar plates had a higher proportion for gram-negative bacteria (P=0.72). The detection of bacterial contamination rates using the swabbing technique was superior to that of the RODAC agar plate method (P<0.001). CONCLUSIONS The swabbing technique offers more advantages in terms of detection of bacterial contamination rates and gram-positive bacteria, while the RODAC agar plate is more sensitive for detection of gram-negative bacteria.

Isolation and Identification of L-asparaginase Producing Bacteria from Soils of Different Agroclimatic Zones of Jammu (J&amp;K), India

A milestone was set in the field of medicine with the discovery of L-asparaginase present in the serum of guinea pig responsible for action against the acute lymphoblastic leukemia. Since then, the use of L-asparaginase as a potential anti-cancer drug has been a great success in the field of modern oncology. Despite its varied sources, new sources are continuously being explored to obtain a high therapeutic index drug. The study aims to isolate potential L-asparaginase producing microorganisms from environmental niches of Northwestern Himalayas. The climatic conditions of the region and ancient agricultural practices which are still being followed in these areas, add up to the diverse microbial repository and a potential habitat which can be explored to obtain a potent asparaginase producing microbial source. In the study, soil samples from different regions of Jammu were collected aseptically. From the isolation studies, a total of 44 bacterial isolates were obtained. Pure cultures were then screened for asparaginase activity both qualitatively as well as quantitatively using agar plate and nesselerization method. Screening studies resulted in the isolation of a potent L-asparaginase producer isolated from black gram soil sample of Rajouri, Jammu showing an enzyme activity of 9.14 U/ml. Based on biochemical and molecular approaches, the isolate was identified as Enterobacter aesburiae strain R16C1 / No. MT93543. The study resulted in the isolation of a pure bacterial culture from the soils of Northwestern Himalayas possessing anti-cancer asparaginase activity. Further, optimization studies can help in considerably increasing the enzyme activity which can be tested against different human cancer lines for its anti-cancer efficacy.

A promising microbial α-amylase production, and purification from Bacillus cereus and its assessment as antibiofilm agent against Pseudomonas aeruginosa pathogen

Background and aimThe purpose of the current study is to isolate a heavily amylase-producing bacteria of the genus Bacillus from soil samples, optimize the production of the enzyme, purify it, and evaluate its activity against biofilm-producing bacteria. A total of 12 soil samples were collected and screened for promising Bacillus species with good amylolytic activity. Isolation was done by serial dilution and plating technique and amylolytic activity was determined by starch agar plate method. Among the 12 Bacillus isolates recovered from soil samples, 7 showed positive α-amylase production. The best isolate that recorded the greatest amylolytic activity was selected for further studies. This isolate was identified by 16S rRNA sequencing as Bacillus cereus and registered under gene bank accession number OP811897. Furthermore, the α-amylase enzyme was produced by a submerged fermentation technique using best production media and partially purified by ammonium sulfate and chilled ethanol and molecular weight had been determined by SDS-PAGE gel electrophoresis. The production of α-amylase was optimized experimentally by one-factor at a time protocol and statistically by Plackett–Burman design as well as RSM CCD design. Data obtained from OFAT and CCD revealed that α-amylase activities were 1.5- and twofold respectively higher as compared to un-optimized conditions. The most significant factors had been identified and optimized by CCD design.ResultsAmong the eleven independent variables tested by PBD, glucose, peptone, (NH4)2SO4, and Mg SO4 were the most significant parameters for α-amylase production with an actual yield of 250U/ml. The best physical parameters affecting the enzyme production were incubation time at 35 °C, and pH 5.5 for 48 h. The partially purified enzyme with 60% ammonium sulphate saturation with 1.38- fold purification showed good stability characteristics at a storage temperature of 4 °C and pH up to 8.5 for 21 days. Antibiofilm activity of purified α-amylase was determined against Pseudomonas aeruginosa (ATCC 35659) by spectrophotometric analysis and CLSM microscopic analysis. Results demonstrated biofilm inhibition by 84% of the formed Pseudomonas biofilm using a microtiter plate assay and thickness inhibition activity by 83% with live/Dead cells percentage of 17%/83% using CLSM protocol.ConclusionsA highly stable purified α-amylase from B. cereus showed promising antibiofilm activity against one of the clinically important biofilm-forming MDR organisms that could be used as a cost-effective tool in pharmaceutical industries.

Studies on Seed Borne Mycoflora of Soybean Seeds by Incubation Methods

The present study was conducted to detect and identify seed-borne pathogenic fungi in some soybean varieties and their effect on seed germination. Six varieties of soybean seed samples viz.JS 95-60, JS 97-52, RSC 10-46, RSC 10-71, CG Soya-1 and local variety were selected for the experiment. Twelve seed-borne mycoflora viz. Aspergillus flavus, Aspergillus niger, Alternaria spp., Cladosporium spp., Curvularia spp., Rhizopus spp., Trichoderma spp., Rhizoctonia spp., Nigrospora spp., Macrophomina spp., Fusarium spp. and Penicillium spp. were detected and identified from the seeds of six soybean varieties by using the standard blotter method, agar plate method, 2,4-D blotter method, roll paper towel method and deep freeze method. The seed sample of local variety recorded the highest percentage of mycoflora with the lowest germination percentage, whereas CG Soya-1 variety found as the least percentage of mycoflora with the highest germination percentage compared to other varieties of soybean taken in the study. Among all of the incubation methods, the agar plate was found as the most effective in detecting seed-related mycoflora, on soybean seeds.

Clinico-microbiological and Risk Factor Analysis of Strongyloides stercoralis Infections in South India

Strongyloides stercoralis is a soil-transmitted nematode infection. It is implicated in causing hyper infection syndrome in immunosuppressed patients. This infection can also present without symptoms. The study aims to analyze the demographic data and risk factors associated with acquiring this infection and detectStrongyloides stercoralis in the stool sample by microscopy and modified agar plate culture. Combining microscopy and culture can facilitate detecting the infection in cases of low worm burden. Evaluation of socio-demographic information and risk factors will help in implementing control measures. A total of 986 stool samples were received. All the samples were examined by saline and Iodine mount examination. All the stool samples were cultured by the modified agar plate method. The risk factors, patient demographic details and clinical features were analyzed for significant association using the Chi-square test and a p-value &lt; 0.05 was considered significant) by quick calls graph pad software. The overall prevalence of Strongyloides stercoralis infection was 22(1.23%), and all these cases were diagnosed on stool examination by the demonstration of rhabditiform larva ofStrongyloides stercoralis and adult females by modified agar plate culture. The positivity for Strongyloides larva was high among males, patients from rural areas and individuals working in agricultural settings. There was a significant association between walking barefoot and the demonstration of the larva. Patients presenting from endemic regions, even with vague, nonspecific gastrointestinal symptoms, especially with risk factors like Diabetes mellitus, should be screened for this infection and treated. Awareness, proper hygiene practices, and appropriate treatment are necessary to prevent this soil-transmitted helminthic infection.

Isolation Of Bacterial Strains And Production of Enzymes For Biodegradation of Biomedical Cotton Waste

In recent times, biodegradation of used hospital cotton by using the bacterial strain is a promising and interesting field attracting worldwide researchers. It was observed that biodegradation of biomedical waste like cotton etc., is becoming a huge problem for both developed as well as developing countries. To overcome this problem, bacterial species were isolated using serial dilution and agar plating methods from different soil sources. Pure colony or single colony was isolated by the streak plate method. The bacterial species were identified with the help of various physical characteristics, staining, and biochemical activities. Strain improvement was done by UV and EtBr to know the best culture for amylase production. Purification of the crude amylase was done by dialysis, and its activity was calculated by DNS assay. Protein concentration was measured by Lowery’s method. The purified enzyme was characterized for the effect of temperature, pH, activator, and inhibitors. The bacterial colonies were isolated and named as IS2015 01 to IS2015 16, the total enzyme activity of the purified enzyme was calculated to be 0.96 mg/ml, and the amount of protein in the purified sample was calculated to be 1.47 mg/ml. Amylase purified here was found stable in a pH range of 7 - 9 and temperature range of 28°C - 37°C. The activity was found to be enhanced under the influence of cations such as Ca2+, Mg2+ and retarded under the influence of anions such as EDTA and SDS. The isolated bacterial strain and enzyme were found effective in degrading the biomedical cotton waste. In conclusion, the isolated bacterial strain and enzyme may be effectively used to degrade the biomedical cotton.

A targeted liquid cultivation method for previously uncultured non-colony forming microbes

A large number of microbes are not able to form colonies using agar-plating methods, which is one of the reasons that cultivation based on solid media leaves the majority of microbial diversity in the environment inaccessible. We developed a new Non-Colony-Forming Liquid Cultivation method (NCFLC) that can selectively isolate non-colony-forming microbes that exclusively grow in liquid culture. The NCFLC method involves physically separating cells using dilution-to-extinction (DTE) cultivation and then selecting those that could not grow on a solid medium. The NCFLC was applied to marine samples from a coastal intertidal zone and soil samples from a forest area, and the results were compared with those from the standard direct plating method (SDP). The NCFLC yielded fastidious bacteria from marine samples such as Acidobacteriota, Epsilonproteobacteria, Oligoflexia , and Verrucomicrobiota . Furthermore, 62% of the isolated strains were potential new species, whereas only 10% were novel species from SDP. From soil samples, isolates belonging to Acidobacteriota and Armatimonadota (which are known as rare species among identified isolates) were exclusively isolated by NCFLC. Colony formation capabilities of isolates cultivated by NCFLC were tested using solid agar plates, among which approximately one-third of the isolates were non-colony-forming, approximately half-formed micro-colonies, and only a minority could form ordinary size colonies. This indicates that the majority of the strains cultivated by NCFLC were previously uncultured microbial species unavailable using the SDP method. The NCFCL method described here can serve as a new approach to accessing the hidden microbial dark matter.

О возможности использования катионных поверхностно-активных веществ для придания текстильным материалам антимикробных свойств

The COVID-19 pandemic has demonstrated the need for improved measures to prevent infectious diseases. Combating pathogens once they have been released into the environment is complicated by their widespread distribution. It is necessary to prevent the contamination of environmental objects. One possible way to do this is to create materials that have antimicrobial action without exposure to disinfectants and thus begin to have an antimicrobial effect on microorganisms immediately upon contact. Textile materials are widely used in medical organizations and are one of the factors of pathogenic microflora spreading. In this work, the possibility of using substances from the group of cationic surfactants to impart antimicrobial properties to textile materials was considered. Substances from different classes were used – tertiary amines, quaternary ammonium compounds, polymeric guanidine derivatives. The substances were applied from aqueous solutions using a laboratory analogue of a drying and a shirring machine. An acrylate binder with thermal initiation of polymerization was used to fix the active substances to the tissues. The content of the active substances in the tissues after application was determined by high-performance liquid chromatography. Antimicrobial activity of the obtained materials was checked by the agar plate method and the area of the growth retardation zone was estimated. Tissues containing N,N-bis(3-aminopropyl)dodecylamine showed the highest activity, tissues with poly (2-hydroxypropyl dimethylammonium) chloride the lowest. Keywords: antimicrobial materials, antimicrobial textile, HAI, cationic surfactants.

Seedborne mycoflora of faba bean (Vicia fabae L.) and evaluation of plant extract and Trichoderma species against mycelium growth of selected fungi

Fungal diseases are among the biotic factors limiting the production of faba bean in Ethiopia. The objective of this study was to isolate and identify seedborne mycoflora associated with faba bean seed samples, determine their effects on seed germination and disease transmission, and evaluate the antimicrobial activities of seven plant extracts and four Trichoderma spp. against the pathogen isolated from the seed. Fifty seed samples were collected from different farmers’ saved seeds of five major faba bean-producing varieties of the Ambo district and were tested by agar plate methods as recommended by the International Seed Testing Association (ISTA). A total of 7 fungal species belonging to 6 genera, viz. Fusarium oxysporum (Schlechlendahl), Fusarium solani (Mart.) Sacc, Aspergillus spp. Penicillium spp. Botrytis spp. Rhizoctonia solani (Kühn) and Alternaria spp. were isolated and identified. Among these, Fusarium spp., Aspergillus spp, and Penicillium spp. were the most predominant fungi in all seed samples. Seed-to-seedling transmission test results confirmed that F. oxysporum, F. solani and R. solani were major causal pathogens that caused root rot and damping-off disease in faba beans and were transmitted from seeds to seedlings. A higher germination rate was observed in Golja-GF2 (97%), and a lower germination rate was observed in Kure Gatira-KF8 (81%). A study on in vitro evaluation of plant extract and Trichoderma spp. against F. oxysporum, F. solani and R. solani revealed that plant extracts at 5%, 10% and 20% concentrations significantly inhibited the mycelial growth of all tested fungi. Inhibitory effects on the three tested fungi (R. solani, F. solani and F. oxysporum) were recorded on T. longibrachiatum (87.91%), T. atroviride (86.87%), Trichoderma virens (86.16%) and T. harzianum (85.45%). The inhibitory effect of the aqueous plant extracts on mycelial growth increased with an increase in concentration, and the hot water extracts showed higher effects compared to the cold water extract in all tested fungi. This study showed that the highest inhibitory effect of Allium sativum L. extracted at a 20% concentration against mycelial growth inhibition of the three test fungi (F. oxysporum, R. solani and F. solani) was 84.60%, 83.61% and 83.47%, respectively. However, Nicandra physalodes (L.) Gaertn.) extracts at the same concentration showed the lowest inhibitory effects on the three tested fungi (74.94%, 73.94% and 73.24%).

Virulence Factors of Clinical and Fecal Isolates of Enterococci Species

Enterococci species are known commensals of the gastrointestinal flora; however, in recent years, they have emerged as important nosocomial pathogens that possess many virulence factors that are attributed to the pathogenesis of diseases caused by them. The study evaluated and compared the virulence factors of Enterococci isolated from fecal and clinical samples. From the obtained isolates, the clinical enterococcal isolates produced 35%, 20%, and 50%, and fecal isolates produced 23%, 13%, and 13% gelatinase, hemolysin, and biofilm, respectively. Biofilm production determined by the Congo Red agar, tube, and microtiter plate methods was 23%, 39%, and 49%, respectively. The sensitivity of the Congo Red agar and tube method compared to the microtiter plate method was 27% and 46%, respectively, whereas the specificity of both tests was 79%. This study showed that biofilm production plays a significant role in the pathogenesis of diseases caused by Enterococci. Detection of biofilm production using the microtiter plate method is more sensitive and specific than the Congo Red agar and tube method.

Deciphering of seed Health of common food grains (wheat, rice) of North Eastern UP and Gurgaon Haryana, India

The stored random samples of food seeds of wheat and rice (60 samples) were purchased from places of Eastern UP and Gurgaon district Haryana. Its moisture contents were estimated. The Mycological investigations of wheat seeds revealed presence of a total number of 16 fungal species viz., Alternaria alternata, Aspergillus candidus, Aspergillus flavus, A. niger, A. ochraceous, A. phoenicis, A. tamari, A. terreus, A. sydowi, Fusarium moniliforme, F. oxysporum F. solani, P. glabrum, Rhizopus nigricans, Trichoderma viride and Trichothecium roseum. While mycological analysis of rice seeds showed presence of 15 fungal species viz., Alternaria padwickii, A. oryzae, Curvularia lunata, Fusarium moniliforme, Aspergillus clavatus, A. flavus, A. niger, Cladosporium sp., Nigrospora oryzae, Alternaria tenuissima, Chaetomium globosum, F. solani, Microascus cirrosus, Helminthosporium oryzae, Pyricularia grisea. It also projected variation in presence of fungal species in blotter and agar plate method of analysis. In wheat Blotter method of analysis showed 16 fungal species while agar plate depicted 13 fungal species. In rice Agar plate method depicted presence of 15 fungal species while blotter method shows presence of 12 fungal species. The insect analysis revealed that wheat samples were infected with Tribolium castaneum. While rice seeds sample showed presence of insect Sitophilus oryzae. The investigations revealed that Aspergillus flavus, A. niger, Sitophilus oryzae and Tribolium castaneum caused reduction in seed weight loss, seed germination, carbohydrate and protein contents of common food grains (wheat, rice). It also revealed that randomly selected A. flavus isolate 1 of wheat showed higher potential of aflatoxin B1 production (1392.940 μg/l) while rice isolate 2 showed 1231.117 μg/l production.

Oxygen Sensor-Based Respirometry and the Landscape of Microbial Testing Methods as Applicable to Food and Beverage Matrices.

The current status of microbiological testing methods for the determination of viable bacteria in complex sample matrices, such as food samples, is the focus of this review. Established methods for the enumeration of microorganisms, particularly, the 'gold standard' agar plating method for the determination of total aerobic viable counts (TVC), bioluminescent detection of total ATP, selective molecular methods (immunoassays, DNA/RNA amplification, sequencing) and instrumental methods (flow cytometry, Raman spectroscopy, mass spectrometry, calorimetry), are analyzed and compared with emerging oxygen sensor-based respirometry techniques. The basic principles of optical O2 sensing and respirometry and the primary materials, detection modes and assay formats employed are described. The existing platforms for bacterial cell respirometry are then described, and examples of particular assays are provided, including the use of rapid TVC tests of food samples and swabs, the toxicological screening and profiling of cells and antimicrobial sterility testing. Overall, O2 sensor-based respirometry and TVC assays have high application potential in the food industry and related areas. They detect viable bacteria via their growth and respiration; the assay is fast (time to result is 2-8 h and dependent on TVC load), operates with complex samples (crude homogenates of food samples) in a simple mix-and-measure format, has low set-up and instrumentation costs and is inexpensive and portable.

Study of physico-chemical and antibacterial properties of DBD plasma treated ahimsa silk coated with natural active agent

This study investigated the effect of dielectric barrier discharge (DBD) plasma on the physicochemical and antibacterial properties of ahimsa silk fabric. The fabric was pre-treated for 1–5 min with DBD plasma in ambient air. The leaf extracts of Camellia sinensis (Green Tea) and Ocimum sanctum (Tulsi) were applied to the fabric to impart an antibacterial finish. Wettability, SEM, AFM, and tensile strength analyses demonstrated increased hydrophilicity and surface roughness with a slight reduction in mechanical strength. Both ATR-FTIR and XPS indicated an increase in the concentration of polar functional groups, such as -OH, -NH, -CHO, and -COOH, on the surface of the plasma-treated fabric. Antimicrobial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was evaluated using the agar plate method and modified Hohenstein test. The results verified the efficacy of plasma-treated fabric, with an approximately 93% reduction in E. coli and a 96% reduction in S. aureus growth that persisted even after three washing cycles. This study suggests that DBD plasma at atmospheric pressure can be used as an eco-friendly technology for modifying the surface of silk fabrics to promote better adherence of plant extracts to the fabric and subsequently enhance their microbial resistance.

즉석섭취식품에 존재하는 Salmonella spp.와 Listeria monocytogenes의 검출을 위한 SureTectTM와 표현형 및 유전자형 방법의 비교

The objective of this study is to compare and assess the effectiveness of real-time polymerase chain reaction (RT-PCR), loop-mediated isothermal amplification (LAMP), and the selective agar plate method for the detection of Salmonella spp. and Listeria monocytogenes in ready-to-eat (RTE) foods. In RTE foods, the detection performance of the three methods (RT-PCR [SureTectTM kit and PowerChekTM kit], LAMP [3M MDS], selective agar) were similar at 0-10, 10-50, 50-100, and 100- CFU/mL of Salmonella spp. and L. monocytogenes. We found that with RT-PCR, the Ct value of salad was significantly higher (p&lt;0.05) than other RTE foods, indicating that fiber plays a critical role as an obstacle to the rapid detection of Salmonella spp. However, the Ct value displayed a mixed pattern according to the inoculation level of L. monocytogenes. The use of rapid detection kits and machines mostly depends on the user’s choice, with accuracy, ease of use, and economy being the primary considerations. As an RT-PCR kit, SureTectTM and PowerChekTM showed high accuracy in detecting Salmonella spp. and L. monocytogenes in RTE foods, showing that they can replace the existing RT-PCR kits available. Additionally, LAMP also showed excellent detection performance, suggesting that it has the potential to be used as a food safety management tool.

Evaluation of antifungal efficacy of chitosan against Aspergillus fumigatus of stored rice (Oryza sativa)

Contamination of stored rice with fungal pathogens results in rice of poor quality and economic value, and may also have harmful effects on human and animal health. This study aimed at evaluating the antifungal efficacy of chitosan against Aspergillus fumigatus of stored rice (Oryza sativa). Four forms of chitosan were used in this study viz; Purchased Low, Medium and high molecular weight chitosan and chitosan synthesized from Crab Shell using deproteinization, demineralization, decolouration and deacetylation. Degree of deacetylation of the synthesized chitosan was determined using Fourier transform infrared (FTIR) analysis. The in vitro antifungal activity of all forms of chitosan were determined using food poisoning method against Aspergillus fumigatus isolated from stored rice seeds using agar plate methods. The percentage inhibition of mycelial radial growth Aspergillus fumigatus by the different forms of chitosan was determined. Fourier Transfrom InfraRed Spectra of synthesized chitosan showed major absorption bands from 3444.72, 2966.17, 2512.60, 2144.84, 1429.74, 1258.12, 1160.05, 1025.2, 869.92, 710.50, 608.40 to 559.36. Absorption peak at 559 was assigned to glucopyranose ring in the chitosan matrix. Degree of deacetylation of synthesized chitosan was at 98.6% degree. Highest mycelia radial growth of 8.00 cm was recorded in control, while 2.00, 0.00, 5.23, and 1.33cm were recorded in 2.0% concentration of High Molecular Weight Chitosan (HMWC), Medium Molecular Weight Chitosan (MMWC), Low Molecular Weight Chitosan (LMWC) and Chitosan synthesized from Crab shell (CSCS) treatment respectively. The result of the percentage inhibition reveals that A. fumigatus had 100% inhibition in 1.5% HMWC and 2.0% MMWC while 85% inhibition in 2.0% CSCS which were significantly different from 2.0% LMWC with 36.5% inhibitions. Results obtained from this study has shown the effectiveness of chitosan as an effective antifungal agent which can improve and maintain the quality of stored rice and ensure a safer environment due to its nontoxic and environmental friendly properties.

Study on organic matter decomposition and siderophore production of rhizobacteria isolated from black pepper grown in Loc Ninh, Binh Phuoc province, Vietnam

This study was carried out determining capability of organic compound decomposition and siderophore synthesis of 39 plant growth promotion rhizobacteria strains isolated from rhizosphere of black pepper (Piper nigrum L.) in a previous study. The ability to degrade organic compounds including proteins, lipids, cellulose and chitin was investigated by agar well diffusion method. The ability to produce siderophore was qualified by liquid CAS method and strains with good results were further investigated by PS-CAS agar plate method. The results showed that the number of bacterial strains capable of degrading protein, cellulose, chitin and lipid were 37, 27, 16 and 6, respectively. Twenty-two strains changed color of CAS agar, of which 6 strains had a band width of 4.5 cm. The seven best strains identified were Proteus mirabilis (LD2), Bacillus megaterium (LT4), B. subtilis (LT2), B. cereus (LD7, LD8, LD16, LT19) by Matrix Assisted Laser Desorption/Ionization-Time of Flight method. These were plant growth-promoting rhizobacteria that had been reported on potential applications in agriculture.

Genomic Analysis of a New Freshwater Cyanophage Lbo240-yong1 Suggests a New Taxonomic Family of Bacteriophages.

A worldwide ecological issue, cyanobacterial blooms in marine and freshwater have caused enormous losses in both the economy and the environment. Virulent cyanophages-specifically, infecting and lysing cyanobacteria-are key ecological factors involved in limiting the overall extent of the population development of cyanobacteria. Over the past three decades, reports have mainly focused on marine Prochlorococcus and Synechococcus cyanophages, while information on freshwater cyanophages remained largely unknown. In this study, a novel freshwater cyanophage, named Lbo240-yong1, was isolated via the double-layer agar plate method using Leptolyngbya boryana FACHB-240 as a host. Transmission electron microscopy observation illustrated the icosahedral head (50 ± 5 nm in diameter) and short tail (20 ± 5 nm in length) of Lbo240-yong1. Experimental infection against 37 cyanobacterial strains revealed that host-strain-specific Lbo240-yong1 could only lyse FACHB-240. The complete genome of Lbo240-yong1 is a double-stranded DNA of 39,740 bp with a G+C content of 51.99%, and it harbors 44 predicted open reading frames (ORFs). A Lbo240-yong1 ORF shared the highest identity with a gene of a filamentous cyanobacterium, hinting at a gene exchange between the cyanophage and cyanobacteria. A BLASTn search illustrated that Lbo240-yong1 had the highest sequence similarity with the Phormidium cyanophage Pf-WMP4 (89.67% identity, 84% query coverage). In the proteomic tree based on genome-wide sequence similarities, Lbo240-yong1, three Phormidium cyanophages (Pf-WMP4, Pf-WMP3, and PP), one Anabaena phage (A-4L), and one unclassified Arthronema cyanophage (Aa-TR020) formed a monophyletic group that was more deeply diverging than several other families. Pf-WMP4 is the only member of the independent genus Wumpquatrovirus that belongs to the Caudovircetes class. Pf-WMP3 and PP formed the independent genus Wumptrevirus. Anabaena phage A-4L is the only member of the independent Kozyakovvirus genus. The six cyanopodoviruses share similar gene arrangements. Eight core genes were found in them. We propose, here, to set up a new taxonomic family comprising the six freshwater cyanopodoviruses infecting filamentous cyanobacteria. This study enriched the field's knowledge of freshwater cyanophages.

Antibacterial activity of green tea leaves extracts against specific bacterial strains

ObjectivesThere is an increase interest in the beneficial effects of green tea extracts which exhibits great activity against several diseases due to the presence of beneficial bioactive compounds. Green tea extracts were investigated for their anti microbial activity using specified Gram positive and Gram negative bacterial strains by specific methods. Therefore, this study aimed at evaluation of green tea aqueous, ethanol, and methanol extracts efficiency against potential gram positive and gram negative bacterial strains. MethodsFifty grams of dry leaves powder were used to prepare three different solutions with three different solvents; 80% ethanol, methanol, and sterile water; with a final concentration of 20% (g/ml). The flasks were placed for two days in a vibrator at 350 rpm at 15 °C. Four bacterial strains - two of them are gram positive and the other two are gram negative strains- were honored from King Fahd Educational Hospital. Qualitative phytochemical analysis technique was used to insure the presence of active compounds such as flavonoids, saponin, and tannins in plant extracts. Also, Gas chromatography mass spectrometry assay was used to determine extracts bioactive compounds. Seven types of antibiotics were used to determine minimum inhibitory concentration with two-fold dilution of plant extracts, by using agar plate method. While the minimum bactericidal concentration was performed using the pour plate technique. ResultsThe three types of plant extracts showed high effectiveness against pathogenic bacterial strains. The highest value of inhibition was (4.3 ± 0.3) mm with ethanol extract against Bacillus subtilis. Gentamicin, Neomycin and Ciprofloxacin showed good values of inhibition against Gram-positive and gram-negative bacteria, while gram-negative bacteria showed resistance to Chloramphenicol, Methicillin, Vancomycin. On the other hand, Gram positive bacteria showed resistance to the Colistin only. ConclusionGreen tea extracts showed effective anti microbial activity against different types of gram positive and negative bacterial strains as they have a good inhibitory and bactericidal activity due to the presence of special bioactive components such as ECGC and catechins.